HDFS-9311. Support optional offload of NameNode HA service health checks to a separate RPC server. Contributed by Chris Nauroth.

(cherry picked from commit bf8e452982)

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

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

@@ -49,6 +49,23 @@ public abstract class HAServiceTarget {
    */
   public abstract InetSocketAddress getAddress();
 
+  /**
+   * Returns an optional separate RPC server address for health checks at the
+   * target node.  If defined, then this address is used by the health monitor
+   * for the {@link HAServiceProtocol#monitorHealth()} and
+   * {@link HAServiceProtocol#getServiceStatus()} calls.  This can be useful for
+   * separating out these calls onto separate RPC handlers to protect against
+   * resource exhaustion in the main RPC handler pool.  If null (which is the
+   * default implementation), then all RPC calls go to the address defined by
+   * {@link #getAddress()}.
+   *
+   * @return IPC address of the lifeline RPC server on the target node, or null
+   *     if no lifeline RPC server is used
+   */
+  public InetSocketAddress getHealthMonitorAddress() {
+    return null;
+  }
+
   /**
    * @return the IPC address of the ZKFC on the target node
    */
@@ -73,12 +90,39 @@ public abstract class HAServiceTarget {
    */
   public HAServiceProtocol getProxy(Configuration conf, int timeoutMs)
       throws IOException {
+    return getProxyForAddress(conf, timeoutMs, getAddress());
+  }
+
+  /**
+   * Returns a proxy to connect to the target HA service for health monitoring.
+   * If {@link #getHealthMonitorAddress()} is implemented to return a non-null
+   * address, then this proxy will connect to that address.  Otherwise, the
+   * returned proxy defaults to using {@link #getAddress()}, which means this
+   * method's behavior is identical to {@link #getProxy(Configuration, int)}.
+   *
+   * @param conf Configuration
+   * @param timeoutMs timeout in milliseconds
+   * @return a proxy to connect to the target HA service for health monitoring
+   * @throws IOException if there is an error
+   */
+  public HAServiceProtocol getHealthMonitorProxy(Configuration conf,
+      int timeoutMs) throws IOException {
+    InetSocketAddress addr = getHealthMonitorAddress();
+    if (addr == null) {
+      addr = getAddress();
+    }
+    return getProxyForAddress(conf, timeoutMs, addr);
+  }
+
+  private HAServiceProtocol getProxyForAddress(Configuration conf,
+      int timeoutMs, InetSocketAddress addr) throws IOException {
     Configuration confCopy = new Configuration(conf);
     // Lower the timeout so we quickly fail to connect
-    confCopy.setInt(CommonConfigurationKeysPublic.IPC_CLIENT_CONNECT_MAX_RETRIES_KEY, 1);
+    confCopy.setInt(
+        CommonConfigurationKeysPublic.IPC_CLIENT_CONNECT_MAX_RETRIES_KEY, 1);
     SocketFactory factory = NetUtils.getDefaultSocketFactory(confCopy);
     return new HAServiceProtocolClientSideTranslatorPB(
-        getAddress(),
+        addr,
         confCopy, factory, timeoutMs);
   }
 

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

@@ -191,7 +191,7 @@ public class HealthMonitor {
    * Connect to the service to be monitored. Stubbed out for easier testing.
    */
   protected HAServiceProtocol createProxy() throws IOException {
-    return targetToMonitor.getProxy(conf, rpcTimeout);
+    return targetToMonitor.getHealthMonitorProxy(conf, rpcTimeout);
   }
 
   private void doHealthChecks() throws InterruptedException {

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

@@ -49,10 +49,10 @@ class DummyHAService extends HAServiceTarget {
   public static final Log LOG = LogFactory.getLog(DummyHAService.class);
   private static final String DUMMY_FENCE_KEY = "dummy.fence.key";
   volatile HAServiceState state;
-  HAServiceProtocol proxy;
+  HAServiceProtocol proxy, healthMonitorProxy;
   ZKFCProtocol zkfcProxy = null;
   NodeFencer fencer;
-  InetSocketAddress address;
+  InetSocketAddress address, healthMonitorAddress;
   boolean isHealthy = true;
   boolean actUnreachable = false;
   boolean failToBecomeActive, failToBecomeStandby, failToFence;
@@ -80,6 +80,7 @@ class DummyHAService extends HAServiceTarget {
     }
     Configuration conf = new Configuration();
     this.proxy = makeMock(conf, HA_HM_RPC_TIMEOUT_DEFAULT);
+    this.healthMonitorProxy = makeHealthMonitorMock(conf, HA_HM_RPC_TIMEOUT_DEFAULT);
     try {
       conf.set(DUMMY_FENCE_KEY, DummyFencer.class.getName());
       this.fencer = Mockito.spy(
@@ -93,6 +94,17 @@ class DummyHAService extends HAServiceTarget {
     }
   }
 
