HDFS-13286. [SBN read] Add haadmin commands to transition between standby and observer. Contributed by Chao Sun.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/FailoverController.java

@@ -129,7 +129,7 @@ private void preFailoverChecks(HAServiceTarget from,
 
     if (!toSvcStatus.getState().equals(HAServiceState.STANDBY)) {
       throw new FailoverFailedException(
-          "Can't failover to an active service");
+          "Can't failover to an " + toSvcStatus.getState() + " service");
     }
     
     if (!toSvcStatus.isReadyToBecomeActive()) {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/HAAdmin.java

@@ -72,6 +72,9 @@ public abstract class HAAdmin extends Configured implements Tool {
         new UsageInfo("[--"+FORCEACTIVE+"] <serviceId>", "Transitions the service into Active state"))
     .put("-transitionToStandby",
         new UsageInfo("<serviceId>", "Transitions the service into Standby state"))
+      .put("-transitionToObserver",
+          new UsageInfo("<serviceId>",
+              "Transitions the service into Observer state"))
     .put("-failover",
         new UsageInfo("[--"+FORCEFENCE+"] [--"+FORCEACTIVE+"] <serviceId> <serviceId>",
             "Failover from the first service to the second.\n" +
@@ -221,6 +224,28 @@ private int transitionToStandby(final CommandLine cmd)
     HAServiceProtocolHelper.transitionToStandby(proto, createReqInfo());
     return 0;
   }
+
+  private int transitionToObserver(final CommandLine cmd)
+      throws IOException, ServiceFailedException {
+    String[] argv = cmd.getArgs();
+    if (argv.length != 1) {
+      errOut.println("transitionToObserver: incorrect number of arguments");
+      printUsage(errOut, "-transitionToObserver");
+      return -1;
+    }
+
+    HAServiceTarget target = resolveTarget(argv[0]);
+    if (!checkSupportObserver(target)) {
+      return -1;
+    }
+    if (!checkManualStateManagementOK(target)) {
+      return -1;
+    }
+    HAServiceProtocol proto = target.getProxy(getConf(), 0);
+    HAServiceProtocolHelper.transitionToObserver(proto, createReqInfo());
+    return 0;
+  }
+
   /**
    * Ensure that we are allowed to manually manage the HA state of the target
    * service. If automatic failover is configured, then the automatic
@@ -249,6 +274,21 @@ private boolean checkManualStateManagementOK(HAServiceTarget target) {
     return true;
   }
 
+  /**
+   * Check if the target supports the Observer state.
+   * @param target the target to check
+   * @return true if the target support Observer state, false otherwise.
+   */
+  private boolean checkSupportObserver(HAServiceTarget target) {
+    if (target.supportObserver()) {
+      return true;
+    } else {
+      errOut.println(
+          "The target " + target + " doesn't support Observer state.");
+      return false;
+    }
+  }
+
   private StateChangeRequestInfo createReqInfo() {
     return new StateChangeRequestInfo(requestSource);
   }
@@ -461,6 +501,8 @@ protected int runCmd(String[] argv) throws Exception {
       return transitionToActive(cmdLine);
     } else if ("-transitionToStandby".equals(cmd)) {
       return transitionToStandby(cmdLine);
+    } else if ("-transitionToObserver".equals(cmd)) {
+      return transitionToObserver(cmdLine);
     } else if ("-failover".equals(cmd)) {
       return failover(cmdLine);
     } else if ("-getServiceState".equals(cmd)) {

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/HAServiceProtocol.java

@@ -51,6 +51,7 @@ public enum HAServiceState {
     INITIALIZING("initializing"),
     ACTIVE("active"),
     STANDBY("standby"),
+    OBSERVER("observer"),
     STOPPING("stopping");
 
     private String name;
@@ -148,6 +149,23 @@ public void transitionToStandby(StateChangeRequestInfo reqInfo)
                                            AccessControlException,
                                            IOException;
 
