001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.conf;
019
020import static org.junit.Assert.assertFalse;
021import static org.junit.Assert.assertTrue;
022import org.apache.hadoop.conf.Configuration;
023import org.apache.hadoop.hbase.HBaseClassTestRule;
024import org.apache.hadoop.hbase.testclassification.ClientTests;
025import org.apache.hadoop.hbase.testclassification.SmallTests;
026import org.junit.ClassRule;
027import org.junit.Test;
028import org.junit.experimental.categories.Category;
029import org.slf4j.Logger;
030import org.slf4j.LoggerFactory;
031
032@Category({SmallTests.class, ClientTests.class})
033public class TestConfigurationManager {
034
035  @ClassRule
036  public static final HBaseClassTestRule CLASS_RULE =
037      HBaseClassTestRule.forClass(TestConfigurationManager.class);
038
039  private static final Logger LOG = LoggerFactory.getLogger(TestConfigurationManager.class);
040
041  static class DummyConfigurationObserver implements ConfigurationObserver {
042    private boolean notifiedOnChange = false;
043    private final ConfigurationManager cm;
044
045    public DummyConfigurationObserver(ConfigurationManager cm) {
046      this.cm = cm;
047      register();
048    }
049
050    @Override
051    public void onConfigurationChange(Configuration conf) {
052      notifiedOnChange = true;
053    }
054
055    // Was the observer notified on Configuration change?
056    public boolean wasNotifiedOnChange() {
057      return notifiedOnChange;
058    }
059
060    public void resetNotifiedOnChange() {
061      notifiedOnChange = false;
062    }
063
064    public void register() {
065      cm.registerObserver(this);
066    }
067
068    public void deregister() {
069      cm.deregisterObserver(this);
070    }
071  }
072
073  /**
074   * Test if observers get notified by the <code>ConfigurationManager</code>
075   * when the Configuration is reloaded.
076   */
077  @Test
078  public void testCheckIfObserversNotified() {
079    Configuration conf = new Configuration();
080    ConfigurationManager cm = new ConfigurationManager();
081    DummyConfigurationObserver d1 = new DummyConfigurationObserver(cm);
082
083    // Check if we get notified.
084    cm.notifyAllObservers(conf);
085    assertTrue(d1.wasNotifiedOnChange());
086    d1.resetNotifiedOnChange();
087
088    // Now check if we get notified on change with more than one observers.
089    DummyConfigurationObserver d2 = new DummyConfigurationObserver(cm);
090    cm.notifyAllObservers(conf);
091    assertTrue(d1.wasNotifiedOnChange());
092    d1.resetNotifiedOnChange();
093    assertTrue(d2.wasNotifiedOnChange());
094    d2.resetNotifiedOnChange();
095
096    // Now try deregistering an observer and verify that it was not notified
097    d2.deregister();
098    cm.notifyAllObservers(conf);
099    assertTrue(d1.wasNotifiedOnChange());
100    d1.resetNotifiedOnChange();
101    assertFalse(d2.wasNotifiedOnChange());
102  }
103
104  // Register an observer that will go out of scope immediately, allowing
105  // us to test that out of scope observers are deregistered.
106  private void registerLocalObserver(ConfigurationManager cm) {
107    new DummyConfigurationObserver(cm);
108  }
109
110  /**
111   * Test if out-of-scope observers are deregistered on GC.
112   */
113  @Test
114  public void testDeregisterOnOutOfScope() {
115    Configuration conf = new Configuration();
116    ConfigurationManager cm = new ConfigurationManager();
117
118    boolean outOfScopeObserversDeregistered = false;
119
120    // On my machine, I was able to cause a GC after around 5 iterations.
121    // If we do not cause a GC in 100k iterations, which is very unlikely,
122    // there might be something wrong with the GC.
123    for (int i = 0; i < 100000; i++) {
124      registerLocalObserver(cm);
125      cm.notifyAllObservers(conf);
126
127      // 'Suggest' the system to do a GC. We should be able to cause GC
128      // atleast once in the 2000 iterations.
129      System.gc();
130
131      // If GC indeed happened, all the observers (which are all out of scope),
132      // should have been deregistered.
133      if (cm.getNumObservers() <= i) {
134        outOfScopeObserversDeregistered = true;
135        break;
136      }
137    }
138    if (!outOfScopeObserversDeregistered) {
139      LOG.warn("Observers were not GC-ed! Something seems to be wrong.");
140    }
141    assertTrue(outOfScopeObserversDeregistered);
142  }
143}