8.7. Clustered Enterprise JavaBeans

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];
  }

}

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);
  }
}

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);

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>

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)

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.

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.

The following example shows how to get UserTransaction reference on a standalone client.

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();
      }
    }