web-container-availability (Sun GlassFish Enterprise Server v2.1.1 Administration Reference)

Sun GlassFish Enterprise Server v2.1.1 Administration Reference

web-container-availability

Enables availability in the web container, including HTTP session persistence. If HADB is installed and you have selected the enterprise profile, sessions are persisted to the HADB.

If availability is disabled, there is no high availability for HTTP session persistence. In other words, persistence-type=memory.

If availability is enabled but no other web-container-availability attributes are specified, the default session persistence configuration is as follows:

persistence-type=replicated
persistence-frequency=time-based
persistence-scope=session

If HADB is installed and you have selected the enterprise profile, the default persistence type is ha.

The default configuration for all applications can be changed by setting the various web-container-availability attributes and properties.

You can override the various web-container-availability attributes and properties for a specific application in sun-web.xml. For details, see the Sun GlassFish Enterprise Server v2.1.1 Developer’s Guide.

For additional replicated session persistence properties you can set, see availability-service.

Superelements

availability-service

Subelements

The following table describes subelements for the web-container-availability element.

Table 1–193 web-container-availability Subelements


Element	Required	Description
property	zero or more	Specifies a property or a variable.

Attributes

The following table describes attributes for the web-container-availability element.

Table 1–194 web-container-availability Attributes


Attribute	Default	Description
`availability-enabled`	`true`	(optional) If set to `true`, and if availability is enabled for the server instance (see availability-service), high-availability features apply to all web applications deployed to the server instance that do not have availability disabled. All instances in a cluster should have the same availability value to ensure consistent behavior.
`persistence-type`	`memory` (availability disabled) `replicated` (availability enabled)	(optional) Specifies the session persistence mechanism for web applications that have availability enabled. Allowed values are `memory` (no persistence), `file` (the file system) and `replicated` (other servers). If HADB is installed and you have selected the enterprise profile, you can also specify `ha`. For production environments that require session persistence, use `ha`. If set to `memory`, the manager-properties element’s `session-file-name` attribute specifies the file system location where the HTTP session state is stored if the server instance is gracefully shut down. This is useful for internal testing but is not supported for production environments. If set to `file`, the store-properties element’s `directory` attribute specifies the file system location where the HTTP session state is stored. Persisting to the file system is useful for internal testing but is not supported for production environments.
`persistence-frequency`	`web-method`	(optional) Specifies how often the session state is stored. Applicable only if the `persistence-type` is `replicated` or `ha`. Allowed values are as follows: `web-method` - The session state is stored at the end of each web request prior to sending a response back to the client. This mode provides the best guarantee that the session state is fully updated in case of failure. `time-based` - The session state is stored in the background at the frequency set by the manager-properties element’s `reap-interval-in-seconds` attribute. This mode provides less of a guarantee that the session state is fully updated. However, it can provide a significant performance improvement because the state is not stored after each request.
`persistence-scope`	`session`	(optional) Specifies how much of the session state is stored. Applicable only if the `persistence-type` is `replicated` or `ha`. Allowed values are as follows: `session` - The entire session state is stored every time. This mode provides the best guarantee that your session data is correctly stored for any distributable web application. `modified-session` - The entire session state is stored if it has been modified. A session is considered to have been modified if `HttpSession.setAttribute()` or `HttpSession.removeAttribute()` was called. You must guarantee that `setAttribute()` is called every time an attribute is changed. This is not a Java EE specification requirement, but it is required for this mode to work properly. `modified-attribute` - Only modified session attributes are stored. For this mode to work properly, you must follow some guidelines, which are explained immediately following this table.
`sso-failover-enabled`	`false`	(optional) If `true`, the single sign-on state is highly available. To enable single sign-on, use the `sso-enabled` property of the virtual-server element.
`http-session-store-pool-name`	availability-service `store-pool-name` attribute value	(optional) Specifies the `jndi-name` of the jdbc-resource used for connections to the HADB for session persistence. Applicable if HADB is installed and you have selected the enterprise profile. For more information about setting up a connection pool and JDBC resource for the HADB, see the description of the `configure-ha-cluster` command in the Sun GlassFish Enterprise Server v2.1.1 Reference Manual.

If the persistence-scope attribute is set to modified-attribute , your web application must follow these guidelines:

Call setAttribute() every time the session state is modified.
Make sure there are no cross-references between attributes. The object graph under each distinct attribute key is serialized and stored separately. If there are any object cross references between the objects under each separate key, they are not serialized and deserialized correctly.
Distribute the session state across multiple attributes, or at least between a read-only attribute and a modifiable attribute.

Properties

The following table describes properties for the web-container-availability element.

Table 1–195 web-container-availability Properties


Property	Default	Description
`uuid-impl-class`	none	Specifies the name of the class that generates session IDs. If this property is not specified, the Enterprise Server's internal session ID generator is used. It is the developer's responsibility to ensure that generated IDs are universally unique even when running on multiple JVMs on multiple machines in a cluster. Failure to ensure this in the algorithm results in nondeterministic behavior and likely corruption of HTTP session data.