YARN-5324. Stateless Federation router policies implementation. (Carlo Curino via Subru).

(cherry picked from commit 1298127bda)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/policies/FederationPolicyInitializationContext.java

@@ -59,13 +59,12 @@ public class FederationPolicyInitializationContext {
   /**
    * Setter for the {@link SubClusterPolicyConfiguration}.
    *
-   * @param federationPolicyConfiguration the
-   * {@link SubClusterPolicyConfiguration}
-   *                                      to be used for initialization.
+   * @param fedPolicyConfiguration the {@link SubClusterPolicyConfiguration}
+   *                               to be used for initialization.
    */
-  public void setFederationPolicyConfiguration(
-      SubClusterPolicyConfiguration federationPolicyConfiguration) {
-    this.federationPolicyConfiguration = federationPolicyConfiguration;
+  public void setSubClusterPolicyConfiguration(
+      SubClusterPolicyConfiguration fedPolicyConfiguration) {
+    this.federationPolicyConfiguration = fedPolicyConfiguration;
   }
 
   /**

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/policies/FederationPolicyManager.java

@@ -18,21 +18,29 @@
 package org.apache.hadoop.yarn.server.federation.policies;
 
 import org.apache.hadoop.yarn.server.federation.policies.amrmproxy.FederationAMRMProxyPolicy;
-
-
 import org.apache.hadoop.yarn.server.federation.policies.exceptions.FederationPolicyInitializationException;
-
-import org.apache.hadoop.yarn.server.federation.policies.router
-    .FederationRouterPolicy;
+import org.apache.hadoop.yarn.server.federation.policies.router.FederationRouterPolicy;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterPolicyConfiguration;
 
 /**
- * Implementors of this interface are capable to instantiate and (re)initalize
- * {@link FederationAMRMProxyPolicy} and {@link FederationRouterPolicy} based on
- * a {@link FederationPolicyInitializationContext}. The reason to bind these two
- * policies together is to make sure we remain consistent across the router and
- * amrmproxy policy decisions.
+ *
+ * Implementors need to provide the ability to serliaze a policy and its
+ * configuration as a {@link SubClusterPolicyConfiguration}, as well as
+ * provide (re)initialization mechanics for the underlying
+ * {@link FederationAMRMProxyPolicy} and {@link FederationRouterPolicy}.
+ *
+ * The serialization aspects are used by admin APIs or a policy engine to
+ * store a serialized configuration in the {@code FederationStateStore},
+ * while the getters methods are used to obtain a propertly inizialized
+ * policy in the {@code Router} and {@code AMRMProxy} respectively.
+ *
+ * This interface by design binds together
+ * {@link FederationAMRMProxyPolicy} and {@link FederationRouterPolicy} and
+ * provide lifecycle support for serialization and deserialization, to reduce
+ * configuration mistakes (combining incompatible policies).
+ *
  */
-public interface FederationPolicyConfigurator {
+public interface FederationPolicyManager {
 
   /**
    * If the current instance is compatible, this method returns the same
@@ -88,4 +96,31 @@ public interface FederationPolicyConfigurator {
       FederationRouterPolicy oldInstance)
       throws FederationPolicyInitializationException;
 
+  /**
+   * This method is invoked to derive a {@link SubClusterPolicyConfiguration}.
+   * This is to be used when writing a policy object in the federation policy
+   * store.
+   *
+   * @return a valid policy configuration representing this object
+   * parametrization.
+   *
+   * @throws FederationPolicyInitializationException if the current state cannot
+   *                                                 be serialized properly
+   */
+  SubClusterPolicyConfiguration serializeConf()
+      throws FederationPolicyInitializationException;
+
+
+  /**
+   * This method returns the queue this policy is configured for.
+   * @return the name of the queue.
+   */
+  String getQueue();
+
+  /**
+   * This methods provides a setter for the queue this policy is specified for.
+   * @param queue the name of the queue.
+   */
+  void setQueue(String queue);
+
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/policies/FederationPolicyWriter.java

@@ -1,45 +0,0 @@
-/**
- * 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.policies;
-
-import org.apache.hadoop.yarn.server.federation.policies.exceptions.FederationPolicyInitializationException;
-import org.apache.hadoop.yarn.server.federation.store.records.SubClusterPolicyConfiguration;
-
-/**
- * Implementors of this class are able to serializeConf the configuraiton of a
- * policy as a {@link SubClusterPolicyConfiguration}. This is used during the
- * lifetime of a policy from the admin APIs or policy engine to serializeConf
- * the policy into the policy store.
- */
-public interface FederationPolicyWriter {
-
-  /**
-   /**
-   * This method is invoked to derive a {@link SubClusterPolicyConfiguration}.
-   * This is to be used when writing a policy object in the federation policy
-   * store.
-   *
-   * @return a valid policy configuration representing this object
-   * parametrization.
-   *
-   * @throws FederationPolicyInitializationException if the current state cannot
-   *                                                 be serialized properly
-   */
-  SubClusterPolicyConfiguration serializeConf()
-      throws FederationPolicyInitializationException;
-}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/policies/dao/WeightedPolicyInfo.java

