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HTTP Connectors Load Balancing Guide

Red Hat JBoss Web Server 1.0

HTTP load balancing for JBoss Enterprise Application Platform and Red Hat JBoss Web Server

Edition 1.0.2

Joshua Wulf

Red Hat Engineering Content Services

Samuel Mendenhall

Red Hat Global Support Services

James Livingston

Red Hat Global Support Services

Jim Tyrell

Red Hat JBoss Solutions Architect

Laura Bailey

Red Hat, Inc. Engineering Content Services

Jared Morgan

ISAPI Section 
Red Hat, Inc. Engineering Content Services

Mandar Joshi

Patches and bug fixes. 
Red Hat, Inc. Engineering Content Services

Abstract

Read this guide to install and configure JBoss Enterprise Application Platform and Red Hat JBoss Web Server HTTP connectors: mod_jk, mod_cluster, ISAPI, and NSAPI. This guide also discusses clustering and load-balancing using these connectors.

Preface

1. File Name Conventions
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The following naming conventions are used in file paths for readability. Each convention is styled differently to help you identify them in context:
JBOSS_EAP_DIST
The installation root of the JBoss Enterprise Application Platform instance. This folder contains the main folders that comprise the server such as /jboss-as, /seam, and /resteasy.
JBOSS_EwP_DIST
The installation root of the JBoss Enterprise Web Platform instance. This folder contains the main folders that comprise the server such as /jboss-as-web, /seam, and /resteasy.
JBOSS_EWS_DIST
The installation root of the JBoss Enterprise Web Server instance. This folder contains the main folders that comprise the server such as /extras, /httpd, and the /tomcat6 folders.
NATIVE
The installation root of the JBoss Native zip, extracted to the same directory level as JBOSS_EAP_DIST.
SJWS
The installation root of the Sun Java Web Server instance. The default file locations for this naming convention are:
  • for Solaris 9 x86 or SPARC 64: /opt/SUNWwbsrv61/
  • for Solaris 10 x86 or SPARC 64: /opt/SUNWwbsrv70/
HTTPD_DIST
The installation root of the Apache httpd Server. This folder contains the main folders that comprise the server such as /conf, /webapps, and /bin. The JBoss Enterprise Web Server JBOSS_EWS_DIST directory contains the root installation of HTTPD_DIST.
PROFILE
The name of the JBoss server profile you use as part of your testing or production configuration. The server profiles reside in JBOSS_EAP_DIST/jboss-as/server or JBOSS_EWS_DIST/jboss-as-web/server.

Part I. Apache Tomcat Connector
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Chapter 1. Overview
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Apache is a well-known web server which can be extended using plug-ins. The Apache Tomcat Connector mod_jk is a plug-in designed to allow request forwarding from Apache httpd Server to a Servlet container. The module also supports load-balancing HTTP calls to a set of Servlet containers while maintaining sticky sessions.
HTTP session replication is used to replicate the state associated with web client sessions to other nodes in a cluster. If one node becomes unavailable, another node in the cluster takes the load of the disabled node. Two distinct functions must be performed:
  • Session state replication
  • Load-balancing HTTP Requests
Sessions state replication is handled by JBoss at the application level (refer to Section 15.1, “Enabling session replication in your application”.
Load balancing, however, requires an external load balancer. A cost effective way of managing load-balancing is to set up a software load balancer using Apache httpd and mod_jk.

Chapter 2. Download and Install
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Apache httpd is included in the JBoss Enterprise Web Server binary you download from https://access.redhat.com.
mod_jk is included in the native installation binaries for JBoss Enterprise Application Platform and JBoss Enterprise Web Server.
Follow the procedures in the JBoss Enterprise Application Platform or JBoss Enterprise Web Server Installation Guide to download and install the correct platform and native binaries.
Follow the tasks in this chapter to correctly configure load balancing using Apache and the mod_jk connector.

Task: Configure Apache to Load mod_jk

Complete this task to configure Apache to load mod_jk.

Prerequisites

  1. Open HTTPD_DIST/conf/httpd.conf and add a single line at the end of the file. 
    # Include mod_jk's specific configuration file  
Include conf/mod-jk.conf
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  2. Create a new file named HTTPD_DIST/conf/mod-jk.conf
  3. Add the following configuration to the mod-jk.conf file.

    Important

    The LoadModule directive must reference the mod_jk library directory location applicable to the native binary you installed.

    Note

    The JkMount directive specifies which URLs Apache should forward to the mod_jk module. Based on the directive's configuration, mod_jk forwards the received URL onto the correct Servlet containers.
    To enable Apache to serve static content (or PHP content) directly, and only use the load balancer for Java applications, the suggested configuration specifies all requests with URL path /application/* are sent to the mod_jk load-balancer.
    If you only use mod_jk as a load balancer, forward all URLs to mod_jk by specifying /* in the directive. 
    # Load mod_jk module
# Specify the filename of the mod_jk lib
LoadModule jk_module modules/mod_jk.so
 
# Where to find workers.properties
JkWorkersFile conf/workers.properties

# Where to put jk logs
JkLogFile logs/mod_jk.log
 
# Set the jk log level [debug/error/info]
JkLogLevel info 
 
# Select the log format
JkLogStampFormat  "[%a %b %d %H:%M:%S %Y]"
 
# JkOptions indicates to send SSK KEY SIZE
JkOptions +ForwardKeySize +ForwardURICompat -ForwardDirectories
 
# JkRequestLogFormat
JkRequestLogFormat "%w %V %T"
               
# Mount your applications
JkMount /application/* loadbalancer
 
# Add shared memory.
# This directive is present with 1.2.10 and
# later versions of mod_jk, and is needed for
# for load balancing to work properly
JkShmFile logs/jk.shm 
              
# Add jkstatus for managing runtime data
<Location /jkstatus/>
    JkMount status
    Order deny,allow
    Deny from all
    Allow from 127.0.0.1
</Location>
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  4. Optional: JKMountFile Directive

    In addition to the JkMount directive, you can use the JkMountFile directive to specify a mount points configuration file. The configuration file contains multiple Tomcat forwarding URL mappings.
    1. Navigate to HTTPD_DIST/conf.
    2. Create a file named uriworkermap.properties.
    3. Specify the URL to forward and the worker name using the following syntax example as a guide.
      The example block will configure mod_jk to forward requests to /jmx-console and /web-console to Apache.
      The syntax required takes the form /url=worker_name. 
      # Simple worker configuration file

# Mount the Servlet context to the ajp13 worker
/jmx-console=loadbalancer
/jmx-console/*=loadbalancer
/web-console=loadbalancer
/web-console/*=loadbalancer
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    4. In HTTPD_DIST/conf/mod-jk.conf, append the following directive. 
      # You can use external file for mount points.
# It will be checked for updates each 60 seconds.
# The format of the file is: /url=worker
# /examples/*=loadbalancer
JkMountFile conf/uriworkermap.properties
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3.1. Configure Worker Nodes in mod_jk
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Task: Configure mod_jk Worker Nodes

Complete this task to configure two mod_jk Worker node definitions in a weighted round robin configuration with sticky sessions active between two servlet containers.

Prerequisites

  1. Navigate to HTTPD_DIST/conf/.
  2. Create a file named workers.properties.
  3. Append the following information into the workers.properties file. 
    # Define list of workers that will be used
# for mapping requests
worker.list=loadbalancer,status

# Define Node1
# modify the host as your host IP or DNS name.
worker.node1.port=8009
worker.node1.host=node1.mydomain.com
worker.node1.type=ajp13
worker.node1.ping_mode=A
worker.node1.lbfactor=1 

# Define Node2
# modify the host as your host IP or DNS name.
worker.node2.port=8009
worker.node2.host=node2.mydomain.com
worker.node2.type=ajp13
worker.node2.ping_mode=A
worker.node2.lbfactor=1

# Load-balancing behavior
worker.loadbalancer.type=lb
worker.loadbalancer.balance_workers=node1,node2
worker.loadbalancer.sticky_session=1

# Status worker for managing load balancer
worker.status.type=status
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3.2. Configuring JBoss to work with mod_jk
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Task: Configure JBoss Enterprise Application Platform to Operate Using mod_jk

Complete this task to correctly prepare a JBoss Enterprise Application Platform instance on a clustered node to receive forwarded requests from the mod_jk load balancer.
Repeat this task for each server instance you require, observing the warnings at each step.

Prerequisites

  1. Navigate to the location of the clustered server instance.
  2. Open JBOSS_EAP_DIST/jboss-as/server/PROFILE/deploy/jbossweb.sar/server.xml.
  3. Specify the node name by appending the jvmRoute attribute to the <Engine> element in server.xml. The jvmRoute attribute value is the node name defined in HTTPD_DIST/conf/workers.properties. 
    <!--Preceeding syntax removed for readability -->
<Engine name="jboss.web" defaultHost="localhost" jvmRoute="node1">
<!--Proceeding syntax removed for readability -->
</Engine>
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    Important

    If you intend to configure more than one server node in a cluster, ensure you change the jvmRoute attribute value to a unique name each time you repeat this step.
  4. In server.xml, ensure the AJP protocol <connector> element is enabled (uncommented). The element is uncommented by default in new installations. 
    <Connector protocol="AJP/1.3" port="8009" address="${jboss.bind.address}"
   redirectPort="8443" />
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  5. You now have a correctly configured Apache httpd Server with mod_jk load balancer, which balances calls to the servlet containers in the cluster, and ensures clients will always use the same servlet container (sticky sessions).

Note

For supplementary information about using mod_jk with JBoss, refer to the JBoss wiki page at http://www.jboss.org/community/wiki/UsingModjk12WithJBoss.

Part II. JBoss HTTP Connector
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Chapter 4. Overview
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The JBoss HTTP Connector mod_cluster is a reduced configuration, intelligent load-balancing solution for JBoss Enterprise Application Platform, based on technology originally developed by the JBoss mod_cluster community project.
The JBoss HTTP connector load-balances HTTP requests to JBoss Enterprise Application Platform and JBoss Enterprise Web Server worker nodes, utilizing Apache as the proxy server.

4.1. Key Features
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Apache HTTP Server-based
The JBoss HTTP Connector mod-cluster uses Apache as the proxy server.
Real-time load-balancing calculation
The JBoss HTTP Connector mod_cluster creates a feedback network between the worker nodes and the proxy server. The mod_cluster service is deployed on each of the worker nodes. This service feeds real-time load information to the proxy server. The proxy server then makes intelligent decisions on where to allocate work, based on the current load on each worker node. This real-time adaptive load distribution results in increased optimization of resources.
The information that is reported by the worker nodes and the load-balancing policy used by the proxy are both customizable.
Routing based on real-time application life cycle
The JBoss HTTP Connector mod_cluster service deployed on the worker nodes relays application lifecycle events to the proxy server. This allows the server to dynamically update its routing table. When an application is undeployed on a node, the proxy server no longer routes traffic for that application to that node.
Automatic Proxy Discovery
The proxy server can be configured to announce its presence via UDP multicast. New worker nodes discover the proxy server and add themselves to the load-balancing cluster automatically. This greatly reduces the configuration and maintenance needed. When UDP multicast is not available or is undesirable, worker nodes are configured with a static list of proxies.
Multiple Protocol Support
The JBoss HTTP Connector mod_cluster can use HTTP, HTTPS, or Apache JServ Protocol (AJP) for communication between the proxy and the worker nodes.

4.2. Components
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Proxy Server

On the proxy server, the JBoss HTTP Connector mod-cluster consists of four Apache modules.
Shared Memory Manager: mod_slotmem.so
The Shared Memory Manager module, mod_slotmem, makes the real-time worker node information available to multiple Apache server processes.
Cluster Manager Module: mod_manager.so
The Cluster Manager module, mod_manager, receives and acknowledges messages from nodes, including worker node registrations, worker node load data, and worker node application life cycle events.
Proxy Balancer Module: mod_proxy_cluster.so
The Proxy Balancer Module, mod_proxy_cluster, handles the routing of requests to cluster nodes. The Proxy Balancer selects the appropriate node to forward the request to, based on application location in the cluster, current state of each of the cluster nodes, and the Session ID (if a request is part of an established session).
Proxy Advertisement Module: mod_advertise.so
The Proxy Advertisement Module, mod_advertise.so, broadcasts the existence of the proxy server via UDP multicast messages. The server advertisement messages contain the IP address and port number where the proxy is listening for responses from nodes that wish to join the load-balancing cluster.

Note

Refer to Section 5.1, “Apache Modules” for detailed information about the available modules including user-configurable parameters.

