Class SlingIdCleanupTask

  • All Implemented Interfaces:
    Runnable, org.apache.sling.discovery.TopologyEventListener

    public class SlingIdCleanupTask
    extends Object
    implements org.apache.sling.discovery.TopologyEventListener, Runnable
    A background task that cleans up garbage slingIds after topology changes.

    A slingId is considered garbage when:

    • it is not in the current topology
    • was not ever seen in previous topologies by the now leader instance
    • it is not in the current idmap (where clusterNodeIds are reused hence that list stays small and does not need cleanup)
    • its leaderElectionId was created more than 7 days ago (the leaderElectionId is created at activate time of the discovery.oak bundle - hence this more or less corresponds to the startup time of that instance)
    The garbage accumulates at the following places, where it will thus be cleaned up from:
    • as child node under /var/discovery/oak/clusterInstances : this is the most performance critical garbage
    • as a property key in /var/discovery/oak/syncTokens
    The task by default is executed:
    • only on the leader
    • 10min after a TOPOLOGY_INIT or TOPOLOGY_CHANGED event
    • with a maximum number of delete operations to avoid repository overload - that maximum is called batchSize and is 50 by default
    • in subsequent intervals of 10min after the initial run, if that had to stop at the batchSize of 50 deletions
    All parameters mentioned above can be configured.

    Additionally, the cleanup is skipped for 13 hours after a successful cleanup. This is to avoid unnecessary load on the repository. The number of 13 incorporates some heuristics such as : about 2 cleanup rounds per day maximum makes sense, if a leader is very long living, then the 1 additional hour makes it spread somewhat throughout the day. This is to further minimize any load side-effects.

    • Field Detail

      • logger

        protected final org.slf4j.Logger logger
      • scheduler

        protected org.apache.sling.commons.scheduler.Scheduler scheduler
      • resourceResolverFactory

        protected org.apache.sling.api.resource.ResourceResolverFactory resourceResolverFactory
    • Constructor Detail

      • SlingIdCleanupTask

        public SlingIdCleanupTask()
    • Method Detail

      • deactivate

        protected void deactivate()
      • handleTopologyEvent

        public void handleTopologyEvent​(org.apache.sling.discovery.TopologyEvent event)
        Specified by:
        handleTopologyEvent in interface org.apache.sling.discovery.TopologyEventListener
      • run

        public void run()
        Invoked via sling.commons.scheduler triggered from resetCleanupSchedule(). By default should get called at max every 5 minutes until cleanup is done or 10min after a topology change.
        Specified by:
        run in interface Runnable