YARN-3672. Create Facade for Federation State and Policy Store. Contributed by Subru Krishnan

(cherry picked from commit 5e976cd2b90ccf1bccb6039edf14140677804c4e)

hadoop-project/pom.xml

@@ -98,6 +98,9 @@
     <apacheds.version>2.0.0-M21</apacheds.version>
     <ldap-api.version>1.0.0-M33</ldap-api.version>
 
+    <jcache.version>1.0.0</jcache.version>
+    <ehcache.version>3.0.3</ehcache.version>
+
     <!-- define the Java language version used by the compiler -->
     <javac.version>1.8</javac.version>
 
@@ -1265,6 +1268,16 @@
           <artifactId>kerb-simplekdc</artifactId>
           <version>1.0.0</version>
         </dependency>
+        <dependency>
+          <groupId>javax.cache</groupId>
+          <artifactId>cache-api</artifactId>
+          <version>${jcache.version}</version>
+        </dependency>
+        <dependency>
+          <groupId>org.ehcache</groupId>
+          <artifactId>ehcache</artifactId>
+          <version>${ehcache.version}</version>
+        </dependency>
     </dependencies>
   </dependencyManagement>
 

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

@@ -2560,6 +2560,19 @@ public static boolean isAclEnabled(Configuration conf) {
   ////////////////////////////////
 
   public static final String FEDERATION_PREFIX = YARN_PREFIX + "federation.";
+
+  public static final String FEDERATION_STATESTORE_CLIENT_CLASS =
+      FEDERATION_PREFIX + "state-store.class";
+
+  public static final String DEFAULT_FEDERATION_STATESTORE_CLIENT_CLASS =
+      "org.apache.hadoop.yarn.server.federation.store.impl.MemoryFederationStateStore";
+
+  public static final String FEDERATION_CACHE_TIME_TO_LIVE_SECS =
+      FEDERATION_PREFIX + "cache-ttl.secs";
+
+  // 5 minutes
+  public static final int DEFAULT_FEDERATION_CACHE_TIME_TO_LIVE_SECS = 5 * 60;
+
   public static final String FEDERATION_MACHINE_LIST =
       FEDERATION_PREFIX + "machine-list";
 

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-api/src/test/java/org/apache/hadoop/yarn/conf/TestYarnConfigurationFields.java

@@ -68,6 +68,10 @@ public void initializeMemberVariables() {
             .YARN_SECURITY_SERVICE_AUTHORIZATION_RESOURCETRACKER_PROTOCOL);
     configurationPropsToSkipCompare.add(YarnConfiguration.CURATOR_LEADER_ELECTOR);
 
+    // Federation default configs to be ignored
+    configurationPropsToSkipCompare
+        .add(YarnConfiguration.DEFAULT_FEDERATION_STATESTORE_CLIENT_CLASS);
+
     // Ignore blacklisting nodes for AM failures feature since it is still a
     // "work in progress"
     configurationPropsToSkipCompare.add(YarnConfiguration.

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

@@ -2686,8 +2686,8 @@
     <description>The arguments to pass to the Node label script.</description>
     <name>yarn.nodemanager.node-labels.provider.script.opts</name>
   </property>
-  <!-- Other Configuration -->
 
+  <!-- Federation Configuration -->
   <property>
     <description>
       Machine list file to be loaded by the FederationSubCluster Resolver
@@ -2695,6 +2695,24 @@
     <name>yarn.federation.machine-list</name>
   </property>
 
+  <property>
+    <description>
+      Store class name for federation state store
+    </description>
+    <name>yarn.federation.state-store.class</name>
+    <value>org.apache.hadoop.yarn.server.federation.store.impl.MemoryFederationStateStore</value>
+  </property>
+
+  <property>
+   <description>
+    The time in seconds after which the federation state store local cache
+    will be refreshed periodically
+   </description>
+   <name>yarn.federation.cache-ttl.secs</name>
+   <value>300</value>
+  </property>
+
+  <!-- Other Configuration -->
   <property>
     <description>The interval that the yarn client library uses to poll the
     completion status of the asynchronous API of application client protocol.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/pom.xml

