8.7. Clustered Enterprise JavaBeans
8.7.1. About Clustered Enterprise JavaBeans (EJBs)
Note
8.7.2. Standalone and In-server Client Configuration
jboss-ejb-client.properties
for standalone EJB client, or even jboss-ejb-client.xml
file for a server-side application must be expanded to include a cluster configuration.
Note
in-server
when the JVM doing the calling to the remote server is itself running inside of a server. In other words, an EAP instance calling out to another EAP instance would be considered an in-server client.
Example 8.4. Standalone client with jboss-ejb-client.properties
configuration
remote.clusters=ejb remote.cluster.ejb.connect.options.org.xnio.Options.SASL_POLICY_NOANONYMOUS=false remote.cluster.ejb.connect.options.org.xnio.Options.SSL_ENABLED=false remote.cluster.ejb.username=test remote.cluster.ejb.password=password
jboss-ejb-client.xml
file and add cluster configuration as shown in the following example:
Example 8.5. Client application which is deployed in another EAP 6 instance (Configuring jboss-ejb-client.xml file)
<jboss-ejb-client xmlns:xsi="urn:jboss:ejb-client:1.2" xsi:noNamespaceSchemaLocation="jboss-ejb-client_1_2.xsd"> <client-context> <ejb-receivers> <!-- this is the connection to access the app-one --> <remoting-ejb-receiver outbound-connection-ref="remote-ejb-connection-1" /> <!-- this is the connection to access the app-two --> <remoting-ejb-receiver outbound-connection-ref="remote-ejb-connection-2" /> </ejb-receivers> <!-- if an outbound connection connects to a cluster; a list of members is provided after successful connection. To connect to this node this cluster element must be defined. --> <clusters> <!-- cluster of remote-ejb-connection-1 --> <cluster name="ejb" security-realm="ejb-security-realm-1" username="quickuser1"> <connection-creation-options> <property name="org.xnio.Options.SSL_ENABLED" value="false" /> <property name="org.xnio.Options.SASL_POLICY_NOANONYMOUS" value="false" /> </connection-creation-options> </cluster> </clusters> </client-context> </jboss-ejb-client>
Note
8.7.3. Implementing a Custom Load Balancing Policy for EJB Calls
AllClusterNodeSelector
for EJB calls. The node selection behavior of AllClusterNodeSelector
is similar to default selector except that AllClusterNodeSelector
uses all available cluster nodes even in case of a large cluster (number of nodes>20). If an unconnected cluster node is returned it is opened automatically. The following example shows AllClusterNodeSelector
implementation:
package org.jboss.as.quickstarts.ejb.clients.selector; import java.util.Arrays; import java.util.Random; import java.util.logging.Level; import java.util.logging.Logger; import org.jboss.ejb.client.ClusterNodeSelector; public class AllClusterNodeSelector implements ClusterNodeSelector { private static final Logger LOGGER = Logger.getLogger(AllClusterNodeSelector.class.getName()); @Override public String selectNode(final String clusterName, final String[] connectedNodes, final String[] availableNodes) { if(LOGGER.isLoggable(Level.FINER)) { LOGGER.finer("INSTANCE "+this+ " : cluster:"+clusterName+" connected:"+Arrays.deepToString(connectedNodes)+" available:"+Arrays.deepToString(availableNodes)); } if (availableNodes.length == 1) { return availableNodes[0]; } final Random random = new Random(); final int randomSelection = random.nextInt(availableNodes.length); return availableNodes[randomSelection]; } }You can also implement the
SimpleLoadFactorNodeSelector
for EJB calls. Load balancing in SimpleLoadFactorNodeSelector
happens based on a load factor. The load factor (2/3/4) is calculated based on the names of nodes (A/B/C) irrespective of the load on each node. The following example shows SimpleLoadFactorNodeSelector