+  DummyHAService(HAServiceState state, InetSocketAddress address,
+        InetSocketAddress healthMonitorAddress, boolean testWithProtoBufRPC) {
+    this(state, address, testWithProtoBufRPC);
+    if (testWithProtoBufRPC) {
+      this.healthMonitorAddress = startAndGetRPCServerAddress(
+          healthMonitorAddress);
+    } else {
+      this.healthMonitorAddress = healthMonitorAddress;
+    }
+  }
+
   public void setSharedResource(DummySharedResource rsrc) {
     this.sharedResource = rsrc;
   }
@@ -134,11 +146,31 @@ class DummyHAService extends HAServiceTarget {
     return Mockito.spy(service);
   }
 
+  private HAServiceProtocol makeHealthMonitorMock(Configuration conf,
+      int timeoutMs) {
+    HAServiceProtocol service;
+    if (!testWithProtoBufRPC) {
+      service = new MockHAProtocolImpl();
+    } else {
+      try {
+        service = super.getHealthMonitorProxy(conf, timeoutMs);
+      } catch (IOException e) {
+        return null;
+      }
+    }
+    return Mockito.spy(service);
+  }
+
   @Override
   public InetSocketAddress getAddress() {
     return address;
   }
 
+  @Override
+  public InetSocketAddress getHealthMonitorAddress() {
+    return healthMonitorAddress;
+  }
+
   @Override
   public InetSocketAddress getZKFCAddress() {
     return null;
@@ -153,6 +185,15 @@ class DummyHAService extends HAServiceTarget {
     return proxy;
   }
 
+  @Override
+  public HAServiceProtocol getHealthMonitorProxy(Configuration conf,
+      int timeout) throws IOException {
+    if (testWithProtoBufRPC) {
+      proxy = makeHealthMonitorMock(conf, timeout);
+    }
+    return proxy;
+  }
+  
   @Override
   public ZKFCProtocol getZKFCProxy(Configuration conf, int timeout)
       throws IOException {

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

@@ -55,8 +55,7 @@ public class TestHealthMonitor {
     conf.setInt(CommonConfigurationKeys.HA_HM_CONNECT_RETRY_INTERVAL_KEY, 50);
     conf.setInt(CommonConfigurationKeys.HA_HM_SLEEP_AFTER_DISCONNECT_KEY, 50);
     
-    svc = new DummyHAService(HAServiceState.ACTIVE,
+    svc = createDummyHAService();
-        new InetSocketAddress("0.0.0.0", 0), true);
     hm = new HealthMonitor(conf, svc) {
       @Override
       protected HAServiceProtocol createProxy() throws IOException {
@@ -74,6 +73,11 @@ public class TestHealthMonitor {
     waitForState(hm, HealthMonitor.State.SERVICE_HEALTHY);
   }
 
+  protected DummyHAService createDummyHAService() {
+    return new DummyHAService(HAServiceState.ACTIVE,
+        new InetSocketAddress("0.0.0.0", 0), true);
+  }
+
   @Test(timeout=15000)
   public void testMonitor() throws Exception {
     LOG.info("Mocking bad health check, waiting for UNHEALTHY");

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

@@ -0,0 +1,37 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.ha;
+
+import java.net.InetSocketAddress;
+
+import org.apache.hadoop.ha.HAServiceProtocol.HAServiceState;
+
+/**
+ * Repeats all tests of {@link TestHealthMonitor}, but using a separate
+ * dedicated health check RPC address.
+ */
+public class TestHealthMonitorWithDedicatedHealthAddress
+    extends TestHealthMonitor {
+
+  @Override
+  protected DummyHAService createDummyHAService() {
+    return new DummyHAService(HAServiceState.ACTIVE,
+        new InetSocketAddress("0.0.0.0", 0),
+        new InetSocketAddress("0.0.0.0", 0), true);
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -757,6 +757,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-9307. fuseConnect should be private to fuse_connect.c (Mingliang Liu
     via Colin P. McCabe)
 
