org.apache.sling.discovery

Interface InstanceDescription

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:

TopologyView

Field Summary

Fields

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

Method Summary

Modifier and Type	Method and 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 Detail

PROPERTY_NAME

static final String PROPERTY_NAME

Property containing a name for the instance. The instance should provide this property.

See Also:

Constant Field Values

PROPERTY_DESCRIPTION

static final String PROPERTY_DESCRIPTION

Property containing a description for the instance. The instance should provide this property.

See Also:

Constant Field Values

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:

Constant Field Values

Method Detail

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.

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

See Also:

DiscoveryService#setProperty(String, String)

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