implementation:
package org.jboss.as.quickstarts.ejb.clients.selector; import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.logging.Level; import java.util.logging.Logger; import org.jboss.ejb.client.DeploymentNodeSelector; public class SimpleLoadFactorNodeSelector implements DeploymentNodeSelector { private static final Logger LOGGER = Logger.getLogger(SimpleLoadFactorNodeSelector.class.getName()); private final Map<String, List<String>[]> nodes = new HashMap<String, List<String>[]>(); private final Map<String, Integer> cursor = new HashMap<String, Integer>(); private ArrayList<String> calculateNodes(Collection<String> eligibleNodes) { ArrayList<String> nodeList = new ArrayList<String>(); for (String string : eligibleNodes) { if(string.contains("A") || string.contains("2")) { nodeList.add(string); nodeList.add(string); } else if(string.contains("B") || string.contains("3")) { nodeList.add(string); nodeList.add(string); nodeList.add(string); } else if(string.contains("C") || string.contains("4")) { nodeList.add(string); nodeList.add(string); nodeList.add(string); nodeList.add(string); } } return nodeList; } @SuppressWarnings("unchecked") private void checkNodeNames(String[] eligibleNodes, String key) { if(!nodes.containsKey(key) || nodes.get(key)[0].size() != eligibleNodes.length || !nodes.get(key)[0].containsAll(Arrays.asList(eligibleNodes))) { // must be synchronized as the client might call it concurrent synchronized (nodes) { if(!nodes.containsKey(key) || nodes.get(key)[0].size() != eligibleNodes.length || !nodes.get(key)[0].containsAll(Arrays.asList(eligibleNodes))) { ArrayList<String> nodeList = new ArrayList<String>(); nodeList.addAll(Arrays.asList(eligibleNodes)); nodes.put(key, new List[] { nodeList, calculateNodes(nodeList) }); } } } } private synchronized String nextNode(String key) { Integer c = cursor.get(key); List<String> nodeList = nodes.get(key)[1]; if(c == null || c >= nodeList.size()) { c = Integer.valueOf(0); } String node = nodeList.get(c); cursor.put(key, Integer.valueOf(c + 1)); return node; } @Override public String selectNode(String[] eligibleNodes, String appName, String moduleName, String distinctName) { if (LOGGER.isLoggable(Level.FINER)) { LOGGER.finer("INSTANCE " + this + " : nodes:" + Arrays.deepToString(eligibleNodes) + " appName:" + appName + " moduleName:" + moduleName + " distinctName:" + distinctName); } // if there is only one there is no sense to choice if (eligibleNodes.length == 1) { return eligibleNodes[0]; } final String key = appName + "|" + moduleName + "|" + distinctName; checkNodeNames(eligibleNodes, key); return nextNode(key); } }
jboss-ejb-client.properties
You need to add the property remote.cluster.ejb.clusternode.selector
with the name of your implementation class (AllClusterNodeSelector
or SimpleLoadFactorNodeSelector
). The selector will see all configured servers which are available at the invocation time. The following example uses AllClusterNodeSelector
as the deployment node selector:
remote.clusters=ejb remote.cluster.ejb.clusternode.selector=org.jboss.as.quickstarts.ejb.clients.selector.AllClusterNodeSelector remote.cluster.ejb.connect.options.org.xnio.Options.SASL_POLICY_NOANONYMOUS=false remote.cluster.ejb.connect.options.org.xnio.Options.SSL_ENABLED=false remote.cluster.ejb.username=test remote.cluster.ejb.password=password remote.connectionprovider.create.options.org.xnio.Options.SSL_ENABLED=false remote.connections=one,two remote.connection.one.host=localhost remote.connection.one.port = 4447 remote.connection.one.connect.options.org.xnio.Options.SASL_POLICY_NOANONYMOUS=false remote.connection.one.username=user remote.connection.one.password=user123 remote.connection.two.host=localhost remote.connection.two.port = 4547 remote.connection.two.connect.options.org.xnio.Options.SASL_POLICY_NOANONYMOUS=false