+    HDFS-9311. Support optional offload of NameNode HA service health checks to
+    a separate RPC server. (cnauroth)
+
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java

@@ -138,6 +138,10 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
   public static final String  DFS_NAMENODE_RPC_BIND_HOST_KEY = "dfs.namenode.rpc-bind-host";
   public static final String  DFS_NAMENODE_SERVICE_RPC_ADDRESS_KEY = "dfs.namenode.servicerpc-address";
   public static final String  DFS_NAMENODE_SERVICE_RPC_BIND_HOST_KEY = "dfs.namenode.servicerpc-bind-host";
+  public static final String  DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY =
+      "dfs.namenode.lifeline.rpc-address";
+  public static final String  DFS_NAMENODE_LIFELINE_RPC_BIND_HOST_KEY =
+      "dfs.namenode.lifeline.rpc-bind-host";
   public static final String  DFS_NAMENODE_MAX_OBJECTS_KEY =
       HdfsClientConfigKeys.DeprecatedKeys.DFS_NAMENODE_MAX_OBJECTS_KEY;
   public static final long    DFS_NAMENODE_MAX_OBJECTS_DEFAULT = 0;
@@ -466,6 +470,8 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
   public static final int     DFS_NAMENODE_DECOMMISSION_MAX_CONCURRENT_TRACKED_NODES_DEFAULT = 100;
   public static final String  DFS_NAMENODE_HANDLER_COUNT_KEY = "dfs.namenode.handler.count";
   public static final int     DFS_NAMENODE_HANDLER_COUNT_DEFAULT = 10;
+  public static final int     DFS_NAMENODE_LIFELINE_HANDLER_COUNT_DEFAULT = 1;
+  public static final String  DFS_NAMENODE_LIFELINE_HANDLER_COUNT_KEY = "dfs.namenode.lifeline.handler.count";
   public static final String  DFS_NAMENODE_SERVICE_HANDLER_COUNT_KEY = "dfs.namenode.service.handler.count";
   public static final int     DFS_NAMENODE_SERVICE_HANDLER_COUNT_DEFAULT = 10;
   public static final String  DFS_SUPPORT_APPEND_KEY = "dfs.support.append";

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSUtil.java

@@ -27,6 +27,7 @@ import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_HTTPS_ADDRESS_DE
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_HTTPS_ADDRESS_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_HTTP_ADDRESS_DEFAULT;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_HTTP_ADDRESS_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_RPC_ADDRESS_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_SECONDARY_HTTP_ADDRESS_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_SERVICE_RPC_ADDRESS_KEY;
@@ -573,6 +574,28 @@ public class DFSUtil {
     return addressList;
   }
 
+  /**
+   * Map a logical namenode ID to its lifeline address.  Use the given
+   * nameservice if specified, or the configured one if none is given.
+   *
+   * @param conf Configuration
+   * @param nsId which nameservice nnId is a part of, optional
+   * @param nnId the namenode ID to get the service addr for
+   * @return the lifeline addr, null if it could not be determined
+   */
+  public static String getNamenodeLifelineAddr(final Configuration conf,
+      String nsId, String nnId) {
+
+    if (nsId == null) {
+      nsId = getOnlyNameServiceIdOrNull(conf);
+    }
+
+    String lifelineAddrKey = DFSUtilClient.concatSuffixes(
+        DFSConfigKeys.DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY, nsId, nnId);
+
+    return conf.get(lifelineAddrKey);
+  }
+
   /**
    * Flatten the given map, as returned by other functions in this class,
    * into a flat list of {@link ConfiguredNNAddress} instances.

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

@@ -121,6 +121,8 @@ import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_HTTP_BIND_HOST_K
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_KERBEROS_INTERNAL_SPNEGO_PRINCIPAL_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_KERBEROS_PRINCIPAL_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_KEYTAB_FILE_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LIFELINE_RPC_BIND_HOST_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_METRICS_LOGGER_PERIOD_SECONDS_DEFAULT;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_METRICS_LOGGER_PERIOD_SECONDS_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_NAME_DIR_KEY;
@@ -227,6 +229,8 @@ public class NameNode implements NameNodeStatusMXBean {
     DFS_NAMENODE_SHARED_EDITS_DIR_KEY,
     DFS_NAMENODE_CHECKPOINT_DIR_KEY,
     DFS_NAMENODE_CHECKPOINT_EDITS_DIR_KEY,
+    DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY,
+    DFS_NAMENODE_LIFELINE_RPC_BIND_HOST_KEY,
     DFS_NAMENODE_SERVICE_RPC_ADDRESS_KEY,
     DFS_NAMENODE_SERVICE_RPC_BIND_HOST_KEY,
     DFS_NAMENODE_HTTP_ADDRESS_KEY,
@@ -487,6 +491,21 @@ public class NameNode implements NameNodeStatusMXBean {
     return role.equals(that);
   }
 