@@ -0,0 +1,253 @@
+/**
+ * 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.policies.dao;
+
+import com.sun.jersey.api.json.JSONConfiguration;
+import com.sun.jersey.api.json.JSONJAXBContext;
+import com.sun.jersey.api.json.JSONMarshaller;
+import com.sun.jersey.api.json.JSONUnmarshaller;
+import org.apache.commons.collections.CollectionUtils;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.yarn.server.federation.policies.exceptions.FederationPolicyInitializationException;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterIdInfo;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.xml.bind.JAXBException;
+import javax.xml.bind.Marshaller;
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.XmlRootElement;
+import java.io.StringReader;
+import java.io.StringWriter;
+import java.nio.ByteBuffer;
+import java.nio.charset.Charset;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * This is a DAO class for the configuration of parameteres for federation
+ * policies. This generalizes several possible configurations as two lists of
+ * {@link SubClusterIdInfo} and corresponding weights as a
+ * {@link Float}. The interpretation of the weight is left to the logic in
+ * the policy.
+ */
+
+@InterfaceAudience.Private
+@InterfaceStability.Evolving
+@XmlRootElement(name = "federation-policy")
+@XmlAccessorType(XmlAccessType.FIELD)
+public class WeightedPolicyInfo {
+
+  private static final Logger LOG =
+      LoggerFactory.getLogger(WeightedPolicyInfo.class);
+
+  private Map<SubClusterIdInfo, Float> routerPolicyWeights = new HashMap<>();
+  private Map<SubClusterIdInfo, Float> amrmPolicyWeights = new HashMap<>();
+  private float headroomAlpha;
+
+  private static JSONJAXBContext jsonjaxbContext = initContext();
+
+  private static JSONJAXBContext initContext() {
+    try {
+      return new JSONJAXBContext(JSONConfiguration.DEFAULT,
+          WeightedPolicyInfo.class);
+    } catch (JAXBException e) {
+      LOG.error("Error parsing the policy.", e);
+    }
+    return null;
+  }
+
+  public WeightedPolicyInfo() {
+    //JAXB needs this
+  }
+
+  /**
+   * Setter method for Router weights.
+   *
+   * @param policyWeights the router weights.
+   */
+  public void setRouterPolicyWeights(
+      Map<SubClusterIdInfo, Float> policyWeights) {
+    this.routerPolicyWeights = policyWeights;
+  }
+
+  /**
+   * Setter method for ARMRMProxy weights.
+   *
+   * @param policyWeights the amrmproxy weights.
+   */
+  public void setAMRMPolicyWeights(
+      Map<SubClusterIdInfo, Float> policyWeights) {
+    this.amrmPolicyWeights = policyWeights;
+  }
+
+  /**
+   * Getter of the router weights.
+   * @return the router weights.
+   */
+  public Map<SubClusterIdInfo, Float> getRouterPolicyWeights() {
+    return routerPolicyWeights;
+  }
+
+  /**
+   * Getter for AMRMProxy weights.
+   * @return the AMRMProxy weights.
+   */
+  public Map<SubClusterIdInfo, Float> getAMRMPolicyWeights() {
+    return amrmPolicyWeights;
+  }
+
+  /**
+   * Deserializes a {@link WeightedPolicyInfo} from a byte UTF-8 JSON
+   * representation.
+   *
+   * @param bb the input byte representation.
+   *
+   * @return the {@link WeightedPolicyInfo} represented.
+   *
+   * @throws FederationPolicyInitializationException if a deserializaiton error
+   *                                                 occurs.
+   */
+  public static WeightedPolicyInfo fromByteBuffer(ByteBuffer bb)
+      throws FederationPolicyInitializationException {
+
+    if (jsonjaxbContext == null) {
+      throw new FederationPolicyInitializationException("JSONJAXBContext should"
+          + " not be null.");
+    }
+
+    try {
+      JSONUnmarshaller unmarshaller = jsonjaxbContext.createJSONUnmarshaller();
+      final byte[] bytes = new byte[bb.remaining()];
+      bb.get(bytes);
+      String params = new String(bytes, Charset.forName("UTF-8"));
+
+      WeightedPolicyInfo weightedPolicyInfo = unmarshaller
+          .unmarshalFromJSON(new StringReader(params),
+              WeightedPolicyInfo.class);
+      return weightedPolicyInfo;
+    } catch (JAXBException j) {
+      throw new FederationPolicyInitializationException(j);
+    }
+  }
+
+  /**
+   * Converts the policy into a byte array representation in the input {@link
+   * ByteBuffer}.
+   *
+   * @return byte array representation of this policy configuration.
+   *
+   * @throws FederationPolicyInitializationException if a serialization error
+   *                                                 occurs.
+   */
+  public ByteBuffer toByteBuffer()
+      throws FederationPolicyInitializationException {
+    if (jsonjaxbContext == null) {
+      throw new FederationPolicyInitializationException("JSONJAXBContext should"
+          + " not be null.");
+    }
+    try {
+      String s = toJSONString();
+      return ByteBuffer.wrap(s.getBytes(Charset.forName("UTF-8")));
+    } catch (JAXBException j) {
+      throw new FederationPolicyInitializationException(j);
+    }
+  }
+
+  private String toJSONString() throws JAXBException {
+    JSONMarshaller marshaller = jsonjaxbContext.createJSONMarshaller();
+    marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
+    StringWriter sw = new StringWriter(256);
+    marshaller.marshallToJSON(this, sw);
+    return sw.toString();
+  }
+
+  @Override
+  public boolean equals(Object other) {
+
+    if (other == null || !other.getClass().equals(this.getClass())) {
+      return false;
+    }
+
+    WeightedPolicyInfo otherPolicy =
+        (WeightedPolicyInfo) other;
+    Map<SubClusterIdInfo, Float> otherAMRMWeights =
+        otherPolicy.getAMRMPolicyWeights();
+    Map<SubClusterIdInfo, Float> otherRouterWeights =
+        otherPolicy.getRouterPolicyWeights();
+
+    boolean amrmWeightsMatch = otherAMRMWeights != null &&
+        getAMRMPolicyWeights() != null &&
+        CollectionUtils.isEqualCollection(otherAMRMWeights.entrySet(),
+            getAMRMPolicyWeights().entrySet());
+
+    boolean routerWeightsMatch = otherRouterWeights != null &&
+        getRouterPolicyWeights() != null &&
+        CollectionUtils.isEqualCollection(otherRouterWeights.entrySet(),
+            getRouterPolicyWeights().entrySet());
+
+    return amrmWeightsMatch && routerWeightsMatch;
+  }
+
+  @Override
+  public int hashCode() {
+    return 31 * amrmPolicyWeights.hashCode() + routerPolicyWeights.hashCode();
+  }
+
+  /**
+   * Return the parameter headroomAlpha, used by policies that balance
+   * weight-based and load-based considerations in their decisions.
+   *
+   * For policies that use this parameter, values close to 1 indicate that
+   * most of the decision should be based on currently observed headroom from
+   * various sub-clusters, values close to zero, indicate that the decision
+   * should be mostly based on weights and practically ignore current load.
+   *
+   * @return the value of headroomAlpha.
+   */
+  public float getHeadroomAlpha() {
+    return headroomAlpha;
+  }
+
+  /**
+   * Set the parameter headroomAlpha, used by policies that balance
+   * weight-based and load-based considerations in their decisions.
+   *
+   * For policies that use this parameter, values close to 1 indicate that
+   * most of the decision should be based on currently observed headroom from
+   * various sub-clusters, values close to zero, indicate that the decision
+   * should be mostly based on weights and practically ignore current load.
+   *
+   * @param headroomAlpha the value to use for balancing.
+   */
+  public void setHeadroomAlpha(float headroomAlpha) {
+    this.headroomAlpha = headroomAlpha;
+  }
+
+  @Override
+  public String toString() {
+    try {
+      return toJSONString();
+    } catch (JAXBException e) {
+      e.printStackTrace();
+      return "Error serializing to string.";
+    }
+  }
+}

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

@@ -0,0 +1,20 @@
+/*
+ * 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.
+ */
+/** DAO objects for serializing/deserializing policy configurations. **/
+package org.apache.hadoop.yarn.server.federation.policies.dao;
+

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/policies/router/BaseWeightedRouterPolicy.java

