import org.apache.hadoop.metrics2.lib.MetricsSourceBuilder; //导入依赖的package包/类
@Override public synchronized <T>
T register(String name, String desc, T source) {
  MetricsSourceBuilder sb = MetricsAnnotations.newSourceBuilder(source);
  final MetricsSource s = sb.build();
  MetricsInfo si = sb.info();
  String name2 = name == null ? si.name() : name;
  final String finalDesc = desc == null ? si.description() : desc;
  final String finalName = // be friendly to non-metrics tests
      DefaultMetricsSystem.sourceName(name2, !monitoring);
  allSources.put(finalName, s);
  LOG.debug(finalName +", "+ finalDesc);
  if (monitoring) {
    registerSource(finalName, finalDesc, s);
  }
  // We want to re-register the source to pick up new config when the
  // metrics system restarts.
  register(finalName, new AbstractCallback() {
    @Override public void postStart() {
      registerSource(finalName, finalDesc, s);
    }
  });
  return source;
}
 

import org.apache.hadoop.metrics2.lib.MetricsSourceBuilder; //导入依赖的package包/类
@Override public synchronized <T>
T register(String name, String desc, T source) {
  MetricsSourceBuilder sb = MetricsAnnotations.newSourceBuilder(source);
  final MetricsSource s = sb.build();
  MetricsInfo si = sb.info();
  String name2 = name == null ? si.name() : name;
  final String finalDesc = desc == null ? si.description() : desc;
  final String finalName = // be friendly to non-metrics tests
      DefaultMetricsSystem.sourceName(name2, !monitoring);
  allSources.put(finalName, s);
  LOG.debug(finalName +", "+ finalDesc);
  if (monitoring) {
    registerSource(finalName, finalDesc, s);
  }
  // We want to re-register the source to pick up new config when the
  // metrics system restarts.
  register(new AbstractCallback() {
    @Override public void postStart() {
      registerSource(finalName, finalDesc, s);
    }
  });
  return source;
}
 

import org.apache.hadoop.metrics2.lib.MetricsSourceBuilder; //导入依赖的package包/类
@Test
public void testGetMetricsAndJmx() throws Exception {
  // create test source with a single metric counter of value 0
  TestSource source = new TestSource("test");
  MetricsSourceBuilder sb = MetricsAnnotations.newSourceBuilder(source);
  final MetricsSource s = sb.build();

  List<MetricsTag> injectedTags = new ArrayList<MetricsTag>();
  MetricsSourceAdapter sa = new MetricsSourceAdapter(
      "test", "test", "test desc", s, injectedTags, null, null, 1, false);

  // all metrics are initially assumed to have changed
  MetricsCollectorImpl builder = new MetricsCollectorImpl();
  Iterable<MetricsRecordImpl> metricsRecords = sa.getMetrics(builder, true);

  // Validate getMetrics and JMX initial values
  MetricsRecordImpl metricsRecord = metricsRecords.iterator().next();
  assertEquals(0L,
      metricsRecord.metrics().iterator().next().value().longValue());

  Thread.sleep(100); // skip JMX cache TTL
  assertEquals(0L, (Number)sa.getAttribute("C1"));

  // change metric value
  source.incrementCnt();

  // validate getMetrics and JMX
  builder = new MetricsCollectorImpl();
  metricsRecords = sa.getMetrics(builder, true);
  metricsRecord = metricsRecords.iterator().next();
  assertTrue(metricsRecord.metrics().iterator().hasNext());
  Thread.sleep(100); // skip JMX cache TTL
  assertEquals(1L, (Number)sa.getAttribute("C1"));
}
 

import org.apache.hadoop.metrics2.lib.MetricsSourceBuilder; //导入依赖的package包/类
static CleanerMetrics create() {
  MetricsSystem ms = DefaultMetricsSystem.instance();

  CleanerMetrics metricObject = new CleanerMetrics();
  MetricsSourceBuilder sb = MetricsAnnotations.newSourceBuilder(metricObject);
  final MetricsSource s = sb.build();
  ms.register("cleaner", "The cleaner service of truly shared cache", s);
  metricObject.metricSource = s;
  return metricObject;
}
 

import org.apache.hadoop.metrics2.lib.MetricsSourceBuilder; //导入依赖的package包/类
/**
 * Test a race condition when updating the JMX cache (HADOOP-12482):
 * 1. Thread A reads the JMX metric every 2 JMX cache TTL. It marks the JMX
 *    cache to be updated by marking lastRecs to null. After this it adds a
 *    new key to the metrics. The next call to read should pick up this new
 *    key.
 * 2. Thread B triggers JMX metric update every 1 JMX cache TTL. It assigns
 *    lastRecs to a new object (not null any more).
 * 3. Thread A tries to read JMX metric again, sees lastRecs is not null and
 *    does not update JMX cache. As a result the read does not pickup the new
 *    metric.
 * @throws Exception
 */
@Test
public void testMetricCacheUpdateRace() throws Exception {
  // Create test source with a single metric counter of value 1.
  TestMetricsSource source = new TestMetricsSource();
  MetricsSourceBuilder sourceBuilder =
      MetricsAnnotations.newSourceBuilder(source);

  final long JMX_CACHE_TTL = 250; // ms
  List<MetricsTag> injectedTags = new ArrayList<>();
  MetricsSourceAdapter sourceAdapter =
      new MetricsSourceAdapter("test", "test",
          "test JMX cache update race condition", sourceBuilder.build(),
          injectedTags, null, null, JMX_CACHE_TTL, false);

  ScheduledExecutorService updaterExecutor =
      Executors.newScheduledThreadPool(1, new ThreadFactoryBuilder().build());
  ScheduledExecutorService readerExecutor =
      Executors.newScheduledThreadPool(1, new ThreadFactoryBuilder().build());

  final AtomicBoolean hasError = new AtomicBoolean(false);

  // Wake up every 1 JMX cache TTL to set lastRecs before updateJmxCache() is
  // called.
  SourceUpdater srcUpdater = new SourceUpdater(sourceAdapter, hasError);
  ScheduledFuture<?> updaterFuture =
      updaterExecutor.scheduleAtFixedRate(srcUpdater,
          sourceAdapter.getJmxCacheTTL(), sourceAdapter.getJmxCacheTTL(),
          TimeUnit.MILLISECONDS);
  srcUpdater.setFuture(updaterFuture);

  // Wake up every 2 JMX cache TTL so updateJmxCache() will try to update
  // JMX cache.
  SourceReader srcReader = new SourceReader(source, sourceAdapter, hasError);
  ScheduledFuture<?> readerFuture =
      readerExecutor.scheduleAtFixedRate(srcReader,
          0, // set JMX info cache at the beginning
          2 * sourceAdapter.getJmxCacheTTL(), TimeUnit.MILLISECONDS);
  srcReader.setFuture(readerFuture);

  // Let the threads do their work.
  Thread.sleep(RACE_TEST_RUNTIME);

  assertFalse("Hit error", hasError.get());

  // cleanup
  updaterExecutor.shutdownNow();
  readerExecutor.shutdownNow();
  updaterExecutor.awaitTermination(1000, TimeUnit.MILLISECONDS);
  readerExecutor.awaitTermination(1000, TimeUnit.MILLISECONDS);
}