+  /**
+   * Given a configuration get the address of the lifeline RPC server.
+   * If the lifeline RPC is not configured returns null.
+   *
+   * @param conf configuration
+   * @return address or null
+   */
+  InetSocketAddress getLifelineRpcServerAddress(Configuration conf) {
+    String addr = getTrimmedOrNull(conf, DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY);
+    if (addr == null) {
+      return null;
+    }
+    return NetUtils.createSocketAddr(addr);
+  }
+
   /**
    * Given a configuration get the address of the service rpc server
    * If the service rpc is not configured returns null
@@ -499,28 +518,59 @@ public class NameNode implements NameNodeStatusMXBean {
     return DFSUtilClient.getNNAddress(conf);
   }
 
+  /**
+   * Given a configuration get the bind host of the lifeline RPC server.
+   * If the bind host is not configured returns null.
+   *
+   * @param conf configuration
+   * @return bind host or null
+   */
+  String getLifelineRpcServerBindHost(Configuration conf) {
+    return getTrimmedOrNull(conf, DFS_NAMENODE_LIFELINE_RPC_BIND_HOST_KEY);
+  }
+
   /** Given a configuration get the bind host of the service rpc server
    *  If the bind host is not configured returns null.
    */
   protected String getServiceRpcServerBindHost(Configuration conf) {
-    String addr = conf.getTrimmed(DFS_NAMENODE_SERVICE_RPC_BIND_HOST_KEY);
+    return getTrimmedOrNull(conf, DFS_NAMENODE_SERVICE_RPC_BIND_HOST_KEY);
-    if (addr == null || addr.isEmpty()) {
-      return null;
-    }
-    return addr;
   }
 
   /** Given a configuration get the bind host of the client rpc server
    *  If the bind host is not configured returns null.
    */
   protected String getRpcServerBindHost(Configuration conf) {
-    String addr = conf.getTrimmed(DFS_NAMENODE_RPC_BIND_HOST_KEY);
+    return getTrimmedOrNull(conf, DFS_NAMENODE_RPC_BIND_HOST_KEY);
+  }
+
+  /**
+   * Gets a trimmed value from configuration, or null if no value is defined.
+   *
+   * @param conf configuration
+   * @param key configuration key to get
+   * @return trimmed value, or null if no value is defined
+   */
+  private static String getTrimmedOrNull(Configuration conf, String key) {
+    String addr = conf.getTrimmed(key);
     if (addr == null || addr.isEmpty()) {
       return null;
     }
     return addr;
   }
    
+  /**
+   * Modifies the configuration to contain the lifeline RPC address setting.
+   *
+   * @param conf configuration to modify
+   * @param lifelineRPCAddress lifeline RPC address
+   */
+  void setRpcLifelineServerAddress(Configuration conf,
+      InetSocketAddress lifelineRPCAddress) {
+    LOG.info("Setting lifeline RPC address {}", lifelineRPCAddress);
+    conf.set(DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY,
+        NetUtils.getHostPortString(lifelineRPCAddress));
+  }
+
   /**
    * Modifies the configuration passed to contain the service rpc address setting
    */

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

@@ -19,6 +19,8 @@ package org.apache.hadoop.hdfs.server.namenode;
 
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_HANDLER_COUNT_DEFAULT;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_HANDLER_COUNT_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LIFELINE_HANDLER_COUNT_DEFAULT;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LIFELINE_HANDLER_COUNT_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_SERVICE_HANDLER_COUNT_DEFAULT;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_SERVICE_HANDLER_COUNT_KEY;
 import static org.apache.hadoop.hdfs.server.common.HdfsServerConstants.MAX_PATH_DEPTH;
@@ -211,6 +213,10 @@ class NameNodeRpcServer implements NamenodeProtocols {
   private final RPC.Server serviceRpcServer;
   private final InetSocketAddress serviceRPCAddress;
 