Worker Node Components

Worker node service: mod-cluster.sar
The JBoss HTTP Connector client service mod-cluster.sar is deployed on each worker node. This service provides the proxy with real-time information on the worker node's state and sends notification of application life cycle events; as well as allowing the node to discover and register itself with any proxies running on the same network.

Chapter 5. Install Proxy Server Components
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Read this chapter to install the JBoss HTTP Connector mod-cluster on a JBoss Enterprise Web Server proxy server.

5.1. Apache Modules
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Read this section for expanded definitions of the Apache proxy server modules discussed in Section 4.2, “Components”. You specify these modules as part of Task: Install Proxy Server Components.

5.1.1. mod_manager.so
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The Cluster Manager module, mod_manager, receives and acknowledges messages from nodes, including worker node registrations, worker node load data, and worker node application life cycle events. 
LoadModule manager_module modules/mod_manager.so
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You can also define the following related directives in the <VirtualHost> element:
MemManagerFile
Defines the location for the files in which mod_manager stores configuration details. mod_manager also uses this location for generated keys for shared memory and lock files. This must be an absolute path name. It is recommended that this path be on a local drive, and not a NFS share. The default value is /logs/.
Maxcontext
The maximum number of contexts JBoss mod_cluster will use. The default value is 100.
Maxnode
The maximum number of worker nodes JBoss mod_cluster will use. The default value is 20.
Maxhost
The maximum number of hosts (aliases) JBoss mod_cluster will use. This is also the maximum number of load balancers. The default value is 10.
Maxsessionid
The maximum number of active session identifiers stored. A session is considered inactive when no information is received from that session within five minutes. The default value is 0, which disables this logic.
ManagerBalancerName
The name of the load balancer to use when the worker node does not provide a load balancer name. The default value is mycluster.
PersistSlots
When set to on, nodes, aliases and contexts are persisted in files. The default value is off.
CheckNonce
When set to on, session identifiers are checked to ensure that they are unique, and have not occurred before. The default is on.

Warning

Setting this directive to off can leave your server vulnerable to replay attacks.
SetHandler
Defines a handler to display information about worker nodes in the cluster. This is defined in the Location element: 
<Location $LOCATION>
  SetHandler mod_cluster-manager
  Order deny,allow
  Deny from all
  Allow from 127.0.0.1
</Location>
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When accessing the $LOCATION defined in the Location element in your browser, you will see something like the following. (In this case, $LOCATION was also defined as mod_cluster-handler.)
View larger image
Transferred corresponds to the POST data sent to the worker node. Connected corresponds to the number of requests that had been processed when this status page was requested. Sessions corresponds to the number of active sessions. This field is not present when Maxsessionid is 0.

5.1.2. mod_proxy_cluster.so
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The Proxy Balancer Module, mod_proxy_cluster, handles the routing of requests to cluster nodes. The Proxy Balancer selects the appropriate node to forward the request to, based on application location in the cluster, current state of each of the cluster nodes, and the Session ID (if a request is part of an established session). 
LoadModule proxy_cluster_module modules/mod_proxy_cluster.so
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You can also define the following related directives in the <VirtualHost> element to change load balancing behavior.

mod_proxy_cluster directives

CreateBalancers
Defines how load balancers are created in the Apache HTTP Server virtual hosts. The following values are valid in CreateBalancers:
0
Create load balancers in all virtual hosts defined in Apache HTTP Server. Remember to configure the load balancers in the ProxyPass directive.
1
Do not create balancers. When using this value, you must also define the load balancer name in the ProxyPass or ProxyPassMatch.
2
Create only the main server. This is the default value for CreateBalancers.
UseAlias
Defines whether to check that the defined Alias corresponds to the ServerName. The following values are valid for UseAlias:
0
Ignore Alias information from worker nodes. This is the default value for UseAlias.
1
Verify that the defined alias corresponds to a worker node's server name.
LBstatusRecalTime
Defines the interval in seconds between the proxy calculating the status of a worker node. The default interval is 5 seconds.
ProxyPassMatch; ProxyPass
ProxyPass maps remote servers into the local server namespace. If the local server has an address http://local.com/, then the following ProxyPass directive would convert a local request for http://local.com/requested/file1 into a proxy request for http://worker.local.com/file1. 
ProxyPass /requested/ http://worker.local.com/
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ProxyPassMatch uses Regular Expressions to match local paths to which the proxied URL should apply.
For either directive, ! indicates that a specified path is local, and a request for that path should not be routed to a remote server. For example, the following directive specifies that .gif files should be served locally. 
ProxyPassMatch ^(/.*\.gif)$ !
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5.1.3. mod_advertise.so
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The Proxy Advertisement Module, mod_advertise.so, broadcasts the existence of the proxy server via UDP multicast messages. The server advertisement messages contain the IP address and port number where the proxy is listening for responses from nodes that wish to join the load-balancing cluster.
This module must be defined alongside mod_manager in the VirtualHost element. Its identifier in the following code snippet is advertise_module. 
LoadModule advertise_module modules/mod_advertise.so
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mod_advertise also takes the following directives:
ServerAdvertise
Defines how the advertising mechanism is used.
When set to On, the advertising mechanism is used to tell worker nodes to send status information to this proxy. You can also specify a hostname and port with the following syntax: ServerAdvertise On http://hostname:port/. This is only required when using a name-based virtual host, or when a virtual host is not defined.
The default value is Off. When set to off, the proxy does not advertise its location.
AdvertiseGroup
Defines the multicast address to advertise on. The syntax is AdvertiseGroup address:port, where address should correspond to AdvertiseGroupAddress, and port should correspond to AdvertisePort in your worker nodes.
If your worker node is JBoss Enterprise Application Platform-based, and the -u switch is used at startup, the default AdvertiseGroupAddress is the value passed via the -u switch.
The default value is 224.0.1.105:23364. If port is not specified, the default port specified is 23364.
AdvertiseFrequency
The interval (in seconds) between multicast messages advertising the IP address and port. The default value is 10.
AdvertiseSecurityKey
Defines a string used to identify the JBoss HTTP Connector mod_cluster in JBoss Web. By default this directive is not set and no information is sent.
AdvertiseManagerUrl
Defines the URL that the worker node should use to send information to the proxy server. By default this directive is not set and no information is sent.
AdvertiseBindAddress
Defines the address and port over which to send multicast messages. The syntax is AdvertiseBindAddress address:port. This allows an address to be specified on machines with multiple IP addresses. The default value is 0.0.0.0:23364.

5.2. Install Proxy Server Components
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Task: Install Proxy Server Components

Follow this task to install the JBoss HTTP Connector on a JBoss Enterprise Web Server.
The JBoss HTTP Connector is supported in production only with JBoss Enterprise Web Server as the proxy server. Refer to the JBoss Enterprise Web Server Installation Guide to download and install the JBoss Enterprise Web Server.
The Native components are Operating System and processor architecture specific. Refer to the JBoss Enterprise Application Platform Installation Guide to download the correct Native Components package for your server Operating System and processor architecture.

Prerequisites

  • JBoss Enterprise Web Server v1.0.1 or later installed.
  • JBoss Enterprise Application Platform 5 Native components downloaded.

  1. Extract Apache modules from Native Components download

    Extract the four modules mod_advertise.so, mod_manager.so, mod_proxy_cluster.so, mod_slotmem.so from the appropriate Native Components package directory for your processor architecture: either native/lib/httpd/modules or native/lib64/httpd/modules.

  2. Copy Apache modules to JBoss Enterprise Web Server

    Copy the JBoss HTTP Connector modules to the JBOSS_EWS_DIST/httpd/modules directory of the JBoss Enterprise Web Server.

  3. Disable the mod_proxy_balancer module

    Edit the JBoss Enterprise Web Server Apache configuration file JBOSS_EWS_DIST/httpd/conf/httpd.conf and comment out the following line by adding an initial #: 
    LoadModule proxy_balancer_module modules/mod_proxy_balancer.so
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    This module is incompatible with the JBoss HTTP Connector.

  4. Configure the server to load the JBoss HTTP Connector modules

    1. Create the file JBOSS_EWS_DIST/httpd/conf.d/JBoss_HTTP.conf.
    2. Add the following lines to the file JBOSS_EWS_DIST/httpd/conf.d/JBoss_HTTP.conf: 
      LoadModule slotmem_module JBOSS_EWS_DIST/modules/mod_slotmem.so
LoadModule manager_module JBOSS_EWS_DIST/modules/mod_manager.so
LoadModule proxy_cluster_module JBOSS_EWS_DIST/modules/mod_proxy_cluster.so
LoadModule advertise_module JBOSS_EWS_DIST/modules/mod_advertise.so
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  5. Restart the JBoss Enterprise Web Server Apache service

    Refer to the JBoss Enterprise Web Server documentation for detailed instructions.

Chapter 6. Configure Basic Proxy Server
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Follow the instructions in this chapter to configure a JBoss Enterprise Web Server to use the JBoss HTTP connector mod_cluster.

6.1. Basic Proxy Configuration Overview
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Configuration of the proxy server consists of one mandatory and one optional portion:
  1. Configure a Proxy Server listener to receive worker node connection requests and worker node feedback.
  2. Optional: Disable server advertisement.
Server Advertisement

The proxy server can advertise itself using UDP multicast. When UDP multicast is available on the network between the proxy server and the worker nodes Server Advertisement allows you to add worker nodes with no further configuration required on the proxy server, and minimal configuration on the worker nodes.

If UDP multicast is not available or undesirable, configure the worker nodes with a static list of proxy servers, as detailed in Section 9.1, “Static Proxy Configuration”. There is no need in either case to configure the proxy server with a list of worker nodes.
Read this section to configure a load balancing proxy that uses the JBoss HTTP Connector.

Task: Configure a Proxy Server Listener

Follow this task to configure a JBoss Enterprise Web Server Apache service to act as a load-balancing proxy using the JBoss HTTP Connector.

Prerequisites

  1. Create a listen directive for the proxy server

    Edit the configuration file JBOSS_EWS_DIST/httpd/conf.d/JBoss_HTTP.conf and add the following: 
    Listen IP_ADDRESS:PORT_NUMBER
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    Where IP_ADDRESS is the IP address of a server network interface to communicate with the worker nodes, and PORT_NUMBER is the port on that interface to listen on.

    Note

    The port PORT_NUMBER must be open on the server firewall for incoming TCP connections.

    Example 6.1. Example Listen Directive

    Listen 10.33.144.3:6666
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  2. Create Virtual Host

    Add the following to the file JBOSS_EWS_DIST/httpd/conf.d/JBoss_HTTP.conf: 
    <VirtualHost IP_ADDRESS:PORT_NUMBER>

   <Directory>
      Order deny,allow
      Deny from all
      Allow from 10.33.144.
   </Directory>

   KeepAliveTimeout 60
   MaxKeepAliveRequests 0

   ManagerBalancerName mycluster
   AdvertiseFrequency 5

</VirtualHost>
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    Where IP_ADDRESS and PORT_NUMBER are the values from the Listen directive.

  3. Optional: Disable Server Advertisement

    The presence of the AdvertiseFrequency directive, which is set to five seconds here, causes the server to periodically send server advertisement messages via UDP multicast.
    These server advertisement messages contain the IP_ADDRESS and PORT_NUMBER specified in the VirtualHost definition. Worker nodes that are configured to respond to server advertisements use this information to register themselves with the proxy server.
    To disable server advertisement, add the following directive to the VirtualHost definition: 
    ServerAdvertise Off
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    If server advertisements are disabled, or UDP multicast is not available on the network between the proxy server and the worker nodes, you must configure worker nodes with a static list of proxy servers. Refer to Section 9.1, “Static Proxy Configuration” for directions.

  4. Restart the JBoss Enterprise Web Server Apache service

    Refer to the JBoss Enterprise Web Server documentation for detailed directions.

Chapter 7. Install Node with Basic Configuration
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Read this chapter to install the JBoss HTTP Connector on a worker node, and implement basic configuration for the node to begin immediate operation.

7.1. Worker Node Requirements
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Supported Worker Node types

  • JBoss Enterprise Platform 5 JBoss Web component
  • JBoss Enterprise Web Server Tomcat service

Note

JBoss Enterprise Platform worker nodes support all JBoss HTTP Connector functionality. JBoss Enterprise Web Server Tomcat worker nodes support a subset of JBoss HTTP Connector functionality.

JBoss HTTP Connector Enterprise Web Server Node Limitations

  • Non-clustered mode only.
  • Only one load metric can be used at a time when calculating the load balance factor.

7.2. Install and Configure a Worker Node
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This section contains a number of tasks. Follow the appropriate task to install and configure a worker node on JBoss Enterprise Application Platform, or JBoss Enterprise Web Server.

