public abstract class BaseTopologyView extends Object implements TopologyView
Constructor and Description |
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BaseTopologyView() |
Modifier and Type | Method and Description |
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InstanceDescription |
getInstance(String slingId)
Simple getter for a particular slingId
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abstract String |
getLocalClusterSyncTokenId()
Returns the id that shall be used in the syncToken
by the ClusterSyncService.
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boolean |
isCurrent()
Checks if this TopologyView is currently valid - or if the
service knows of a topology change just going on (or another
uncertainty about the topology such as IOException etc)
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void |
setNotCurrent()
Marks this view as no longer current - this typically
results in a TOPOLOGY_CHANGING event to be sent.
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String |
toShortString() |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
findInstances, getClusterViews, getInstances, getLocalInstance
public boolean isCurrent()
isCurrent
in interface TopologyView
public void setNotCurrent()
Note that once marked as not current, it can no longer be reverted to current==true
public abstract String getLocalClusterSyncTokenId()
The clusterSyncId uniquely identifies each change of the local cluster for all participating instances. That means, all participating instances know of the clusterSyncId and it is the same for all instances. Whenever an instance joins/leaves the cluster, this clusterSyncId must change.
Since this method returns the *local* clusterSyncId, it doesn't care if a remote cluster experienced changes - it must only change when the local cluster changes. However, it *can* change when a remote cluster changes too. So the requirement is just that it changes *at least* when the local cluster changes - but implementations can opt to regard this rather as a TopologyView-ID too (ie an ID that identifies a particular incarnation of the TopologyView for all participating instances in the whole topology).
This id can further safely be used by the ClusterSyncService to identify a syncToken that it writes and that all other instances in the lcoal cluster wait for, before sending a TOPOLOGY_CHANGED event.
Note that this is obviously not to be confused with the ClusterView.getId() which is stable throughout the lifetime of a cluster.
public String toShortString()
public InstanceDescription getInstance(String slingId)
slingId
- the slingId for which to lookup the InstanceDescriptionCopyright © 2017 The Apache Software Foundation. All rights reserved.