@@ -0,0 +1,150 @@
+/**
+ * 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.policies.router;
+
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.policies.FederationPolicyInitializationContext;
+import org.apache.hadoop.yarn.server.federation.policies.FederationPolicyInitializationContextValidator;
+import org.apache.hadoop.yarn.server.federation.policies.dao.WeightedPolicyInfo;
+import org.apache.hadoop.yarn.server.federation.policies.exceptions.FederationPolicyInitializationException;
+import org.apache.hadoop.yarn.server.federation.policies.exceptions.NoActiveSubclustersException;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterIdInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+
+import java.util.Map;
+
+/**
+ * Abstract class provides common validation of reinitialize(), for all
+ * policies that are "weight-based".
+ */
+public abstract class BaseWeightedRouterPolicy
+    implements FederationRouterPolicy {
+
+  private WeightedPolicyInfo policyInfo = null;
+  private FederationPolicyInitializationContext policyContext;
+
+  public BaseWeightedRouterPolicy() {
+  }
+
+  @Override
+  public void reinitialize(FederationPolicyInitializationContext
+      federationPolicyContext)
+      throws FederationPolicyInitializationException {
+    FederationPolicyInitializationContextValidator
+        .validate(federationPolicyContext, this.getClass().getCanonicalName());
+
+    // perform consistency checks
+    WeightedPolicyInfo newPolicyInfo = WeightedPolicyInfo
+        .fromByteBuffer(
+            federationPolicyContext.getSubClusterPolicyConfiguration()
+                .getParams());
+
+    // if nothing has changed skip the rest of initialization
+    if (policyInfo != null && policyInfo.equals(newPolicyInfo)) {
+      return;
+    }
+
+    validate(newPolicyInfo);
+    setPolicyInfo(newPolicyInfo);
+    this.policyContext = federationPolicyContext;
+  }
+
+  /**
+   * Overridable validation step for the policy configuration.
+   * @param newPolicyInfo the configuration to test.
+   * @throws FederationPolicyInitializationException if the configuration is
+   * not valid.
+   */
+  public void validate(WeightedPolicyInfo newPolicyInfo) throws
+      FederationPolicyInitializationException {
+    if (newPolicyInfo == null) {
+      throw new FederationPolicyInitializationException("The policy to "
+          + "validate should not be null.");
+    }
+    Map<SubClusterIdInfo, Float> newWeights =
+        newPolicyInfo.getRouterPolicyWeights();
+    if (newWeights == null || newWeights.size() < 1) {
+      throw new FederationPolicyInitializationException(
+          "Weight vector cannot be null/empty.");
+    }
+  }
+
+
+  /**
+   * Getter method for the configuration weights.
+   *
+   * @return the {@link WeightedPolicyInfo} representing the policy
+   * configuration.
+   */
+  public WeightedPolicyInfo getPolicyInfo() {
+    return policyInfo;
+  }
+
+  /**
+   * Setter method for the configuration weights.
+   *
+   * @param policyInfo the {@link WeightedPolicyInfo} representing the policy
+   *                   configuration.
+   */
+  public void setPolicyInfo(
+      WeightedPolicyInfo policyInfo) {
+    this.policyInfo = policyInfo;
+  }
+
+  /**
+   * Getter method for the {@link FederationPolicyInitializationContext}.
+   * @return the context for this policy.
+   */
+  public FederationPolicyInitializationContext getPolicyContext() {
+    return policyContext;
+  }
+
+  /**
+   * Setter method for the {@link FederationPolicyInitializationContext}.
+   * @param policyContext the context to assign to this policy.
+   */
+  public void setPolicyContext(
+      FederationPolicyInitializationContext policyContext) {
+    this.policyContext = policyContext;
+  }
+
+  /**
+   * This methods gets active subclusters map from the {@code
+   * FederationStateStoreFacade} and validate it not being null/empty.
+   *
+   * @return the map of ids to info for all active subclusters.
+   * @throws YarnException if we can't get the list.
+   */
+  protected Map<SubClusterId, SubClusterInfo> getActiveSubclusters()
+      throws YarnException {
+
+    Map<SubClusterId, SubClusterInfo> activeSubclusters = getPolicyContext()
+        .getFederationStateStoreFacade().getSubClusters(true);
+
+    if (activeSubclusters == null || activeSubclusters.size() < 1) {
+      throw new NoActiveSubclustersException(
+          "Zero active subclusters, cannot pick where to send job.");
+    }
+    return activeSubclusters;
+  }
+
+
+
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/policies/router/LoadBasedRouterPolicy.java

@@ -0,0 +1,109 @@
+/**
+ * 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.policies.router;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.yarn.api.records.ApplicationSubmissionContext;
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.policies.FederationPolicyInitializationContext;
+import org.apache.hadoop.yarn.server.federation.policies.dao.WeightedPolicyInfo;
+import org.apache.hadoop.yarn.server.federation.policies.exceptions.FederationPolicyInitializationException;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterIdInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+import org.codehaus.jettison.json.JSONException;
+import org.codehaus.jettison.json.JSONObject;
+
+import java.util.Map;
+
+/**
+ * This implements a simple load-balancing policy. The policy "weights" are
+ * binary 0/1 values that enable/disable each sub-cluster, and the policy peaks
+ * the sub-cluster with the least load to forward this application.
+ */
+public class LoadBasedRouterPolicy
+    extends BaseWeightedRouterPolicy {
+
+  private static final Log LOG =
+      LogFactory.getLog(LoadBasedRouterPolicy.class);
+
+  @Override
+  public void reinitialize(FederationPolicyInitializationContext
+      federationPolicyContext)
+      throws FederationPolicyInitializationException {
+
+    // remember old policyInfo
+    WeightedPolicyInfo tempPolicy = getPolicyInfo();
+
+    //attempt new initialization
+    super.reinitialize(federationPolicyContext);
+
+    //check extra constraints
+    for (Float weight : getPolicyInfo().getRouterPolicyWeights().values()) {
+      if (weight != 0 && weight != 1) {
+        //reset to old policyInfo if check fails
+        setPolicyInfo(tempPolicy);
+        throw new FederationPolicyInitializationException(
+            this.getClass().getCanonicalName()
+                + " policy expects all weights to be either "
+                + "\"0\" or \"1\"");
+      }
+    }
+  }
+
+  @Override
+  public SubClusterId getHomeSubcluster(
+      ApplicationSubmissionContext appSubmissionContext)
+      throws YarnException {
+
+    Map<SubClusterId, SubClusterInfo> activeSubclusters =
+        getActiveSubclusters();
+
+    Map<SubClusterIdInfo, Float> weights = getPolicyInfo()
+        .getRouterPolicyWeights();
+    SubClusterIdInfo chosen = null;
+    long currBestMem = -1;
+    for (Map.Entry<SubClusterId, SubClusterInfo> entry :
+        activeSubclusters
+        .entrySet()) {
+      SubClusterIdInfo id = new SubClusterIdInfo(entry.getKey());
+      if (weights.containsKey(id) && weights.get(id) > 0) {
+        long availableMemory = getAvailableMemory(entry.getValue());
+        if (availableMemory > currBestMem) {
+          currBestMem = availableMemory;
+          chosen = id;
+        }
+      }
+    }
+
+    return chosen.toId();
+  }
+
+  private long getAvailableMemory(SubClusterInfo value)
+      throws YarnException {
+    try {
+      long mem = -1;
+      JSONObject obj = new JSONObject(value.getCapability());
+      mem = obj.getJSONObject("clusterMetrics").getLong("availableMB");
+      return mem;
+    } catch (JSONException j) {
+      throw new YarnException("FederationSubCluserInfo cannot be parsed", j);
+    }
+  }
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/policies/router/PriorityRouterPolicy.java

