HDFS-14750. RBF: Support dynamic handler allocation in routers

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/fairness/AbstractRouterRpcFairnessPolicyController.java

@@ -26,6 +26,8 @@
 import org.codehaus.jettison.json.JSONException;
 import org.codehaus.jettison.json.JSONObject;
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hdfs.server.federation.utils.AdjustableSemaphore;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -40,7 +42,8 @@ public class AbstractRouterRpcFairnessPolicyController
       LoggerFactory.getLogger(AbstractRouterRpcFairnessPolicyController.class);
 
   /** Hash table to hold semaphore for each configured name service. */
-  private Map<String, Semaphore> permits;
+  private Map<String, AdjustableSemaphore> permits;
+  private final Map<String, Integer> permitSizes = new HashMap<>();
 
   public void init(Configuration conf) {
     this.permits = new HashMap<>();
@@ -72,7 +75,7 @@ public void shutdown() {
   }
 
   protected void insertNameServiceWithPermits(String nsId, int maxPermits) {
-    this.permits.put(nsId, new Semaphore(maxPermits));
+    this.permits.put(nsId, new AdjustableSemaphore(maxPermits));
   }
 
   protected int getAvailablePermits(String nsId) {
@@ -82,7 +85,7 @@ protected int getAvailablePermits(String nsId) {
   @Override
   public String getAvailableHandlerOnPerNs() {
     JSONObject json = new JSONObject();
-    for (Map.Entry<String, Semaphore> entry : permits.entrySet()) {
+    for (Map.Entry<String, AdjustableSemaphore> entry : permits.entrySet()) {
       try {
         String nsId = entry.getKey();
         int availableHandler = entry.getValue().availablePermits();
@@ -93,4 +96,24 @@ public String getAvailableHandlerOnPerNs() {
     }
     return json.toString();
   }
+
+  @Override
+  public String getPermitCapacityPerNs() {
+    JSONObject json = new JSONObject();
+    for (Map.Entry<String, Integer> entry : permitSizes.entrySet()) {
+      try {
+        json.put(entry.getKey(), entry.getValue());
+      } catch (JSONException e) {
+        LOG.warn("Cannot put {} into JSONObject", entry.getKey(), e);
+      }
+    }
+    return json.toString();
+  }
+
+  protected Map<String, AdjustableSemaphore> getPermits() {
+    return permits;
+  }
+  protected Map<String, Integer> getPermitSizes() {
+    return permitSizes;
+  }
 }

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/fairness/DynamicRouterRpcFairnessPolicyController.java

