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Chapter 39. Externalize Sessions

39.1. Externalize Sessions

Red Hat JBoss Data Grid can be used as an external cache for containers, such as JBoss Enterprise Application Platform (EAP). This allows JBoss Data Grid to store HTTP Sessions, among other data, independent of the application layer, which provides the following benefits:

Application Elasticity

By making the application stateless additional nodes may be added to the EAP cluster without expensive data rebalancing operations. The EAP cluster may also be replaced without downtime by keeping the state in the JBoss Data Grid layer, as upgraded nodes may be brought online and retrieve the sessions.

Failover Across Data Centers

Should a data center become unavailable the session data persists, as it is stored safely within the JBoss Data Grid cluster. This allows a load balancer to redirect incoming requests to a second cluster to retrieve the session information.

Reduced Memory Footprint

There is reduced memory pressure, resulting in shorter garbage collection time and frequency of collections, as the HTTP Sessions have been moved out of the application layer and into the backing caches.

39.2. Externalize HTTP Session from JBoss EAP to JBoss Data Grid

The following procedure applies for both standalone and domain mode of EAP; however, in domain mode each server group requires a unique remote cache configured.

While multiple server groups can utilize the same Red Hat JBoss Data Grid cluster the respective remote caches will be unique to the EAP server group.

Note

The following procedures have been tested and validated on JBoss EAP 7.0 and JBoss Data Grid 7.0.

Externalize HTTP Sessions

  1. Ensure the remote cache containers are defined in EAP’s infinispan subsystem; in the example below the cache attribute in the remote-store element defines the cache name on the remote JBoss Data Grid server: 

    <subsystem xmlns="urn:jboss:domain:infinispan:4.0">
  [...]
  <cache-container name="web" default-cache="dist" module="org.wildfly.clustering.web.infinispan" statistics-enabled="true">
    <transport lock-timeout="60000"/>
    <invalidation-cache name="jdg">
      <locking isolation="REPEATABLE_READ"/>
      <transaction mode="BATCH"/>
      <remote-store remote-servers="remote-jdg-server1 remote-jdg-server2"
                    cache="default" socket-timeout="60000"
                    preload="true" passivation="false" purge="false" shared="true"/>
    </invalidation-cache>
  </cache-container>
</subsystem>

  2. Define the location of the remote Red Hat JBoss Data Grid server by adding the networking information to the socket-binding-group: 

    <socket-binding-group ...>
  <outbound-socket-binding name="remote-jdg-server1">
    <remote-destination host="JDGHostName1" port="11222"/>
  </outbound-socket-binding>
  <outbound-socket-binding name="remote-jdg-server2">
    <remote-destination host="JDGHostName2" port="11222"/>
  </outbound-socket-binding>
</socket-binding-group>
  3. Repeat the above steps for each cache-container and each Red Hat JBoss Data Grid server. Each server defined must have a separate <outbound-socket-binding> element defined.

  4. Add passivation and cache information into the application’s jboss-web.xml. In the following example web is the name of the cache container, and jdg is the name of the default cache located in this container. An example file is shown below: 

    <?xml version="1.0" encoding="UTF-8"?>
<jboss-web xmlns="http://www.jboss.com/xml/ns/javaee"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.jboss.com/xml/ns/javaee http://www.jboss.org/j2ee/schema/jboss-web_10_0.xsd"
           version="10.0">

    <distributable/>

    <replication-config>
        <replication-granularity>SESSION</replication-granularity>
        <cache-name>web.jdg</cache-name>
    </replication-config>

</jboss-web>
Note

The passivation timeouts above are provided assuming that a typical session is abandoned within 15 minutes and uses the default HTTP session timeout in JBoss EAP of 30 minutes. These values may need to be adjusted based on each application’s workload.

39.3. Externalize HTTP Sessions from JBoss Web Server (JWS) to JBoss Data Grid

39.3.1. Externalize HTTP Session from JBoss Web Server (JWS) to JBoss Data Grid

A session manager has been provided as part of the JBoss Data Grid distribution, allowing JWS users to externalize sessions to JBoss Data Grid by integrating with an extension of Tomcat’s Manager. This allows the Tomcat layer to remain stateless while providing session management persistence.

