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 java.lang.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 Summary

Constructors

Constructor and Description
DefaultClusterView(java.lang.String id)

Method Summary

Modifier and Type	Method and Description
void	addInstanceDescription(DefaultInstanceDescription instance) Add the given instance to this cluster and set the cluster on the instance (back pointer)
boolean	equals(java.lang.Object obj)
java.lang.String	getId() Returns a stable id of the cluster represented by this cluster view.
java.util.List<InstanceDescription>	getInstances() Provides the list of InstanceDescriptions with a stable ordering.
InstanceDescription	getLeader() Provides the InstanceDescription belonging to the leader instance.
InstanceDescription	getLocalInstance() Returns the local InstanceDescription or null if no local instance is listed
int	hashCode()
boolean	removeInstanceDescription(InstanceDescription instance) Removes the given instance from this cluster.
java.lang.String	toString()

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

DefaultClusterView

public DefaultClusterView(java.lang.String id)

Method Detail

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

getId

public java.lang.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:

SLING-3164

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 java.util.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:

java.lang.IllegalStateException - if multiple local instances are listed