+  /**
+   * Request service to transition to observer state. No operation, if the
+   * service is already in observer state.
+   *
+   * @throws ServiceFailedException
+   *           if transition from standby to observer fails.
+   * @throws AccessControlException
+   *           if access is denied.
+   * @throws IOException
+   *           if other errors happen
+   */
+  @Idempotent
+  void transitionToObserver(StateChangeRequestInfo reqInfo)
+                              throws ServiceFailedException,
+                                     AccessControlException,
+                                     IOException;
+
   /**
    * Return the current status of the service. The status indicates
    * the current <em>state</em> (e.g ACTIVE/STANDBY) as well as

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/HAServiceProtocolHelper.java

@@ -60,4 +60,13 @@ public static void transitionToStandby(HAServiceProtocol svc,
       throw e.unwrapRemoteException(ServiceFailedException.class);
     }
   }
+
+  public static void transitionToObserver(HAServiceProtocol svc,
+      StateChangeRequestInfo reqInfo) throws IOException {
+    try {
+      svc.transitionToObserver(reqInfo);
+    } catch (RemoteException e) {
+      throw e.unwrapRemoteException(ServiceFailedException.class);
+    }
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/HAServiceTarget.java

@@ -170,4 +170,11 @@ protected void addFencingParameters(Map<String, String> ret) {
   public boolean isAutoFailoverEnabled() {
     return false;
   }
+
+  /**
+   * @return true if this target supports the Observer state, false otherwise.
+   */
+  public boolean supportObserver() {
+    return false;
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/protocolPB/HAServiceProtocolClientSideTranslatorPB.java

@@ -36,6 +36,7 @@
 import org.apache.hadoop.ha.proto.HAServiceProtocolProtos.MonitorHealthRequestProto;
 import org.apache.hadoop.ha.proto.HAServiceProtocolProtos.TransitionToActiveRequestProto;
 import org.apache.hadoop.ha.proto.HAServiceProtocolProtos.TransitionToStandbyRequestProto;
+import org.apache.hadoop.ha.proto.HAServiceProtocolProtos.TransitionToObserverRequestProto;
 import org.apache.hadoop.ipc.ProtobufHelper;
 import org.apache.hadoop.ipc.ProtobufRpcEngine;
 import org.apache.hadoop.ipc.ProtocolTranslator;
@@ -115,6 +116,19 @@ public void transitionToStandby(StateChangeRequestInfo reqInfo) throws IOExcepti
     }
   }
 
+  @Override
+  public void transitionToObserver(StateChangeRequestInfo reqInfo)
+      throws IOException {
+    try {
+      TransitionToObserverRequestProto req =
+          TransitionToObserverRequestProto.newBuilder()
+              .setReqInfo(convert(reqInfo)).build();
+      rpcProxy.transitionToObserver(NULL_CONTROLLER, req);
+    } catch (ServiceException e) {
+      throw ProtobufHelper.getRemoteException(e);
+    }
+  }
+
   @Override
   public HAServiceStatus getServiceStatus() throws IOException {
     GetServiceStatusResponseProto status;
@@ -141,6 +155,8 @@ private HAServiceState convert(HAServiceStateProto state) {
       return HAServiceState.ACTIVE;
     case STANDBY:
       return HAServiceState.STANDBY;
+    case OBSERVER:
+      return HAServiceState.OBSERVER;
     case INITIALIZING:
     default:
       return HAServiceState.INITIALIZING;

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/protocolPB/HAServiceProtocolServerSideTranslatorPB.java