You need to add the property remote.cluster.ejb.clusternode.selector
to the list for the PropertiesBasedEJBClientConfiguration
constructor. The following example uses AllClusterNodeSelector
as the deployment node selector:
Properties p = new Properties(); p.put("remote.clusters", "ejb"); p.put("remote.cluster.ejb.clusternode.selector", "org.jboss.as.quickstarts.ejb.clients.selector.AllClusterNodeSelector"); p.put("remote.cluster.ejb.connect.options.org.xnio.Options.SASL_POLICY_NOANONYMOUS", "false"); p.put("remote.cluster.ejb.connect.options.org.xnio.Options.SSL_ENABLED", "false"); p.put("remote.cluster.ejb.username", "test"); p.put("remote.cluster.ejb.password", "password"); p.put("remote.connectionprovider.create.options.org.xnio.Options.SSL_ENABLED", "false"); p.put("remote.connections", "one,two"); p.put("remote.connection.one.port", "4447"); p.put("remote.connection.one.host", "localhost"); p.put("remote.connection.two.port", "4547"); p.put("remote.connection.two.host", "localhost"); EJBClientConfiguration cc = new PropertiesBasedEJBClientConfiguration(p); ContextSelector<EJBClientContext> selector = new ConfigBasedEJBClientContextSelector(cc); EJBClientContext.setSelector(selector); p = new Properties(); p.put(Context.URL_PKG_PREFIXES, "org.jboss.ejb.client.naming"); InitialContext context = new InitialContext(p);
jboss-ejb-client.xml
To use the load balancing policy for server to server communication; package the class together with the application and configure it within the jboss-ejb-client.xml
settings (located in META-INF
folder). The following example uses AllClusterNodeSelector
as the deployment node selector:
<jboss-ejb-client xmlns:xsi="urn:jboss:ejb-client:1.2" xsi:noNamespaceSchemaLocation="jboss-ejb-client_1_2.xsd"> <client-context deployment-node-selector="org.jboss.ejb.client.DeploymentNodeSelector"> <ejb-receivers> <!-- this is the connection to access the app --> <remoting-ejb-receiver outbound-connection-ref="remote-ejb-connection-1" /> </ejb-receivers> <!-- if an outbound connection connect to a cluster a list of members is provided after successful connection. To connect to this node this cluster element must be defined. --> <clusters> <!-- cluster of remote-ejb-connection-1 --> <cluster name="ejb" security-realm="ejb-security-realm-1" username="test" cluster-node-selector="org.jboss.as.quickstarts.ejb.clients.selector.AllClusterNodeSelector"> <connection-creation-options> <property name="org.xnio.Options.SSL_ENABLED" value="false" /> <property name="org.xnio.Options.SASL_POLICY_NOANONYMOUS" value="false" /> </connection-creation-options> </cluster> </clusters> </client-context> </jboss-ejb-client>To use the above configuration with security, you will need to add
ejb-security-realm-1
to client-server configuration. The following example shows the CLI commands for adding security realm (ejb-security-realm-1
) the value is the base64 encoded password for the user "test":
core-service=management/security-realm=ejb-security-realm-1:add() core-service=management/security-realm=ejb-security-realm-1/server-identity=secret:add(value=cXVpY2sxMjMr)
Note
-Djboss.node.name=
or the server configuration file standalone.xml
to configure the server name (server name=""). Ensure that the server name is unique. In domain mode, the controller automatically validates that the names are unique.
8.7.4. Transaction Behavior of EJB Invocations
Transaction attributes for distributed JBoss EAP applications need to be handled in a way as if the application is called on the same server. To discontinue a transaction, the destination method must be marked REQUIRES_NEW
using different interfaces.
