Enabling the High Availability Session Persistence Service

This section explains how to configure and enable the high availability session persistence service.

To Enable Availability for a Cluster, Standalone Instance or Container
Configuring Availability for Individual Web Applications
Configuring Replication and Multi-Threaded Concurrent Access to HttpSessions
Using Single Sign-on with Session Failover
Using Coherence*Web for HTTP Session Persistence

To Enable Availability for a Cluster, Standalone Instance or Container

This procedure explains how to enable high availability for a cluster as a whole, or for Web, EJB, or JMS containers that run in a cluster, or for a standalone server instance that is not part of a cluster.

Create a GlassFish Server cluster.
For more information, see To Create a Cluster.
Set up load balancing for the cluster.
For instructions, see Setting Up HTTP Load Balancing.
Verify that the cluster and all instances within the cluster for which you want to enable availability is running.
These steps are also necessary when enabling availability for a Web, EJB, or JMS container running in a cluster. The cluster and all instances in the cluster for which you want to enable availability must be running.
1. Verify that the cluster is running.
```
asadmin> list-clusters
```
  A list of clusters and their status (running, not running) is displayed. If the cluster for which you want to enable availability is not running, you can start it with the following command:
```
asadmin> start-cluster cluster-name
```
2. Verify that all instances in the cluster are running.
```
asadmin> list-instances
```
  A list of instances and their status is displayed. If the instances for which you want to enable availability are not running, you can start them by using the following command for each instance:
```
asadmin> start-instance instance-name
```

Use one of the following asadmin set(1) subcommands to enable availability for a specific cluster, or for a specific Web, EJB, or JMS container.

For a cluster as a whole

asadmin> set cluster-name-config.availability-service.availability-enabled=true

For example, for a cluster named c1:

asadmin> set c1-config.availability-service.availability-enabled=true

For the Web container in a cluster

asadmin> set cluster-name-config.availability-service \
.web-container-availability.availability-enabled=true

For the EJB container in a cluster

asadmin> set cluster-name-config.availability-service \
.ejb-container-availability.availability-enabled=true

For the JMS container in a cluster

asadmin> set cluster-name-config.availability-service \
.jms-availability.availability-enabled=true

For a standalone server instance (not part of a cluster)

asadmin> set instance-name-config.availability-service.availability-enabled=true

Restart the standalone server instance or each server instance in the cluster.
If the instance is currently serving requests, quiesce the instance before restarting it so that the instance gets enough time to serve the requests it is handling. For more information, see Disabling (Quiescing) a Server Instance or Cluster.
Enable availability for any SFSB that requires it.
Select methods for which checkpointing the session state is necessary. For more information, see Configuring Availability for an Individual Bean.
Make each web module distributable if you want it to be highly available.
For more information, see Web Module Deployment Guidelines in Oracle GlassFish Server 3.1 Application Deployment Guide.
(Optional) Enable availability for individual applications, web modules, or EJB modules during deployment.
See the links below for instructions.

Configuring Availability for Individual Web Applications

To enable and configure availability for an individual web application, edit the application deployment descriptor file, glassfish-web.xml. The settings in an application’s deployment descriptor override the web container’s availability settings.

The session-manager element’s persistence-type attribute determines the type of session persistence an application uses. It must be set to replicated to enable high availability session persistence.

Example

<glassfish-web-app> ... 
  <session-config> 
    <session-manager persistence-type="replicated"> 
      <manager-properties> 
        <property name="persistenceFrequency" value="web-method" /> 
      </manager-properties> 
      <store-properties> 
        <property name="persistenceScope" value="session" /> 
      </store-properties> 
    </session-manager> ... 
</session-config> ...

Configuring Replication and Multi-Threaded Concurrent Access to `HttpSessions`

If you are using Memory Replication and your web application involves multiple client threads concurrently accessing the same session ID, then you may experience session loss even without any instance failure. The problem is that the GlassFish Server 3.1 memory replication framework makes use of session versioning. This feature was designed with the more traditional HTTP request/response communication model in mind.