@@ -35,6 +35,8 @@
 import org.apache.hadoop.ha.proto.HAServiceProtocolProtos.TransitionToActiveResponseProto;
 import org.apache.hadoop.ha.proto.HAServiceProtocolProtos.TransitionToStandbyRequestProto;
 import org.apache.hadoop.ha.proto.HAServiceProtocolProtos.TransitionToStandbyResponseProto;
+import org.apache.hadoop.ha.proto.HAServiceProtocolProtos.TransitionToObserverRequestProto;
+import org.apache.hadoop.ha.proto.HAServiceProtocolProtos.TransitionToObserverResponseProto;
 import org.apache.hadoop.ipc.ProtocolSignature;
 import org.apache.hadoop.ipc.RPC;
 
@@ -61,6 +63,9 @@ public class HAServiceProtocolServerSideTranslatorPB implements
       TransitionToActiveResponseProto.newBuilder().build();
   private static final TransitionToStandbyResponseProto TRANSITION_TO_STANDBY_RESP = 
       TransitionToStandbyResponseProto.newBuilder().build();
+  private static final TransitionToObserverResponseProto
+      TRANSITION_TO_OBSERVER_RESP =
+      TransitionToObserverResponseProto.newBuilder().build();
   private static final Logger LOG = LoggerFactory.getLogger(
       HAServiceProtocolServerSideTranslatorPB.class);
   
@@ -123,6 +128,18 @@ public TransitionToStandbyResponseProto transitionToStandby(
     }
   }
 
+  @Override
+  public TransitionToObserverResponseProto transitionToObserver(
+      RpcController controller, TransitionToObserverRequestProto request)
+      throws ServiceException {
+    try {
+      server.transitionToObserver(convert(request.getReqInfo()));
+      return TRANSITION_TO_OBSERVER_RESP;
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
+
   @Override
   public GetServiceStatusResponseProto getServiceStatus(RpcController controller,
       GetServiceStatusRequestProto request) throws ServiceException {
@@ -141,6 +158,9 @@ public GetServiceStatusResponseProto getServiceStatus(RpcController controller,
     case STANDBY:
       retState = HAServiceStateProto.STANDBY;
       break;
+    case OBSERVER:
+      retState = HAServiceStateProto.OBSERVER;
+      break;
     case INITIALIZING:
     default:
       retState = HAServiceStateProto.INITIALIZING;

hadoop-common-project/hadoop-common/src/main/proto/HAServiceProtocol.proto

@@ -32,6 +32,7 @@ enum HAServiceStateProto {
   INITIALIZING = 0;
   ACTIVE = 1;
   STANDBY = 2;
+  OBSERVER = 3;
 }
 
 enum HARequestSource {
@@ -82,6 +83,19 @@ message TransitionToStandbyRequestProto {
 message TransitionToStandbyResponseProto { 
 }
 
+/**
+ * void request
+ */
+message TransitionToObserverRequestProto {
+  required HAStateChangeRequestInfoProto reqInfo = 1;
+}
+
+/**
+ * void response
+ */
+message TransitionToObserverResponseProto {
+}
+
 /**
  * void request
  */
@@ -126,6 +140,12 @@ service HAServiceProtocolService {
   rpc transitionToStandby(TransitionToStandbyRequestProto)
       returns(TransitionToStandbyResponseProto);
 
+  /**
+   * Request service to transition to observer state.
+   */
+  rpc transitionToObserver(TransitionToObserverRequestProto)
+      returns(TransitionToObserverResponseProto);
+
   /**
    * Get the current status of the service.
    */

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/ha/DummyHAService.java

@@ -56,7 +56,8 @@ class DummyHAService extends HAServiceTarget {
   InetSocketAddress address, healthMonitorAddress;
   boolean isHealthy = true;
   boolean actUnreachable = false;
-  boolean failToBecomeActive, failToBecomeStandby, failToFence;
+  boolean failToBecomeActive, failToBecomeStandby, failToBecomeObserver,
+      failToFence;
   
   DummySharedResource sharedResource;
   public int fenceCount = 0;
@@ -216,6 +217,11 @@ public boolean isAutoFailoverEnabled() {
     return true;
   }
 