@@ -102,6 +102,16 @@
       <groupId>org.fusesource.leveldbjni</groupId>
       <artifactId>leveldbjni-all</artifactId>
     </dependency>
+    <dependency>
+      <groupId>javax.cache</groupId>
+      <artifactId>cache-api</artifactId>
+      <version>${jcache.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>org.ehcache</groupId>
+      <artifactId>ehcache</artifactId>
+      <version>${ehcache.version}</version>
+    </dependency>
   </dependencies>
 
   <build>

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/utils/FederationStateStoreFacade.java

@@ -0,0 +1,532 @@
+/**
+ * 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.server.federation.utils;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+
+import javax.cache.Cache;
+import javax.cache.CacheManager;
+import javax.cache.Caching;
+import javax.cache.configuration.CompleteConfiguration;
+import javax.cache.configuration.FactoryBuilder;
+import javax.cache.configuration.MutableConfiguration;
+import javax.cache.expiry.CreatedExpiryPolicy;
+import javax.cache.expiry.Duration;
+import javax.cache.expiry.ExpiryPolicy;
+import javax.cache.integration.CacheLoader;
+import javax.cache.integration.CacheLoaderException;
+import javax.cache.spi.CachingProvider;
+
+import org.apache.commons.lang.NotImplementedException;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.io.retry.RetryPolicies;
+import org.apache.hadoop.io.retry.RetryPolicy;
+import org.apache.hadoop.io.retry.RetryProxy;
+import org.apache.hadoop.util.ReflectionUtils;
+import org.apache.hadoop.yarn.api.records.ApplicationId;
+import org.apache.hadoop.yarn.conf.YarnConfiguration;
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.exceptions.YarnRuntimeException;
+import org.apache.hadoop.yarn.server.federation.store.FederationStateStore;
+import org.apache.hadoop.yarn.server.federation.store.records.AddApplicationHomeSubClusterRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.ApplicationHomeSubCluster;
+import org.apache.hadoop.yarn.server.federation.store.records.GetApplicationHomeSubClusterRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.GetApplicationHomeSubClusterResponse;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClusterInfoRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClusterPoliciesConfigurationsRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClusterPoliciesConfigurationsResponse;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClusterPolicyConfigurationRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClustersInfoRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClustersInfoResponse;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterPolicyConfiguration;
+import org.apache.hadoop.yarn.server.federation.store.records.UpdateApplicationHomeSubClusterRequest;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.common.annotations.VisibleForTesting;
+
+/**
+ *
+ * The FederationStateStoreFacade is an utility wrapper that provides singleton
+ * access to the Federation state store. It abstracts out retries and in
+ * addition, it also implements the caching for various objects.
+ *
+ */
+public final class FederationStateStoreFacade {
+  private static final Logger LOG =
+      LoggerFactory.getLogger(FederationStateStoreFacade.class);
+
+  private static final String GET_SUBCLUSTERS_CACHEID = "getSubClusters";
+  private static final String GET_POLICIES_CONFIGURATIONS_CACHEID =
+      "getPoliciesConfigurations";
+
+  private static final FederationStateStoreFacade FACADE =
+      new FederationStateStoreFacade();
+
+  private FederationStateStore stateStore;
+  private int cacheTimeToLive;
+  private Configuration conf;
+  private Cache<Object, Object> cache;
+
+  private FederationStateStoreFacade() {
+    initializeFacadeInternal(new Configuration());
+  }
+
+  private void initializeFacadeInternal(Configuration config) {
+    this.conf = config;
+    try {
+      this.stateStore = (FederationStateStore) createRetryInstance(this.conf,
+          YarnConfiguration.FEDERATION_STATESTORE_CLIENT_CLASS,