Task: Install and Configure a JBoss Enterprise Application Platform Worker Node

Follow this procedure to install the JBoss HTTP Connector on a JBoss Enterprise Application Platform node and configure it for non-clustered operation.

Prerequisites

  • Install a supported JBoss Enterprise Application Platform.

  1. Deploy the worker node service

    Copy mod-cluster.sar from the JBOSS_EAP_DIST/mod_cluster directory to jboss-as/server/PROFILE/deploy.

  2. Add a Listener to JBoss Web

    Add the following Listener element beneath the other Listeners in JBOSS_EAP_DIST/jboss-as/server/PROFILE/deploy/jbossweb.sar/server.xml: 
    <Listener className="org.jboss.web.tomcat.service.deployers.MicrocontainerIntegrationLifecycleListener" delegateBeanName="ModClusterService"/>
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  3. Configure the service dependency

    Add the following depends element beneath the other depends elements in JBOSS_EAP_DIST/jboss-as/server/PROFILE/deploy/jbossweb.sar/META-INF/jboss-beans.xml: 
    <depends>ModClusterService</depends>
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  4. Give the worker a unique identity

    Edit the file JBOSS_EAP_DIST/jboss-as/server/PROFILE/deploy/jbossweb.sar/server.xml and add a jvmRoute attribute and value to the Engine element, as shown: 
    <Engine name="jboss.web" defaultHost="localhost" jvmRoute="worker01">
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    Use a unique jvmRoute value for each node.

  5. Optional: Configure firewall to receive multicast Proxy Server advertisements

    A proxy server using the JBoss HTTP Connector can advertise itself via UDP multicast. To enable the worker node to dynamically discover proxy servers, open port 23364 for UDP connections on the worker node's firewall.
    For Linux users: 
    /sbin/iptables -A INPUT -m state --state NEW -m udp -p udp --dport 23364 -j ACCEPT 
-m comment --comment "receive mod_cluster proxy server advertisements"
/sbin/iptables save
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    If you are not using Automatic Proxy Discovery (see Automatic Proxy Discovery), configure worker nodes with a static list of proxies. Refer to Section 9.1, “Static Proxy Configuration” for directions. In this case you can safely ignore the following warning message: 
    [warning] mod_advertise: ServerAdvertise Address or Port not defined, Advertise disabled!!!
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    Important

    If your nodes are on different machines that run Red Hat Enterpise Linux, they may not acknowledge each other automatically. JBoss Clustering relies on the UDP (User Datagram Protocol) multi-casting provided by jGroups.
    The SELinux configuration that ships with Red Hat Enterprise Linux blocks these packets by default. To allow the packets, modify the iptables rules (as root). The following commands apply to an IP address that matches 192.168.1.x: 
    /sbin/iptables -I RH-Firewall-1-INPUT 5 -p udp -D 224.0.1.0/24 -j ACCEPT
/etc/init.d/iptables save
/sbin/iptables -I RH-Firewall-1-INPUT 5 -p udp -d 224.0.0.0/4 -j ACCEPT
  /sbin/iptables -I RH-Firewall-1-INPUT 9 -p udp -s 192.168.1.0/24 -j ACCEPT
  /sbin/iptables -I RH-Firewall-1-INPUT 10 -p tcp -s 192.168.1.0/24 -j ACCEPT
  /etc/init.d/iptables save
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Task: Install and Configure a JBoss Enterprise Web Server Worker Node

Follow this procedure to install the JBoss HTTP Connector on a JBoss Enterprise Web Server node and configure it for non-clustered operation.

Prerequisites

  1. Deploy worker node service

    Copy all of the library files in the JBOSS_EAP_DIST/mod_cluster/JBossWeb-Tomcat/lib directory. Move these files to JBOSS_EWS_DIST/tomcat6/lib/

  2. Add a Listener to Tomcat

    Add the following Listener element beneath the other Listener elements in JBOSS_EWS_DIST/tomcat6/conf/server.xml. 
    <Listener className="org.jboss.modcluster.ModClusterListener" advertise="true" stickySession="true" stickySessionForce="false" stickySessionRemove="true"/>
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  3. Give this worker a unique identity

    Edit JBOSS_EWS_DIST/tomcat6/conf/server.xml and add a jvmRoute attribute and value to the Engine element, as shown: 
    <Engine name="Catalina" defaultHost="localhost" jvmRoute="worker01">
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  4. Optional: Configure firewall to receive Proxy Server advertisements

    A proxy server using the JBoss HTTP Connector can advertise itself via UDP multicast. To receive these multicast messages, open port 23364 for UDP connections on the worker node's firewall.
    For Linux users: 
    /sbin/iptables -A INPUT -m state --state NEW -m udp -p udp --dport
 23364 -j ACCEPT 
-m comment -comment "receive mod_cluster proxy server advertisements"
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    If you are not using Automatic Proxy Discovery (see Automatic Proxy Discovery), configure worker nodes with a static list of proxies. Refer to Section 9.1, “Static Proxy Configuration” for directions. In this case you can safely ignore the following warning message: 
    [warning] mod_advertise: ServerAdvertise Address or Port not defined, Advertise disabled!!!
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Chapter 8. Further Server Configuration
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Read this chapter to implement further server configuration.

8.1. Apache Server Directives
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Add the following Apache server directives to the Apache server configuration for server-wide effect.

8.1.1. CreateBalancers
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The CreateBalancers directive determines how HTTP balancers are created in VirtualHosts.

CreateBalancers values

0
Create a balancer in all VirtualHosts.
1
Do not create balancers.
2
Create a balancer for the main server only.

Chapter 9. Advanced Configuration
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Read this chapter to configure advanced features of the JBoss HTTP Connector.

9.1. Static Proxy Configuration
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Server advertisement allows worker nodes to dynamically discover and register themselves with proxy servers. If UDP broadcast is not available or server advertisement is disabled then worker nodes must be configured with a static list of proxy server addresses and ports.

Task: Configure Application Platform Worker Node with Static Proxy List

Follow this task to configure a JBoss Enterprise Application Platform worker node to operate with a static list of proxy servers.

Prerequisites

  1. Disable dynamic proxy discovery

    Edit the file JBOSS_EAP_DIST/jboss-as/server/PROFILE/mod-cluster.sar/META-INF/mod-cluster-jboss-beans.xml and set the advertise property to false: 
    <property name="advertise">false</property>
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  2. Choose, and implement, one of the following static proxy options:

    • Option 1: Create a static proxy server list

      Edit the file JBOSS_EAP_DIST/jboss-as/server/PROFILE/mod-cluster.sar/META-INF/mod-cluster-jboss-beans.xml and add a comma separated list of proxies in the form of IP_ADDRESS:PORT in the proxyList property.

      Example 9.1. Example Static Proxy List

      <property name="proxyList">10.33.144.3:6666,10.33.144.1:6666</property>
      Copy to Clipboard Toggle word wrap

    • Option 2: Start the worker node with a static proxy list as a parameter

      1. Edit JBOSS_EAP_DIST/server/PROFILE/mod-cluster.sar/META-INF/mod-cluster-jboss-beans.xml
      2. Add the following line: 
        <property name="proxyList">${jboss.modcluster.proxyList:}</property>
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      3. Add a comma separated list of proxies in the form of IP_ADDRESS:PORT as the jboss.modcluster.proxyList parameter when starting the node.

        Example 9.2. Example Static Proxy List Parameter

        -Djboss.modcluster.proxyList=10.33.144.3:6666,10.33.144.1:6666
        Copy to Clipboard Toggle word wrap

Task: Configure Web Server Worker Node with Static Proxy List

Follow this procedure to configure a JBoss Enterprise Web Server worker node to operate with a static list of proxy servers.

Prerequisites

  1. Disable dynamic proxy discovery

    Edit the file JBOSS_EWS_DIST/tomcat6/conf/server.xml. and set the advertise property of the ModClusterListener to false:

  2. Define a mod_cluster listener

    Add a <Listener> element to the server.xml file . 
    <Listener className="org.jboss.modcluster.ModClusterListener" advertise="false" stickySession="true" stickySessionForce="false" stickySessionRemove="true"/>
    Copy to Clipboard Toggle word wrap

  3. Create a static proxy server list

    Add a comma separated list of proxies in the form of IP_ADDRESS:PORT as the proxyList property of the ModClusterListener <Listener> element.

    Example 9.3. Example Static Proxy List

    <Listener className="org.jboss.modcluster.ModClusterListener" advertise="false" stickySession="true" stickySessionForce="false" stickySessionRemove="true" proxyList="10.33.144.3:6666,10.33.144.1:6666"/>
    Copy to Clipboard Toggle word wrap

9.2. Clustered Node Operation
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The JBoss HTTP Connector can operate in non-clustered or clustered mode.

Note

Only JBoss Enterprise Application Platform nodes support clustered operation with the JBoss HTTP Connector. JBoss Enterprise Web Server nodes support non-clustered operation only.
JBoss HTTP Connector non-clustered operation
In non-clustered mode each worker node communicates directly with the proxy.
JBoss HTTP Connector clustered operation
In clustered mode multiple worker nodes form a JBoss HA (High Availability) cluster domain. A single worker node communicates with the proxy on behalf of the other nodes in the cluster domain.

Chapter 10. Load Balancing Demonstration
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The JBoss HTTP Connector includes a load balancing demonstration to show how different server-side scenarios affect the client request routing performed by the load balancing proxy server. The required configuration is located in the jboss-eap-5.1/mod_cluster/demo directory.
The application consists of two primary components:
/server/load-demo.war
A WAR file to be deployed in JBoss Enterprise Application Platform or JBoss Enterprise Web Server. This WAR includes a number of servlets.
/client/lib/mod-cluster-demo.jar
A web application that lets users launch a pool of threads, which send requests through the load balancer to load-demo.war's primary servlet. The application displays information about which servers are handling the requests. It can also send separate requests to load-demo.war's load generation servlets, allowing the user to see how certain load conditions affect request load balancing.
The demo can be used to demonstrate how different worker-side scenarios impact the routing decisions of the proxy server.

Note

The demo does not show the maximum load a cluster configuration can handle.

10.1. Set up the Demonstration
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The following procedure summarizes how set up and start the demonstration. These steps will then be explained in further detail. Once the demo is running, refer to Section 10.3, “Interact with the Demonstration”.

Task: Start the Demo

Complete this task to set up the base requirements of the demonstration.

Prerequisites

  1. Start the Proxy Server

    Navigate to HTTPD_DIST/sbin and start the proxy server. 
    [sbin]$ apachectl start
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  2. Start the Worker Node

    In a terminal, execute the following command:
    • For JBoss Enterprise Web Server: 
      [home]$ ./JBOSS_EWS_DIST/tomcat6/bin/startup.sh
      Copy to Clipboard Toggle word wrap
    • For JBoss Enterprise Application Platform: 
      [home]$ ./JBOSS_EAP_DIST/bin/run.sh
      Copy to Clipboard Toggle word wrap

  3. Specify the Catalina Service Name

    AWAITING CONFIRMATON ON JBPAPP-6550

  4. Deploy Demo Web Archive to Worker Node

    Copy load-demo.war from JBOSS-EAP_DIST/mod_cluster/demo/server into one of the following directories:
    • For JBoss Enterprise Web Server:
      JBOSS_EWS_DIST/tomcat6/webapps
    • For JBoss Enterprise Application Platform:
      JBOSS_EAP_DIST/jboss-as/server/PROFILE/deploy

  5. Start the Demonstration

    Navigate to JBOSS_EAP_DIST/mod_cluster/demo/client/, and start the demonstration. 
    [client]$ ./run-demo.sh
    Copy to Clipboard Toggle word wrap
    Result

    The demonstration starts, and the Load Balancing Demonstration window opens. Proceed to Task: Configure Client Control Tab Fields

    View larger image

10.2. Configure the Demo Client
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You must configure the demonstration's Client Control parameters to ensure the client operates as expected throughout the demonstration.

Task: Configure Client Control Tab Fields

Complete this task to learn the values you must supply in the Client Control tab of the Load Balancing Demonstration.

