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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.chaos.monkies;
20  
21  import org.apache.hadoop.hbase.Stoppable;
22  
23  /**
24   * A utility to injects faults in a running cluster.
25   * <p>
26   * ChaosMonkey defines Action's and Policy's. Actions are sequences of events, like
27   *  - Select a random server to kill
28   *  - Sleep for 5 sec
29   *  - Start the server on the same host
30   * Actions can also be complex events, like rolling restart of all of the servers.
31   * <p>
32   * Policies on the other hand are responsible for executing the actions based on a strategy.
33   * The default policy is to execute a random action every minute based on predefined action
34   * weights. ChaosMonkey executes predefined named policies until it is stopped. More than one
35   * policy can be active at any time.
36   * <p>
37   * Chaos monkey can be run from the command line, or can be invoked from integration tests.
38   * See {@link org.apache.hadoop.hbase.IntegrationTestIngest} or other integration tests that use
39   * chaos monkey for code examples.
40   * <p>
41   * ChaosMonkey class is indeed inspired by the Netflix's same-named tool:
42   * http://techblog.netflix.com/2012/07/chaos-monkey-released-into-wild.html
43   */
44  public abstract class ChaosMonkey implements Stoppable {
45    public abstract void start() throws Exception;
46  
47    @Override
48    public abstract void stop(String why);
49  
50    @Override
51    public abstract boolean isStopped();
52  
53    public abstract void waitForStop() throws InterruptedException;
54  
55    /**
56     * Returns whether the CM does destructive actions (killing servers) so that a cluster restore
57     * is needed after CM is stopped. Otherwise cluster will be left as it is
58     */
59    public abstract boolean isDestructive();
60  }