+          YarnConfiguration.DEFAULT_FEDERATION_STATESTORE_CLIENT_CLASS,
+          FederationStateStore.class, createRetryPolicy(conf));
+      this.stateStore.init(conf);
+
+      initCache();
+
+    } catch (YarnException ex) {
+      LOG.error("Failed to initialize the FederationStateStoreFacade object",
+          ex);
+      throw new RuntimeException(ex);
+    }
+  }
+
+  /**
+   * Delete and re-initialize the cache, to force it to use the given
+   * configuration.
+   *
+   * @param store the {@link FederationStateStore} instance to reinitialize with
+   * @param config the updated configuration to reinitialize with
+   */
+  @VisibleForTesting
+  public synchronized void reinitialize(FederationStateStore store,
+      Configuration config) {
+    this.conf = config;
+    this.stateStore = store;
+    clearCache();
+    initCache();
+  }
+
+  public static RetryPolicy createRetryPolicy(Configuration conf) {
+    // Retry settings for StateStore
+    RetryPolicy retryPolicy = RetryPolicies.exponentialBackoffRetry(
+        conf.getInt(YarnConfiguration.CLIENT_FAILOVER_RETRIES, Integer.SIZE),
+        conf.getLong(YarnConfiguration.CLIENT_FAILOVER_SLEEPTIME_BASE_MS,
+            YarnConfiguration.DEFAULT_RESOURCEMANAGER_CONNECT_RETRY_INTERVAL_MS),
+        TimeUnit.MILLISECONDS);
+
+    return retryPolicy;
+  }
+
+  private boolean isCachingEnabled() {
+    return (cacheTimeToLive > 0);
+  }
+
+  private void initCache() {
+    // Picking the JCache provider from classpath, need to make sure there's
+    // no conflict or pick up a specific one in the future
+    cacheTimeToLive =
+        conf.getInt(YarnConfiguration.FEDERATION_CACHE_TIME_TO_LIVE_SECS,
+            YarnConfiguration.DEFAULT_FEDERATION_CACHE_TIME_TO_LIVE_SECS);
+    if (isCachingEnabled()) {
+      CachingProvider jcacheProvider = Caching.getCachingProvider();
+      CacheManager jcacheManager = jcacheProvider.getCacheManager();
+      this.cache = jcacheManager.getCache(this.getClass().getSimpleName());
+      if (this.cache == null) {
+        LOG.info("Creating a JCache Manager with name "
+            + this.getClass().getSimpleName());
+        Duration cacheExpiry = new Duration(TimeUnit.SECONDS, cacheTimeToLive);
+        CompleteConfiguration<Object, Object> configuration =
+            new MutableConfiguration<Object, Object>().setStoreByValue(false)
+                .setReadThrough(true)
+                .setExpiryPolicyFactory(
+                    new FactoryBuilder.SingletonFactory<ExpiryPolicy>(
+                        new CreatedExpiryPolicy(cacheExpiry)))
+                .setCacheLoaderFactory(
+                    new FactoryBuilder.SingletonFactory<CacheLoader<Object, Object>>(
+                        new CacheLoaderImpl<Object, Object>()));
+        this.cache = jcacheManager.createCache(this.getClass().getSimpleName(),
+            configuration);
+      }
+    }
+  }
+
+  private void clearCache() {
+    CachingProvider jcacheProvider = Caching.getCachingProvider();
+    CacheManager jcacheManager = jcacheProvider.getCacheManager();
+
+    jcacheManager.destroyCache(this.getClass().getSimpleName());
+    this.cache = null;
+  }
+
+  /**
+   * Returns the singleton instance of the FederationStateStoreFacade object.
+   *
+   * @return the singleton {@link FederationStateStoreFacade} instance
+   */
+  public static FederationStateStoreFacade getInstance() {
+    return FACADE;
+  }
+
+  /**
+   * Returns the {@link SubClusterInfo} for the specified {@link SubClusterId}.
+   *
+   * @param subClusterId the identifier of the sub-cluster
+   * @return the sub cluster information
+   * @throws YarnException if the call to the state store is unsuccessful
+   */
+  public SubClusterInfo getSubCluster(final SubClusterId subClusterId)
+      throws YarnException {
+    if (isCachingEnabled()) {
+      return getSubClusters(false).get(subClusterId);
+    } else {
+      return stateStore
+          .getSubCluster(GetSubClusterInfoRequest.newInstance(subClusterId))
