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1   /**
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.hadoop.hbase.ipc;
20  
21  import java.util.ArrayList;
22  import java.util.List;
23  import java.util.Random;
24  import java.util.concurrent.BlockingQueue;
25  import java.util.concurrent.atomic.AtomicInteger;
26  
27  import org.apache.commons.logging.Log;
28  import org.apache.commons.logging.LogFactory;
29  import org.apache.hadoop.conf.Configuration;
30  import org.apache.hadoop.hbase.Abortable;
31  import org.apache.hadoop.hbase.HConstants;
32  import org.apache.hadoop.hbase.classification.InterfaceAudience;
33  import org.apache.hadoop.hbase.classification.InterfaceStability;
34  import org.apache.hadoop.hbase.monitoring.MonitoredRPCHandler;
35  import org.apache.hadoop.util.StringUtils;
36  
37  import com.google.common.base.Preconditions;
38  import com.google.common.base.Strings;
39  
40  @InterfaceAudience.Private
41  @InterfaceStability.Evolving
42  public abstract class RpcExecutor {
43    private static final Log LOG = LogFactory.getLog(RpcExecutor.class);
44  
45    private final AtomicInteger activeHandlerCount = new AtomicInteger(0);
46    private final List<Thread> handlers;
47    private final int handlerCount;
48    private final String name;
49    private final AtomicInteger failedHandlerCount = new AtomicInteger(0);
50  
51    private boolean running;
52  
53    private Configuration conf = null;
54    private Abortable abortable = null;
55  
56    public RpcExecutor(final String name, final int handlerCount) {
57      this.handlers = new ArrayList<Thread>(handlerCount);
58      this.handlerCount = handlerCount;
59      this.name = Strings.nullToEmpty(name);
60    }
61  
62    public RpcExecutor(final String name, final int handlerCount, final Configuration conf,
63        final Abortable abortable) {
64      this(name, handlerCount);
65      this.conf = conf;
66      this.abortable = abortable;
67    }
68    
69    public void start(final int port) {
70      running = true;
71      startHandlers(port);
72    }
73  
74    public void stop() {
75      running = false;
76      for (Thread handler : handlers) {
77        handler.interrupt();
78      }
79    }
80  
81    public int getActiveHandlerCount() {
82      return activeHandlerCount.get();
83    }
84  
85    /** Returns the length of the pending queue */
86    public abstract int getQueueLength();
87  
88    /** Add the request to the executor queue */
89    public abstract void dispatch(final CallRunner callTask) throws InterruptedException;
90  
91    /** Returns the list of request queues */
92    protected abstract List<BlockingQueue<CallRunner>> getQueues();
93  
94    protected void startHandlers(final int port) {
95      List<BlockingQueue<CallRunner>> callQueues = getQueues();
96      startHandlers(null, handlerCount, callQueues, 0, callQueues.size(), port);
97    }
98  
99    protected void startHandlers(final String nameSuffix, final int numHandlers,
100       final List<BlockingQueue<CallRunner>> callQueues,
101       final int qindex, final int qsize, final int port) {
102     final String threadPrefix = name + Strings.nullToEmpty(nameSuffix);
103     for (int i = 0; i < numHandlers; i++) {
104       final int index = qindex + (i % qsize);
105       Thread t = new Thread(new Runnable() {
106         @Override
107         public void run() {
108           consumerLoop(callQueues.get(index));
109         }
110       });
111       t.setDaemon(true);
112       t.setName(threadPrefix + "RpcServer.handler=" + handlers.size() +
113           ",queue=" + index + ",port=" + port);
114       t.start();
115       LOG.debug(threadPrefix + " Start Handler index=" + handlers.size() + " queue=" + index);
116       handlers.add(t);
117     }
118   }
119 
120   protected void consumerLoop(final BlockingQueue<CallRunner> myQueue) {
121     boolean interrupted = false;
122     double handlerFailureThreshhold =
123         conf == null ? 1.0 : conf.getFloat(HConstants.REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT,
124           HConstants.DEFAULT_REGION_SERVER_HANDLER_ABORT_ON_ERROR_PERCENT);
125     try {
126       while (running) {
127         try {
128           MonitoredRPCHandler status = RpcServer.getStatus();
129           CallRunner task = myQueue.take();
130           task.setStatus(status);
131           try {
132             activeHandlerCount.incrementAndGet();
133             task.run();
134           } catch (Error e) {
135             int failedCount = failedHandlerCount.incrementAndGet();
136             if (handlerFailureThreshhold >= 0
137                 && failedCount > handlerCount * handlerFailureThreshhold) {
138               String message =
139                   "Number of failed RpcServer handler exceeded threshhold "
140                       + handlerFailureThreshhold + "  with failed reason: "
141                       + StringUtils.stringifyException(e);
142               if (abortable != null) {
143                 abortable.abort(message, e);
144               } else {
145                 LOG.error("Received " + StringUtils.stringifyException(e)
146                   + " but not aborting due to abortable being null");
147                 throw e;
148               }
149             } else {
150               LOG.warn("RpcServer handler threads encountered errors "
151                   + StringUtils.stringifyException(e));
152             }
153           } finally {
154             activeHandlerCount.decrementAndGet();
155           }
156         } catch (InterruptedException e) {
157           interrupted = true;
158         }
159       }
160     } finally {
161       if (interrupted) {
162         Thread.currentThread().interrupt();
163       }
164     }
165   }
166 
167   public static abstract class QueueBalancer {
168     /**
169      * @return the index of the next queue to which a request should be inserted
170      */
171     public abstract int getNextQueue();
172   }
173 
174   public static QueueBalancer getBalancer(int queueSize) {
175     Preconditions.checkArgument(queueSize > 0, "Queue size is <= 0, must be at least 1");
176     if (queueSize == 1) {
177       return ONE_QUEUE;
178     } else {
179       return new RandomQueueBalancer(queueSize);
180     }
181   }
182 
183   /**
184    * All requests go to the first queue, at index 0
185    */
186   private static QueueBalancer ONE_QUEUE = new QueueBalancer() {
187 
188     @Override
189     public int getNextQueue() {
190       return 0;
191     }
192   };
193 
194   /**
195    * Queue balancer that just randomly selects a queue in the range [0, num queues).
196    */
197   private static class RandomQueueBalancer extends QueueBalancer {
198     private final int queueSize;
199 
200     private final ThreadLocal<Random> threadRandom =
201       new ThreadLocal<Random>() {
202         @Override
203         protected Random initialValue() {
204           return new Random();
205         }
206       };
207 
208     public RandomQueueBalancer(int queueSize) {
209       this.queueSize = queueSize;
210     }
211 
212     public int getNextQueue() {
213       return threadRandom.get().nextInt(queueSize);
214     }
215   }
216 }