@@ -0,0 +1,66 @@
+/**
+ * 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.policies.router;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.yarn.api.records.ApplicationSubmissionContext;
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterIdInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+
+import java.util.Map;
+
+/**
+ * This implements a policy that interprets "weights" as a ordered list of
+ * preferences among sub-clusters. Highest weight among active subclusters is
+ * chosen.
+ */
+public class PriorityRouterPolicy
+    extends BaseWeightedRouterPolicy {
+
+  private static final Log LOG =
+      LogFactory.getLog(PriorityRouterPolicy.class);
+
+  @Override
+  public SubClusterId getHomeSubcluster(
+      ApplicationSubmissionContext appSubmissionContext)
+      throws YarnException {
+
+    Map<SubClusterId, SubClusterInfo> activeSubclusters =
+        getActiveSubclusters();
+
+    // This finds the sub-cluster with the highest weight among the
+    // currently active ones.
+    Map<SubClusterIdInfo, Float> weights = getPolicyInfo()
+        .getRouterPolicyWeights();
+    SubClusterId chosen = null;
+    Float currentBest = Float.MIN_VALUE;
+    for (SubClusterId id : activeSubclusters.keySet()) {
+      SubClusterIdInfo idInfo = new SubClusterIdInfo(id);
+      if (weights.containsKey(idInfo) && weights.get(idInfo) > currentBest) {
+        currentBest = weights.get(idInfo);
+        chosen = id;
+      }
+    }
+
+    return chosen;
+  }
+
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/policies/router/UniformRandomRouterPolicy.java

@@ -0,0 +1,85 @@
+/**
+ * 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.policies.router;
+
+import org.apache.hadoop.yarn.api.records.ApplicationSubmissionContext;
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.policies.FederationPolicyInitializationContext;
+import org.apache.hadoop.yarn.server.federation.policies.FederationPolicyInitializationContextValidator;
+import org.apache.hadoop.yarn.server.federation.policies.exceptions.FederationPolicyInitializationException;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Random;
+
+/**
+ * This simple policy picks at uniform random among any of the currently active
+ * subclusters. This policy is easy to use and good for testing.
+ *
+ * NOTE: this is "almost" subsumed by the {@code WeightedRandomRouterPolicy}.
+ * Behavior only diverges when there are active sub-clusters that are not part
+ * of the "weights", in which case the {@link UniformRandomRouterPolicy} send
+ * load to them, while {@code WeightedRandomRouterPolicy} does not.
+ */
+public class UniformRandomRouterPolicy extends BaseWeightedRouterPolicy {
+
+  private Random rand;
+
+  public UniformRandomRouterPolicy() {
+    rand = new Random(System.currentTimeMillis());
+  }
+
+  @Override
+  public void reinitialize(
+      FederationPolicyInitializationContext federationPolicyContext)
+      throws FederationPolicyInitializationException {
+    FederationPolicyInitializationContextValidator
+        .validate(federationPolicyContext, this.getClass().getCanonicalName());
+
+    //note: this overrides BaseWeighterRouterPolicy and ignores the weights
+
+    setPolicyContext(federationPolicyContext);
+  }
+
+  /**
+   * Simply picks a random active subcluster to start the AM (this does NOT
+   * depend on the weights in the policy).
+   *
+   * @param appSubmissionContext the context for the app being submitted
+   *                             (ignored).
+   *
+   * @return a randomly chosen subcluster.
+   *
+   * @throws YarnException if there are no active subclusters.
+   */
+  public SubClusterId getHomeSubcluster(
+      ApplicationSubmissionContext appSubmissionContext)
+      throws YarnException {
+
+    Map<SubClusterId, SubClusterInfo> activeSubclusters =
+        getActiveSubclusters();
+
+    List<SubClusterId> list =
+        new ArrayList<>(activeSubclusters.keySet());
+    return list.get(rand.nextInt(list.size()));
+  }
+
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/policies/router/WeightedRandomRouterPolicy.java

@@ -0,0 +1,79 @@
+/**
+ * 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.policies.router;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.yarn.api.records.ApplicationSubmissionContext;
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterIdInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+
+import java.util.Map;
+import java.util.Random;
+
+/**
+ * This policy implements a weighted random sample among currently active
+ * sub-clusters.
+ */
+public class WeightedRandomRouterPolicy
+    extends BaseWeightedRouterPolicy {
+
+  private static final Log LOG =
+      LogFactory.getLog(WeightedRandomRouterPolicy.class);
+  private Random rand = new Random(System.currentTimeMillis());
+
+  @Override
+  public SubClusterId getHomeSubcluster(
+      ApplicationSubmissionContext appSubmissionContext)
+      throws YarnException {
+
+    Map<SubClusterId, SubClusterInfo> activeSubclusters =
+        getActiveSubclusters();
+
+    // note: we cannot pre-compute the weights, as the set of activeSubcluster
+    // changes dynamically (and this would unfairly spread the load to
+    // sub-clusters adjacent to an inactive one), hence we need to count/scan
+    // the list and based on weight pick the next sub-cluster.
+    Map<SubClusterIdInfo, Float> weights = getPolicyInfo()
+        .getRouterPolicyWeights();
+
+    float totActiveWeight = 0;
+    for(Map.Entry<SubClusterIdInfo, Float> entry : weights.entrySet()){
+      if(entry.getKey()!=null && activeSubclusters.containsKey(entry.getKey()
+          .toId())){
+        totActiveWeight += entry.getValue();
+      }
+    }
+    float lookupValue = rand.nextFloat() * totActiveWeight;
+
+    for (SubClusterId id : activeSubclusters.keySet()) {
+      SubClusterIdInfo idInfo = new SubClusterIdInfo(id);
+      if (weights.containsKey(idInfo)) {
+        lookupValue -= weights.get(idInfo);
+      }
+      if (lookupValue <= 0) {
+        return id;
+      }
+    }
+    //should never happen
+    return null;
+  }
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/main/java/org/apache/hadoop/yarn/server/federation/store/records/SubClusterIdInfo.java