Note
To invoke EJB session beans with a JBoss EAP 6 standalone client, the client must have a reference to the InitialContext
object while the EJB proxies or UserTransaction
are used. It is also important to keep the InitialContext
object open while EJB proxies or UserTransaction
are being used. Control of the connections will be inside the classes created by the InitialContext
with the properties.
InitialContext
object.
Example 8.6. EJB client API referencing InitialContext
object
package org.jboss.as.quickstarts.ejb.multi.server; import java.util.Date; import java.util.Properties; import java.util.logging.Level; import java.util.logging.Logger; import javax.naming.Context; import javax.naming.InitialContext; import org.jboss.as.quickstarts.ejb.multi.server.app.MainApp; import org.jboss.ejb.client.ContextSelector; import org.jboss.ejb.client.EJBClientConfiguration; import org.jboss.ejb.client.EJBClientContext; import org.jboss.ejb.client.PropertiesBasedEJBClientConfiguration; import org.jboss.ejb.client.remoting.ConfigBasedEJBClientContextSelector; public class Client { /** * @param args no args needed * @throws Exception */ public static void main(String[] args) throws Exception { // suppress output of client messages Logger.getLogger("org.jboss").setLevel(Level.OFF); Logger.getLogger("org.xnio").setLevel(Level.OFF); Properties p = new Properties(); p.put("remote.connectionprovider.create.options.org.xnio.Options.SSL_ENABLED", "false"); p.put("remote.connections", "one"); p.put("remote.connection.one.port", "4447"); p.put("remote.connection.one.host", "localhost"); p.put("remote.connection.one.username", "quickuser"); p.put("remote.connection.one.password", "quick-123"); EJBClientConfiguration cc = new PropertiesBasedEJBClientConfiguration(p); ContextSelector<EJBClientContext> selector = new ConfigBasedEJBClientContextSelector(cc); EJBClientContext.setSelector(selector); Properties props = new Properties(); props.put(Context.URL_PKG_PREFIXES, "org.jboss.ejb.client.naming"); InitialContext context = new InitialContext(props); final String rcal = "ejb:jboss-ejb-multi-server-app-main/ejb//" + ("MainAppBean") + "!" + MainApp.class.getName(); final MainApp remote = (MainApp) context.lookup(rcal); final String result = remote.invokeAll("Client call at "+new Date()); System.out.println("InvokeAll succeed: "+result); } }
Note
UserTransaction
reference on the client is unsupported for scenarios with a scoped EJB client context and for invocations which use the remote-naming
protocol. This is because in these scenarios, InitialContext
encapsulates its own EJB client context instance; which cannot be accessed using the static methods of the EJBClient
class. When EJBClient.getUserTransaction()
is called, it returns a transaction from default (global) EJB client context (which might not be initialized) and not from the desired one.
The following example shows how to get UserTransaction
reference on a standalone client.
Example 8.7. Standalone client referencing UserTransaction
object
import org.jboss.ejb.client.EJBClient; import javax.transaction.UserTransaction; . . Context context=null; UserTransaction tx=null; try { Properties props = new Properties(); // REMEMBER: there must be a jboss-ejb-client.properties with the connection parameter // in the clients classpath props.put(Context.URL_PKG_PREFIXES, "org.jboss.ejb.client.naming"); context = new InitialContext(props); System.out.println("\n\tGot initial Context: "+context); tx=EJBClient.getUserTransaction("yourServerName"); System.out.println("UserTransaction = "+tx.getStatus()); tx.begin(); // do some work ... }catch (Exception e) { e.printStackTrace(); tx.rollback(); }finally{ if(context != null) { context.close(); } }
Note
UserTransaction
reference on the client side; start your server with the following system property -Djboss.node.name=yourServerName
and then use it on client side as following:
tx=EJBClient.getUserTransaction("yourServerName");Replace "yourServerName" with the name of your server. If a user transaction is started on a node all invocations are sticky on the node and the node must have all the needed EJBs. It is not possible to use
UserTransaction
with remote-naming protocol and scoped-context.