Prerequisites

Complete Task: Start the Demo before continuing with this task.
  1. Click the Client Control tab.
  2. Based on the following field definitions, supply values for all fields on the Client Control tab.
    Proxy Hostname
    Hostname of the load-balancing proxy server, or the IP address on which the proxy server is listening for requests. The default value for this field is localhost, or determined by the mod_cluster.proxy.host system property, if set.
    Edit the -Dmod_cluster.proxy.host=localhost value in run-demo.sh to avoid re-setting this value each time you use the demo.
    Proxy Port
    Port on which the load-balancing proxy server listens for requests. The default value is 8000, or determined by the mod_cluster.proxy.port property, if set.
    Edit the -Dmod_cluster.proxy.port=8000 value in run-demo.sh to avoid re-setting this value each time you use the demo.
    Context Path
    The part of the request URL that specifies the request is for load-demo.war.
    Session Life
    Number of seconds a client thread should use a session before invalidating or abandoning it. This should be a small value, or session stickiness can prevent changes in server load from affecting the proxy server's routing decisions. When sticky sessions are enabled (strongly recommended), the creation of new sessions allows the proxy to balance the workload.
    Invalidate
    When checked, specifies that a session is invalidated by the client thread when the thread stops using a session. When unchecked, the session is abandoned, and exists on the worker node until the session timeout expires.
    Session Timeout
    The number of seconds a session can remain unused before the worker node can expire and remove the session.
    Deselecting Invalidate and setting a high value relative to session life causes a significant number of unused sessions to accumulate on the server.
    Num Threads
    Number of client threads to launch. Each thread repeatedly makes requests until the Stop button is pressed, or a request receives a response other than HTTP 200.
    Sleep Time
    Number of milliseconds that client threads should sleep between requests.
    Startup Time
    Number of seconds over which the application should stagger client thread start-up. Staggering the start time of sessions avoids the unrealistic situation where all sessions start and end almost simultaneously. Staggering the start time allows the proxy to continually see new sessions and decide how to route them.
  3. Once you have specified the values, proceed to Task: Interact with the Demonstration.

10.3. Interact with the Demonstration
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Terms

Active Sessions
A session is considered active if a client thread will ever send a request associated with the session. When client threads stop using a session, they can either send a request to invalidate it, or abandon it by no longer including its session cookie in requests.
Once a session has been abandoned, it is no longer reflected in the Session Balancing chart, but will continue to exist on the worker node until it is removed based on session timeout values.
Total Clients
The number of client threads created since the last time the Start button was clicked.
Live Clients
The number of client threads currently running.
Failed Clients
The number of clients threads that terminated abnormally, for example, a request that resulted in something other than a HTTP 200 response.
This section shows you how to configure and start using the demo.

Task: Interact with the Demonstration

Complete this task to experiment with load balancing in the demonstration.

Task Prerequesites

  1. Click on the Request Balancing tab to see how many requests are going to each of your worker nodes.
  2. Click on the Session Balancing tab to see how many active sessions are being hosted by each of your worker nodes.
  3. Stop some of the worker nodes, or undeploy load-demo.war, and observe the effect that this has on request and session balancing.
  4. Restart some of your worker nodes, or re-deploy the load-demo.war to some of your workers, and observe the effect that this has on request and session balancing.
  5. Experiment with adding artificial load to one or more worker nodes and observe the effects on load and session balancing. (See Section 10.3.1, “Generating Artificial Load” for details.)

10.3.1. Generating Artificial Load
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You can use the Load Balancing Demonstration to instruct your worker nodes to generate various types of load, and then track how that load affects request and session balancing. Load generation is controlled in the Server Load Control tab:
Target Hostname, Target Port
The hostname and port number of the server on which to generate load. There are two strategies for setting these values:
  1. Use the hostname and port of the proxy server. The proxy will route the load to a worker node. However, the client does not maintain a session cookie for these requests, so subsequent generated load will not necessarily be routed to the same worker.
  2. If your worker nodes are running the HttpConnector and the AJP connector, you can specify the IP address and port on which a worker's HttpConnector is listening. (The default is 8080.)
Load Creation Action
Specifies the type of load the worker node should generate.

Available Actions

Active Sessions
Generates server load by causing session creation on the target server.
Datasource Use
Generates server load by taking connections from the java:DefaultDS datasource for a set time.
Connection Pool Use
Generates server load by blocking threads in the webserver connections pool for a set time.
Heap Memory Pool Use
Generates server load by filling 50% of free heap memory for a set time.
CPU Use
Generates server CPU load by initiating a tight loop in a thread.
Server Receive Traffic
Generates server traffic receipt load by POSTing a large byte array to the server once per second for a set time.
Server Send Traffic
Generates server traffic send load by making a request once per second, to which the server responds with a large byte array.
Request Count
Generates server load by making numerous requests, increasing the request count on the target server.
Params
Zero or more parameters to pass to the specified load creation servlet, for example, Number of Connections and Duration, as seen in the screenshot. The parameters displayed, their name, and their meaning depend on the selected Load Creation Action. The label for each parameter includes a tooltip that explains its use.

Part III. Internet Server API
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Chapter 11. Overview
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Read this chapter to get a brief introduction about the Internet Server Application Programming Interface (ISAPI).

11.1. What is Internet Server API
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Internet Server Application Programming Interface (ISAPI) is a multi-tier application programming interface for Microsoft Internet Information Services (IIS) web servers, and other compatible third-party web servers.
Two application types exist for ISAPI applications:
  • Extensions (full applications that run on IIS)
  • Filters (applications that modify or enhance IIS functionality by constantly filtering for requests relevant to their functionality).
You implement the ISAPI applications by compiling Extensions or Filters into Dynamic Link Library (DLL) files. The DLLs are registered with the web server which makes them available to use.
Read this chapter to learn how to configure the ISAPI connector to use JBoss Enterprise Application Platform as a worker node for a Windows Server 2003 or 2008 master node.

12.1. Prerequisites and Configuration Assumptions
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Complete the following prerequisites before continuing with the tasks that follow:

Important

The tasks in this chapter assume all server instances are on the same machine. To use different machines for each instance, use the -b switch to bind your instance of JBoss Enterprise Platform to a public IP address. Ensure you edit the workers.properties file on the IIS machine to reflect the IP address changes.
  • Configure the master node by installing any of the technology combinations, and the appropriate Native binary for its operating system and architecture.
    • Windows Server 2003 (32-bit) with Microsoft IIS 6
    • Windows Server 2003 (64-bit) with Microsoft IIS 6
    • Windows Server 2008 (32-bit) with Microsoft IIS 7.0
    • Windows Server 2008 (64-bit) with Microsoft IIS 7.0
  • Configure worker nodes by installing JBoss Enterprise Application Platform 5.1.0 or later. The Native components are optional for worker nodes.

Note

Refer to the Installation Guide for installation instructions, and to learn more about native components.

12.2. Configure Server Instance as a Worker Node
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Task: Configure Server Instance as a Worker Node

Complete this task to correctly configure your JBoss Enterprise Application Platform instance as a worker node for use with Microsoft Internet Information Services (IIS).

  1. Create a server profile for each worker node

    Make a copy of the default server profile you want to configure as a worker node, and rename it to default-01.

  2. Give each instance a unique name

    Edit the following line in the deploy\jbossweb.sar\server.xml file of each new worker instance: 
    <Engine name="jboss.web" defaultHost="localhost">
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    Add a unique jvmRoute value, as shown. This value is the identifier for this node in the cluster.
    For the default-01 server profile: 
    <Engine name="jboss.web" defaultHost="localhost" jvmRoute="worker01">
    Copy to Clipboard Toggle word wrap
    For the default-02 server profile: 
    <Engine name="jboss.web" defaultHost="localhost" jvmRoute="worker02">
    Copy to Clipboard Toggle word wrap

  3. Enable session handling

    Uncomment the following line in the deployers\jbossweb.deployer\META-INF\war-deployers-jboss-beans.xml file of each worker node: 
    <property name="useJK">false</property>
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    This property controls whether special session handling is used to coordinate with mod_jk and other connector variants. Set this property to true in both worker nodes: 
    <property name="useJK">true</property>
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  4. Start worker nodes

    Start each worker node in a separate command line interface. Ensure that each node is bound to a different IP address with the --host switch. 
    JBOSS_EAP_DIST\bin\run.bat --host=127.0.0.1 -c default-01
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    JBOSS_EAP_DIST\bin\run.bat --host=127.0.0.100 -c default
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Microsoft IIS 6 contains basic ISAPI filters and ISAPI mapping as part of the default installation.

Task: Define ISAPI Filter

Complete this task to define the ISAPI Filter on the Master Server using the management console.
  1. On the Master server, open IIS Manager:
    • Start → Run, then type inetmgr.
    • Start → Control Panel → Administrative Tools → Internet Information Services (IIS) Manager
    The IIS 6 Manager window opens.
  2. In the tree view pane, expand Web Sites.
  3. Right click on Default Web Site, and then click Properties.
    The Properties window opens.
  4. Click the ISAPI Filters tab.
  5. Click the Add button, and specify the following values in the Add/Edit Filter Properties window:
    Filter name:
    Specify jboss (exactly as written)
    Executable:
    Specify C:\connectors\jboss-ep-5.1\native\sbin\isapi_redirect.dll
  6. Click OK to save the values, and close the Add/Edit Filter Properties dialog.

    Note

    The ISAPI Filters tab now displays the jboss filter status and priority as Unknown because IIS has not yet received requests for the resource. The status and priority will change to Loaded and High respectively once a request is executed.

Task: Define ISAPI Virtual Directory

Complete this task to define the ISAPI virtual directory using the IIS management console.
  1. Right click on Default Web Site, and then click New → Add Virtual Directory .
    The Add Virtual Directory window opens
  2. Specify the following values in the Add Virtual Directory window:
    Alias:
    Specify jboss (exactly as written)
    Physical path:
    Specify C:\connectors\jboss-ep-5.1\native\sbin\
  3. Click OK to save the values and close the Add Virtual Directory window.
  4. In the tree view pane, expand Web Sites → Default Web Site
  5. Right click on the jboss virtual directory, and then click Properties.
  6. Click the Virtual Directory tab, and make the following changes:
    Execute Permissions:
    Select Scrips and Executables
    Read check box:
    Select to activate Read access
  7. Click OK to save the values and close the jboss Properties window.

Task: Define ISAPI Web Service Extension

Complete this task to define the ISAPI web service extension using the management console.
  1. Click Web Service Extensions, and in the Tasks group select Add a new Web service extension.
    The New Web Service Extension window opens.
  2. Add the following values to the New Web Service Extension window:
    Extension name:
    Specify jboss
    Required files:
    Specify the path C:\connectors\jboss-ep-5.1\native\sbin\isapi_redirect.dll
    Set extension status to Allowed:
    Select the check box.
  3. Click OK to save the values and close the New Web Service Extension window.
  4. Confirm the jboss Web Service Extension displays in the list.
Microsoft IIS 7 can be managed using the Management Console, or through the command prompt using the APPCMD.EXE command tool.

Terms

ISAPI and CGI Restrictions
ISAPI and CGI restrictions are request handlers that allow dynamic content to execute on a server. These restrictions are either CGI files (.exe) or ISAPI extensions (.dll). You can add custom ISAPI or CGI restrictions if the IIS configuration system allows this. [http://technet.microsoft.com/en-us/library/cc730912(WS.10).aspx].

Task: Define a JBoss Native ISAPI Restriction

Complete this task to define an ISAPI Restriction using the management console.
  1. On the Master server, open IIS Manager:
    • Start → Run, then type inetmgr.
    • Start → Control Panel → Administrative Tools → Internet Information Services (IIS) Manager
    The IIS 7 Manager window opens.
  2. In the tree view pane, select IIS 7 (referred to as Server Home).
    The IIS 7 Home Features View opens in the
  3. Double-click ISAPI and CGI Restrictions.
    The ISAPI and CGI Restrictions Features View opens.
  4. In the Actions pane, click Add.
    The Add ISAPI or CGI Restriction window opens.
  5. Specify the following values in the Add ISAPI or CGI Restriction window:
    ISAPI or CGI Path:
    Specify c:\connectors\jboss-ep-5.1\native\sbin\isapi_redirect.dll
    Description:
    Specify jboss (exactly as written).
    Allow extension path to execute
    Select the check box.
  6. Click OK to save the values, and close the Add ISAPI or CGI Restriction window.

    Note

    The ISAPI and CGI Restrictions Features View now displays the jboss restriction and path.

Task: Define an JBoss Native Virtual Directory

Complete this task to define a virtual directory for the JBoss Native binary using the management console.
  1. Right click on Default Web Site, and then click Add Virtual Directory.
    The Add Virtual Directory window opens
  2. Specify the following values in the Add Virtual Directory window:
    Alias:
    Specify jboss (exactly as written)
    Physical path:
    Specify C:\connectors\jboss-ep-5.1\native\sbin\
  3. Click OK to save the values and close the Add Virtual Directory window.