+  /** The RPC server that listens to lifeline requests */
+  private final RPC.Server lifelineRpcServer;
+  private final InetSocketAddress lifelineRPCAddress;
+  
   /** The RPC server that listens to requests from clients */
   protected final RPC.Server clientRpcServer;
   protected final InetSocketAddress clientRpcAddress;
@@ -336,6 +342,42 @@ class NameNodeRpcServer implements NamenodeProtocols {
       serviceRpcServer = null;
       serviceRPCAddress = null;
     }
+
+    InetSocketAddress lifelineRpcAddr = nn.getLifelineRpcServerAddress(conf);
+    if (lifelineRpcAddr != null) {
+      RPC.setProtocolEngine(conf, HAServiceProtocolPB.class,
+          ProtobufRpcEngine.class);
+      String bindHost = nn.getLifelineRpcServerBindHost(conf);
+      if (bindHost == null) {
+        bindHost = lifelineRpcAddr.getHostName();
+      }
+      LOG.info("Lifeline RPC server is binding to {}:{}", bindHost,
+          lifelineRpcAddr.getPort());
+
+      int lifelineHandlerCount = conf.getInt(
+          DFS_NAMENODE_LIFELINE_HANDLER_COUNT_KEY,
+          DFS_NAMENODE_LIFELINE_HANDLER_COUNT_DEFAULT);
+
+      lifelineRpcServer = new RPC.Builder(conf)
+          .setProtocol(HAServiceProtocolPB.class)
+          .setInstance(haPbService)
+          .setBindAddress(bindHost)
+          .setPort(lifelineRpcAddr.getPort())
+          .setNumHandlers(lifelineHandlerCount)
+          .setVerbose(false)
+          .setSecretManager(namesystem.getDelegationTokenSecretManager())
+          .build();
+
+      // Update the address with the correct port
+      InetSocketAddress listenAddr = lifelineRpcServer.getListenerAddress();
+      lifelineRPCAddress = new InetSocketAddress(lifelineRpcAddr.getHostName(),
+          listenAddr.getPort());
+      nn.setRpcLifelineServerAddress(conf, lifelineRPCAddress);
+    } else {
+      lifelineRpcServer = null;
+      lifelineRPCAddress = null;
+    }
+
     InetSocketAddress rpcAddr = nn.getRpcServerAddress(conf);
     String bindHost = nn.getRpcServerBindHost(conf);
     if (bindHost == null) {
@@ -379,6 +421,9 @@ class NameNodeRpcServer implements NamenodeProtocols {
       if (serviceRpcServer != null) {
         serviceRpcServer.refreshServiceAcl(conf, new HDFSPolicyProvider());
       }
+      if (lifelineRpcServer != null) {
+        lifelineRpcServer.refreshServiceAcl(conf, new HDFSPolicyProvider());
+      }
     }
 
     // The rpc-server port can be ephemeral... ensure we have the correct info
@@ -416,6 +461,15 @@ class NameNodeRpcServer implements NamenodeProtocols {
     if (serviceRpcServer != null) {
       serviceRpcServer.setTracer(nn.tracer);
     }
+    if (lifelineRpcServer != null) {
+      lifelineRpcServer.setTracer(nn.tracer);
+    }
+  }
+
+  /** Allow access to the lifeline RPC server for testing */
+  @VisibleForTesting
+  RPC.Server getLifelineRpcServer() {
+    return lifelineRpcServer;
   }
 
   /** Allow access to the client RPC server for testing */
@@ -438,6 +492,9 @@ class NameNodeRpcServer implements NamenodeProtocols {
     if (serviceRpcServer != null) {
       serviceRpcServer.start();      
     }
+    if (lifelineRpcServer != null) {
+      lifelineRpcServer.start();
+    }
   }
   
   /**
@@ -448,6 +505,9 @@ class NameNodeRpcServer implements NamenodeProtocols {
     if (serviceRpcServer != null) {
       serviceRpcServer.join();      
     }
+    if (lifelineRpcServer != null) {
+      lifelineRpcServer.join();
+    }
   }
 