@@ -0,0 +1,75 @@
+/**
+ * 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.store.records;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+
+import javax.xml.bind.annotation.XmlAccessType;
+import javax.xml.bind.annotation.XmlAccessorType;
+import javax.xml.bind.annotation.XmlRootElement;
+
+/**
+ * This class represent a sub-cluster identifier in the JSON representation
+ * of the policy configuration.
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Evolving
+@XmlRootElement(name = "federation-policy")
+@XmlAccessorType(XmlAccessType.FIELD)
+public class SubClusterIdInfo {
+
+  private String id;
+
+  public SubClusterIdInfo() {
+    //JAXB needs this
+  }
+
+  public SubClusterIdInfo(String subClusterId) {
+    this.id = subClusterId;
+  }
+
+  public SubClusterIdInfo(SubClusterId subClusterId) {
+    this.id = subClusterId.getId();
+  }
+
+  /**
+   * Get the sub-cluster identifier as {@link SubClusterId}.
+   * @return the sub-cluster id.
+   */
+  public SubClusterId toId() {
+    return SubClusterId.newInstance(id);
+  }
+
+  @Override
+  public boolean equals(Object other) {
+    if (other instanceof SubClusterIdInfo) {
+      if (((SubClusterIdInfo) other).id.equals(this.id)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  @Override
+  public int hashCode() {
+    return id.hashCode();
+  }
+
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/policies/BaseFederationPoliciesTest.java

@@ -0,0 +1,155 @@
+/**
+ * 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.policies;
+
+import static org.mockito.Mockito.mock;
+
+import java.nio.ByteBuffer;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Random;
+
+import org.apache.hadoop.yarn.api.records.ApplicationSubmissionContext;
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.policies.dao.WeightedPolicyInfo;
+import org.apache.hadoop.yarn.server.federation.policies.exceptions.FederationPolicyInitializationException;
+import org.apache.hadoop.yarn.server.federation.policies.exceptions.NoActiveSubclustersException;
+import org.apache.hadoop.yarn.server.federation.policies.router.FederationRouterPolicy;
+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.utils.FederationPoliciesTestUtil;
+import org.junit.Test;
+
+/**
+ * Base class for policies tests, tests for common reinitialization cases.
+ */
+public abstract class BaseFederationPoliciesTest {
+
+  private ConfigurableFederationPolicy policy;
+  private WeightedPolicyInfo policyInfo;
+  private Map<SubClusterId, SubClusterInfo> activeSubclusters = new HashMap<>();
+  private FederationPolicyInitializationContext federationPolicyContext;
+  private ApplicationSubmissionContext applicationSubmissionContext =
+      mock(ApplicationSubmissionContext.class);
+  private Random rand = new Random();
+
+  @Test
+  public void testReinitilialize() throws YarnException {
+    FederationPolicyInitializationContext fpc =
+        new FederationPolicyInitializationContext();
+    ByteBuffer buf = getPolicyInfo().toByteBuffer();
+    fpc.setSubClusterPolicyConfiguration(SubClusterPolicyConfiguration
+        .newInstance("queue1", getPolicy().getClass().getCanonicalName(), buf));
+    fpc.setFederationSubclusterResolver(
+        FederationPoliciesTestUtil.initResolver());
+    fpc.setFederationStateStoreFacade(FederationPoliciesTestUtil.initFacade());
+    getPolicy().reinitialize(fpc);
+  }
+
+  @Test(expected = FederationPolicyInitializationException.class)
+  public void testReinitilializeBad1() throws YarnException {
+    getPolicy().reinitialize(null);
+  }
+
+  @Test(expected = FederationPolicyInitializationException.class)
+  public void testReinitilializeBad2() throws YarnException {
+    FederationPolicyInitializationContext fpc =
+        new FederationPolicyInitializationContext();
+    getPolicy().reinitialize(fpc);
+  }
+
+  @Test(expected = FederationPolicyInitializationException.class)
+  public void testReinitilializeBad3() throws YarnException {
+    FederationPolicyInitializationContext fpc =
+        new FederationPolicyInitializationContext();
+    ByteBuffer buf = mock(ByteBuffer.class);
+    fpc.setSubClusterPolicyConfiguration(SubClusterPolicyConfiguration
+        .newInstance("queue1", "WrongPolicyName", buf));
+    fpc.setFederationSubclusterResolver(
+        FederationPoliciesTestUtil.initResolver());
+    fpc.setFederationStateStoreFacade(FederationPoliciesTestUtil.initFacade());
+    getPolicy().reinitialize(fpc);
+  }
+
+  @Test(expected = NoActiveSubclustersException.class)
+  public void testNoSubclusters() throws YarnException {
+    // empty the activeSubclusters map
+    FederationPoliciesTestUtil.initializePolicyContext(getPolicy(),
+        getPolicyInfo(), new HashMap<>());
+
+    ConfigurableFederationPolicy currentPolicy = getPolicy();
+    if (currentPolicy instanceof FederationRouterPolicy) {
+      ((FederationRouterPolicy) currentPolicy)
+          .getHomeSubcluster(getApplicationSubmissionContext());
+    }
+  }
+
+  public ConfigurableFederationPolicy getPolicy() {
+    return policy;
+  }
+
+  public void setPolicy(ConfigurableFederationPolicy policy) {
+    this.policy = policy;
+  }
+
+  public WeightedPolicyInfo getPolicyInfo() {
+    return policyInfo;
+  }
+
+  public void setPolicyInfo(WeightedPolicyInfo policyInfo) {
+    this.policyInfo = policyInfo;
+  }
+
+  public Map<SubClusterId, SubClusterInfo> getActiveSubclusters() {
+    return activeSubclusters;
+  }
+
+  public void setActiveSubclusters(
+      Map<SubClusterId, SubClusterInfo> activeSubclusters) {
+    this.activeSubclusters = activeSubclusters;
+  }
+
+  public FederationPolicyInitializationContext getFederationPolicyContext() {
+    return federationPolicyContext;
+  }
+
+  public void setFederationPolicyContext(
+      FederationPolicyInitializationContext federationPolicyContext) {
+    this.federationPolicyContext = federationPolicyContext;
+  }
+
+  public ApplicationSubmissionContext getApplicationSubmissionContext() {
+    return applicationSubmissionContext;
+  }
+
+  public void setApplicationSubmissionContext(
+      ApplicationSubmissionContext applicationSubmissionContext) {
+    this.applicationSubmissionContext = applicationSubmissionContext;
+  }
+
+  public Random getRand() {
+    return rand;
+  }
+
+  public void setRand(Random rand) {
+    this.rand = rand;
+  }
+
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/policies/TestFederationPolicyInitializationContextValidator.java

