Java 类org.apache.curator.framework.recipes.leader.Participant 实例源码

/**
 * It's possible an Oracle has gone into a bad state. Upon the leader being changed, we want to
 * update our state
 */
@Override
public void childEvent(CuratorFramework curatorFramework, PathChildrenCacheEvent event)
    throws Exception {

  if (event.getType().equals(PathChildrenCacheEvent.Type.CHILD_REMOVED)
      || event.getType().equals(PathChildrenCacheEvent.Type.CHILD_ADDED)
      || event.getType().equals(PathChildrenCacheEvent.Type.CHILD_UPDATED)) {

    Participant participant = leaderSelector.getLeader();
    synchronized (this) {
      if (isLeader(participant)) {
        currentLeader = leaderSelector.getLeader();
      } else {
        currentLeader = null;
      }
    }
  }
}

@Override
public void childEvent(CuratorFramework curatorFramework, PathChildrenCacheEvent event)
    throws Exception {

  try {
    if (isConnected() && (event.getType().equals(PathChildrenCacheEvent.Type.CHILD_ADDED)
        || event.getType().equals(PathChildrenCacheEvent.Type.CHILD_REMOVED)
        || event.getType().equals(PathChildrenCacheEvent.Type.CHILD_UPDATED))) {
      synchronized (this) {
        Participant participant = leaderSelector.getLeader();
        if (isLeader(participant) && !leaderSelector.hasLeadership()) {
          // in case current instance becomes leader, we want to know who came before it.
          currentLeader = participant;
        }
      }
    }
  } catch (InterruptedException e) {
    log.warn("Oracle leadership watcher has been interrupted unexpectedly");
  }
}

public List<String> getParticipants() {
  try {
    List<Participant> participants =
        new ArrayList<Participant>(LEADER_SELECTOR.getParticipants());
    List<String> results = new ArrayList<String>();
    for (Participant part : participants) {
      results.add(part.getId());
    }
    return results;
  } catch (Exception e) {
    LOG.error(e.getMessage(), e);
    return null;
  }
}

/** Test starting and stopping a single instance of LeaderService. */
@Test
public void testLifeCycle() throws Exception {
    ServiceTriggers triggers = new ServiceTriggers();
    LeaderService leader = newLeaderService(1, TimeUnit.HOURS, supply(triggers.listenTo(new NopService())));
    assertEquals("test-id", leader.getId());
    assertFalse(leader.hasLeadership());

    // Start trying to obtain leadership
    leader.startAsync();
    assertTrue(triggers.getRunning().firedWithin(1, TimeUnit.MINUTES));
    assertTrue(leader.isRunning());
    assertTrue(leader.hasLeadership());
    assertEquals(new Participant("test-id", true), leader.getLeader());
    assertEquals(Collections.singletonList(new Participant("test-id", true)), leader.getParticipants());
    assertFalse(triggers.getTerminated().hasFired());
    assertTrue(leader.getCurrentDelegateService().get().isRunning());

    // Start watching ZooKeeper directly for changes
    WatchTrigger childrenTrigger = WatchTrigger.childrenTrigger();
    _curator.getChildren().usingWatcher(childrenTrigger).forPath(PATH);

    // Stop trying to obtain leadership
    leader.stopAsync();
    assertTrue(triggers.getTerminated().firedWithin(1, TimeUnit.SECONDS));
    assertFalse(leader.isRunning());
    assertFalse(leader.getCurrentDelegateService().isPresent());

    // Wait for stopped state to reflect in ZooKeeper then poll ZooKeeper for leadership participants state
    assertTrue(childrenTrigger.firedWithin(1, TimeUnit.SECONDS));
    assertFalse(leader.hasLeadership());
    assertTrue(_curator.getChildren().forPath(PATH).isEmpty());
    assertEquals(new Participant("", false), leader.getLeader());
    assertEquals(Collections.<Participant>emptyList(), leader.getParticipants());
}

public Participant currentLeader() throws Exception{
    return leaderLatch.getLeader();
}

public Participant currentLeader() throws Exception {
    return leaderLatch.getLeader();
}

private boolean isLeader(Participant participant) {
  return participant != null && participant.isLeader();
}

private boolean isLeader(Participant participant) {
  return participant != null && participant.isLeader();
}

/**
 * @return The set of current participants in the leader selection.
 * <p>
 * <B>NOTE</B> - this method polls the ZooKeeper server. Therefore it may return a value that does not match
 * {@link #hasLeadership()} as hasLeadership returns a cached value.
 */
public Collection<Participant> getParticipants() throws Exception {
    return _latch.getParticipants();
}

/**
 * @return The id for the current leader. If for some reason there is no current leader, a dummy participant
 * is returned.
 * <p>
 * <B>NOTE</B> - this method polls the ZooKeeper server. Therefore it may return a value that does not match
 * {@link #hasLeadership()} as hasLeadership returns a cached value.
 */
public Participant getLeader() throws Exception {
    return _latch.getLeader();
}