   /**
@@ -460,6 +520,13 @@ class NameNodeRpcServer implements NamenodeProtocols {
     if (serviceRpcServer != null) {
       serviceRpcServer.stop();
     }
+    if (lifelineRpcServer != null) {
+      lifelineRpcServer.stop();
+    }
+  }
+
+  InetSocketAddress getLifelineRpcAddress() {
+    return lifelineRPCAddress;
   }
 
   InetSocketAddress getServiceRpcAddress() {

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

@@ -49,6 +49,7 @@ public class NNHAServiceTarget extends HAServiceTarget {
   private static final String NAMENODE_ID_KEY = "namenodeid";
   
   private final InetSocketAddress addr;
+  private final InetSocketAddress lifelineAddr;
   private InetSocketAddress zkfcAddr;
   private NodeFencer fencer;
   private BadFencingConfigurationException fenceConfigError;
@@ -90,6 +91,11 @@ public class NNHAServiceTarget extends HAServiceTarget {
     this.addr = NetUtils.createSocketAddr(serviceAddr,
         HdfsClientConfigKeys.DFS_NAMENODE_RPC_PORT_DEFAULT);
 
+    String lifelineAddrStr =
+        DFSUtil.getNamenodeLifelineAddr(targetConf, nsId, nnId);
+    this.lifelineAddr = (lifelineAddrStr != null) ?
+        NetUtils.createSocketAddr(lifelineAddrStr) : null;
+
     this.autoFailoverEnabled = targetConf.getBoolean(
         DFSConfigKeys.DFS_HA_AUTO_FAILOVER_ENABLED_KEY,
         DFSConfigKeys.DFS_HA_AUTO_FAILOVER_ENABLED_DEFAULT);
@@ -119,6 +125,11 @@ public class NNHAServiceTarget extends HAServiceTarget {
     return addr;
   }
 
+  @Override
+  public InetSocketAddress getHealthMonitorAddress() {
+    return lifelineAddr;
+  }
+
   @Override
   public InetSocketAddress getZKFCAddress() {
     Preconditions.checkState(autoFailoverEnabled,

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -78,6 +78,33 @@
   </description>
 </property>
 
+<property>
+  <name>dfs.namenode.lifeline.rpc-address</name>
+  <value></value>
+  <description>
+    NameNode RPC lifeline address.  This is an optional separate RPC address
+    that can be used to isolate health checks and liveness to protect against
+    resource exhaustion in the main RPC handler pool.  In the case of
+    HA/Federation where multiple NameNodes exist, the name service ID is added
+    to the name e.g. dfs.namenode.lifeline.rpc-address.ns1.  The value of this
+    property will take the form of nn-host1:rpc-port.  If this property is not
+    defined, then the NameNode will not start a lifeline RPC server.  By
+    default, the property is not defined.
+  </description>
+</property>
+
+<property>
+  <name>dfs.namenode.lifeline.rpc-bind-host</name>
+  <value></value>
+  <description>
+    The actual address the lifeline RPC server will bind to.  If this optional
+    address is set, it overrides only the hostname portion of
+    dfs.namenode.lifeline.rpc-address.  It can also be specified per name node
+    or name service for HA/Federation.  This is useful for making the name node
+    listen on all interfaces by setting it to 0.0.0.0.
+  </description>
+</property>
+
 <property>
   <name>dfs.namenode.secondary.http-address</name>
   <value>0.0.0.0:50090</value>
@@ -681,6 +708,18 @@
   </description>
 </property>
 
+<property>
+  <name>dfs.namenode.lifeline.handler.count</name>
+  <value>1</value>
+  <description>
+    Sets number of RPC server threads the NameNode runs for handling the
+    lifeline RPC server.  The default value is 1, because this RPC server
+    handles only HA health check requests from ZKFC.  These are lightweight
+    requests that run single-threaded from the ZKFC client side.  This property
+    has no effect if dfs.namenode.lifeline.rpc-address is not defined.
+  </description>
+</property>
+
 <property>
   <name>dfs.namenode.safemode.threshold-pct</name>
   <value>0.999f</value>

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/MiniDFSCluster.java

@@ -37,6 +37,7 @@ import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_CHECKPOINT_DIR_K
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_DECOMMISSION_INTERVAL_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_HTTPS_ADDRESS_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_HTTP_ADDRESS_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_NAME_DIR_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_RPC_ADDRESS_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_SAFEMODE_EXTENSION_KEY;
@@ -869,26 +870,23 @@ public class MiniDFSCluster {
       nameserviceId, nnId);
     destConf.set(key, srcConf.get(key));
 