+          .getSubClusterInfo();
+    }
+  }
+
+  /**
+   * Updates the cache with the central {@link FederationStateStore} and returns
+   * the {@link SubClusterInfo} for the specified {@link SubClusterId}.
+   *
+   * @param subClusterId the identifier of the sub-cluster
+   * @param flushCache flag to indicate if the cache should be flushed or not
+   * @return the sub cluster information
+   * @throws YarnException if the call to the state store is unsuccessful
+   */
+  public SubClusterInfo getSubCluster(final SubClusterId subClusterId,
+      final boolean flushCache) throws YarnException {
+    if (flushCache && isCachingEnabled()) {
+      LOG.info("Flushing subClusters from cache and rehydrating from store,"
+          + " most likely on account of RM failover.");
+      cache.remove(buildGetSubClustersCacheRequest(false));
+    }
+    return getSubCluster(subClusterId);
+  }
+
+  /**
+   * Returns the {@link SubClusterInfo} of all active sub cluster(s).
+   *
+   * @param filterInactiveSubClusters whether to filter out inactive
+   *          sub-clusters
+   * @return the information of all active sub cluster(s)
+   * @throws YarnException if the call to the state store is unsuccessful
+   */
+  @SuppressWarnings("unchecked")
+  public Map<SubClusterId, SubClusterInfo> getSubClusters(
+      final boolean filterInactiveSubClusters) throws YarnException {
+    try {
+      if (isCachingEnabled()) {
+        return (Map<SubClusterId, SubClusterInfo>) cache
+            .get(buildGetSubClustersCacheRequest(filterInactiveSubClusters));
+      } else {
+        return buildSubClusterInfoMap(stateStore.getSubClusters(
+            GetSubClustersInfoRequest.newInstance(filterInactiveSubClusters)));
+      }
+    } catch (Throwable ex) {
+      throw new YarnException(ex);
+    }
+  }
+
+  /**
+   * Returns the {@link SubClusterPolicyConfiguration} for the specified queue.
+   *
+   * @param queue the queue whose policy is required
+   * @return the corresponding configured policy
+   * @throws YarnException if the call to the state store is unsuccessful
+   */
+  public SubClusterPolicyConfiguration getPolicyConfiguration(
+      final String queue) throws YarnException {
+    if (isCachingEnabled()) {
+      return getPoliciesConfigurations().get(queue);
+    } else {
+      return stateStore
+          .getPolicyConfiguration(
+              GetSubClusterPolicyConfigurationRequest.newInstance(queue))
+          .getPolicyConfiguration();
+    }
+
+  }
+
+  /**
+   * Get the policies that is represented as
+   * {@link SubClusterPolicyConfiguration} for all currently active queues in
+   * the system.
+   *
+   * @return the policies for all currently active queues in the system
+   * @throws YarnException if the call to the state store is unsuccessful
+   */
+  @SuppressWarnings("unchecked")
+  public Map<String, SubClusterPolicyConfiguration> getPoliciesConfigurations()
+      throws YarnException {
+    try {
+      if (isCachingEnabled()) {
+        return (Map<String, SubClusterPolicyConfiguration>) cache
+            .get(buildGetPoliciesConfigurationsCacheRequest());
+      } else {
+        return buildPolicyConfigMap(stateStore.getPoliciesConfigurations(
+            GetSubClusterPoliciesConfigurationsRequest.newInstance()));
+      }
+    } catch (Throwable ex) {
+      throw new YarnException(ex);
+    }
+  }
+
+  /**
+   * Adds the home {@link SubClusterId} for the specified {@link ApplicationId}.
+   *
+   * @param appHomeSubCluster the mapping of the application to it's home
+   *          sub-cluster
+   * @throws YarnException if the call to the state store is unsuccessful
+   */
+  public void addApplicationHomeSubCluster(
+      ApplicationHomeSubCluster appHomeSubCluster) throws YarnException {
+    stateStore.addApplicationHomeSubCluster(
+        AddApplicationHomeSubClusterRequest.newInstance(appHomeSubCluster));
+    return;
+  }
+
+  /**
+   * Updates the home {@link SubClusterId} for the specified
+   * {@link ApplicationId}.