@@ -0,0 +1,234 @@
+/**
+ * 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.hdfs.server.federation.fairness;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.LongAdder;
+
+import org.apache.hadoop.thirdparty.com.google.common.util.concurrent.ThreadFactoryBuilder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import org.apache.hadoop.classification.VisibleForTesting;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hdfs.server.federation.utils.AdjustableSemaphore;
+import org.apache.hadoop.util.concurrent.HadoopExecutors;
+
+import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_DYNAMIC_FAIRNESS_CONTROLLER_REFRESH_INTERVAL_SECONDS_DEFAULT;
+import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_DYNAMIC_FAIRNESS_CONTROLLER_REFRESH_INTERVAL_SECONDS_KEY;
+import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_FAIR_MINIMUM_HANDLER_COUNT_DEFAULT;
+import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_FAIR_MINIMUM_HANDLER_COUNT_KEY;
+import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_HANDLER_COUNT_DEFAULT;
+import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_HANDLER_COUNT_KEY;
+
+/**
+ * Dynamic fairness policy extending {@link StaticRouterRpcFairnessPolicyController}
+ * and fetching handlers from configuration for all available name services.
+ * The handlers count changes according to traffic to namespaces.
+ * Total handlers might NOT strictly add up to the value defined by DFS_ROUTER_HANDLER_COUNT_KEY
+ * but will not exceed initial handler count + number of nameservices.
+ */
+public class DynamicRouterRpcFairnessPolicyController
+    extends StaticRouterRpcFairnessPolicyController {
+
+  public static final Logger LOG =
+      LoggerFactory.getLogger(DynamicRouterRpcFairnessPolicyController.class);
+
+  private static final ScheduledExecutorService SCHEDULED_EXECUTOR = HadoopExecutors
+      .newSingleThreadScheduledExecutor(new ThreadFactoryBuilder().setDaemon(true)
+          .setNameFormat("DynamicRouterRpcFairnessPolicyControllerPermitsResizer").build());
+  private PermitsResizerService permitsResizerService;
+  private ScheduledFuture<?> refreshTask;
+  private int handlerCount;
+  private int minimumHandlerPerNs;
+  private final Map<String, LongAdder> rejectedPermitsPerNs = new ConcurrentHashMap<>();
+  private final Map<String, LongAdder> acceptedPermitsPerNs = new ConcurrentHashMap<>();
+
+  /**
+   * Initializes using the same logic as {@link StaticRouterRpcFairnessPolicyController}
+   * and starts a periodic semaphore resizer thread.
+   *
+   * @param conf configuration
+   */
+  public DynamicRouterRpcFairnessPolicyController(Configuration conf) {
+    super(conf);
+    minimumHandlerPerNs = conf.getInt(DFS_ROUTER_FAIR_MINIMUM_HANDLER_COUNT_KEY,
+        DFS_ROUTER_FAIR_MINIMUM_HANDLER_COUNT_DEFAULT);
+    handlerCount = conf.getInt(DFS_ROUTER_HANDLER_COUNT_KEY, DFS_ROUTER_HANDLER_COUNT_DEFAULT);
+    long refreshInterval =
+        conf.getTimeDuration(DFS_ROUTER_DYNAMIC_FAIRNESS_CONTROLLER_REFRESH_INTERVAL_SECONDS_KEY,
+            DFS_ROUTER_DYNAMIC_FAIRNESS_CONTROLLER_REFRESH_INTERVAL_SECONDS_DEFAULT,
+            TimeUnit.SECONDS);
+    permitsResizerService = new PermitsResizerService();
+    refreshTask = SCHEDULED_EXECUTOR
+        .scheduleWithFixedDelay(permitsResizerService, refreshInterval, refreshInterval,
+            TimeUnit.SECONDS);
+  }
+
+  @VisibleForTesting
+  public DynamicRouterRpcFairnessPolicyController(Configuration conf, long refreshInterval) {
+    super(conf);
+    minimumHandlerPerNs = conf.getInt(DFS_ROUTER_FAIR_MINIMUM_HANDLER_COUNT_KEY,
+        DFS_ROUTER_FAIR_MINIMUM_HANDLER_COUNT_DEFAULT);
+    handlerCount = conf.getInt(DFS_ROUTER_HANDLER_COUNT_KEY, DFS_ROUTER_HANDLER_COUNT_DEFAULT);
+    permitsResizerService = new PermitsResizerService();
+    refreshTask = SCHEDULED_EXECUTOR
+        .scheduleWithFixedDelay(permitsResizerService, refreshInterval, refreshInterval,
+            TimeUnit.SECONDS);
+  }
+
+  @VisibleForTesting
+  public void refreshPermitsCap() {
+    permitsResizerService.run();
+  }
+
+  @VisibleForTesting
+  public PermitsResizerService getResizerService() {
+    return permitsResizerService;
+  }
+
+  @Override
+  public void shutdown() {
+    super.shutdown();
+    if (refreshTask != null) {
+      refreshTask.cancel(true);
+    }
+  }
+
+  @Override
