Listening for Cluster Events

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The interface net.sf.ehcache.cluster.ClusterTopologyListener provides methods for detecting the following cluster events:

public interface ClusterTopologyListener { 
/** 
* A node has joined the cluster 
* 
* @param node The joining node 
*/ 
void nodeJoined(ClusterNode node); 
/** 
* A node has left the cluster 
* 
* @param node The departing node 
*/ 
void nodeLeft(ClusterNode node); 
/** 
* This node has established contact with the cluster and can execute clustered 
* operations. 
* 
* @param node The current node 
*/ 
void clusterOnline(ClusterNode node); 
/** 
* This node has lost contact (possibly temporarily) with the cluster and 
* cannot execute clustered operations 
* 
* @param node The current node 
*/ 
void clusterOffline(ClusterNode node); 
} 
/** 
* This node lost contact and rejoined the cluster again. 
* 
* This event is only fired in the node which rejoined and not to all the 
* connected nodes 
* @param oldNode The old node which got disconnected 
* @param newNode The new node after rejoin 
*/ 
void clusterRejoined(ClusterNode oldNode, ClusterNode newNode);

Example Code

This example prints out the cluster nodes and then registers a ClusterTopologyListener, which prints out events as they happen.

CacheManager mgr = ... 
CacheCluster cluster = mgr.getCluster("TERRACOTTA"); 
  // Get current nodes 
Collection<ClusterNode> nodes = cluster.getNodes(); 
for(ClusterNode node : nodes) { 
  System.out.println(node.getId() + " " + node.getHostname() + " " + node.getIp()); 
} 
  // Register listener 
cluster.addTopologyListener(new ClusterTopologyListener() { 
  public void nodeJoined(ClusterNode node) { System.out.println(node + 
      " joined"); } 
  public void nodeLeft(ClusterNode node) { System.out.println(node + " left"); } 
  public void clusterOnline(ClusterNode node) { System.out.println(node + 
      " enabled"); } 
  public void clusterOffline(ClusterNode node) { System.out.println(node + 
      " disabled"); } 
  public void clusterRejoined(ClusterNode node, ClusterNode newNode) { 
    System.out.println(node + " rejoined the cluster as " + newNode); 
  } 
});