39.3.2. Prerequisites

This manager requires the following versions, or later, be installed:

  • JBoss Web Server 3.0
  • JBoss Data Grid 7.1

39.3.3. Installation

Complete the following steps to install this manager for either Tomcat 7 or Tomcat 8:

  1. Download one of the following from the JBoss Data Grid product page:

    • jboss-datagrid-7.2.0-tomcat7-session-client.zip
    • jboss-datagrid-7.2.0-tomcat8-session-client.zip
  2. Extract the archive.
  3. Copy the lib/ directory from the extracted archive into $CATALINA_HOME.

  4. Define the implementation of the Session Manager in context.xml, as seen below: 

    <Manager className="org.wildfly.clustering.tomcat.hotrod.HotRodManager"
         server_list="www.server1.com:7600;www.server2.com:7600"
         <!-- Additional Configuration Elements -->
         />

39.3.4. Session Management Details

When using the HotRodManager all sessions are placed into the default cache located on the Remote JBoss Data Grid server. Cache names are not configurable.

Sessions stored in JBoss Web Server are all mutable by default. If an object changes during the course of the request then it will be replicated after the request ends. To define immutable objects, use one of the following annotations:

  • The Wildfly specific annotation - org.wildfly.clustering.web.annotation.Immutable.
  • Any generic immutable annotation.
  • Any known immutable type from the JDK implementation.

Objects may have custom marshalling by defining an Externalizer. By default the Wildfly Externalizer is recognized; however, any implementation of this Externalizer may be used. Additionally, non-serializable objects may be stored without issue as long as they have an Externalizer defined.

39.3.5. Configure the JBoss Web Server Session Manager

The HotRodManager is configured by defining properties on the Manager element inside of context.xml. These are pulled from two separate lists:

  • org.apache.catalina.Manager - As the session manager implements this class many of the Common Attributes are configurable.
  • ConfigurationParameters - This session manager also uses the HotRod Configuration Properties.

The following table displays all of the configurable elements

Table 39.1. Common Attributes from Tomcat’s Manager
AttributeDescription

name

The name of this cluster manager. The name is used to identify a session manager on a node. The name might get modified by the Cluster element to make it unique to the container.

sessionIdLength

The length of session ids created by this Manager, measured in bytes, excluding subsequent conversion to a hexadecimal string and excluding any JVM route information used for load balancing. This attribute is deprecated. Set the length on a nested SessionIdGenerator element instead.

secureRandomClass

Name of the Java class that extends java.security.SecureRandom to use to generate session IDs. If not specified, the default value is java.security.SecureRandom.

secureRandomProvider

Name of the provider to use to create the java.security.SecureRandom instances that generate session IDs. If an invalid algorithm and/or provider is specified, the Manager will use the platform default provider and the default algorithm. If not specified, the platform default provider will be used.

secureRandomAlgorithm

Name of the algorithm to use to create the java.security.SecureRandom instances that generate session IDs. If an invalid algorithm and/or provider is specified, the Manager will use the platform default provider and the default algorithm. If not specified, the default algorithm of SHA1PRNG will be used. If the default algorithm is not supported, the platform default will be used. To specify that the platform default should be used, do not set the secureRandomProvider attribute and set this attribute to the empty string.

recordAllActions

Flag whether send all actions for session across Tomcat cluster nodes. If set to false, if already done something to the same attribute, make sure don’t send multiple actions across Tomcat cluster nodes. In that case, sends only the actions that have been added at last. Default is false.

There is also a property specific to the JWS HotRodManager, shown below:

AttributeDescription

persistenceStrategy

Determines whether or not all attributes that compose a session should be serialized together (COARSE) or individually (FINE). When using a COARSE strategy relationships between objects will be preserved. FINE uses less memory, as only the attributes that have changed are serialized. Defaults to COARSE.

In addition to the attributes inherited from Tomcat, the HotRodManager may use any of the properties typically available to a RemoteCacheManager. These are outlined in HotRod Properties.

When using HotRod properties only the property name itself is required. For instance, to configure TCP KEEPALIVE and TCP NODELAY on the manager the following xml snippet would be used: 

<Manager className="org.wildfly.clustering.tomcat.hotrod.HotRodManager"
         tcp_no_delay="true"
         tcp_keep_alive="true"/>
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