+  public boolean acquirePermit(String nsId) {
+    boolean result = super.acquirePermit(nsId);
+    if (result) {
+      acceptedPermitsPerNs.computeIfAbsent(nsId, k -> new LongAdder()).increment();
+    } else {
+      rejectedPermitsPerNs.computeIfAbsent(nsId, k -> new LongAdder()).increment();
+    }
+    return result;
+  }
+
+  @VisibleForTesting
+  public void setAcceptedPermitsPerNs(Map<String, LongAdder> metrics) {
+    for (Map.Entry<String, LongAdder> entry: metrics.entrySet()) {
+      acceptedPermitsPerNs.put(entry.getKey(), new LongAdder());
+      acceptedPermitsPerNs.get(entry.getKey()).add(entry.getValue().longValue());
+    }
+    List<String> toRemove = new ArrayList<>();
+    for (String key: acceptedPermitsPerNs.keySet()) {
+      if (!metrics.containsKey(key)) {
+        toRemove.add(key);
+      }
+    }
+    for (String key: toRemove) {
+      acceptedPermitsPerNs.remove(key);
+    }
+  }
+
+  @VisibleForTesting
+  public void setRejectedPermitsPerNs(Map<String, LongAdder> metrics) {
+    for (Map.Entry<String, LongAdder> entry: metrics.entrySet()) {
+      rejectedPermitsPerNs.put(entry.getKey(), new LongAdder());
+      rejectedPermitsPerNs.get(entry.getKey()).add(entry.getValue().longValue());
+    }
+    List<String> toRemove = new ArrayList<>();
+    for (String key: rejectedPermitsPerNs.keySet()) {
+      if (!metrics.containsKey(key)) {
+        toRemove.add(key);
+      }
+    }
+    for (String key: toRemove) {
+      rejectedPermitsPerNs.remove(key);
+    }
+  }
+
+  class PermitsResizerService implements Runnable {
+
+    @Override
+    public synchronized void run() {
+      if (rejectedPermitsPerNs == null || acceptedPermitsPerNs == null || (
+          rejectedPermitsPerNs.isEmpty() && acceptedPermitsPerNs.isEmpty())) {
+        return;
+      }
+      long totalOps = 0;
+      Map<String, Long> nsOps = new HashMap<>();
+      for (Map.Entry<String, AdjustableSemaphore> entry : getPermits().entrySet()) {
+        long ops = (rejectedPermitsPerNs.containsKey(entry.getKey()) ?
+            rejectedPermitsPerNs.get(entry.getKey()).longValue() :
+            0) + (acceptedPermitsPerNs.containsKey(entry.getKey()) ?
+            acceptedPermitsPerNs.get(entry.getKey()).longValue() :
+            0);
+        nsOps.put(entry.getKey(), ops);
+        totalOps += ops;
+      }
+
+      List<String> underMinimumNss = new ArrayList<>();
+      List<String> overMinimumNss = new ArrayList<>();
+      int effectiveOps = 0;
+
+      // First iteration: split namespaces into those underused and those that are not.
+      for (Map.Entry<String, AdjustableSemaphore> entry : getPermits().entrySet()) {
+        String ns = entry.getKey();
+        int newPermitCap = (int) Math.ceil((float) nsOps.get(ns) / totalOps * handlerCount);
+
+        if (newPermitCap <= minimumHandlerPerNs) {
+          underMinimumNss.add(ns);
+        } else {
+          overMinimumNss.add(ns);
+          effectiveOps += nsOps.get(ns);
+        }
+      }
+
+      // Second iteration part 1: assign minimum handlers
+      for (String ns: underMinimumNss) {
+        resizeNsHandlerCapacity(ns, minimumHandlerPerNs);
+      }
+      // Second iteration part 2: assign handlers to the rest
+      int leftoverPermits = handlerCount - minimumHandlerPerNs * underMinimumNss.size();
+      for (String ns: overMinimumNss) {
+        int newPermitCap = (int) Math.ceil((float) nsOps.get(ns) / effectiveOps * leftoverPermits);
+        resizeNsHandlerCapacity(ns, newPermitCap);
+      }
+
+      // Reset the metrics
+      rejectedPermitsPerNs.replaceAll((k, v) -> new LongAdder());
+      acceptedPermitsPerNs.replaceAll((k, v) -> new LongAdder());
+    }
+
+    private void resizeNsHandlerCapacity(String ns, int newPermitCap) {
+      AdjustableSemaphore semaphore = getPermits().get(ns);
+      int oldPermitCap = getPermitSizes().get(ns);
+      if (newPermitCap <= minimumHandlerPerNs) {
+        newPermitCap = minimumHandlerPerNs;
+      }
+      getPermitSizes().put(ns, newPermitCap);
+      if (newPermitCap > oldPermitCap) {
+        semaphore.release(newPermitCap - oldPermitCap);
+      } else if (newPermitCap < oldPermitCap) {
+        semaphore.reducePermits(oldPermitCap - newPermitCap);
+      }
+      LOG.info("Resized handlers for nsId {} from {} to {}", ns, oldPermitCap, newPermitCap);
+    }
+  }
+}

