HADOOP-16938. Make non-HA proxy providers pluggable

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/main/java/org/apache/hadoop/yarn/conf/YarnConfiguration.java

@@ -958,6 +958,10 @@ public static boolean isAclEnabled(Configuration conf) {
       CLIENT_FAILOVER_PREFIX + "proxy-provider";
   public static final String DEFAULT_CLIENT_FAILOVER_PROXY_PROVIDER =
       "org.apache.hadoop.yarn.client.ConfiguredRMFailoverProxyProvider";
+  public static final String CLIENT_FAILOVER_NO_HA_PROXY_PROVIDER =
+      CLIENT_FAILOVER_PREFIX + "no-ha-proxy-provider";
+  public static final String DEFAULT_CLIENT_FAILOVER_NO_HA_PROXY_PROVIDER =
+      "org.apache.hadoop.yarn.client.DefaultNoHARMFailoverProxyProvider";
 
   public static final String CLIENT_FAILOVER_MAX_ATTEMPTS =
       CLIENT_FAILOVER_PREFIX + "max-attempts";

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/client/DefaultNoHARMFailoverProxyProvider.java

@@ -0,0 +1,98 @@
+/**
+ * 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.yarn.client;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.io.retry.DefaultFailoverProxyProvider;
+import org.apache.hadoop.ipc.RPC;
+import org.apache.hadoop.yarn.conf.YarnConfiguration;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+
+/**
+ * An implementation of {@link RMFailoverProxyProvider} which does nothing in
+ * the event of failover, and always returns the same proxy object.
+ * This is the default non-HA RM Failover proxy provider. It is used to replace
+ * {@link DefaultFailoverProxyProvider} which was used as Yarn default non-HA.
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Unstable
+public class DefaultNoHARMFailoverProxyProvider<T>
+    implements RMFailoverProxyProvider<T> {
+  private static final Logger LOG =
+      LoggerFactory.getLogger(DefaultNoHARMFailoverProxyProvider.class);
+
+  protected T proxy;
+  protected Class<T> protocol;
+
+  /**
+   * Initialize internal data structures, invoked right after instantiation.
+   *
+   * @param conf     Configuration to use
+   * @param proxy    The {@link RMProxy} instance to use
+   * @param protocol The communication protocol to use
+   */
+  @Override
+  public void init(Configuration conf, RMProxy<T> proxy,
+                    Class<T> protocol) {
+    this.protocol = protocol;
+    try {
+      YarnConfiguration yarnConf = new YarnConfiguration(conf);
+      InetSocketAddress rmAddress =
+          proxy.getRMAddress(yarnConf, protocol);
+      LOG.info("Connecting to ResourceManager at {}", rmAddress);
+      this.proxy = proxy.getProxy(yarnConf, protocol, rmAddress);
+    } catch (IOException ioe) {
+      LOG.error("Unable to create proxy to the ResourceManager ", ioe);
+    }
+  }
+
+  @Override
+  public Class<T> getInterface() {
+    return protocol;
+  }
+
+  @Override
+  public ProxyInfo<T> getProxy() {
+    return new ProxyInfo<T>(proxy, null);
+  }
+
+  /**
+   * PerformFailover does nothing in this class.
+   * @param currentProxy
+   */
+  @Override
+  public void performFailover(T currentProxy) {
+    // Nothing to do.
+  }
+
+  /**
+   * Close the current proxy.
+   * @throws IOException
+   */
+  @Override
+  public void close() throws IOException {
+    RPC.stopProxy(proxy);
+  }
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/client/RMProxy.java

@@ -56,8 +56,7 @@
 @SuppressWarnings("unchecked")
 public class RMProxy<T> {
 
-  private static final Logger LOG =
+  private static final Logger LOG = LoggerFactory.getLogger(RMProxy.class);
-      LoggerFactory.getLogger(RMProxy.class);
   private UserGroupInformation user;
 
   protected RMProxy() {
@@ -125,16 +124,13 @@ protected static <T> T createRMProxy(final Configuration configuration,
   private static <T> T newProxyInstance(final YarnConfiguration conf,
       final Class<T> protocol, RMProxy<T> instance, RetryPolicy retryPolicy)
           throws IOException{
+    RMFailoverProxyProvider<T> provider;
     if (HAUtil.isHAEnabled(conf) || HAUtil.isFederationEnabled(conf)) {
-      RMFailoverProxyProvider<T> provider =
+      provider = instance.createRMFailoverProxyProvider(conf, protocol);
-          instance.createRMFailoverProxyProvider(conf, protocol);
-      return (T) RetryProxy.create(protocol, provider, retryPolicy);
     } else {
-      InetSocketAddress rmAddress = instance.getRMAddress(conf, protocol);
+      provider = instance.createNonHaRMFailoverProxyProvider(conf, protocol);
-      LOG.info("Connecting to ResourceManager at " + rmAddress);
-      T proxy = instance.getProxy(conf, protocol, rmAddress);
-      return (T) RetryProxy.create(protocol, proxy, retryPolicy);
     }
+    return (T) RetryProxy.create(protocol, provider, retryPolicy);
   }
 