Task: Define a JBoss Native ISAPI Redirect Filter

Complete this task to define a JBoss Native ISAPI Redirect Filter using the management console.
  1. In the tree view pane, expand Sites → Default Web Site.
  2. Double-click ISAPI Filters.
    The ISAPI Filters Features View opens.
  3. In the Actions pane, click Add.
    The Add ISAPI Filter window opens.
  4. Specify the following values in the Add ISAPI Filter window:
    Filter name:
    Specify jboss (exactly as written)
    Executable:
    Specify C:\connectors\jboss-ep-5.1\native\sbin\isapi_redirect.dll
  5. Click OK to save the values and close the Add ISAPI Filters window.

Task: Enable the ISAPI-dll Handler

Complete this task to enable the ISAPI-dll handler using the management console.
  1. In the tree view pane, select IIS 7 (referred to as Server Home).
    The IIS 7 Home Features View opens in the
  2. Double-click Handler Mappings.
    The Handler Mappings Features View opens.
  3. In the Group by drop down box, select State.
    The Handler Mappings are displayed in Enabled and Disabled groups.
  4. If ISAPI-dll is in the Disabled group, right mouse click and select Edit Feature Permissions
  5. Ensure the Read, Script, and Execute check boxes are selected.
  6. Click OK to save the values and close the Edit Feature Permissions window.

12.5. Configure a Basic Cluster with ISAPI
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Task: Configure ISAPI to serve a Basic Cluster

Complete this task to configure ISAPI to manage applications common to all servers on a single IP address range, and route application requests to the correct server instance.
Use the configuration as an example when configuring your ISAPI cluster.

Note

This task does not provide instructions for load-balancing or server outage fail over. Refer to Section 12.6, “Configure a Load-balancing Cluster with ISAPI” for configuration instructions.

Prerequisites

  1. Create isapi_redirect.properties file

    Create a new file named isapi_redirect.properties in the C:\connectors\jboss-ep-5.1\native\sbin\ directory.

    Important

    The isapi_redirect.properties file must be in the same directory as the isapi_redirect.dll file.
    Append the following configuration lines into the file: 
    # Configuration file for the ISAPI Redirector
# Extension uri definition
extension_uri=/jboss/isapi_redirect.dll

# Full path to the log file for the ISAPI Redirector
log_file=c:\connectors\isapi_redirect.log

# Log level (debug, info, warn, error or trace)
# Use debug only testing phase, for production switch to info
log_level=debug

# Full path to the workers.properties file
worker_file=c:\connectors\workers.properties

# Full path to the uriworkermap.properties file
worker_mount_file=c:\connectors\uriworkermap.properties

#Full path to the rewrite.properties file 
rewrite_rule_file=c:\connectors\rewrite.properties
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  2. Optional: Create rewrite.properties file

    The rewrite.properties file allows you to specify simple URL rewrites specific to an application. This configuration file is optional, and can be excluded from the isapi_redirect.properties file if URL rewrites are not required.
    The functionality offered is similar to Apache mod_rewrite, but is less powerful. You specify the rewrite path using name-value pairs. A simple example is where the app_01 application has an abstract directory name containing images, and you want to remap that directory to something more intuitive. 
    #Simple example, images are accessible under abc path
/app-01/abc/=/app-01/images/
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  3. Create uriworkermap.properties file

    The uriworkermap.properties file contains deployed application mapping configuration information. Append the following lines into the file. 
    # images and css files for path /status are provided by worker01
/status=worker01
/images/*=worker01
/css/*=worker01

# Path /web-console is provided by worker02
# IIS (customized) error page is used for http errors with number greater or equal to 400
# css files are provided by worker01
/web-console/*=worker02;use_server_errors=400
/web-console/css/*=worker01

# Example of exclusion from mapping, logo.gif won't be displayed  
# !/web-console/images/logo.gif=*

# Requests to /app-01 or /app-01/something will be routed to worker01
/app-01|/*=worker01

# Requests to /app-02 or /app-02/something will be routed to worker02
/app-02|/*=worker02
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  4. Create workers.properties file

    The worker.properties file contains mapping definitions between worker labels and server instances. Append the following lines into the file. 
    # An entry that lists all the workers defined
worker.list=worker01, worker02

# Entries that define the host and port associated with these workers

# First EAP server definition, port 8009 is standard port for AJP in EAP 
worker.worker01.host=127.0.0.1
worker.worker01.port=8009
worker.worker01.type=ajp13

# Second EAP server definition
worker.worker02.host= 127.0.0.100
worker.worker02.port=8009
worker.worker02.type=ajp13
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  5. Restart IIS

    Restart your IIS server to implement the changes. Execute the following commands for the IIS version you are running:
    IIS 6
    C:\> net stop iisadmin /Y
C:\> net start w3svc
    Copy to Clipboard Toggle word wrap
    IIS 7
    C:\> net stop was /Y
C:\> net start w3svc
    Copy to Clipboard Toggle word wrap

  6. Verify the Logs

    Ensure you check the ISAPI logs once IIS has restarted. The logs are saved to the file location specified in the log_file property in isapi_redirect.properties. You should also check IIS logs and the Event Viewer for other events.

Task: Configure ISAPI to serve a Load Balancing Cluster

Complete this task to configure ISAPI to manage applications common to all servers, route requests to JBoss Enterprise Application Platform instances, and redirect requests to live nodes when some nodes are not online or experiencing connectivity issues.
Use the configuration as an example when configuring your ISAPI cluster.

Prerequisites

  1. Create isapi_redirect.properties file

    Create a new file named isapi_redirect.properties in the C:\connectors\jboss-ep-5.1\native\sbin\ directory.

    Important

    The isapi_redirect.properties file must be in the same directory as the isapi_redirect.dll file.
    Append the following configuration lines into the file: 
    # Configuration file for the ISAPI Redirector
# Extension uri definition
extension_uri=/jboss/isapi_redirect.dll

# Full path to the log file for the ISAPI Redirector
log_file=c:\connectors\isapi_redirect.log

# Log level (debug, info, warn, error or trace)
# Use debug only testing phase, for production switch to info
log_level=debug

# Full path to the workers.properties file
worker_file=c:\connectors\workers.properties

# Full path to the uriworkermap.properties file
worker_mount_file=c:\connectors\uriworkermap.properties

#OPTIONAL: Full path to the rewrite.properties file 
rewrite_rule_file=c:\connectors\rewrite.properties
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  2. Optional: Create rewrite.properties file

    The rewrite.properties file allows you to specify simple URL rewrites specific to an application. This configuration file is optional, and can be excluded from the isapi_redirect.properties file if URL rewrites are not required.
    The functionality offered is similar to Apache mod_rewrite, but is less powerful. You specify the rewrite path using name-value pairs. A simple example is where the app_01 application has an abstract directory name containing images, and you want to remap that directory to something more intuitive. 
    #Simple example, images are accessible under abc path
/app-01/abc/=/app-01/images/
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  3. Create uriworkermap.properties file

    The uriworkermap.properties file contains deployed application mapping configuration information. Append the following lines into the file. 
    # images, css files, path /status and /web-console will provided by nodes defined in load-balancer
/css/*=router
/images/*=router
/status=router
/web-console|/*=router

# Example of exclusion from mapping, logo.gif won't be displayed  
!/web-console/images/logo.gif=*

# Requests to /app-01 and /app-02 will be routed to nodes defined in load-balancer
/app-01|/*=router
/app-02|/*=router

# mapping for management console, nodes in cluster can be enabled or disabled here
/jkmanager|/*=status
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  4. Create workers.properties file

    The worker.properties file contains mapping definitions between worker labels and server instances. Append the following lines into the file. 
    # The advanced router LB worker
worker.list=router,status

# First EAP server definition, port 8009 is standard port for AJP in EAP
#
# lbfactor defines how much the worker will be used. 
# The higher the number, the more requests are served
# lbfactor is useful when one machine is more powerful 
# ping_mode=A – all possible probes will be used to determine that
# connections are still working

worker.worker01.port=8009
worker.worker01.host=127.0.0.1
worker.worker01.type=ajp13
worker.worker01.ping_mode=A
worker.worker01.socket_timeout=10
worker.worker01.lbfactor=3

# Second EAP server definition
worker.worker02.port=8009
worker.worker02.host= 127.0.0.100
worker.worker02.type=ajp13
worker.worker02.ping_mode=A
worker.worker02.socket_timeout=10
worker.worker02.lbfactor=1

# Define the LB worker
worker.router.type=lb
worker.router.balance_workers=worker01,worker02

# Define the status worker for jkmanager
worker.status.type=status
    Copy to Clipboard Toggle word wrap

    Note

    For an explanation of workers.properties directives, refer to Appendix A, workers.properties Reference.

  5. Restart IIS

    Restart your IIS server to implement the changes. Execute the following commands for the IIS version you are running:
    IIS 6
    C:\> net stop iisadmin /Y
C:\> net start w3svc
    Copy to Clipboard Toggle word wrap
    IIS 7
    C:\> net stop was /Y
C:\> net start w3svc
    Copy to Clipboard Toggle word wrap

  6. Verify the Logs

    Ensure you check the ISAPI logs once IIS has restarted. The logs are saved to the file location specified in the log_file property in isapi_redirect.properties. You should also check IIS logs and the Event Viewer for other events.

Part IV. Netscape Server API
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Chapter 13. What Is Netscape Server API
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Read this chapter to gain a basic understand about the Netscape Server API (NSAPI).
NSAPI is a programming interface that allows developers to extend the functionality of web server software by creating applications (referred to as plug-ins) that run inside the server process itself.
The goal of NSAPI, and its plug-ins, is to provide a method of creating different functional interfaces between the HTTP Server and the back-end applications which run on it.
The NSAPI plug-ins are designed to implement Server Application Functions (SAFs). SAFs consume a HTTP request and take input from a server configuration database, and return a response to the client based on the inputs. Each SAF is linked to a particular class, which directly relates to the request-response step it helps implement.
The request-response steps (classes) are summarized in the following list:
  1. Authorization translation
  2. Name translation
  3. Path checks
  4. Object type
  5. Request response
  6. Log transaction.
You are not required to provide a SAF for each request-response step: NSAPI allows you to substitute your own custom functionality to the core request-response steps. You also have the choice of applying the SAF globally, or constraining the SAF to a directory, file group, or individual file.
The following tasks describe how to configure the NSAPI connector to use a JBoss Enterprise Platform as a worker node for a Sun Java System Web Server (SJWS) master node.

Note

Sun Java System Web Server has been renamed to the Oracle iPlanet Web Server. The old name is used throughout this guide for clarity.
In this section, all of the server instances are on the same machine. To use different machines for each instance, use the -b switch to bind your instance of JBoss Enterprise Platform to a public IP address. Remember to edit the workers.properties file on the SJWS machine to reflect these changes in IP address.

14.1. Prerequisites and Configuration Assumptions
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  • Worker nodes are already installed with a JBoss Enterprise Platform 5.1 or later. The Native components are not a requirement of the NSAPI connector. Refer to the Installation Guide for assistance with this prerequisite.
  • The master node is already installed with one of the following technology combinations, and the appropriate Native binary for its operating system and architecture. Refer to the Installation Guide for assistance with this installation prerequisite.
    • Solaris 9 x86 with Sun Java System Web Server 6.1 SP12
    • Solaris 9 SPARC 64 with Sun Java System Web Server 6.1 SP12
    • Solaris 10 x86 with Sun Java System Web Server 7.0 U8
    • Solaris 10 SPARC 64 with Sun Java System Web Server 7.0 U8

14.2. Configure Server Instance as a Worker Node
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Task: Configure a JBoss Enterprise Application Platform Worker Node

Follow this task to correctly configure a JBoss Enterprise Application Platform instance as a SJWS worker node.