+   *
+   * @param appHomeSubCluster the mapping of the application to it's home
+   *          sub-cluster
+   * @throws YarnException if the call to the state store is unsuccessful
+   */
+  public void updateApplicationHomeSubCluster(
+      ApplicationHomeSubCluster appHomeSubCluster) throws YarnException {
+    stateStore.updateApplicationHomeSubCluster(
+        UpdateApplicationHomeSubClusterRequest.newInstance(appHomeSubCluster));
+    return;
+  }
+
+  /**
+   * Returns the home {@link SubClusterId} for the specified
+   * {@link ApplicationId}.
+   *
+   * @param appId the identifier of the application
+   * @return the home sub cluster identifier
+   * @throws YarnException if the call to the state store is unsuccessful
+   */
+  public SubClusterId getApplicationHomeSubCluster(ApplicationId appId)
+      throws YarnException {
+    GetApplicationHomeSubClusterResponse response =
+        stateStore.getApplicationHomeSubCluster(
+            GetApplicationHomeSubClusterRequest.newInstance(appId));
+    return response.getApplicationHomeSubCluster().getHomeSubCluster();
+  }
+
+  /**
+   * Helper method to create instances of Object using the class name defined in
+   * the configuration object. The instances creates {@link RetryProxy} using
+   * the specific {@link RetryPolicy}.
+   *
+   * @param conf the yarn configuration
+   * @param configuredClassName the configuration provider key
+   * @param defaultValue the default implementation for fallback
+   * @param type the class for which a retry proxy is required
+   * @param retryPolicy the policy for retrying method call failures
+   * @return a retry proxy for the specified interface
+   */
+  @SuppressWarnings("unchecked")
+  public static <T> Object createRetryInstance(Configuration conf,
+      String configuredClassName, String defaultValue, Class<T> type,
+      RetryPolicy retryPolicy) {
+
+    String className = conf.get(configuredClassName, defaultValue);
+    try {
+      Class<?> clusterResolverClass = conf.getClassByName(className);
+      if (type.isAssignableFrom(clusterResolverClass)) {
+        return RetryProxy.create(type,
+            (T) ReflectionUtils.newInstance(clusterResolverClass, conf),
+            retryPolicy);
+      } else {
+        throw new YarnRuntimeException(
+            "Class: " + className + " not instance of " + type.getSimpleName());
+      }
+    } catch (Exception e) {
+      throw new YarnRuntimeException("Could not instantiate : " + className, e);
+    }
+  }
+
+  private Map<SubClusterId, SubClusterInfo> buildSubClusterInfoMap(
+      final GetSubClustersInfoResponse response) {
+    List<SubClusterInfo> subClusters = response.getSubClusters();
+    Map<SubClusterId, SubClusterInfo> subClustersMap =
+        new HashMap<>(subClusters.size());
+    for (SubClusterInfo subCluster : subClusters) {
+      subClustersMap.put(subCluster.getSubClusterId(), subCluster);
+    }
+    return subClustersMap;
+  }
+
+  private Object buildGetSubClustersCacheRequest(
+      final boolean filterInactiveSubClusters) {
+    final String cacheKey = buildCacheKey(getClass().getSimpleName(),
+        GET_SUBCLUSTERS_CACHEID, null);
+    CacheRequest<String, Map<SubClusterId, SubClusterInfo>> cacheRequest =
+        new CacheRequest<String, Map<SubClusterId, SubClusterInfo>>(cacheKey,
+            new Func<String, Map<SubClusterId, SubClusterInfo>>() {
+              @Override
+              public Map<SubClusterId, SubClusterInfo> invoke(String key)
+                  throws Exception {
+                GetSubClustersInfoResponse subClusters =
+                    stateStore.getSubClusters(GetSubClustersInfoRequest
+                        .newInstance(filterInactiveSubClusters));
+                return buildSubClusterInfoMap(subClusters);
+              }
+            });
+    return cacheRequest;
+  }
+
+  private Map<String, SubClusterPolicyConfiguration> buildPolicyConfigMap(
+      GetSubClusterPoliciesConfigurationsResponse response) {
