Remove `discovery.zen.rejoin_on_master_gone`

That setting was built as an escape hatch for the work done in 1.4. I never heard it being used once. We can safely remove it.

Closes #16353

core/src/main/java/org/elasticsearch/common/settings/ClusterSettings.java

@@ -58,7 +58,6 @@ import org.elasticsearch.env.NodeEnvironment;
 import org.elasticsearch.gateway.GatewayService;
 import org.elasticsearch.gateway.PrimaryShardAllocator;
 import org.elasticsearch.http.HttpTransportSettings;
-import org.elasticsearch.http.netty.NettyHttpServerTransport;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.store.IndexStoreConfig;
 import org.elasticsearch.indices.analysis.HunspellService;
@@ -160,7 +159,6 @@ public final class ClusterSettings extends AbstractScopedSettings {
         ConcurrentRebalanceAllocationDecider.CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_REBALANCE_SETTING,
         EnableAllocationDecider.CLUSTER_ROUTING_ALLOCATION_ENABLE_SETTING,
         EnableAllocationDecider.CLUSTER_ROUTING_REBALANCE_ENABLE_SETTING,
-        ZenDiscovery.REJOIN_ON_MASTER_GONE_SETTING,
         FilterAllocationDecider.CLUSTER_ROUTING_INCLUDE_GROUP_SETTING,
         FilterAllocationDecider.CLUSTER_ROUTING_EXCLUDE_GROUP_SETTING,
         FilterAllocationDecider.CLUSTER_ROUTING_REQUIRE_GROUP_SETTING,

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

@@ -89,17 +89,16 @@ import static org.elasticsearch.common.unit.TimeValue.timeValueSeconds;
  */
 public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implements Discovery, PingContextProvider {
 
-    public final static Setting<Boolean> REJOIN_ON_MASTER_GONE_SETTING = Setting.boolSetting("discovery.zen.rejoin_on_master_gone", true, true, Setting.Scope.CLUSTER);
     public final static Setting<TimeValue> PING_TIMEOUT_SETTING = Setting.positiveTimeSetting("discovery.zen.ping_timeout", timeValueSeconds(3), false, Setting.Scope.CLUSTER);
     public final static Setting<TimeValue> JOIN_TIMEOUT_SETTING = Setting.timeSetting("discovery.zen.join_timeout",
-        settings -> TimeValue.timeValueMillis(PING_TIMEOUT_SETTING.get(settings).millis() * 20).toString(), TimeValue.timeValueMillis(0), false, Setting.Scope.CLUSTER);
+            settings -> TimeValue.timeValueMillis(PING_TIMEOUT_SETTING.get(settings).millis() * 20).toString(), TimeValue.timeValueMillis(0), false, Setting.Scope.CLUSTER);
     public final static Setting<Integer> JOIN_RETRY_ATTEMPTS_SETTING = Setting.intSetting("discovery.zen.join_retry_attempts", 3, 1, false, Setting.Scope.CLUSTER);
     public final static Setting<TimeValue> JOIN_RETRY_DELAY_SETTING = Setting.positiveTimeSetting("discovery.zen.join_retry_delay", TimeValue.timeValueMillis(100), false, Setting.Scope.CLUSTER);
     public final static Setting<Integer> MAX_PINGS_FROM_ANOTHER_MASTER_SETTING = Setting.intSetting("discovery.zen.max_pings_from_another_master", 3, 1, false, Setting.Scope.CLUSTER);
     public final static Setting<Boolean> SEND_LEAVE_REQUEST_SETTING = Setting.boolSetting("discovery.zen.send_leave_request", true, false, Setting.Scope.CLUSTER);
     public final static Setting<Boolean> MASTER_ELECTION_FILTER_CLIENT_SETTING = Setting.boolSetting("discovery.zen.master_election.filter_client", true, false, Setting.Scope.CLUSTER);
     public final static Setting<TimeValue> MASTER_ELECTION_WAIT_FOR_JOINS_TIMEOUT_SETTING = Setting.timeSetting("discovery.zen.master_election.wait_for_joins_timeout",
-        settings -> TimeValue.timeValueMillis(JOIN_TIMEOUT_SETTING.get(settings).millis() / 2).toString(), TimeValue.timeValueMillis(0), false, Setting.Scope.CLUSTER);
+            settings -> TimeValue.timeValueMillis(JOIN_TIMEOUT_SETTING.get(settings).millis() / 2).toString(), TimeValue.timeValueMillis(0), false, Setting.Scope.CLUSTER);
     public final static Setting<Boolean> MASTER_ELECTION_FILTER_DATA_SETTING = Setting.boolSetting("discovery.zen.master_election.filter_data", false, false, Setting.Scope.CLUSTER);
 
     public static final String DISCOVERY_REJOIN_ACTION_NAME = "internal:discovery/zen/rejoin";
@@ -142,8 +141,6 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
 
     private final AtomicBoolean initialStateSent = new AtomicBoolean();
 
-    private volatile boolean rejoinOnMasterGone;
-
     /** counts the time this node has joined the cluster or have elected it self as master */
     private final AtomicLong clusterJoinsCounter = new AtomicLong();
 
@@ -177,7 +174,6 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
         this.masterElectionFilterClientNodes = MASTER_ELECTION_FILTER_CLIENT_SETTING.get(settings);
         this.masterElectionFilterDataNodes = MASTER_ELECTION_FILTER_DATA_SETTING.get(settings);
         this.masterElectionWaitForJoinsTimeout = MASTER_ELECTION_WAIT_FOR_JOINS_TIMEOUT_SETTING.get(settings);
-        this.rejoinOnMasterGone = REJOIN_ON_MASTER_GONE_SETTING.get(settings);
 
         logger.debug("using ping_timeout [{}], join.timeout [{}], master_election.filter_client [{}], master_election.filter_data [{}]", this.pingTimeout, joinTimeout, masterElectionFilterClientNodes, masterElectionFilterDataNodes);
 