  1. Create a server profile for each worker node

    Make a copy of the server profile that you wish to configure as a worker node. (This procedure uses the default server profile.) 
    [user@workstation jboss-ep-5.1]$ cd jboss-as/server
[user@workstation server]$ cp -r default/ default-01
[user@workstation server]$ cp -r default/ default-02
    Copy to Clipboard Toggle word wrap

  2. Give each instance a unique name

    Edit the following line in the deploy/jbossweb.sar/server.xml file of each new worker instance: 
    <Engine name="jboss.web" defaultHost="localhost">
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    Add a unique jvmRoute value, as shown. This value is the identifier for this node in the cluster.
    For the default-01 server profile: 
    <Engine name="jboss.web" defaultHost="localhost" jvmRoute="worker01">
    Copy to Clipboard Toggle word wrap
    For the default-02 server profile: 
    <Engine name="jboss.web" defaultHost="localhost" jvmRoute="worker02">
    Copy to Clipboard Toggle word wrap

  3. Enable session handling

    Uncomment the following line in the deployers/jbossweb.deployer/META-INF/war-deployers-jboss-beans.xml file of each worker node: 
    <property name="useJK">false</property>
    Copy to Clipboard Toggle word wrap
    This property controls whether special session handling is used to coordinate with mod_jk and other connector variants. Set this property to true in both worker nodes: 
    <property name="useJK">true</property>
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  4. Start your worker nodes

    Start each worker node in a separate command line interface. Ensure that each node is bound to a different IP address with the -b switch. 
    [user@workstation jboss-eap-5.1]$ ./jboss-as/bin/run.sh -b 127.0.0.1 -c default-01
    Copy to Clipboard Toggle word wrap 
    [user@workstation jboss-eap-5.1]$ ./jboss-as/bin/run.sh -b 127.0.0.100 -c default-02
    Copy to Clipboard Toggle word wrap

14.3. Initial Clustering Configuration
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Task: Configure Initial Clustering Behavior

Complete this task to configure the basic elements required for clustering using Sun Java Web Server (SJWS) and NSAPI.

Prerequisites

  1. Disable servlet mappings

    Under Built In Servlet Mappings in the SJWS/PROFILE/config/default-web.xml file, disable the mappings for the following servlets, as shown in the code sample:
    • default
    • invoker
    • jsp 
    <!-- ==================== Built In Servlet Mappings ===================== -->

<!-- The servlet mappings for the built in servlets defined above. -->

<!-- The mapping for the default servlet -->
<!--servlet-mapping>
 <servlet-name>default</servlet-name>
 <url-pattern>/</url-pattern>
</servlet-mapping-->

<!-- The mapping for the invoker servlet -->
<!--servlet-mapping>
 <servlet-name>invoker</servlet-name>
 <url-pattern>/servlet/*</url-pattern>
</servlet-mapping-->

<!-- The mapping for the JSP servlet -->
<!--servlet-mapping>
 <servlet-name>jsp</servlet-name>
 <url-pattern>*.jsp</url-pattern>
</servlet-mapping-->
    Copy to Clipboard Toggle word wrap

  2. Load the required modules and properties

    Append the following lines to the SJWS/PROFILE/config/magnus.conf file: 
    Init fn="load-modules" funcs="jk_init,jk_service" shlib="NATIVE/lib/nsapi_redirector.so" shlib_flags="(global|now)"
Init fn="jk_init" worker_file="/tmp/connectors/workers.properties" log_level="debug" log_file="/tmp/connectors/nsapi.log" shm_file="/tmp/connectors/jk_shm"
    Copy to Clipboard Toggle word wrap
    These lines define the location of the nsapi_redirector.so module used by the jk_init and jk_service functions, and the location of the workers.properties file, which defines the worker nodes and their attributes.

    Note

    The lib directory in the NATIVE/lib/nsapi_redirector.so path applies only to 32-bit machines. On 64-bit machines, this directory is called lib64.

14.4. Configure a Basic Cluster with NSAPI
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Use the following procedure

Task: Configure a Basic Cluster with NSAPI

Complete this task to configure a basic cluster, where requests for particular paths are forwarded to particular worker nodes. The procedure specifies worker02 serves the /nc path, while worker01 serves /status and all other paths defined in the first part of the obj.conf file.

Prerequisites

  1. Define the paths to serve via NSAPI

    Edit the SJWS/PROFILE/config/obj.conf file. Define paths that should be served via NSAPI at the end of the default Object definition, as shown: 
    <Object name="default">
      [...]
   NameTrans fn="assign-name" from="/status" name="jknsapi"
   NameTrans fn="assign-name" from="/images(|/*)" name="jknsapi"
   NameTrans fn="assign-name" from="/css(|/*)" name="jknsapi"
   NameTrans fn="assign-name" from="/nc(|/*)" name="jknsapi"
   NameTrans fn="assign-name" from="/jmx-console(|/*)" name="jknsapi"
</Object>
    Copy to Clipboard Toggle word wrap
    You can map the path of any application deployed on your JBoss Enterprise Platform instance in this obj.conf file. In the example code, the /nc path is mapped to an application deployed under the name nc.

  2. Define the worker that serves each path

    Edit the SJWS/PROFILE/config/obj.conf file and add the following jknsapi Object definition after the default Object definition. 
    <Object name="jknsapi">
   ObjectType fn=force-type type=text/plain
   Service fn="jk_service" worker="worker01" path="/status"
   Service fn="jk_service" worker="worker02" path="/nc(/*)"
   Service fn="jk_service" worker="worker01"
</Object>
    Copy to Clipboard Toggle word wrap
    This jknsapi Object defines the worker nodes used to serve each path that was assigned to name="jknsapi" in the default Object.
    In the example code, the third Service definition does not specify a path value, so the worker node defined (worker01) serves all of the paths assigned to jknsapi by default. In this case, the first Service definition in the example code, which assigns the /status path to worker01, is superfluous.

  3. Define the workers and their attributes

    Create a workers.properties file in the location you defined in Step 2.
    Define the list of worker nodes and each worker node's properties in this file: 
    # An entry that lists all the workers defined
worker.list=worker01, worker02

# Entries that define the host and port associated with these workers
worker.worker01.host=127.0.0.1
worker.worker01.port=8009
worker.worker01.type=ajp13

worker.worker02.host=127.0.0.100
worker.worker02.port=8009
worker.worker02.type=ajp13
    Copy to Clipboard Toggle word wrap

  4. Restart the server

    Once your Sun Java System Web Server instance is configured, restart it so that your changes take effect.
    For Sun Java System Web Server 6.1: 
    SJWS/PROFILE/stop
SJWS/PROFILE/start
    Copy to Clipboard Toggle word wrap
    For Sun Java System Web Server 7.0: 
    SJWS/PROFILE/bin/stopserv
SJWS/PROFILE/bin/startserv
    Copy to Clipboard Toggle word wrap

14.5. Configure a Load-balanced Cluster with NSAPI
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Task: Configure a Load-balanced Cluster with NSAPI

Complete this task to configure a load-balanced cluster consisting of two worker nodes.

Prerequisites

  1. Define the paths to serve via NSAPI

    Open SJWS/PROFILE/config/obj.conf and define paths that should be served through NSAPI at the end of the default Object definition, as shown: 
    <Object name="default">
      [...]
   NameTrans fn="assign-name" from="/status" name="jknsapi"
   NameTrans fn="assign-name" from="/images(|/*)" name="jknsapi"
   NameTrans fn="assign-name" from="/css(|/*)" name="jknsapi"
   NameTrans fn="assign-name" from="/nc(|/*)" name="jknsapi"
   NameTrans fn="assign-name" from="/jmx-console(|/*)" name="jknsapi"
   NameTrans fn="assign-name" from="/jkmanager/*" name="jknsapi"
</Object>
    Copy to Clipboard Toggle word wrap
    You can map the path of any application deployed on your JBoss Enterprise Platform instance in this obj.conf file. In the example code, the /nc path is mapped to an application deployed under the name nc.

  2. Define the worker that serves each path

    Open SJWS/PROFILE/config/obj.conf and add the following jknsapi Object definition after the default Object definition. 
    <Object name="jknsapi">
   ObjectType fn=force-type type=text/plain
   Service fn="jk_service" worker="status" path="/jkmanager(/*)"
   Service fn="jk_service" worker="router"
</Object>
    Copy to Clipboard Toggle word wrap
    This jknsapi Object defines the worker nodes used to serve each path that was assigned to name="jknsapi" in the default Object.

  3. Define the workers and their attributes

    Create SJWS/PROFILE/config/workers.properties.
    Define the list of worker nodes and each worker node's properties in this file:

    Note

    For an explanation of workers.properties directives, refer to Appendix A, workers.properties Reference 
    # The advanced router LB worker
worker.list=router,status

#First EAP server definition, port 8009 is standard port for AJP in EAP
#
#lbfactor defines how much the worker will be used. 
#The higher the number, the more requests are served
#lbfactor is useful when one machine is more powerful 
#ping_mode=A – all possible probes will be used to determine that
#connections are still working
worker.worker01.port=8009
worker.worker01.host=127.0.0.1
worker.worker01.type=ajp13
worker.worker01.ping_mode=A
worker.worker01.socket_timeout=10
worker.worker01.lbfactor=3

#Second EAP server definition
worker.worker02.port=8009
worker.worker02.host=127.0.0.100
worker.worker02.type=ajp13
worker.worker02.ping_mode=A
worker.worker02.socket_timeout=10
worker.worker02.lbfactor=1

# Define the LB worker
worker.router.type=lb
worker.router.balance_workers=worker01,worker02

# Define the status worker
worker.status.type=status
    Copy to Clipboard Toggle word wrap

  4. Restart the server

    Once your Sun Java System Web Server instance is configured, restart it so that your changes take effect.
    For Sun Java System Web Server 6.1: 
    SJWS/PROFILE/stop
SJWS/PROFILE/start
    Copy to Clipboard Toggle word wrap
    For Sun Java System Web Server 7.0: 
    SJWS/PROFILE/bin/stopserv
SJWS/PROFILE/bin/startserv
    Copy to Clipboard Toggle word wrap

Part V. Common Load Balancing Tasks
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Chapter 15. HTTP Session State Replication
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Software Load Balancer

A dedicated software-based service designed to distribute HTTP client session requests across multiple computer servers (cluster). The primary directive of a software load balancer is to maximize resource utilization, reduce request response times, and prevent server overload. The load balancer forwards client session requests to a server cluster, based on server load and availability.

Client Session

A semi-permanent connection between the client (an application) and the server. The load balancer determines whether the client session is created with persistence, or whether a client session is redistributed based on server load and availability.

Session Persistence

A client session that is exclusively allocated to a single server instance. The load balancer routes all HTTP requests associated with the client session to the allocated server instance only. Session persistence is commonly referred to as a sticky session.

Sticky Session

See Session Persistence.

Section 3.1, “Configure Worker Nodes in mod_jk” describes how to configure session state persistence in the load balancer to ensure a client in a session is always routed to the same server node.
Session persistence on its own is not a best-practice solution because if a server fails, all session state data is lost. For example, if a customer is about to make a purchase on a web site, and the server hosting the shopping cart instance fails, session state data associated with the cart is lost permanently.
One way of preventing client session data loss is to replicate session data across the servers in the cluster. If a server node fails or is shut down, the load balancer can fail over the next client request to any server node and obtain the same session state.
Using a load-balancer that supports session persistence, but not configuring web applications for session replication allows you to scale your implementation by avoiding the cost of session state replication: each request for a session will always be handled by the same node.
Session state replication is more expensive than basic session persistence, but the reliability it provides for session state data makes it important when creating a load balanced cluster.
To enable replication of your web application you must tag the application as distributable in the web.xml descriptor. Here's an example: 
<?xml version="1.0"?> 
<web-app  xmlns="http://java.sun.com/xml/ns/j2ee"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
          xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
                              http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" 
          version="2.4">
          
    <distributable/>
    
</web-app>
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You can further configure session replication using the replication-config element in the jboss-web.xml file. However, the replication-config element only needs to be set if one or more of the default values described below is unacceptable. Here is an example: 
<!DOCTYPE jboss-web PUBLIC
    -//JBoss//DTD Web Application 5.0//EN
    http://www.jboss.org/j2ee/dtd/jboss-web_5_0.dtd>

<jboss-web>
   
   <replication-config>
      <cache-name>custom-session-cache</cache-name>
      <replication-trigger>SET</replication-trigger>
      <replication-granularity>ATTRIBUTE</replication-granularity>
      <replication-field-batch-mode>true</replication-field-batch-mode>
      <use-jk>false</use-jk>
      <max-unreplicated-interval>30</max-unreplicated-interval>
      <snapshot-mode>INSTANT</snapshot-mode>
      <snapshot-interval>1000</snapshot-interval>
      <session-notification-policy>com.example.CustomSessionNotificationPolicy</session-notification-policy>
   </replication-config>