@@ -77,7 +77,7 @@ public class TestFederationPolicyInitializationContextValidator {
 
   @Test(expected = FederationPolicyInitializationException.class)
   public void nullConf() throws Exception {
-    context.setFederationPolicyConfiguration(null);
+    context.setSubClusterPolicyConfiguration(null);
     FederationPolicyInitializationContextValidator.validate(context,
         MockPolicyManager.class.getCanonicalName());
   }
@@ -96,8 +96,8 @@ public class TestFederationPolicyInitializationContextValidator {
         MockPolicyManager.class.getCanonicalName());
   }
 
-  private class MockPolicyManager
-      implements FederationPolicyWriter, FederationPolicyConfigurator {
+  private class MockPolicyManager implements FederationPolicyManager {
+
     @Override
     public FederationAMRMProxyPolicy getAMRMPolicy(
         FederationPolicyInitializationContext
@@ -123,6 +123,17 @@ public class TestFederationPolicyInitializationContextValidator {
       return SubClusterPolicyConfiguration
           .newInstance("queue1", this.getClass().getCanonicalName(), buf);
     }
+
+    @Override
+    public String getQueue() {
+      return "default";
+    }
+
+    @Override
+    public void setQueue(String queue) {
+
+    }
+
   }
 
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/policies/router/TestLoadBasedRouterPolicy.java

@@ -0,0 +1,109 @@
+/**
+ * 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.policies.router;
+
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.policies.BaseFederationPoliciesTest;
+import org.apache.hadoop.yarn.server.federation.policies.dao.WeightedPolicyInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterIdInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterState;
+import org.apache.hadoop.yarn.server.federation.utils.FederationPoliciesTestUtil;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Simple test class for the {@link LoadBasedRouterPolicy}. Test that the
+ * load is properly considered for allocation.
+ */
+public class TestLoadBasedRouterPolicy extends BaseFederationPoliciesTest {
+
+  @Before
+  public void setUp() throws Exception {
+    setPolicy(new LoadBasedRouterPolicy());
+    setPolicyInfo(new WeightedPolicyInfo());
+    Map<SubClusterIdInfo, Float> routerWeights = new HashMap<>();
+    Map<SubClusterIdInfo, Float> amrmWeights = new HashMap<>();
+
+    // simulate 20 active subclusters
+    for (int i = 0; i < 20; i++) {
+      SubClusterIdInfo sc =
+          new SubClusterIdInfo(String.format("sc%02d", i));
+      SubClusterInfo federationSubClusterInfo =
+          SubClusterInfo.newInstance(sc.toId(), null, null, null, null, -1,
+              SubClusterState.SC_RUNNING, -1,
+              generateClusterMetricsInfo(i));
+      getActiveSubclusters().put(sc.toId(), federationSubClusterInfo);
+      float weight = getRand().nextInt(2);
+      if (i == 5) {
+        weight = 1.0f;
+      }
+
+      // 5% chance we omit one of the weights
+      if (i <= 5 || getRand().nextFloat() > 0.05f) {
+        routerWeights.put(sc, weight);
+        amrmWeights.put(sc, weight);
+      }
+    }
+    getPolicyInfo().setRouterPolicyWeights(routerWeights);
+    getPolicyInfo().setAMRMPolicyWeights(amrmWeights);
+
+    FederationPoliciesTestUtil.initializePolicyContext(getPolicy(),
+        getPolicyInfo(), getActiveSubclusters());
+
+  }
+
+  private String generateClusterMetricsInfo(int id) {
+
+    long mem = 1024 * getRand().nextInt(277 * 100 - 1);
+    //plant a best cluster
+    if (id == 5) {
+      mem = 1024 * 277 * 100;
+    }
+    String clusterMetrics =
+        "{\"clusterMetrics\":{\"appsSubmitted\":65," + "\"appsCompleted\":64,"
+            + "\"appsPending\":0,\"appsRunning\":0,\"appsFailed\":0,"
+            + "\"appsKilled\":1,\"reservedMB\":0,\"availableMB\":" + mem + ","
+            + "\"allocatedMB\":0,\"reservedVirtualCores\":0,"
+            + "\"availableVirtualCores\":2216,\"allocatedVirtualCores\":0,"
+            + "\"containersAllocated\":0,\"containersReserved\":0,"
+            + "\"containersPending\":0,\"totalMB\":28364800,"
+            + "\"totalVirtualCores\":2216,\"totalNodes\":278,\"lostNodes\":1,"
+            + "\"unhealthyNodes\":0,\"decommissionedNodes\":0,"
+            + "\"rebootedNodes\":0,\"activeNodes\":277}}\n";
+
+    return clusterMetrics;
+
+  }
+
+  @Test
+  public void testLoadIsRespected() throws YarnException {
+
+    SubClusterId chosen = ((FederationRouterPolicy) getPolicy())
+        .getHomeSubcluster(getApplicationSubmissionContext());
+
+    // check the "planted" best cluster is chosen
+    Assert.assertEquals("sc05", chosen.getId());
+  }
+
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/policies/router/TestPriorityRouterPolicy.java