+  @Override
+  public boolean supportObserver() {
+    return true;
+  }
+
   @Override
   public String toString() {
     return "DummyHAService #" + index;
@@ -263,6 +269,16 @@ public void transitionToStandby(StateChangeRequestInfo req) throws ServiceFailed
       state = HAServiceState.STANDBY;
     }
     
+    @Override
+    public void transitionToObserver(StateChangeRequestInfo req)
+        throws ServiceFailedException, AccessControlException, IOException {
+      checkUnreachable();
+      if (failToBecomeObserver) {
+        throw new ServiceFailedException("injected failure");
+      }
+      state = HAServiceState.OBSERVER;
+    }
+
     @Override
     public HAServiceStatus getServiceStatus() throws IOException {
       checkUnreachable();

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/ha/MiniZKFCCluster.java

@@ -187,6 +187,10 @@ public void setUnreachable(int idx, boolean unreachable) {
     svcs.get(idx).actUnreachable = unreachable;
   }
 
+  public void setFailToBecomeObserver(int idx, boolean doFail) {
+    svcs.get(idx).failToBecomeObserver = doFail;
+  }
+
   /**
    * Wait for the given HA service to enter the given HA state.
    * This is based on the state of ZKFC, not the state of HA service.

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/resolver/FederationNamenodeServiceState.java

@@ -35,6 +35,9 @@ public static FederationNamenodeServiceState getState(HAServiceState state) {
     case ACTIVE:
       return FederationNamenodeServiceState.ACTIVE;
     case STANDBY:
+    // TODO: we should probably have a separate state OBSERVER for RBF and
+    // treat it differently.
+    case OBSERVER:
       return FederationNamenodeServiceState.STANDBY;
     case INITIALIZING:
       return FederationNamenodeServiceState.UNAVAILABLE;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/PBHelper.java

@@ -779,6 +779,8 @@ public static HAServiceState convert(NNHAStatusHeartbeatProto.State s) {
       return HAServiceState.ACTIVE;
     case STANDBY:
       return HAServiceState.STANDBY;
+    case OBSERVER:
+      return HAServiceState.OBSERVER;
     default:
       throw new IllegalArgumentException("Unexpected HAServiceStateProto:"
           + s);
@@ -794,6 +796,8 @@ public static NNHAStatusHeartbeatProto.State convert(HAServiceState s) {
       return NNHAStatusHeartbeatProto.State.ACTIVE;
     case STANDBY:
       return NNHAStatusHeartbeatProto.State.STANDBY;
+    case OBSERVER:
+      return NNHAStatusHeartbeatProto.State.OBSERVER;
     default:
       throw new IllegalArgumentException("Unexpected HAServiceState:"
           + s);

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java

@@ -928,7 +928,7 @@ void reRegister() throws IOException {
       scheduler.scheduleHeartbeat();
       // HDFS-9917,Standby NN IBR can be very huge if standby namenode is down
       // for sometime.
-      if (state == HAServiceState.STANDBY) {
+      if (state == HAServiceState.STANDBY || state == HAServiceState.OBSERVER) {
         ibrManager.clearIBRs();
       }
     }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java

@@ -1733,7 +1733,8 @@ public boolean isInStandbyState() {
       return haEnabled;
     }
 
-    return HAServiceState.STANDBY == haContext.getState().getServiceState();
+    return HAServiceState.STANDBY == haContext.getState().getServiceState() ||
+        HAServiceState.OBSERVER == haContext.getState().getServiceState();
   }
 
