hbase-server/src/test/java/org/apache/hadoop/hbase/master/AlwaysStandByHMaster.java

   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 package org.apache.hadoop.hbase.master;
  19
  20 import java.io.IOException;
  21 import org.apache.hadoop.conf.Configuration;
  22 import org.apache.hadoop.hbase.Server;
  23 import org.apache.hadoop.hbase.ServerName;
  24 import org.apache.hadoop.hbase.monitoring.MonitoredTask;
  25 import org.apache.hadoop.hbase.util.Threads;
  26 import org.apache.hadoop.hbase.zookeeper.MasterAddressTracker;
  27 import org.apache.hadoop.hbase.zookeeper.ZKWatcher;
  28 import org.apache.zookeeper.KeeperException;
  29 import org.slf4j.Logger;
  30 import org.slf4j.LoggerFactory;
  31
  32 /**
  33  * An implementation of HMaster that always runs as a stand by and never transitions to active.
  34  */
  35 public class AlwaysStandByHMaster extends HMaster {
  36   /**
  37    * An implementation of ActiveMasterManager that never transitions it's master to active state. It
  38    * always remains as a stand by master. With the master registry implementation (HBASE-18095) it
  39    * is expected to have at least one active / standby master always running at any point in time
  40    * since they serve as the gateway for client connections.
  41    *
  42    * With this implementation, tests can simulate the scenario of not having an active master yet
  43    * the client connections to the cluster succeed.
  44    */
  45   private static class AlwaysStandByMasterManager extends ActiveMasterManager {
  46     private static final Logger LOG =
  47         LoggerFactory.getLogger(AlwaysStandByMasterManager.class);
  48
  49     AlwaysStandByMasterManager(ZKWatcher watcher, ServerName sn, Server master) {
  50       super(watcher, sn, master);
  51     }
  52
  53     /**
  54      * An implementation that never transitions to an active master.
  55      */
  56     boolean blockUntilBecomingActiveMaster(int checkInterval, MonitoredTask startupStatus) {
  57       while (!(master.isAborted() || master.isStopped())) {
  58         startupStatus.setStatus("Forever looping to stay as a standby master.");
  59         try {
  60           activeMasterServerName = null;
  61           try {
  62             if (MasterAddressTracker.getMasterAddress(watcher) != null) {
  63               clusterHasActiveMaster.set(true);
  64             }
  65             Threads.sleepWithoutInterrupt(100);
  66           } catch (IOException e) {
  67             // pass, we will get notified when some other active master creates the znode.
  68           }
  69         } catch (KeeperException e) {
  70           master.abort("Received an unexpected KeeperException, aborting", e);
  71           return false;
  72         }
  73         synchronized (this.clusterHasActiveMaster) {
  74           while (clusterHasActiveMaster.get() && !master.isStopped()) {
  75             try {
  76               clusterHasActiveMaster.wait(checkInterval);
  77             } catch (InterruptedException e) {
  78               // We expect to be interrupted when a master dies,
  79               //  will fall out if so
  80               LOG.debug("Interrupted waiting for master to die", e);
  81             }
  82           }
  83           if (clusterShutDown.get()) {
  84             this.master.stop(
  85                 "Cluster went down before this master became active");
  86           }
  87         }
  88       }
  89       return false;
  90     }
  91   }
  92
  93   public AlwaysStandByHMaster(Configuration conf) throws IOException {
  94     super(conf);
  95   }
  96
  97   protected ActiveMasterManager createActiveMasterManager(
  98       ZKWatcher zk, ServerName sn, org.apache.hadoop.hbase.Server server) {
  99     return new AlwaysStandByMasterManager(zk, sn, server);
 100   }
 101 }