@@ -0,0 +1,87 @@
+/**
+ * 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.policies.router;
+
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.policies.BaseFederationPoliciesTest;
+import org.apache.hadoop.yarn.server.federation.policies.dao.WeightedPolicyInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterIdInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterState;
+import org.apache.hadoop.yarn.server.federation.utils.FederationPoliciesTestUtil;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+/**
+ * Simple test class for the {@link PriorityRouterPolicy}. Tests that the
+ * weights are correctly used for ordering the choice of sub-clusters.
+ */
+public class TestPriorityRouterPolicy extends BaseFederationPoliciesTest {
+
+  @Before
+  public void setUp() throws Exception {
+    setPolicy(new PriorityRouterPolicy());
+    setPolicyInfo(new WeightedPolicyInfo());
+    Map<SubClusterIdInfo, Float> routerWeights = new HashMap<>();
+    Map<SubClusterIdInfo, Float> amrmWeights = new HashMap<>();
+
+    // simulate 20 subclusters with a 5% chance of being inactive
+    for (int i = 0; i < 20; i++) {
+      SubClusterIdInfo sc = new SubClusterIdInfo("sc" + i);
+
+      // with 5% omit a subcluster
+      if (getRand().nextFloat() < 0.95f || i == 5) {
+        SubClusterInfo sci = mock(SubClusterInfo.class);
+        when(sci.getState()).thenReturn(SubClusterState.SC_RUNNING);
+        when(sci.getSubClusterId()).thenReturn(sc.toId());
+        getActiveSubclusters().put(sc.toId(), sci);
+      }
+      float weight = getRand().nextFloat();
+      if (i == 5) {
+        weight = 1.1f; // guaranteed to be the largest.
+      }
+
+      // 5% chance we omit one of the weights
+      if (i <= 5 || getRand().nextFloat() > 0.05f) {
+        routerWeights.put(sc, weight);
+        amrmWeights.put(sc, weight);
+      }
+    }
+    getPolicyInfo().setRouterPolicyWeights(routerWeights);
+    getPolicyInfo().setAMRMPolicyWeights(amrmWeights);
+    FederationPoliciesTestUtil.initializePolicyContext(getPolicy(),
+        getPolicyInfo(),
+        getActiveSubclusters());
+
+  }
+
+  @Test
+  public void testPickLowestWeight() throws YarnException {
+    SubClusterId chosen = ((FederationRouterPolicy) getPolicy())
+        .getHomeSubcluster(getApplicationSubmissionContext());
+    Assert.assertEquals("sc5", chosen.getId());
+  }
+
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/policies/router/TestUniformRandomRouterPolicy.java

@@ -0,0 +1,65 @@
+/**
+ * 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.policies.router;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.policies.BaseFederationPoliciesTest;
+import org.apache.hadoop.yarn.server.federation.policies.dao.WeightedPolicyInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterIdInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterState;
+import org.apache.hadoop.yarn.server.federation.utils.FederationPoliciesTestUtil;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+/**
+ * Simple test class for the {@link UniformRandomRouterPolicy}. Tests that one
+ * of the active subcluster is chosen.
+ */
+public class TestUniformRandomRouterPolicy extends BaseFederationPoliciesTest {
+
+  @Before
+  public void setUp() throws Exception {
+    setPolicy(new UniformRandomRouterPolicy());
+    // needed for base test to work
+    setPolicyInfo(mock(WeightedPolicyInfo.class));
+    for (int i = 1; i <= 2; i++) {
+      SubClusterIdInfo sc = new SubClusterIdInfo("sc" + i);
+      SubClusterInfo sci = mock(SubClusterInfo.class);
+      when(sci.getState()).thenReturn(SubClusterState.SC_RUNNING);
+      when(sci.getSubClusterId()).thenReturn(sc.toId());
+      getActiveSubclusters().put(sc.toId(), sci);
+    }
+
+    FederationPoliciesTestUtil.initializePolicyContext(getPolicy(),
+        mock(WeightedPolicyInfo.class), getActiveSubclusters());
+  }
+
+  @Test
+  public void testOneSubclusterIsChosen() throws YarnException {
+    SubClusterId chosen = ((FederationRouterPolicy) getPolicy())
+        .getHomeSubcluster(getApplicationSubmissionContext());
+    Assert.assertTrue(getActiveSubclusters().keySet().contains(chosen));
+  }
+
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-common/src/test/java/org/apache/hadoop/yarn/server/federation/policies/router/TestWeightedRandomRouterPolicy.java

@@ -0,0 +1,127 @@
+/**
+ * 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.policies.router;
+
+import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.policies.BaseFederationPoliciesTest;
+import org.apache.hadoop.yarn.server.federation.policies.dao.WeightedPolicyInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterId;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterIdInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterInfo;
+import org.apache.hadoop.yarn.server.federation.store.records.SubClusterState;
+import org.apache.hadoop.yarn.server.federation.utils.FederationPoliciesTestUtil;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicLong;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+/**
+ * Simple test class for the {@link WeightedRandomRouterPolicy}. Generate large
+ * number of randomized tests to check we are weighiting correctly even if
+ * clusters go inactive.
+ */
+public class TestWeightedRandomRouterPolicy extends BaseFederationPoliciesTest {
+
+  @Before
+  public void setUp() throws Exception {
+    setPolicy(new WeightedRandomRouterPolicy());
+    setPolicyInfo(new WeightedPolicyInfo());
+    Map<SubClusterIdInfo, Float> routerWeights = new HashMap<>();
+    Map<SubClusterIdInfo, Float> amrmWeights = new HashMap<>();
+
+    // simulate 20 subclusters with a 5% chance of being inactive
+    for (int i = 0; i < 20; i++) {
+      SubClusterIdInfo sc = new SubClusterIdInfo("sc" + i);
+      // with 5% omit a subcluster
+      if (getRand().nextFloat() < 0.95f) {
+        SubClusterInfo sci = mock(SubClusterInfo.class);
+        when(sci.getState()).thenReturn(SubClusterState.SC_RUNNING);
+        when(sci.getSubClusterId()).thenReturn(sc.toId());
+        getActiveSubclusters().put(sc.toId(), sci);
+      }
+      // 5% chance we omit one of the weights
+      float weight = getRand().nextFloat();
+      if (i <= 5 || getRand().nextFloat() > 0.05f) {
+        routerWeights.put(sc, weight);
+        amrmWeights.put(sc, weight);
+      }
+    }
+    getPolicyInfo().setRouterPolicyWeights(routerWeights);
+    getPolicyInfo().setAMRMPolicyWeights(amrmWeights);
+
+    FederationPoliciesTestUtil.initializePolicyContext(getPolicy(),
+        getPolicyInfo(),
+        getActiveSubclusters());
+
+  }
+
+  @Test
+  public void testClusterChosenWithRightProbability() throws YarnException {
+
+    Map<SubClusterId, AtomicLong> counter = new HashMap<>();
+    for (SubClusterIdInfo id : getPolicyInfo().getRouterPolicyWeights()
+        .keySet()) {
+      counter.put(id.toId(), new AtomicLong(0));
+    }
+
+    float numberOfDraws = 1000000;
+
+    for (float i = 0; i < numberOfDraws; i++) {
+      SubClusterId chosenId = ((FederationRouterPolicy) getPolicy()).
+          getHomeSubcluster(getApplicationSubmissionContext());
+      counter.get(chosenId).incrementAndGet();
+    }
+
+    float totalActiveWeight = 0;
+    for (SubClusterId id : getActiveSubclusters().keySet()) {
+      SubClusterIdInfo idInfo = new SubClusterIdInfo(id);
+      if (getPolicyInfo().getRouterPolicyWeights().containsKey(idInfo)) {
+        totalActiveWeight +=
+            getPolicyInfo().getRouterPolicyWeights().get(idInfo);
+      }
+    }
+
+    for (Map.Entry<SubClusterId, AtomicLong> counterEntry : counter
+        .entrySet()) {
+      float expectedWeight = getPolicyInfo().getRouterPolicyWeights()
+          .get(new SubClusterIdInfo(counterEntry.getKey())) / totalActiveWeight;
+      float actualWeight = counterEntry.getValue().floatValue() / numberOfDraws;
+
+      // make sure that the weights is respected among active subclusters
+      // and no jobs are routed to inactive subclusters.
+      if (getActiveSubclusters().containsKey(counterEntry.getKey())) {
+        Assert.assertTrue(
+            "Id " + counterEntry.getKey() + " Actual weight: " + actualWeight
+                + " expected weight: " + expectedWeight, expectedWeight == 0 ||
+                (actualWeight / expectedWeight) < 1.1
+                    && (actualWeight / expectedWeight) > 0.9);
+      } else {
+        Assert.assertTrue(
+            "Id " + counterEntry.getKey() + " Actual weight: " + actualWeight
+                + " expected weight: " + expectedWeight, actualWeight == 0);
+
+      }
+    }
+  }
+}

