== Logout

There are multiple ways you can log out from a web application.
For Jakarta EE servlet containers, you can call `HttpServletRequest.logout()`. For any other browser application, you can point
the browser at any url of your web application that has a security constraint and pass in a query parameter GLO, i.e. `$$http://myapp?GLO=true$$`.
This will log you out if you have an SSO session with your browser.

[[_saml_logout_in_cluster]]
=== Logout in clustered environment

Internally, the SAML adapter stores a mapping between the SAML session index, principal name (when known), and HTTP session ID.
This mapping can be maintained in JBoss application server family (WildFly 10/11, EAP 6/7) across cluster for distributable
applications. As a precondition, the HTTP sessions need to be distributed across cluster (i.e. application is marked with
`<distributable/>` tag in application's `web.xml`).

To enable the functionality, add the following section to your `/WEB_INF/web.xml` file:

[source,xml]
----
<context-param>
    <param-name>keycloak.sessionIdMapperUpdater.classes</param-name>
    <param-value>org.keycloak.adapters.saml.wildfly.infinispan.InfinispanSessionCacheIdMapperUpdater</param-value>
</context-param>
----

If the session cache of the deployment is named `_deployment-cache_`, the cache used for SAML mapping will be named
as `_deployment-cache_.ssoCache`. The name of the cache can be overridden by a context parameter
`keycloak.sessionIdMapperUpdater.infinispan.cacheName`. The cache container containing the cache will be the same as
the one containing the deployment session cache, but can be overridden by a context parameter
`keycloak.sessionIdMapperUpdater.infinispan.containerName`.

By default, the configuration of the SAML mapping cache will be derived from session cache. The configuration can
be manually overridden in cache configuration section of the server just the same as other caches.

Currently, to provide reliable service, it is recommended to use replicated cache for the SAML session cache.
Using distributed cache may lead to results where the SAML logout request would land to a node with no access
to SAML session index to HTTP session mapping which would lead to unsuccessful logout.

[[_saml_logout_in_cross_dc]]
=== Logout in cross-site scenario

Special handling is needed for handling sessions that span multiple data centers. Imagine the following scenario:

1. Login requests are handled within cluster in data center 1.

2. Admin issues logout request for a particular SAML session, the request lands in data center 2.

The data center 2 has to log out all sessions that are present in data center 1 (and all other data centers that
share HTTP sessions).

To cover this case, the SAML session cache described <<_saml_logout_in_cluster,above>> needs to be replicated
not only within individual clusters but across all the data centers for example
https://docs.redhat.com/en/documentation/red_hat_data_grid/6.6/html/administration_and_configuration_guide/chap-externalize_sessions#Externalize_HTTP_Session_from_JBoss_EAP_6.x_to_JBoss_Data_Grid[via standalone Infinispan/JDG server]:

1. A cache has to be added to the standalone Infinispan/JDG server.

2. The cache from previous item has to be added as a remote store for the respective SAML session cache.

Once remote store is found to be present on SAML session cache during deployment, it is watched for changes
and the local SAML session cache is updated accordingly.