</jboss-web>
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All of the configuration elements are optional, and can be omitted if the default value is acceptable. A couple are commonly used; the rest are very infrequently changed from the defaults. We'll cover the commonly used ones first.
The <replication-trigger> element determines when the container should consider that session data must be replicated across the cluster. The rationale for this setting is that after a mutable object stored as a session attribute is accessed from the session, in the absence of a setAttribute call the container has no clear way to know if the object (and hence the session state) has been modified and needs to be replicated. This element has 3 valid values:
  • SET_AND_GET is conservative but not optimal (performance-wise): it will always replicate session data even if its content has not been modified but simply accessed. This setting made (a little) sense in JBoss Enterprise Application Platform 4 since using it was a way to ensure that every request triggered replication of the session's timestamp. Since setting max_unreplicated_interval to 0 accomplishes the same thing at much lower cost, using SET_AND_GET makes no sense with Enterprise Application Platform 5.
  • SET_AND_NON_PRIMITIVE_GET is conservative but will only replicate if an object of a non-primitive type has been accessed (i.e. the object is not of a well-known immutable JDK type such as Integer, Long, String, etc.) This is the default value.
  • SET assumes that the developer will explicitly call setAttribute on the session if the data needs to be replicated. This setting prevents unnecessary replication and can have a major beneficial impact on performance, but requires very good coding practices to ensure setAttribute is always called whenever a mutable object stored in the session is modified.
In all cases, calling setAttribute marks the session as needing replication.
The <replication-granularity> element determines the granularity of what gets replicated if the container determines session replication is needed. The supported values are:
SESSION
Specifies the entire session attribute map should be replicated when any attribute is considered modified. Replication occurs at request end. This option replicates the most data and thus incurs the highest replication cost, but since all attributes values are always replicated together it ensures that any references between attribute values will not be broken when the session is deserialized. For this reason it is the default setting.
ATTRIBUTE
Specifies only attributes that the session considers to be potentially modified are replicated. Replication occurs at request end. For sessions carrying large amounts of data, parts of which are infrequently updated, this option can significantly increase replication performance. However, it is not suitable for applications that store objects in different attributes that share references with each other (e.g. a Person object in the "husband" attribute sharing with another Person in the "wife" attribute a reference to an Address object). This is because if the attributes are separately replicated, when the session is deserialized on remote nodes the shared references will be broken.
The other elements under the replication-config element are much less frequently used.
<cacheName>
Specifies the name of the JBoss Cache configuration that should be used for storing distributable sessions and replicating them around the cluster. This element lets web applications that require different caching characteristics specify the use of separate, differently configured, JBoss Cache instances. In JBoss Enterprise Application Platform 4 the cache to use was a server-wide configuration that could not be changed per web application. The default value is standard-session-cache See Section 15.3, “Configuring the JBoss Cache instance used for session state replication” for more details on JBoss Cache configuration for web tier clustering.
<replication-field-batch-mode>
Specifies whether all replication messages associated with a request will be batched into one message. This is applicable only if replication-granularity is FIELD. If replication-field-batch-mode is set to true, fine-grained changes made to objects stored in the session attribute map will replicate only when the HTTP request is finished; otherwise they replicate as they occur. Setting this to false is not advised. Default is true.
<useJK>
Specifies whether the container should assume that a JK-based software load balancer (e.g. mod_jk, mod_proxy, mod_cluster) is being used for load balancing for this web application. If set to true, the container will examine the session ID associated with every request and replace the jvmRoute portion of the session ID if it detects a failover.
You need only set this to false for web applications whose URL cannot be handled by the JK load balancer.
<max-unreplicated-interval>
Specifies the maximum interval between requests, in seconds, after which a request will trigger replication of the session's timestamp regardless of whether the request has otherwise made the session dirty. Such replication ensures that other nodes in the cluster are aware of the most recent value for the session's timestamp and won't incorrectly expire an unreplicated session upon failover. It also results in correct values for HttpSession.getLastAccessedTime() calls following failover.
The default value is null (i.e. unspecified). In this case the session manager will use the presence or absence of a jvmRoute configuration on its enclosing JBoss Web Engine (see Section 3.2, “Configuring JBoss to work with mod_jk”) to determine whether JK is used.
A value of 0 means the timestamp will be replicated whenever the session is accessed. A value of -1 means the timestamp will be replicated only if some other activity during the request (e.g. modifying an attribute) has resulted in other replication work involving the session. A positive value greater than the HttpSession.getMaxInactiveInterval() value will be treated as probable misconfiguration and converted to 0; i.e. replicate the metadata on every request. Default value is 60.
<snapshot-mode>
Specifies when sessions are replicated to the other nodes. Possible values are INSTANT (the default) and INTERVAL.
The typical value, INSTANT, replicates changes to the other nodes at the end of requests, using the request processing thread to perform the replication. In this case, the snapshot-interval property is ignored.
With INTERVAL mode, a background task is created that runs every snapshot-interval milliseconds, checking for modified sessions and replicating them.
Note that this property has no effect if replication-granularity is set to FIELD. If it is FIELD, instant mode will be used.
<snapshot-interval>
Specifies how often (in milliseconds) the background task that replicates modified sessions should be started for this web application. Only meaningful if snapshot-mode is set to interval.
<session-notification-policy>
Specifies the fully qualified class name of the implementation of the ClusteredSessionNotificationPolicy interface that should be used to govern whether servlet specification notifications should be emitted to any registered HttpSessionListener, HttpSessionAttributeListener and/or HttpSessionBindingListener.

Important

Event notifications that may be appropriate in non-clustered environment may not necessarily be appropriate in a clustered environment; see https://jira.jboss.org/jira/browse/JBAS-5778 for an example of why a notification may not be desired. Configuring an appropriate ClusteredSessionNotificationPolicy gives the application author fine-grained control over what notifications are issued.

15.2. HttpSession Passivation and Activation
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Passivation

The process of controlling memory usage by removing relatively unused sessions from memory while storing them in persistent storage.

If a passivated session is requested by a client, it can be "activated" back into memory and removed from the persistent store. JBoss Enterprise Application Platform 5 supports HttpSessions passivation from clustered web applications where the web.xml file includes the distributable directive.
Passivation occurs at three points during the lifecycle of a web application:
  • When the container requests the creation of a new session. If the number of currently active sessions exceeds a configurable limit, an attempt is made to passivate sessions to make room in memory.
  • Periodically (by default every ten seconds) as the JBoss Web background task thread runs.
  • When the web application is deployed and a backup copy of sessions active on other servers is acquired by the newly deploying web application's session manager.
A session is passivated if one of the following conditions is true:
  • The session has not been in use for longer than a configurable maximum idle time.
  • The number of active sessions exceeds a configurable maximum and the session has not been in use for longer than a configurable minimum idle time.
In both cases, sessions are passivated on a Least Recently Used (LRU) basis.

15.2.1. Configuring HttpSession Passivation
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Session passivation behavior is configured via the jboss-web.xml deployment descriptor in your web application's WEB-INF directory. 
<!DOCTYPE jboss-web PUBLIC
    -//JBoss//DTD Web Application 5.0//EN
    http://www.jboss.org/j2ee/dtd/jboss-web_5_0.dtd>

<jboss-web>
   
   <max-active-sessions>20</max-active-sessions>
   <passivation-config>
      <use-session-passivation>true</use-session-passivation>
      <passivation-min-idle-time>60</passivation-min-idle-time>
      <passivation-max-idle-time>600</passivation-max-idle-time>
   </passivation-config>


</jboss-web>
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  • max-active-session
    Determines the maximum number of active sessions allowed. If the number of sessions managed by the the session manager exceeds this value and passivation is enabled, the excess will be passivated based on the configured passivation-min-idle-time. If after passivation is completed (or if passivation is disabled), the number of active sessions still exceeds this limit, attempts to create new sessions will be rejected. If set to -1 (the default), there is no limit.
  • use-session-passivation
    Determines whether session passivation will be enabled for the web application. Default is false.
  • passivation-min-idle-time
    Determines the minimum time (in seconds) that a session must have been inactive before the container will consider passivating it in order to reduce the active session count to obey the value defined by max-active-sessions. A value of -1 (the default) disables passivating sessions before passivation-max-idle-time. Neither a value of -1 nor a high value are recommended if max-active-sessions is set.
  • passivation-max-idle-time
    Determines the maximum time (in seconds) that a session can be inactive before the container should attempt to passivate it to save memory. Passivation of such sessions will take place regardless of whether the active session count exceeds max-active-sessions. Should be less than the web.xml session-timeout setting. A value of -1 (the default) disables passivation based on maximum inactivity.
The total number of sessions in memory includes sessions replicated from other cluster nodes that are not being accessed on this node. Take this into account when setting max-active-sessions. The number of sessions replicated from other nodes will also depend on whether buddy replication is enabled.
Say, for example, that you have an eight node cluster, and each node handles requests from 100 users. With total replication, each node would store 800 sessions in memory. With buddy replication enabled, and the default numBuddies setting (1), each node will store 200 sessions in memory.
The container for a distributable web application makes use of JBoss Cache to provide HTTP session replication services around the cluster. The container integrates with the CacheManager service to obtain a reference to a JBoss Cache instance. For more information, refer to the Distributed Caching with JBoss Cache Chapter in the Administration and Configuration Guide
The name of the JBoss Cache configuration to use is controlled by the cacheName element in the application's jboss-web.xml (see Section 15.1, “Enabling session replication in your application”). In most cases this does not need to be set because the default value of standard-session-cache is appropriate.
The JBoss Cache configurations in the CacheManager service expose a number of options.

Note

For more information, refer to the JBoss Cache chapter in the Administration and Configuration Guide
The standard-session-cache configuration is already optimized for the web session replication use case, and most of the settings should not be altered. Administrators may be interested in altering the following settings:
  • cacheMode
    The default is REPL_ASYNC, which specifies that a session replication message sent to the cluster does not wait for responses from other cluster nodes confirming that the message has been received and processed. The alternative mode, REPL_SYNC, offers a greater degree of confirmation that session state has been received, but reduces performance significantly.

    Note

    For more information about the other available parameters for cacheMode, refer to the Cache Mode section in the Administration and Configuration Guide.
  • enabled property in the buddyReplicationConfig section
    Set to true to enable buddy replication. Default is false.

    Note

    For more information about the other available parameters for cacheMode, refer to the Buddy Replication section in the Administration and Configuration Guide.
  • numBuddies property in the buddyReplicationConfig section
    Set to a value greater than the default (1) to increase the number of backup nodes onto which sessions are replicated. Only relevant if buddy replication is enabled.

    Note

    For more information about the other available parameters for cacheMode, refer to the Buddy Replication section in the Administration and Configuration Guide.
  • buddyPoolName property in the buddyReplicationConfig section
    A way to specify a preferred replication group when buddy replication is enabled. JBoss Cache tries to pick a buddy who shares the same pool name (falling back to other buddies if not available). Only relevant if buddy replication is enabled.

    Note

    For more information about the other available parameters for cacheMode, refer to the Buddy Replication section in the Administration and Configuration Guide.
  • multiplexerStack
    Name of the JGroups protocol stack the cache should use.

    Note

    For more information about the other available parameters for cacheMode, refer to The Channel Factory Service section in the Administration and Configuration Guide.
  • clusterName
    Identifying name JGroups will use for this cache's channel. Only change this if you create a new cache configuration, in which case this property should have a different value from all other cache configurations.
If you wish to use a completely new JBoss Cache configuration rather than editing one of the existing ones, refer to Deployment Via the CacheManager Service section in the Administration and Configuration Guide.

Chapter 16. Using Clustered Single Sign-on
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JBoss supports clustered single sign-on (SSO), allowing a user to authenticate to one web application and to be recognized on all web applications that are deployed on the same virtual host, whether or not they are deployed on that same machine or on another node in the cluster.
Authentication replication is handled by JBoss Cache. Clustered single sign-on support is a JBoss-specific extension of the non-clustered org.apache.catalina.authenticator.SingleSignOn valve that is a standard part of Tomcat and JBoss Web.

16.1. Configuration
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To enable clustered single sign-on, you must add the ClusteredSingleSignOn valve to the appropriate Host elements of the JBOSS_HOME/server/PROFILE/deploy/jbossweb.sar/server.xml file. The valve element is already included in the standard file; you just need to uncomment it. The valve configuration is shown here: 
<Valve className="org.jboss.web.tomcat.service.sso.ClusteredSingleSignOn" />
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The element supports the following attributes:
  • className is a required attribute to set the Java class name of the valve implementation to use. This must be set to org.jboss.web.tomcat.service.sso.ClusteredSingleSign.
  • cacheConfig is the name of the cache configuration to use for the clustered SSO cache. Default is clustered-sso.