-    key = DFSUtil.addKeySuffixes(DFS_NAMENODE_HTTP_ADDRESS_KEY,
+    copyKey(srcConf, destConf, nameserviceId, nnId,
-        nameserviceId, nnId);
+        DFS_NAMENODE_HTTP_ADDRESS_KEY);
+    copyKey(srcConf, destConf, nameserviceId, nnId,
+        DFS_NAMENODE_HTTPS_ADDRESS_KEY);
+    copyKey(srcConf, destConf, nameserviceId, nnId,
+        DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY);
+    copyKey(srcConf, destConf, nameserviceId, nnId,
+        DFS_NAMENODE_SERVICE_RPC_ADDRESS_KEY);
+  }
+
+  private static void copyKey(Configuration srcConf, Configuration destConf,
+      String nameserviceId, String nnId, String baseKey) {
+    String key = DFSUtil.addKeySuffixes(baseKey, nameserviceId, nnId);
     String val = srcConf.get(key);
     if (val != null) {
       destConf.set(key, srcConf.get(key));
     }
-
-    key = DFSUtil.addKeySuffixes(DFS_NAMENODE_HTTPS_ADDRESS_KEY,
-        nameserviceId, nnId);
-    val = srcConf.get(key);
-    if (val != null) {
-      destConf.set(key, srcConf.get(key));
-    }
-
-    key = DFSUtil.addKeySuffixes(DFS_NAMENODE_SERVICE_RPC_ADDRESS_KEY,
-        nameserviceId, nnId);
-    val = srcConf.get(key);
-    if (val != null) {
-      destConf.set(key, srcConf.get(key));
-    }
   }
   
   /**

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestNameNodeRespectsBindHostKeys.java

@@ -47,9 +47,9 @@ import org.apache.hadoop.hdfs.MiniDFSCluster;
  *
  *  - DFS_NAMENODE_RPC_BIND_HOST_KEY
  *  - DFS_NAMENODE_SERVICE_RPC_BIND_HOST_KEY
+ *  - DFS_NAMENODE_LIFELINE_RPC_BIND_HOST_KEY
  *  - DFS_NAMENODE_HTTP_BIND_HOST_KEY
  *  - DFS_NAMENODE_HTTPS_BIND_HOST_KEY
-
  */
 public class TestNameNodeRespectsBindHostKeys {
   public static final Log LOG = LogFactory.getLog(TestNameNodeRespectsBindHostKeys.class);
@@ -66,6 +66,12 @@ public class TestNameNodeRespectsBindHostKeys {
     return rpcServer.getServiceRpcServer().getListenerAddress().getAddress().toString();
   }
 
+  private static String getLifelineRpcServerAddress(MiniDFSCluster cluster) {
+    NameNodeRpcServer rpcServer = (NameNodeRpcServer) cluster.getNameNodeRpc();
+    return rpcServer.getLifelineRpcServer().getListenerAddress().getAddress()
+        .toString();
+  }
+
   @Test (timeout=300000)
   public void testRpcBindHostKey() throws IOException {
     Configuration conf = new HdfsConfiguration();
@@ -148,6 +154,48 @@ public class TestNameNodeRespectsBindHostKeys {
     }
   }
 
+  @Test (timeout=300000)
+  public void testLifelineRpcBindHostKey() throws IOException {
+    Configuration conf = new HdfsConfiguration();
+    MiniDFSCluster cluster = null;
+
+    LOG.info("Testing without " + DFS_NAMENODE_LIFELINE_RPC_BIND_HOST_KEY);
+
+    conf.set(DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY, LOCALHOST_SERVER_ADDRESS);
+
+    // NN should not bind the wildcard address by default.
+    try {
+      cluster = new MiniDFSCluster.Builder(conf).numDataNodes(0).build();
+      cluster.waitActive();
+      String address = getLifelineRpcServerAddress(cluster);
+      assertThat("Bind address not expected to be wildcard by default.",
+                 address, not("/" + WILDCARD_ADDRESS));
+    } finally {
+      if (cluster != null) {
+        cluster.shutdown();
+        cluster = null;
+      }
+    }
+
+    LOG.info("Testing with " + DFS_NAMENODE_LIFELINE_RPC_BIND_HOST_KEY);
+
+    // Tell NN to bind the wildcard address.
+    conf.set(DFS_NAMENODE_LIFELINE_RPC_BIND_HOST_KEY, WILDCARD_ADDRESS);
+
+    // Verify that NN binds wildcard address now.
+    try {
+      cluster = new MiniDFSCluster.Builder(conf).numDataNodes(0).build();
+      cluster.waitActive();
+      String address = getLifelineRpcServerAddress(cluster);
+      assertThat("Bind address " + address + " is not wildcard.",
+                 address, is("/" + WILDCARD_ADDRESS));
+    } finally {
+      if (cluster != null) {
+        cluster.shutdown();
+      }
+    }
+  }
+
   @Test(timeout=300000)
   public void testHttpBindHostKey() throws IOException {
     Configuration conf = new HdfsConfiguration();