   /**
@@ -154,6 +150,28 @@ public T run() {
       });
   }
 
+  /**
+   * Helper method to create non-HA RMFailoverProxyProvider.
+   */
+  private <T> RMFailoverProxyProvider<T> createNonHaRMFailoverProxyProvider(
+      Configuration conf, Class<T> protocol) {
+    Class<? extends RMFailoverProxyProvider<T>> defaultProviderClass;
+    try {
+      defaultProviderClass = (Class<? extends RMFailoverProxyProvider<T>>)
+          Class.forName(
+              YarnConfiguration.DEFAULT_CLIENT_FAILOVER_NO_HA_PROXY_PROVIDER);
+    } catch (Exception e) {
+      throw new YarnRuntimeException("Invalid default failover provider class" +
+          YarnConfiguration.DEFAULT_CLIENT_FAILOVER_NO_HA_PROXY_PROVIDER, e);
+    }
+
+    RMFailoverProxyProvider<T> provider = ReflectionUtils.newInstance(
+        conf.getClass(YarnConfiguration.CLIENT_FAILOVER_NO_HA_PROXY_PROVIDER,
+            defaultProviderClass, RMFailoverProxyProvider.class), conf);
+    provider.init(conf, (RMProxy<T>) this, protocol);
+    return provider;
+  }
+
   /**
    * Helper method to create FailoverProxyProvider.
    */

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/resources/yarn-default.xml

@@ -728,6 +728,14 @@
     <value>org.apache.hadoop.yarn.client.ConfiguredRMFailoverProxyProvider</value>
   </property>
 
+  <property>
+    <description>When HA is not enabled, the class to be used by Clients, AMs and
+      NMs to retry connecting to the Active RM. It should extend
+      org.apache.hadoop.yarn.client.RMFailoverProxyProvider</description>
+    <name>yarn.client.failover-no-ha-proxy-provider</name>
+    <value>org.apache.hadoop.yarn.client.DefaultNoHARMFailoverProxyProvider</value>
+  </property>
+
   <property>
     <description>When HA is enabled, the max number of times
       FailoverProxyProvider should attempt failover. When set,

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/ResourceManagerHA.md

@@ -41,7 +41,7 @@ The RMs have an option to embed the Zookeeper-based ActiveStandbyElector to deci
 
 #### Client, ApplicationMaster and NodeManager on RM failover
 
-When there are multiple RMs, the configuration (yarn-site.xml) used by clients and nodes is expected to list all the RMs. Clients, ApplicationMasters (AMs) and NodeManagers (NMs) try connecting to the RMs in a round-robin fashion until they hit the Active RM. If the Active goes down, they resume the round-robin polling until they hit the "new" Active. This default retry logic is implemented as `org.apache.hadoop.yarn.client.ConfiguredRMFailoverProxyProvider`. You can override the logic by implementing `org.apache.hadoop.yarn.client.RMFailoverProxyProvider` and setting the value of `yarn.client.failover-proxy-provider` to the class name.
+When there are multiple RMs, the configuration (yarn-site.xml) used by clients and nodes is expected to list all the RMs. Clients, ApplicationMasters (AMs) and NodeManagers (NMs) try connecting to the RMs in a round-robin fashion until they hit the Active RM. If the Active goes down, they resume the round-robin polling until they hit the "new" Active. This default retry logic is implemented as `org.apache.hadoop.yarn.client.ConfiguredRMFailoverProxyProvider`. You can override the logic by implementing `org.apache.hadoop.yarn.client.RMFailoverProxyProvider` and setting the value of `yarn.client.failover-proxy-provider` to the class name. When running in non-ha mode, set the value of `yarn.client.failover-no-ha-proxy-provider` instead
 
 ### Recovering previous active-RM's state
 
@@ -71,6 +71,7 @@ Most of the failover functionality is tunable using various configuration proper
 | `yarn.resourcemanager.ha.automatic-failover.embedded` | Use embedded leader-elector to pick the Active RM, when automatic failover is enabled. By default, it is enabled only when HA is enabled. |
 | `yarn.resourcemanager.cluster-id` | Identifies the cluster. Used by the elector to ensure an RM doesn't take over as Active for another cluster. |
 | `yarn.client.failover-proxy-provider` | The class to be used by Clients, AMs and NMs to failover to the Active RM. |
+| `yarn.client.failover-no-ha-proxy-provider` | The class to be used by Clients, AMs and NMs to failover to the Active RM, when not running in HA mode |
 | `yarn.client.failover-max-attempts` | The max number of times FailoverProxyProvider should attempt failover. |
 | `yarn.client.failover-sleep-base-ms` | The sleep base (in milliseconds) to be used for calculating the exponential delay between failovers. |
 | `yarn.client.failover-sleep-max-ms` | The maximum sleep time (in milliseconds) between failovers. |