Package org.apache.sling.discovery

Interface InstanceDescription

All Known Implementing Classes:
DefaultInstanceDescription, NonLocalInstanceDescription
@ProviderType public interface InstanceDescription
An InstanceDescription represents and contains information about an instance that is part of a TopologyView.

Note that all methods are idempotent - they always return the same values on subsequent calls. Rather, on any change new InstanceDescriptions are created.

See Also:

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final String
    PROPERTY_DESCRIPTION
    Property containing a description for the instance.
    static final String
    PROPERTY_ENDPOINTS
    Property containing endpoints to connect to the instance.
    static final String
    PROPERTY_NAME
    Property containing a name for the instance.

  • Method Summary

    Modifier and Type
    Method
    Description
    ClusterView
    getClusterView()
    Returns the ClusterView of which this instance is part of.
    Map<String,String>
    getProperties()
    Returns a Map containing all properties of this instance.
    String
    getProperty(String name)
    Returns the value of a particular property.
    String
    getSlingId()
    The identifier of the running Sling instance.
    boolean
    isLeader()
    If an instance is part of a cluster, it can potentially be a leader of that cluster - this information is queried here.
    boolean
    isLocal()
    Determines whether this InstanceDescription is representing the local instance.

  • Field Details

    • PROPERTY_NAME

      static final String PROPERTY_NAME
      Property containing a name for the instance. The instance should provide this property.
      See Also:

    • PROPERTY_DESCRIPTION

      static final String PROPERTY_DESCRIPTION
      Property containing a description for the instance. The instance should provide this property.
      See Also:

    • PROPERTY_ENDPOINTS

      static final String PROPERTY_ENDPOINTS
      Property containing endpoints to connect to the instance. The value is a comma separated list. The instance should provide this property.
      See Also:

  • Method Details

    • getClusterView

      ClusterView getClusterView()
      Returns the ClusterView of which this instance is part of. Every instance is part of a ClusterView even if it is standalone.
      Returns:
      the ClusterView

    • isLeader

      boolean isLeader()
      If an instance is part of a cluster, it can potentially be a leader of that cluster - this information is queried here. If an instance is not part of a cluster, this method returns true. Only one instance of a cluster is guaranteed to be the leader at any time. This guarantee is provided by this service. If the leader goes down, the service elects a new leader and announces it to TopologyEventListener listeners.
      Returns:
      true if this instance is the - only - leader in this cluster, false if it is one of the slaves, or true if it is not at all part of a cluster

    • isLocal

      boolean isLocal()
      Determines whether this InstanceDescription is representing the local instance.
      Returns:
      whether this InstanceDescription is representing the local instance.

    • getSlingId

      String getSlingId()
      The identifier of the running Sling instance.
      Returns:
      the identifier of this instance

    • getProperty

      String getProperty(String name)
      Returns the value of a particular property. Note that there are no hard guarantees or requirements as to how quickly a property is available once it is set on a distant instance.
      Parameters:
      name - The property name
      Returns:
      The value of the property or null

    • getProperties

      Map<String,String> getProperties()
      Returns a Map containing all properties of this instance. This method always returns a map, it might be empty. The returned map is not modifiable.
      Returns:
      a Map containing all properties of this instance