   /**

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java

@@ -1800,27 +1800,37 @@ synchronized void transitionToActive()
       throw new ServiceFailedException("HA for namenode is not enabled");
     }
     if (state == OBSERVER_STATE) {
-      // TODO: we may need to remove this when enabling failover for observer
       throw new ServiceFailedException(
-          "Cannot transition from Observer to Active");
+          "Cannot transition from '" + OBSERVER_STATE + "' to '" +
+              ACTIVE_STATE + "'");
     }
     state.setState(haContext, ACTIVE_STATE);
   }
-  
+
-  synchronized void transitionToStandby() 
+  synchronized void transitionToStandby()
       throws ServiceFailedException, AccessControlException {
     namesystem.checkSuperuserPrivilege();
     if (!haEnabled) {
       throw new ServiceFailedException("HA for namenode is not enabled");
     }
-    if (state == OBSERVER_STATE) {
-      // TODO: we may need to remove this when enabling failover for observer
-      throw new ServiceFailedException(
-          "Cannot transition from Observer to Standby");
-    }
     state.setState(haContext, STANDBY_STATE);
   }
 
+  synchronized void transitionToObserver()
+      throws ServiceFailedException, AccessControlException {
+    namesystem.checkSuperuserPrivilege();
+    if (!haEnabled) {
+      throw new ServiceFailedException("HA for namenode is not enabled");
+    }
+    // Transition from ACTIVE to OBSERVER is forbidden.
+    if (state == ACTIVE_STATE) {
+      throw new ServiceFailedException(
+          "Cannot transition from '" + ACTIVE_STATE + "' to '" +
+              OBSERVER_STATE + "'");
+    }
+    state.setState(haContext, OBSERVER_STATE);
+  }
+
   synchronized HAServiceStatus getServiceStatus()
       throws ServiceFailedException, AccessControlException {
     if (!haEnabled) {
@@ -1872,7 +1882,6 @@ public String getNNRole() {
 
   @Override // NameNodeStatusMXBean
   public String getState() {
-    // TODO: maybe we should return a different result for observer namenode?
     String servStateStr = "";
     HAServiceState servState = getServiceState();
     if (null != servState) {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java

@@ -1765,6 +1765,14 @@ public synchronized void transitionToStandby(StateChangeRequestInfo req)
     nn.transitionToStandby();
   }
 
+  @Override // HAServiceProtocol
+  public synchronized void transitionToObserver(StateChangeRequestInfo req)
+      throws ServiceFailedException, AccessControlException, IOException {
+    checkNNStartup();
+    nn.checkHaStateChange(req);
+    nn.transitionToObserver();
+  }
+
   @Override // HAServiceProtocol
   public synchronized HAServiceStatus getServiceStatus() 
       throws AccessControlException, ServiceFailedException, IOException {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/StandbyState.java

@@ -39,6 +39,7 @@
  */
 @InterfaceAudience.Private
 public class StandbyState extends HAState {
+  // TODO: consider implementing a ObserverState instead of using the flag.
   private final boolean isObserver;
 
   public StandbyState() {
@@ -46,21 +47,18 @@ public StandbyState() {
   }
 
   public StandbyState(boolean isObserver) {
-    super(HAServiceState.STANDBY);
+    super(isObserver ? HAServiceState.OBSERVER : HAServiceState.STANDBY);
     this.isObserver = isObserver;
   }
 
   @Override
   public void setState(HAContext context, HAState s) throws ServiceFailedException {
-    if (s == NameNode.ACTIVE_STATE) {
+    if (s == NameNode.ACTIVE_STATE ||
+        (!isObserver && s == NameNode.OBSERVER_STATE) ||
+        (isObserver && s == NameNode.STANDBY_STATE)) {
       setStateInternal(context, s);
       return;
     }
-    if (isObserver && s == NameNode.STANDBY_STATE) {
-      // To guard against the exception in the following super call.
-      // The other case, standby -> observer, should not happen.
-      return;
-    }
     super.setState(context, s);
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/NNHAServiceTarget.java

@@ -186,4 +186,9 @@ protected void addFencingParameters(Map<String, String> ret) {
   public boolean isAutoFailoverEnabled() {
     return autoFailoverEnabled;
   }
+
+  @Override
+  public boolean supportObserver() {
+    return true;
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/proto/HdfsServer.proto