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestNNHealthCheck.java

@@ -17,39 +17,75 @@
  */
 package org.apache.hadoop.hdfs.server.namenode.ha;
 
+import static org.apache.hadoop.fs.CommonConfigurationKeys.HA_HM_RPC_TIMEOUT_DEFAULT;
+import static org.apache.hadoop.fs.CommonConfigurationKeys.HA_HM_RPC_TIMEOUT_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY;
 import static org.junit.Assert.fail;
 
 import java.io.IOException;
 
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.ha.HAServiceProtocol;
 import org.apache.hadoop.ha.HealthCheckFailedException;
+import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.MiniDFSNNTopology;
 import org.apache.hadoop.hdfs.server.namenode.NameNodeResourceChecker;
-import org.apache.hadoop.hdfs.server.protocol.NamenodeProtocols;
+import org.apache.hadoop.hdfs.tools.NNHAServiceTarget;
+import org.apache.hadoop.ipc.RemoteException;
 import org.apache.hadoop.test.GenericTestUtils;
+import org.junit.After;
+import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mockito;
 
 public class TestNNHealthCheck {
 
+  private MiniDFSCluster cluster;
+  private Configuration conf;
+
+  @Before
+  public void setup() {
+    conf = new Configuration();
+  }
+
+  @After
+  public void shutdown() {
+    if (cluster != null) {
+      cluster.shutdown();
+    }
+  }
+
   @Test
   public void testNNHealthCheck() throws IOException {
-    MiniDFSCluster cluster = null;
-    try {
-      Configuration conf = new Configuration();
     cluster = new MiniDFSCluster.Builder(conf)
         .numDataNodes(0)
         .nnTopology(MiniDFSNNTopology.simpleHATopology())
         .build();
+    doNNHealthCheckTest();
+  }
 
+  @Test
+  public void testNNHealthCheckWithLifelineAddress() throws IOException {
+    conf.set(DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY, "0.0.0.0:0");
+    cluster = new MiniDFSCluster.Builder(conf)
+          .numDataNodes(0)
+          .nnTopology(MiniDFSNNTopology.simpleHATopology())
+          .build();
+    doNNHealthCheckTest();
+  }
+
+  private void doNNHealthCheckTest() throws IOException {
     NameNodeResourceChecker mockResourceChecker = Mockito.mock(
         NameNodeResourceChecker.class);
     Mockito.doReturn(true).when(mockResourceChecker).hasAvailableDiskSpace();
     cluster.getNameNode(0).getNamesystem()
         .setNNResourceChecker(mockResourceChecker);
 
-      NamenodeProtocols rpc = cluster.getNameNodeRpc(0);
+    NNHAServiceTarget haTarget = new NNHAServiceTarget(conf,
+        DFSUtil.getNamenodeNameServiceId(conf), "nn1");
+    HAServiceProtocol rpc = haTarget.getHealthMonitorProxy(conf, conf.getInt(
+        HA_HM_RPC_TIMEOUT_KEY, HA_HM_RPC_TIMEOUT_DEFAULT));
 
     // Should not throw error, which indicates healthy.
     rpc.monitorHealth();
@@ -63,11 +99,10 @@ public class TestNNHealthCheck {
     } catch (HealthCheckFailedException hcfe) {
       GenericTestUtils.assertExceptionContains(
           "The NameNode has no resources available", hcfe);
-      }
+    } catch (RemoteException re) {
-    } finally {
+      GenericTestUtils.assertExceptionContains(
-      if (cluster != null) {
+          "The NameNode has no resources available",
-        cluster.shutdown();
+          re.unwrapRemoteException(HealthCheckFailedException.class));
-      }
     }
   }
 }