+    List<SubClusterPolicyConfiguration> policyConfigs =
+        response.getPoliciesConfigs();
+    Map<String, SubClusterPolicyConfiguration> queuePolicyConfigs =
+        new HashMap<>();
+    for (SubClusterPolicyConfiguration policyConfig : policyConfigs) {
+      queuePolicyConfigs.put(policyConfig.getQueue(), policyConfig);
+    }
+    return queuePolicyConfigs;
+  }
+
+  private Object buildGetPoliciesConfigurationsCacheRequest() {
+    final String cacheKey = buildCacheKey(getClass().getSimpleName(),
+        GET_POLICIES_CONFIGURATIONS_CACHEID, null);
+    CacheRequest<String, Map<String, SubClusterPolicyConfiguration>> cacheRequest =
+        new CacheRequest<String, Map<String, SubClusterPolicyConfiguration>>(
+            cacheKey,
+            new Func<String, Map<String, SubClusterPolicyConfiguration>>() {
+              @Override
+              public Map<String, SubClusterPolicyConfiguration> invoke(
+                  String key) throws Exception {
+                GetSubClusterPoliciesConfigurationsResponse policyConfigs =
+                    stateStore.getPoliciesConfigurations(
+                        GetSubClusterPoliciesConfigurationsRequest
+                            .newInstance());
+                return buildPolicyConfigMap(policyConfigs);
+              }
+            });
+    return cacheRequest;
+  }
+
+  protected String buildCacheKey(String typeName, String methodName,
+      String argName) {
+    StringBuilder buffer = new StringBuilder();
+    buffer.append(typeName).append(".");
+    buffer.append(methodName);
+    if (argName != null) {
+      buffer.append("::");
+      buffer.append(argName);
+    }
+    return buffer.toString();
+  }
+
+  /**
+   * Internal class that implements the CacheLoader interface that can be
+   * plugged into the CacheManager to load objects into the cache for specified
+   * keys.
+   */
+  private static class CacheLoaderImpl<K, V> implements CacheLoader<K, V> {
+    @SuppressWarnings("unchecked")
+    @Override
+    public V load(K key) throws CacheLoaderException {
+      try {
+        CacheRequest<K, V> query = (CacheRequest<K, V>) key;
+        assert query != null;
+        return query.getValue();
+      } catch (Throwable ex) {
+        throw new CacheLoaderException(ex);
+      }
+    }
+
+    @Override
+    public Map<K, V> loadAll(Iterable<? extends K> keys)
+        throws CacheLoaderException {
+      // The FACADE does not use the Cache's getAll API. Hence this is not
+      // required to be implemented
+      throw new NotImplementedException();
+    }
+  }
+
+  /**
+   * Internal class that encapsulates the cache key and a function that returns
+   * the value for the specified key.
+   */
+  private static class CacheRequest<K, V> {
+    private K key;
+    private Func<K, V> func;
+
+    public CacheRequest(K key, Func<K, V> func) {
+      this.key = key;
+      this.func = func;
+    }
+
+    public V getValue() throws Exception {
+      return func.invoke(key);
+    }
+
+    @Override
+    public int hashCode() {
+      final int prime = 31;
+      int result = 1;
+      result = prime * result + ((key == null) ? 0 : key.hashCode());
+      return result;
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public boolean equals(Object obj) {
+      if (this == obj) {
+        return true;
+      }
+      if (obj == null) {
+        return false;
+      }
+      if (getClass() != obj.getClass()) {
+        return false;
+      }
+      CacheRequest<K, V> other = (CacheRequest<K, V>) obj;
+      if (key == null) {
+        if (other.key != null) {
+          return false;
+        }
+      } else if (!key.equals(other.key)) {
+        return false;
+      }
+
+      return true;
+    }
+  }
+
+  /**
+   * Encapsulates a method that has one parameter and returns a value of the
+   * type specified by the TResult parameter.
+   */
+  protected interface Func<T, TResult> {
+    TResult invoke(T input) throws Exception;
+  }
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/utils/package-info.java

