Zen Discovery: Control which nodes are allowed to become masters, closes #248.

modules/elasticsearch/src/main/java/org/elasticsearch/discovery/zen/ZenDiscovery.java

@@ -22,6 +22,9 @@ package org.elasticsearch.discovery.zen;
 import org.elasticsearch.ElasticSearchException;
 import org.elasticsearch.ElasticSearchIllegalStateException;
 import org.elasticsearch.cluster.*;
+import org.elasticsearch.cluster.block.ClusterBlock;
+import org.elasticsearch.cluster.block.ClusterBlockLevel;
+import org.elasticsearch.cluster.block.ClusterBlocks;
 import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.node.DiscoveryNodes;
 import org.elasticsearch.common.UUID;
@@ -58,6 +61,8 @@ import static org.elasticsearch.common.unit.TimeValue.*;
  */
 public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implements Discovery, DiscoveryNodesProvider {
 
+    public final ClusterBlock NO_MASTER_BLOCK = new ClusterBlock(2, "no master", ClusterBlockLevel.ALL);
+
     private final ThreadPool threadPool;
 
     private final TransportService transportService;
@@ -82,6 +87,8 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
     // a flag that should be used only for testing
     private final boolean sendLeaveRequest;
 
+    private final boolean blockClusterOnNoMaster;
+
     private final ElectMasterService electMaster;
 
 
@@ -107,6 +114,7 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
 
         this.initialPingTimeout = componentSettings.getAsTime("initial_ping_timeout", timeValueSeconds(3));
         this.sendLeaveRequest = componentSettings.getAsBoolean("send_leave_request", true);
+        this.blockClusterOnNoMaster = componentSettings.getAsBoolean("block_on_no_master", true);
 
         logger.debug("using initial_ping_timeout [{}]", initialPingTimeout);
 
@@ -232,7 +240,7 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
             if (localNode.equals(masterNode)) {
                 this.master = true;
                 nodesFD.start(); // start the nodes FD
-                clusterService.submitStateUpdateTask("zen-disco-initial_connect(master)", new ProcessedClusterStateUpdateTask() {
+                clusterService.submitStateUpdateTask("zen-disco-join (elected_as_master)", new ProcessedClusterStateUpdateTask() {
                     @Override public ClusterState execute(ClusterState currentState) {
                         DiscoveryNodes.Builder builder = new DiscoveryNodes.Builder()
                                 .localNodeId(localNode.id())
@@ -241,7 +249,8 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
                                 .put(localNode);
                         // update the fact that we are the master...
                         latestDiscoNodes = builder.build();
-                        return newClusterStateBuilder().state(currentState).nodes(builder).build();
+                        ClusterBlocks clusterBlocks = ClusterBlocks.builder().blocks(currentState.blocks()).removeGlobalBlock(NO_MASTER_BLOCK).build();
+                        return newClusterStateBuilder().state(currentState).nodes(builder).blocks(clusterBlocks).build();
                     }
 
                     @Override public void clusterStateProcessed(ClusterState clusterState) {
@@ -274,8 +283,17 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
                     retry = true;
                     continue;
                 }
-                // cool, we found a master, start an FD on it
                 masterFD.start(masterNode, "initial_join");
+                clusterService.submitStateUpdateTask("zen-disco-join (detected master)", new ProcessedClusterStateUpdateTask() {
+                    @Override public ClusterState execute(ClusterState currentState) {
+                        ClusterBlocks clusterBlocks = ClusterBlocks.builder().blocks(currentState.blocks()).removeGlobalBlock(NO_MASTER_BLOCK).build();
+                        return newClusterStateBuilder().state(currentState).blocks(clusterBlocks).build();
+                    }
+
+                    @Override public void clusterStateProcessed(ClusterState clusterState) {
+                        sendInitialStateEventIfNeeded();
+                    }
+                });
             }
         }
     }
@@ -323,6 +341,7 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
                     return currentState;
                 }
 
+                ClusterBlocks clusterBlocks = currentState.blocks();
                 List<DiscoveryNode> nodes = newArrayList(currentState.nodes().nodes().values());
                 nodes.remove(masterNode); // remove the master node from the list, it has failed
                 final DiscoveryNode electedMaster = electMaster.electMaster(nodes); // elect master
@@ -346,6 +365,7 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
                         masterFD.restart(electedMaster, "possible elected master since master left (reason = " + reason + ")");
                     } else {
                         builder.masterNodeId(null);
+                        clusterBlocks = ClusterBlocks.builder().blocks(clusterBlocks).addGlobalBlock(NO_MASTER_BLOCK).build();
                         masterFD.stop("no master elected since master left (reason = " + reason + ")");
                         // try and join the cluster again...
                         threadPool.execute(new Runnable() {
@@ -355,7 +375,7 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
                         });
                     }
                     latestDiscoNodes = builder.build();
-                    return newClusterStateBuilder().state(currentState).nodes(latestDiscoNodes).build();
+                    return newClusterStateBuilder().state(currentState).blocks(clusterBlocks).nodes(latestDiscoNodes).build();
                 }
             }