    Note

    For more information about cache configuration, refer to The JBoss Enterprise Application Platform CacheManager Service section in the Administration and Configuration Guide.
  • treeCacheName is deprecated; use cacheConfig. Specifies a JMX ObjectName of the JBoss Cache MBean to use for the clustered SSO cache. If no cache can be located from the CacheManager service using the value of cacheConfig, an attempt to locate an mbean registered in JMX under this ObjectName will be made. Default value is jboss.cache:service=TomcatClusteringCache.
  • cookieDomain is used to set the host domain to be used for SSO cookies. See Section 16.4, “Configuring the Cookie Domain” for more. Default is "/".
  • maxEmptyLife is the maximum number of seconds an SSO with no active sessions will be usable by a request. The clustered SSO valve tracks what cluster nodes are managing sessions related to an SSO. A positive value for this attribute allows proper handling of shutdown of a node that is the only one that had handled any of the sessions associated with an SSO. The shutdown invalidates the local copy of the sessions, eliminating all sessions from the SSO. If maxEmptyLife were zero, the SSO would terminate along with the local session copies. But, backup copies of the sessions (if they are from clustered webapps) are available on other cluster nodes. Allowing the SSO to live beyond the life of its managed sessions gives the user time to make another request which can fail over to a different cluster node, where it activates the the backup copy of the session. Default is 1800, i.e. 30 minutes.
  • processExpiresInterval is the minimum number of seconds between efforts by the valve to find and invalidate SSO's that have exceeded their 'maxEmptyLife'. Does not imply effort will be spent on such cleanup every 'processExpiresInterval', just that it won't occur more frequently than that. Default is 60.
  • requireReauthentication is a flag to determine whether each request needs to be reauthenticated to the security Realm. If "true", this Valve uses cached security credentials (username and password) to reauthenticate to the JBoss Web security Realm each request associated with an SSO session. If false, the valve can itself authenticate requests based on the presence of a valid SSO cookie, without rechecking with the Realm. Setting to true can allow web applications with different security-domain configurations to share an SSO. Default is false.

16.2. SSO Behavior
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The user will not be challenged as long as they access only unprotected resources in any of the web applications on the virtual host.
Upon access to a protected resource in any web app, the user will be challenged to authenticate, using the login method defined for the web app.
Once authenticated, the roles associated with this user will be utilized for access control decisions across all of the associated web applications, without challenging the user to authenticate themselves to each application individually.
If the web application invalidates a session (by invoking the javax.servlet.http.HttpSession.invalidate() method), the user's sessions in all web applications will be invalidated.
A session timeout does not invalidate the SSO if other sessions are still valid.

16.3. Limitations
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There are a number of known limitations to this Tomcat valve-based SSO implementation:
  • Only useful within a cluster of JBoss servers; SSO does not propagate to other resources.
  • Requires use of container managed authentication (via <login-config> element in web.xml)
  • Requires cookies. SSO is maintained via a cookie and URL rewriting is not supported.
  • Unless requireReauthentication is set to true, all web applications configured for the same SSO valve must share the same JBoss Web Realm and JBoss Security security-domain. This means:
    • In server.xml you can nest the Realm element inside the Host element (or the surrounding Engine element), but not inside a context.xml packaged with one of the involved web applications.
    • The security-domain configured in jboss-web.xml or jboss-app.xml must be consistent for all of the web applications.
    • Even if you set requireReauthentication to true and use a different security-domain (or, less likely, a different Realm) for different webapps, the varying security integrations must all accept the same credentials (e.g. username and password).

Chapter 17. Complete Working Example
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Following are a set of example configuration files for a complete working example.
Proxy Server

A proxy server listening on localhost: 

<LoadModule slotmem_module modules/mod_slotmem.so
LoadModule manager_module modules/mod_manager.so
LoadModule proxy_cluster_module modules/mod_proxy_cluster.so
LoadModule advertise_module modules/mod_advertise.so

Listen 127.0.0.1:6666
<VirtualHost 127.0.0.1:6666>

    <Directory />
        Order deny,allow
        Deny from all
        Allow from 127.0.0.1
    </Directory>

    KeepAliveTimeout 60
    MaxKeepAliveRequests 0

    ManagerBalancerName mycluster
    ServerAdvertise On
    AdvertiseFrequency 5

</VirtualHost>

<Location /mod_cluster-manager>
    SetHandler mod_cluster-manager
    Order deny,allow
    Deny from all
    Allow from 127.0.0.1
</Location>
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JBoss Web Client Listener

Following are the listener definitions for JBOSS_EAP_DIST/server/PROFILE/deploy/jbossweb.sar/server.xml. 

<!-- Non-clustered mode -->
<Listener className="org.jboss.web.tomcat.service.deployers.MicrocontainerIntegrationLifecycleListener" delegateBeanName="ModClusterService"/>
<!-- Clustered mode
 Listener className="org.jboss.web.tomcat.service.deployers.MicrocontainerIntegrationLifecycleListener" delegateBeanName="HAModClusterService"/-->
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JBoss Web Client Service Dependencies

Following are the required dependencies for the WebServer bean in JBOSS_EAP_DIST/server/PROFILE/deploy/jbossweb.sar/META-INF/jboss-beans.xml. Add them to the existing dependencies. 

<bean name="WebServer" class="org.jboss.web.tomcat.service.deployers.TomcatService">
  <!-- ... -->
  <depends>ModClusterService</depends><!-- Non-clustered mode -->
  <!--depends>HAModClusterService</depends--><!-- Clustered mode -->
  <!-- ... -->
</bean>
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Example iptables Firewall Rules

Following are a set of example firewall rules using iptables, for a cluster node on the 192.168.1.0/24 subnet. 

/sbin/iptables -I INPUT 5 -p udp -d 224.0.1.0/24 -j ACCEPT -m comment --comment "mod_cluster traffic"
/sbin/iptables -I INPUT 6 -p udp -d 224.0.0.0/4 -j ACCEPT -m comment --comment "JBoss Cluster traffic"
/sbin/iptables -I INPUT 9 -p udp -s 192.168.1.0/24 -j ACCEPT -m comment --comment "cluster subnet for inter-node communication"
/sbin/iptables -I INPUT 10 -p tcp -s 192.168.1.0/24 -j ACCEPT -m comment --comment "cluster subnet for inter-node communication"
/etc/init.d/iptables save
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Appendix A. workers.properties Reference
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Apache httpd Server worker nodes are Servlet containers that are mapped to the mod_jk load balancer. The worker nodes are defined in HTTPD_DIST/conf/workers.properties. This file specifies where the different Servlet containers are located, and how calls should be load-balanced across them.
The workers.properties file contains two sections:
Global Properties
This section contains directives that apply to all workers.
Worker Properties
This section contains directives that apply to each individual worker.
Each node is defined using the Worker Properties naming convention. The worker name can only contain alphanumeric characters, limited to [a-z][A-Z][0-9][_-/].
The structure of a Worker Property is worker.worker_name.directive
worker
The constant prefix for all worker properties.
worker_name
The arbitrary name given to the worker. For example: node1, node_01, Node_1.
directive
The specific directive required.
The main directives required to configure worker nodes are described below.

Note

For the full list of worker.properties configuration directives, refer directly to the Apache Tomcat Connector - Reference Guide

worker.properties Global Directives

worker.list
Specifies the list of worker names used by mod_jk. The workers in this list are available to map requests to.

Note

A single node configuration, which is not managed by a load balancer, must be set to worker.list=[worker name].

workers.properties Mandatory Directives

type
Specifies the type of worker, which determines the directives applicable to the worker. The default value is ajp13, which is the preferred worker type to select for communication between the web server and Apache httpd Server.
Other values include ajp14, lb, status.
For detailed information about ajp13, refer to The Apache Tomcat Connector - AJP Protocol Reference

workers.properties Connection Directives

host
The hostname or IP address of the worker. The worker node must support the ajp13 protocol stack. The default value is localhost.
You can specify the port directive as part of the host directive by appending the port number after the hostname or IP address. For example: worker.node1.host=192.168.2.1:8009 or worker.node1.host=node1.example.com:8009
port
The port number of the remote server instance listening for defined protocol requests. The default value is 8009, which is the default listen port for AJP13 workers. If you are using AJP14 workers, this value must be set to 8011.
ping_mode
Specifies the conditions under which connections are probed for their current network health.
The probe uses an empty AJP13 packet for the CPing, and expects a CPong in return, within a specified timeout.
You specify the conditions by using a combination of the directive flags. The flags are not comma-separated. For example, a correct directive flag set is worker.node1.ping_mode=CI
C (connect)
Specifies the connection is probed once after connecting to the server. You specify the timeout using the connect_timeout directive, otherwise the value for ping_timeout is used.
P (prepost)
Specifies the connection is probed before sending each request to the server. You specify the timeout using the prepost_timeout directive, otherwise the value for ping_timeout is used.
I (interval)
Specifies the connection is probed during regular internal maintenance cycles. You specify the idle time between each interval using the connection_ping_interval directive, otherwise the value for ping_timeout is used.
A (all)
The most common setting, which specifies all directive flags are applied. For information about the *_timeout advanced directives, refer directly to Apache Tomcat Connector - Reference Guide.
ping_timeout
Specifies the time to wait for CPong answers to a CPing connection probe (refer to ping_mode). The default value is 10000 (milliseconds).

worker.properties Load Balancing Directives

lbfactor
Specifies the load-balancing factor for an individual worker, and is only specified for a member worker of a load balancer.
This directive defines the relative amount of HTTP request load distributed to the worker compared to other workers in the cluster.
A common example where this directive applies is where you want to differentiate servers with greater processing power than others in the cluster. For example, if you require a worker to take three times the load than other workers, specify worker.worker name.lbfactor=3
balance_workers
Specifies the worker nodes that the load balancer must manage. The directive can be used multiple times for the same load balancer, and consists of a comma-separated list of worker names as specified in the workers.properties file.
sticky_session
Specifies whether requests for workers with SESSION IDs are routed back to the same worker. The default is 0 (false). When set to 1 (true), load balancer persistence is enabled.
For example, if you specify worker.loadbalancer.sticky_session=0, each request is load balanced between each node in the cluster. In other words, different requests for the same session will go to different servers based on server load.
If worker.loadbalancer.sticky_session=1, each session is persisted (locked) to one server until the session is terminated, providing that server is available.

Appendix B. Java Properties Reference
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Read this appendix to learn about the JBoss HTTP Connector mod_cluster configuration properties that apply to a JBoss Enterprise Application Platform server node.

B.1. Proxy Configuration
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The configuration values are sent to proxies under the following conditions:
  • During server startup
  • When a proxy is detected through the advertise mechanism
  • During error recovery, when a proxy's configuration is reset.

Proxy Configuration Values

stickySession (defaults to true)
Specifies whether subsequent requests for a given session should be routed to the same node, if possible.
stickySessionRemove (defaults to false)
Specifies whether the httpd proxy should remove session stickiness if the balancer is unable to route a request to the node to which it is stuck. This property is ignored if stickySession is false.
stickySessionForce (defaults to true)
Specifies whether the httpd proxy should return an error if the balancer is unable to route a request to the node to which it is stuck. This property is ignored if stickySession is false.
workerTimeout (defaults to -1)
Specifies the number of seconds to wait for a worker to become available to handle a request. When all the workers of a balancer are usable, mod_cluster will retry after a while (workerTimeout/100) to find an usable worker.
A value of -1 indicates that the httpd will not wait for a worker to be available and will return an error if no workers are available.
maxAttempts (defaults to 1)
Specifies the number of times the httpd proxy will attempt to send a given request to a worker before aborting. The minimum value is 1: try once before aborting.
flushPackets (defaults to false)
Specifies whether packet flushing is enabled or disabled.
flushWait (defaults to -1)
Specifies the time to wait before flushing packets. A value of -1 means wait forever.
ping (defaults to 10)
Time to wait (in seconds) for a pong answer to a ping.
smax
Specifies the soft maximum idle connection count. The maximum value is determined by the httpd thread configuration (ThreadsPerChild or 1).
ttl (defaults to 60)
Specifies the time (in seconds) idle connections persist, above the smax threshold.
nodeTimeout (defaults to -1)
Specifies the time (in seconds) mod_cluster waits for the back-end server response before returning an error.
mod_cluster always uses a cping/cpong before forwarding a request. The connectiontimeout value used by mod_cluster is the ping value.
balancer (defaults to mycluster)
Specifies the name of the load-balancer.
domain (no default)
Optional parameter, which specifies how load is balanced across jvmRoutes within the same domain. domain is used in conjunction with partitioned session replication (for example, buddy replication).

B.2. Load Configuration
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Appendix C. Revision History
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Revision History
Revision 1.0.2-22.1Wed Feb 11 2015Lucas Costi
Updated the Product Name to reflect the new name grouping for the product. No update was made to details in the guide.
Revision 1.0.2-22Thu Sep 05 2013Mandar Joshi
BZ-825989: Fixed minor error

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