@@ -0,0 +1,17 @@
+/**
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.server.federation.utils;

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/utils/FederationStateStoreTestUtil.java

@@ -0,0 +1,149 @@
+/**
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.server.federation.utils;
+
+import java.nio.ByteBuffer;
+
+import org.apache.hadoop.yarn.api.records.ApplicationId;
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.store.FederationStateStore;
+import org.apache.hadoop.yarn.server.federation.store.records.AddApplicationHomeSubClusterRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.ApplicationHomeSubCluster;
+import org.apache.hadoop.yarn.server.federation.store.records.GetApplicationHomeSubClusterRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.GetApplicationHomeSubClusterResponse;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClusterInfoRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClusterPolicyConfigurationRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.GetSubClusterPolicyConfigurationResponse;
+import org.apache.hadoop.yarn.server.federation.store.records.SetSubClusterPolicyConfigurationRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterPolicyConfiguration;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterRegisterRequest;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterState;
+import org.apache.hadoop.yarn.util.MonotonicClock;
+
+/**
+ * Utility class for FederationStateStore unit tests.
+ */
+public class FederationStateStoreTestUtil {
+
+  private static final MonotonicClock CLOCK = new MonotonicClock();
+
+  public static final String SC_PREFIX = "SC-";
+  public static final String Q_PREFIX = "queue-";
+  public static final String POLICY_PREFIX = "policy-";
+
+  private FederationStateStore stateStore;
+
+  public FederationStateStoreTestUtil(FederationStateStore stateStore) {
+    this.stateStore = stateStore;
+  }
+
+  private SubClusterInfo createSubClusterInfo(SubClusterId subClusterId) {
+
+    String amRMAddress = "1.2.3.4:1";
+    String clientRMAddress = "1.2.3.4:2";
+    String rmAdminAddress = "1.2.3.4:3";
+    String webAppAddress = "1.2.3.4:4";
+
+    return SubClusterInfo.newInstance(subClusterId, amRMAddress,
+        clientRMAddress, rmAdminAddress, webAppAddress, SubClusterState.SC_NEW,
+        CLOCK.getTime(), "capability");
+  }
+
+  private void registerSubCluster(SubClusterId subClusterId)
+      throws YarnException {
+
+    SubClusterInfo subClusterInfo = createSubClusterInfo(subClusterId);
+    stateStore.registerSubCluster(
+        SubClusterRegisterRequest.newInstance(subClusterInfo));
+  }
+
+  public void registerSubClusters(int numSubClusters) throws YarnException {
+
+    for (int i = 0; i < numSubClusters; i++) {
+      registerSubCluster(SubClusterId.newInstance(SC_PREFIX + i));
+    }
+  }
+
+  private void addApplicationHomeSC(ApplicationId appId,
+      SubClusterId subClusterId) throws YarnException {
+    ApplicationHomeSubCluster ahsc =
+        ApplicationHomeSubCluster.newInstance(appId, subClusterId);
+    AddApplicationHomeSubClusterRequest request =
+        AddApplicationHomeSubClusterRequest.newInstance(ahsc);
+    stateStore.addApplicationHomeSubCluster(request);
+  }
+
+  public void addAppsHomeSC(long clusterTs, int numApps) throws YarnException {
+    for (int i = 0; i < numApps; i++) {
+      addApplicationHomeSC(ApplicationId.newInstance(clusterTs, i),
+          SubClusterId.newInstance(SC_PREFIX + i));
+    }
+  }
+
+  private SubClusterPolicyConfiguration createSCPolicyConf(String queueName,
+      String policyType) {
+    return SubClusterPolicyConfiguration.newInstance(queueName, policyType,
+        ByteBuffer.allocate(1));
+  }
+
+  private void setPolicyConf(String queue, String policyType)
+      throws YarnException {
+    SetSubClusterPolicyConfigurationRequest request =
+        SetSubClusterPolicyConfigurationRequest
+            .newInstance(createSCPolicyConf(queue, policyType));
+    stateStore.setPolicyConfiguration(request);
+  }
+
+  public void addPolicyConfigs(int numQueues) throws YarnException {
+
+    for (int i = 0; i < numQueues; i++) {
+      setPolicyConf(Q_PREFIX + i, POLICY_PREFIX + i);
+    }
+  }
+
+  public SubClusterInfo querySubClusterInfo(SubClusterId subClusterId)
+      throws YarnException {
+    GetSubClusterInfoRequest request =
+        GetSubClusterInfoRequest.newInstance(subClusterId);
+    return stateStore.getSubCluster(request).getSubClusterInfo();
+  }
+
+  public SubClusterId queryApplicationHomeSC(ApplicationId appId)
+      throws YarnException {
+    GetApplicationHomeSubClusterRequest request =
+        GetApplicationHomeSubClusterRequest.newInstance(appId);
+
+    GetApplicationHomeSubClusterResponse response =
+        stateStore.getApplicationHomeSubCluster(request);
+
+    return response.getApplicationHomeSubCluster().getHomeSubCluster();
+  }
+
+  public SubClusterPolicyConfiguration queryPolicyConfiguration(String queue)
+      throws YarnException {
+    GetSubClusterPolicyConfigurationRequest request =
+        GetSubClusterPolicyConfigurationRequest.newInstance(queue);
+
+    GetSubClusterPolicyConfigurationResponse result =
+        stateStore.getPolicyConfiguration(request);
+    return result.getPolicyConfiguration();
+  }
+
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/utils/TestFederationStateStoreFacade.java