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/fairness/NoRouterRpcFairnessPolicyController.java

@@ -51,4 +51,9 @@ public void shutdown() {
   public String getAvailableHandlerOnPerNs(){
     return "N/A";
   }
+
+  @Override
+  public String getPermitCapacityPerNs() {
+    return "N/A";
+  }
 }

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/fairness/RouterRpcFairnessPolicyController.java

@@ -67,4 +67,9 @@ public interface RouterRpcFairnessPolicyController {
    * Returns the JSON string of the available handler for each Ns.
    */
   String getAvailableHandlerOnPerNs();
+
+  /**
+   * Returns the JSON string of the max handler count for each ns.
+   */
+  String getPermitCapacityPerNs();
 }

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/fairness/StaticRouterRpcFairnessPolicyController.java

@@ -27,6 +27,8 @@
 import java.util.HashSet;
 
 import static org.apache.hadoop.hdfs.server.federation.fairness.RouterRpcFairnessConstants.CONCURRENT_NS;
+import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_FAIR_MINIMUM_HANDLER_COUNT_DEFAULT;
+import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_FAIR_MINIMUM_HANDLER_COUNT_KEY;
 import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_HANDLER_COUNT_KEY;
 import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_HANDLER_COUNT_DEFAULT;
 import static org.apache.hadoop.hdfs.server.federation.router.RBFConfigKeys.DFS_ROUTER_FAIR_HANDLER_COUNT_KEY_PREFIX;
@@ -45,6 +47,9 @@ public class StaticRouterRpcFairnessPolicyController extends
   public static final String ERROR_MSG = "Configured handlers "
       + DFS_ROUTER_HANDLER_COUNT_KEY + '='
       + " %d is less than the minimum required handlers %d";
+  public static final String ERROR_NS_MSG =
+      "Configured handlers %s=%d is less than the minimum required handlers %d";
+
 
   public StaticRouterRpcFairnessPolicyController(Configuration conf) {
     init(conf);
@@ -78,6 +83,7 @@ public void init(Configuration conf)
         handlerCount -= dedicatedHandlers;
         insertNameServiceWithPermits(nsId, dedicatedHandlers);
         logAssignment(nsId, dedicatedHandlers);
+        getPermitSizes().put(nsId, dedicatedHandlers);
       } else {
         unassignedNS.add(nsId);
       }
@@ -92,6 +98,7 @@ public void init(Configuration conf)
       for (String nsId : unassignedNS) {
         insertNameServiceWithPermits(nsId, handlersPerNS);
         logAssignment(nsId, handlersPerNS);
+        getPermitSizes().put(nsId, handlersPerNS);
       }
     }
 
@@ -103,6 +110,7 @@ public void init(Configuration conf)
       LOG.info("Assigned extra {} handlers to commons pool", leftOverHandlers);
       insertNameServiceWithPermits(CONCURRENT_NS,
           existingPermits + leftOverHandlers);
+      getPermitSizes().put(CONCURRENT_NS, existingPermits + leftOverHandlers);
     }
     LOG.info("Final permit allocation for concurrent ns: {}",
         getAvailablePermits(CONCURRENT_NS));
@@ -116,15 +124,23 @@ private static void logAssignment(String nsId, int count) {
   private void validateHandlersCount(Configuration conf, int handlerCount,
                                      Set<String> allConfiguredNS) {
     int totalDedicatedHandlers = 0;
+    int minimumHandlerPerNs = conf.getInt(DFS_ROUTER_FAIR_MINIMUM_HANDLER_COUNT_KEY,
+        DFS_ROUTER_FAIR_MINIMUM_HANDLER_COUNT_DEFAULT);
     for (String nsId : allConfiguredNS) {
       int dedicatedHandlers =
               conf.getInt(DFS_ROUTER_FAIR_HANDLER_COUNT_KEY_PREFIX + nsId, 0);
       if (dedicatedHandlers > 0) {
+        if (dedicatedHandlers < minimumHandlerPerNs) {
+          String msg = String.format(ERROR_NS_MSG, DFS_ROUTER_FAIR_HANDLER_COUNT_KEY_PREFIX + nsId,
+              dedicatedHandlers, minimumHandlerPerNs);
+          LOG.error(msg);
+          throw new IllegalArgumentException(msg);
+        }
         // Total handlers should not be less than sum of dedicated handlers.
         totalDedicatedHandlers += dedicatedHandlers;
       } else {
-        // Each NS should have at least one handler assigned.
-        totalDedicatedHandlers++;
+        // Each NS has to have a minimum number of handlers assigned.
+        totalDedicatedHandlers += minimumHandlerPerNs;
       }
     }
     if (totalDedicatedHandlers > handlerCount) {
@@ -134,5 +150,4 @@ private void validateHandlersCount(Configuration conf, int handlerCount,
       throw new IllegalArgumentException(msg);
     }
   }
-
 }