keycloak-scim/docs/documentation/upgrading/topics/changes/changes-26_0_0.adoc

= Infinispan marshalling changes

Marshalling is the process of converting Java objects into bytes to send them across the network between {project_name} servers.
With {project_name} 26, the marshalling library has changed from JBoss Marshalling to Infinispan Protostream.
The libraries are not compatible between each other and, it requires some steps to ensure the session data is not lost.

WARNING: JBoss Marshalling and Infinispan Protostream are not compatible with each other and incorrect usage may lead to data loss.
Consequently, all caches are cleared when upgrading to this version.

To prevent losing user sessions upgrade to Keycloak 25 first and enable the persistent sessions feature as outlined in the migration guide for {project_name} 25.

= New method in `ClusterProvider` API

The following method was added to `org.keycloak.cluster.ClusterProvider`:

* `void notify(String taskKey, Collection<? extends ClusterEvent> events, boolean ignoreSender, DCNotify dcNotify)`

When multiple events are sent to the same `taskKey`, this method batches events and just perform a single network call.
This is an optimization to reduce traffic and network related resources.

In {project_name} 26, the new method has a default implementation to keep backward compatibility with custom implementation.
The default implementation performs a single network call per an event, and it will be removed in a future version of {project_name}.