@@ -0,0 +1,148 @@
+/**
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.server.federation.utils;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Map;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.yarn.api.records.ApplicationId;
+import org.apache.hadoop.yarn.conf.YarnConfiguration;
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.store.FederationStateStore;
+import org.apache.hadoop.yarn.server.federation.store.impl.MemoryFederationStateStore;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterPolicyConfiguration;
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameters;
+
+/**
+ * Unit tests for FederationStateStoreFacade.
+ */
+@RunWith(Parameterized.class)
+public class TestFederationStateStoreFacade {
+
+  @Parameters
+  public static Collection<Boolean[]> getParameters() {
+    return Arrays
+        .asList(new Boolean[][] {{Boolean.FALSE }, {Boolean.TRUE } });
+  }
+
+  private final long clusterTs = System.currentTimeMillis();
+  private final int numSubClusters = 3;
+  private final int numApps = 5;
+  private final int numQueues = 2;
+
+  private Configuration conf;
+  private FederationStateStore stateStore;
+  private FederationStateStoreTestUtil stateStoreTestUtil;
+  private FederationStateStoreFacade facade =
+      FederationStateStoreFacade.getInstance();
+
+  public TestFederationStateStoreFacade(Boolean isCachingEnabled) {
+    conf = new Configuration();
+    if (!(isCachingEnabled.booleanValue())) {
+      conf.setInt(YarnConfiguration.FEDERATION_CACHE_TIME_TO_LIVE_SECS, 0);
+    }
+  }
+
+  @Before
+  public void setUp() throws IOException, YarnException {
+    stateStore = new MemoryFederationStateStore();
+    stateStore.init(conf);
+    facade.reinitialize(stateStore, conf);
+    // hydrate the store
+    stateStoreTestUtil = new FederationStateStoreTestUtil(stateStore);
+    stateStoreTestUtil.registerSubClusters(numSubClusters);
+    stateStoreTestUtil.addAppsHomeSC(clusterTs, numApps);
+    stateStoreTestUtil.addPolicyConfigs(numQueues);
+  }
+
+  @After
+  public void tearDown() throws Exception {
+    stateStore.close();
+    stateStore = null;
+  }
+
+  @Test
+  public void testGetSubCluster() throws YarnException {
+    for (int i = 0; i < numSubClusters; i++) {
+      SubClusterId subClusterId =
+          SubClusterId.newInstance(FederationStateStoreTestUtil.SC_PREFIX + i);
+      Assert.assertEquals(stateStoreTestUtil.querySubClusterInfo(subClusterId),
+          facade.getSubCluster(subClusterId));
+    }
+  }
+
+  @Test
+  public void testGetSubClusterFlushCache() throws YarnException {
+    for (int i = 0; i < numSubClusters; i++) {
+      SubClusterId subClusterId =
+          SubClusterId.newInstance(FederationStateStoreTestUtil.SC_PREFIX + i);
+      Assert.assertEquals(stateStoreTestUtil.querySubClusterInfo(subClusterId),
+          facade.getSubCluster(subClusterId, true));
+    }
+  }
+
+  @Test
+  public void testGetSubClusters() throws YarnException {
+    Map<SubClusterId, SubClusterInfo> subClusters =
+        facade.getSubClusters(false);
+    for (SubClusterId subClusterId : subClusters.keySet()) {
+      Assert.assertEquals(stateStoreTestUtil.querySubClusterInfo(subClusterId),
+          subClusters.get(subClusterId));
+    }
+  }
+
+  @Test
+  public void testGetPolicyConfiguration() throws YarnException {
+    for (int i = 0; i < numQueues; i++) {
+      String queue = FederationStateStoreTestUtil.Q_PREFIX + i;
+      Assert.assertEquals(stateStoreTestUtil.queryPolicyConfiguration(queue),
+          facade.getPolicyConfiguration(queue));
+    }
+  }
+
+  @Test
+  public void testGetPoliciesConfigurations() throws YarnException {
+    Map<String, SubClusterPolicyConfiguration> queuePolicies =
+        facade.getPoliciesConfigurations();
+    for (String queue : queuePolicies.keySet()) {
+      Assert.assertEquals(stateStoreTestUtil.queryPolicyConfiguration(queue),
+          queuePolicies.get(queue));
+    }
+  }
+
+  @Test
+  public void testGetHomeSubClusterForApp() throws YarnException {
+    for (int i = 0; i < numApps; i++) {
+      ApplicationId appId = ApplicationId.newInstance(clusterTs, i);
+      Assert.assertEquals(stateStoreTestUtil.queryApplicationHomeSC(appId),
+          facade.getApplicationHomeSubCluster(appId));
+    }
+  }
+
+}