Package org.apache.sling.discovery.commons.providers

Class DefaultClusterView

java.lang.Object
org.apache.sling.discovery.commons.providers.DefaultClusterView
All Implemented Interfaces:
ClusterView
Direct Known Subclasses:
LocalClusterView
public class DefaultClusterView extends Object implements ClusterView
Default implementation of the ClusterView interface.

Besides implementing the interface methods it also adds add/remove of InstanceDescriptions as well as implementing equals and hashCode.

  • Constructor Details

    • DefaultClusterView

      public DefaultClusterView(String id)

  • Method Details

    • equals

      public boolean equals(Object obj)
      Overrides:
      equals in class Object

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • getId

      public String getId()
      Description copied from interface: ClusterView
      Returns a stable id of the cluster represented by this cluster view.

      Similar to the SlingID, this id is persisted and thus remains stable accross instance/cluster restarts.

      When an instance joins a cluster, it will inherit the id from the joined cluster (thus incurs a cluster id change).

      Note: When instances part from a cluster (eg due to a network partitioning) the cluster id is retained. This results in potentially multiple clusters with the same id. This fact could be used to detect such partitioning/split brain situations. It also implies though that the cluster id is not guaranteed to be unique in a topology!

      Addition in 1.0.4: this id must consist only of alphanumeric characters plus dash '-' and underscore '_'.

      Specified by:
      getId in interface ClusterView
      Returns:
      an id of this cluster view
      See Also:

    • addInstanceDescription

      public void addInstanceDescription(DefaultInstanceDescription instance)
      Add the given instance to this cluster and set the cluster on the instance (back pointer)
      Parameters:
      instance - the instance to add to this cluster

    • getInstances

      public List<InstanceDescription> getInstances()
      Description copied from interface: ClusterView
      Provides the list of InstanceDescriptions with a stable ordering.

      Stable ordering implies that unless an instance leaves the cluster (due to shutdown/crash/network problems) the instance keeps the relative position in the list.

      Specified by:
      getInstances in interface ClusterView
      Returns:
      the list of InstanceDescriptions (with a stable ordering)

    • getLeader

      public InstanceDescription getLeader()
      Description copied from interface: ClusterView
      Provides the InstanceDescription belonging to the leader instance.

      Every ClusterView is guaranteed to have one and only one leader.

      The leader is stable: once a leader is elected it stays leader unless it leaves the cluster (due to shutdown/crash/network problems)

      Specified by:
      getLeader in interface ClusterView
      Returns:
      the InstanceDescription belonging to the leader instance

    • removeInstanceDescription

      public boolean removeInstanceDescription(InstanceDescription instance)
      Removes the given instance from this cluster.

      Note that the instance will still have a pointer to this cluster however.

      Parameters:
      instance - the instance to remove from this cluster

    • getLocalInstance

      public InstanceDescription getLocalInstance()
      Returns the local InstanceDescription or null if no local instance is listed
      Returns:
      the local InstanceDescription or null if no local instance is listed
      Throws:
      IllegalStateException - if multiple local instances are listed