However, for some types of applications, the traditional request/response model does not work. Examples include many Ajax-related frameworks and the use of Frames. Another example is when a page includes many static resources, such as JPG files. In these situations, most browsers will optimize the loading of these resources by using multiple parallel connections, each of which is handled by a separate request processing thread. If the application has already established a session, then this will also involve more than one thread at a time accessing a single HttpSession.

The solution in such cases is to use the relaxVersionSemantics property in the glassfish-web.xml deployment descriptor file for the application. This enables the web container to return for each requesting thread whatever version of the session that is in the active cache regardless of the version number. This is critical when multiple threads are interacting in an essentially non-deterministic fashion with the container.

Example

The following is an example snippet from a glassfish-web.xml file that illustrates where to add the relaxVersionSemantics property.

<glassfish-web-app>
  <session-config>
    <session-manager persistence-type="replicated">
      <manager-properties>
    <property name="relaxCacheVersionSemantics" value="true"/>
      </manager-properties>
    </session-manager>
  </session-config>

.....
</glassfish-web-app>

Using Single Sign-on with Session Failover

In a single application server instance, once a user is authenticated by an application, the user is not required to re-authenticate individually to other applications running on the same instance. This is called single sign-on.

For this feature to continue to work even when an HTTP session fails over to another instance in a cluster, single sign-on information must be persisted using in-memory replication. To persist single sign-on information, first, enable availability for the server instance and the web container, then enable single-sign-on state failover.

You can enable single sign-on state failover by using the asadmin set command to set the configuration’s availability-service.web-container-availability.sso-failover-enabled property to true.

For example, use the set command as follows, where config1 is the configuration name:

asadmin> set config1.availability-service.web-container-availability. \ sso-failover-enabled="true"

Single Sign-On Groups

Applications that can be accessed through a single name and password combination constitute a single sign-on group. For HTTP sessions corresponding to applications that are part of a single sign-on group, if one of the sessions times out, other sessions are not invalidated and continue to be available. This is because time out of one session should not affect the availability of other sessions.

As a corollary of this behavior, if a session times out and you try to access the corresponding application from the same browser window that was running the session, you are not required to authenticate again. However, a new session is created.

Take the example of a shopping cart application that is a part of a single sign-on group with two other applications. Assume that the session time out value for the other two applications is higher than the session time out value for the shopping cart application. If your session for the shopping cart application times out and you try to run the shopping cart application from the same browser window that was running the session, you are not required to authenticate again. However, the previous shopping cart is lost, and you have to create a new shopping cart. The other two applications continue to run as usual even though the session running the shopping cart application has timed out.

Similarly, suppose a session corresponding to any of the other two applications times out. You are not required to authenticate again while connecting to the application from the same browser window in which you were running the session.

Note - This behavior applies only to cases where the session times out. If single sign-on is enabled and you invalidate one of the sessions using HttpSession.invalidate() , the sessions for all applications belonging to the single sign-on group are invalidated. If you try to access any application belonging to the single sign-on group, you are required to authenticate again, and a new session is created for the client accessing the application.

Using Coherence*Web for HTTP Session Persistence

Built on top of Oracle Coherence, Coherence*Web is an HTTP session management module dedicated to managing session state in clustered environments. Starting with Coherence 3.7 and GlassFish Server 3.1, there is a new feature of Coherence*Web called ActiveCache for GlassFish. ActiveCache for GlassFish provides Coherence*Web functionality in web applications deployed on GlassFish Servers. Within GlassFish Server, Coherence*Web functions as an additional web container persistence type, named coherence-web.

For information about how to configure and deploy Coherence*Web on GlassFish Server, see Using Coherence*Web with GlassFish Server.

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	Oracle GlassFish Server 3.1-3.1.1 High Availability Administration Guide