@@ -188,7 +184,6 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
                 throw new IllegalArgumentException("cannot set " + ElectMasterService.DISCOVERY_ZEN_MINIMUM_MASTER_NODES_SETTING.getKey() + " to more than the current master nodes count [" + masterNodes + "]");
             }
         });
-        clusterSettings.addSettingsUpdateConsumer(REJOIN_ON_MASTER_GONE_SETTING, this::setRejoingOnMasterGone);
 
         this.masterFD = new MasterFaultDetection(settings, threadPool, transportService, clusterName, clusterService);
         this.masterFD.addListener(new MasterNodeFailureListener());
@@ -323,10 +318,6 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
         return clusterJoinsCounter.get() > 0;
     }
 
-    private void setRejoingOnMasterGone(boolean rejoin) {
-        this.rejoinOnMasterGone = rejoin;
-    }
-
     /** end of {@link org.elasticsearch.discovery.zen.ping.PingContextProvider } implementation */
 
 
@@ -670,35 +661,7 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
                 // flush any pending cluster states from old master, so it will not be set as master again
                 publishClusterState.pendingStatesQueue().failAllStatesAndClear(new ElasticsearchException("master left [{}]", reason));
 
-                if (rejoinOnMasterGone) {
+                return rejoin(ClusterState.builder(currentState).nodes(discoveryNodes).build(), "master left (reason = " + reason + ")");
-                    return rejoin(ClusterState.builder(currentState).nodes(discoveryNodes).build(), "master left (reason = " + reason + ")");
-                }
-
-                if (!electMaster.hasEnoughMasterNodes(discoveryNodes)) {
-                    return rejoin(ClusterState.builder(currentState).nodes(discoveryNodes).build(), "not enough master nodes after master left (reason = " + reason + ")");
-                }
-
-                final DiscoveryNode electedMaster = electMaster.electMaster(discoveryNodes); // elect master
-                final DiscoveryNode localNode = currentState.nodes().localNode();
-                if (localNode.equals(electedMaster)) {
-                    masterFD.stop("got elected as new master since master left (reason = " + reason + ")");
-                    discoveryNodes = DiscoveryNodes.builder(discoveryNodes).masterNodeId(localNode.id()).build();
-                    ClusterState newState = ClusterState.builder(currentState).nodes(discoveryNodes).build();
-                    nodesFD.updateNodesAndPing(newState);
-                    return newState;
-
-                } else {
-                    nodesFD.stop();
-                    if (electedMaster != null) {
-                        discoveryNodes = DiscoveryNodes.builder(discoveryNodes).masterNodeId(electedMaster.id()).build();
-                        masterFD.restart(electedMaster, "possible elected master since master left (reason = " + reason + ")");
-                        return ClusterState.builder(currentState)
-                                .nodes(discoveryNodes)
-                                .build();
-                    } else {
-                        return rejoin(ClusterState.builder(currentState).nodes(discoveryNodes).build(), "master_left and no other node elected to become master");
-                    }
-                }
             }
 
             @Override
@@ -857,7 +820,7 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
             // Sanity check: maybe we don't end up here, because serialization may have failed.
             if (node.getVersion().before(minimumNodeJoinVersion)) {
                 callback.onFailure(
-                    new IllegalStateException("Can't handle join request from a node with a version [" + node.getVersion() + "] that is lower than the minimum compatible version [" + minimumNodeJoinVersion.minimumCompatibilityVersion() + "]")
+                        new IllegalStateException("Can't handle join request from a node with a version [" + node.getVersion() + "] that is lower than the minimum compatible version [" + minimumNodeJoinVersion.minimumCompatibilityVersion() + "]")
                 );
                 return;
             }
@@ -1109,10 +1072,6 @@ public class ZenDiscovery extends AbstractLifecycleComponent<Discovery> implemen
         }
     }
 
-    boolean isRejoinOnMasterGone() {
-        return rejoinOnMasterGone;
-    }
-
     public static class RejoinClusterRequest extends TransportRequest {
 
         private String fromNodeId;

core/src/test/java/org/elasticsearch/discovery/zen/ZenDiscoveryIT.java

@@ -80,20 +80,6 @@ import static org.hamcrest.Matchers.sameInstance;
 @ESIntegTestCase.SuppressLocalMode
 @TestLogging("_root:DEBUG")
 public class ZenDiscoveryIT extends ESIntegTestCase {
-    public void testChangeRejoinOnMasterOptionIsDynamic() throws Exception {
-        Settings nodeSettings = Settings.settingsBuilder()
-                .put("discovery.type", "zen") // <-- To override the local setting if set externally
-                .build();
-        String nodeName = internalCluster().startNode(nodeSettings);
-        ZenDiscovery zenDiscovery = (ZenDiscovery) internalCluster().getInstance(Discovery.class, nodeName);
-        assertThat(zenDiscovery.isRejoinOnMasterGone(), is(true));
-
-        client().admin().cluster().prepareUpdateSettings()
-                .setTransientSettings(Settings.builder().put(ZenDiscovery.REJOIN_ON_MASTER_GONE_SETTING.getKey(), false))
-                .get();
-
-        assertThat(zenDiscovery.isRejoinOnMasterGone(), is(false));
-    }
 
     public void testNoShardRelocationsOccurWhenElectedMasterNodeFails() throws Exception {
         Settings defaultSettings = Settings.builder()