[keycloak-dev] Concurrent sync in cluster

We had a bug https://issues.jboss.org/browse/KEYCLOAK-2412 that there are errors when sync of users from federationProvider is triggered concurrently in more cluster nodes. This affects periodic sync as well. To avoid concurrent executions of same task, I've added ClusterProvider. This is based on infinispan and it provides some locking functionality to ensures that sync from federation can be executed just by one cluster node at a time. Even on single node (non-cluster setup), now you can't trigger sync multiple times concurrently. So for example if there is periodic sync in progress and you click in admin console on "Sync users", the sync won't happen. The same mechanism is now also used for scheduled tasks (Removing expired user sessions and expired events). Nobody reported any bug yet, however when removing of expired events/sessions is triggered concurrently by more cluster nodes, it can be issue too. So this is now avoided. Maybe we can improve even more and ensure that just cluster coordinator will run scheduled tasks and other nodes will just ignore them? ClusterProvider also adds possibility to register ClusterListener with any task, that should be executed once notification from any cluster node comes. This allows that when some federation provider is created/updated/removed, then all nodes are aware of the change and will immediately change (or remove) scheduled timer. PR is here https://github.com/keycloak/keycloak/pull/2234 Marek