@@ -212,6 +212,7 @@ message NNHAStatusHeartbeatProto {
   enum State {
     ACTIVE = 0;
     STANDBY = 1;
+    OBSERVER = 2;
   }
   required State state = 1;
   required uint64 txid = 2;

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/tools/TestDFSHAAdmin.java

@@ -275,6 +275,12 @@ public void testTransitionToStandby() throws Exception {
     Mockito.verify(mockProtocol).transitionToStandby(anyReqInfo());
   }
 
+  @Test
+  public void testTransitionToObserver() throws Exception {
+    assertEquals(0, runTool("-transitionToObserver", "nn1"));
+    Mockito.verify(mockProtocol).transitionToObserver(anyReqInfo());
+  }
+
   @Test
   public void testFailoverWithNoFencerConfigured() throws Exception {
     Mockito.doReturn(STANDBY_READY_RESULT).when(mockProtocol).getServiceStatus();

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/tools/TestDFSHAAdminMiniCluster.java

@@ -116,6 +116,50 @@ public void testStateTransition() throws Exception {
     assertFalse(nnode2.isStandbyState());
     assertEquals(0, runTool("-transitionToStandby", "nn2"));
     assertTrue(nnode2.isStandbyState());
+    assertEquals(0, runTool("-transitionToObserver", "nn2"));
+    assertFalse(nnode2.isStandbyState());
+    assertTrue(nnode2.isObserverState());
+  }
+
+  @Test
+  public void testObserverTransition() throws Exception {
+    NameNode nnode1 = cluster.getNameNode(0);
+    assertTrue(nnode1.isStandbyState());
+
+    // Should be able to transition from STANDBY to OBSERVER
+    assertEquals(0, runTool("-transitionToObserver", "nn1"));
+    assertFalse(nnode1.isStandbyState());
+    assertTrue(nnode1.isObserverState());
+
+    // Transition from Observer to Observer should be no-op
+    assertEquals(0, runTool("-transitionToObserver", "nn1"));
+    assertTrue(nnode1.isObserverState());
+
+    // Should also be able to transition back from OBSERVER to STANDBY
+    assertEquals(0, runTool("-transitionToStandby", "nn1"));
+    assertTrue(nnode1.isStandbyState());
+    assertFalse(nnode1.isObserverState());
+  }
+
+  @Test
+  public void testObserverIllegalTransition() throws Exception {
+    NameNode nnode1 = cluster.getNameNode(0);
+    assertTrue(nnode1.isStandbyState());
+    assertEquals(0, runTool("-transitionToActive", "nn1"));
+    assertFalse(nnode1.isStandbyState());
+    assertTrue(nnode1.isActiveState());
+
+    // Should NOT be able to transition from ACTIVE to OBSERVER
+    assertEquals(-1, runTool("-transitionToObserver", "nn1"));
+    assertTrue(nnode1.isActiveState());
+
+    // Should NOT be able to transition from OBSERVER to ACTIVE
+    assertEquals(0, runTool("-transitionToStandby", "nn1"));
+    assertTrue(nnode1.isStandbyState());
+    assertEquals(0, runTool("-transitionToObserver", "nn1"));
+    assertTrue(nnode1.isObserverState());
+    assertEquals(-1, runTool("-transitionToActive", "nn1"));
+    assertFalse(nnode1.isActiveState());
   }
   
   @Test

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/AdminService.java

@@ -362,6 +362,13 @@ public synchronized void transitionToStandby(
     }
   }
 
+  @Override
+  public synchronized void transitionToObserver(
+      StateChangeRequestInfo reqInfo) throws IOException {
+    // Should NOT get here, as RMHAServiceTarget doesn't support observer.
+    throw new ServiceFailedException("Does not support transition to Observer");
+  }
+
   /**
    * Return the HA status of this RM. This includes the current state and
    * whether the RM is ready to become active.