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

@@ -19,13 +19,20 @@ package org.apache.hadoop.yarn.server.federation.utils;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.yarn.conf.YarnConfiguration;
 import org.apache.hadoop.yarn.exceptions.YarnException;
+import org.apache.hadoop.yarn.server.federation.policies.ConfigurableFederationPolicy;
+import org.apache.hadoop.yarn.server.federation.policies.FederationPolicyInitializationContext;
+import org.apache.hadoop.yarn.server.federation.policies.dao.WeightedPolicyInfo;
 import org.apache.hadoop.yarn.server.federation.resolver.DefaultSubClusterResolverImpl;
 import org.apache.hadoop.yarn.server.federation.resolver.SubClusterResolver;
 import org.apache.hadoop.yarn.server.federation.store.FederationStateStore;
-import org.apache.hadoop.yarn.server.federation.store.records.GetSubClustersInfoResponse;
+import org.apache.hadoop.yarn.server.federation.store.records.*;
 
 import java.net.URL;
+import java.nio.ByteBuffer;
 import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 
 import static org.mockito.Matchers.any;
 import static org.mockito.Mockito.mock;
@@ -41,6 +48,41 @@ public final class FederationPoliciesTestUtil {
     // disabled.
   }
 
+
+  public static void initializePolicyContext(
+      FederationPolicyInitializationContext fpc, ConfigurableFederationPolicy
+      policy, WeightedPolicyInfo policyInfo,
+      Map<SubClusterId, SubClusterInfo> activeSubclusters)
+      throws YarnException {
+    ByteBuffer buf = policyInfo.toByteBuffer();
+    fpc.setSubClusterPolicyConfiguration(SubClusterPolicyConfiguration
+        .newInstance("queue1", policy.getClass().getCanonicalName(), buf));
+    FederationStateStoreFacade facade = FederationStateStoreFacade
+        .getInstance();
+    FederationStateStore fss = mock(FederationStateStore.class);
+
+    if (activeSubclusters == null) {
+      activeSubclusters = new HashMap<SubClusterId, SubClusterInfo>();
+    }
+    GetSubClustersInfoResponse response = GetSubClustersInfoResponse
+        .newInstance(new ArrayList<SubClusterInfo>(activeSubclusters.values()));
+
+    when(fss.getSubClusters(any())).thenReturn(response);
+    facade.reinitialize(fss, new Configuration());
+    fpc.setFederationStateStoreFacade(facade);
+    policy.reinitialize(fpc);
+  }
+
+  public static void initializePolicyContext(
+      ConfigurableFederationPolicy policy,
+      WeightedPolicyInfo policyInfo, Map<SubClusterId,
+      SubClusterInfo> activeSubclusters) throws YarnException {
+    FederationPolicyInitializationContext context =
+        new FederationPolicyInitializationContext(null, initResolver(),
+            initFacade());
+    initializePolicyContext(context, policy, policyInfo, activeSubclusters);
+  }
+
   /**
    * Initialize a {@link SubClusterResolver}.
    *
@@ -62,6 +104,45 @@ public final class FederationPoliciesTestUtil {
     return resolver;
   }
 
+  /**
+   * Initialiaze a main-memory {@link FederationStateStoreFacade} used for
+   * testing, wiht a mock resolver.
+   *
+   * @param subClusterInfos the list of subclusters to be served on
+   *                        getSubClusters invocations.
+   *
+   * @return the facade.
+   *
+   * @throws YarnException in case the initialization is not successful.
+   */
+
+  public static FederationStateStoreFacade initFacade(
+      List<SubClusterInfo> subClusterInfos, SubClusterPolicyConfiguration
+      policyConfiguration) throws YarnException {
+    FederationStateStoreFacade goodFacade = FederationStateStoreFacade
+        .getInstance();
+    FederationStateStore fss = mock(FederationStateStore.class);
+    GetSubClustersInfoResponse response = GetSubClustersInfoResponse
+        .newInstance(subClusterInfos);
+    when(fss.getSubClusters(any())).thenReturn(response);
+
+    List<SubClusterPolicyConfiguration> configurations = new ArrayList<>();
+    configurations.add(policyConfiguration);
+
+    GetSubClusterPoliciesConfigurationsResponse policiesResponse =
+        GetSubClusterPoliciesConfigurationsResponse
+            .newInstance(configurations);
+    when(fss.getPoliciesConfigurations(any())).thenReturn(policiesResponse);
+
+    GetSubClusterPolicyConfigurationResponse policyResponse =
+        GetSubClusterPolicyConfigurationResponse
+            .newInstance(policyConfiguration);
+    when(fss.getPolicyConfiguration(any())).thenReturn(policyResponse);
+
+    goodFacade.reinitialize(fss, new Configuration());
+    return goodFacade;
+  }
+
   /**
    * Initialiaze a main-memory {@link FederationStateStoreFacade} used for
    * testing, wiht a mock resolver.
@@ -71,13 +152,8 @@ public final class FederationPoliciesTestUtil {
    * @throws YarnException in case the initialization is not successful.
    */
   public static FederationStateStoreFacade initFacade() throws YarnException {
-    FederationStateStoreFacade goodFacade = FederationStateStoreFacade
-        .getInstance();
-    FederationStateStore fss = mock(FederationStateStore.class);
-    GetSubClustersInfoResponse response = GetSubClustersInfoResponse
-        .newInstance(new ArrayList<>());
-    when(fss.getSubClusters(any())).thenReturn(response);
-    goodFacade.reinitialize(fss, new Configuration());
-    return goodFacade;
+    return initFacade(new ArrayList<>(), mock(SubClusterPolicyConfiguration
+        .class));
   }
+
 }