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HADOOP-9183. Potential deadlock in ActiveStandbyElector. 

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1431251 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Thomas White 2013-01-10 10:05:53 +00:00
parent 6449f52455
commit d863f7a1e4
2 changed files with 12 additions and 25 deletions
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2
hadoop-common-project/hadoop-common/CHANGES.txt
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@ -528,6 +528,8 @@ Release 2.0.3-alpha - Unreleased
HADOOP-9155. FsPermission should have different default value, 777 for
directory and 666 for file. (Binglin Chang via atm)
HADOOP-9183. Potential deadlock in ActiveStandbyElector. (tomwhite)
Release 2.0.2-alpha - 2012-09-07
INCOMPATIBLE CHANGES

35
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/ActiveStandbyElector.java
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@ -613,7 +613,7 @@ public class ActiveStandbyElector implements StatCallback, StringCallback {
// Unfortunately, the ZooKeeper constructor connects to ZooKeeper and
// may trigger the Connected event immediately. So, if we register the
// watcher after constructing ZooKeeper, we may miss that event. Instead,
// we construct the watcher first, and have it queue any events it receives
// we construct the watcher first, and have it block any events it receives
// before we can set its ZooKeeper reference.
WatcherWithClientRef watcher = new WatcherWithClientRef();
ZooKeeper zk = new ZooKeeper(zkHostPort, zkSessionTimeout, watcher);
@ -1002,19 +1002,17 @@ public class ActiveStandbyElector implements StatCallback, StringCallback {
private CountDownLatch hasReceivedEvent = new CountDownLatch(1);
/**
* If any events arrive before the reference to ZooKeeper is set,
* they get queued up and later forwarded when the reference is
* available.
* Latch used to wait until the reference to ZooKeeper is set.
*/
private final List<WatchedEvent> queuedEvents = Lists.newLinkedList();
private CountDownLatch hasSetZooKeeper = new CountDownLatch(1);
private WatcherWithClientRef() {
}
private WatcherWithClientRef(ZooKeeper zk) {
this.zk = zk;
setZooKeeperRef(zk);
}
/**
* Waits for the next event from ZooKeeper to arrive.
*
@ -1029,9 +1027,7 @@ public class ActiveStandbyElector implements StatCallback, StringCallback {
if (!hasReceivedEvent.await(connectionTimeoutMs, TimeUnit.MILLISECONDS)) {
LOG.error("Connection timed out: couldn't connect to ZooKeeper in "
+ connectionTimeoutMs + " milliseconds");
synchronized (this) {
zk.close();
}
zk.close();
throw KeeperException.create(Code.CONNECTIONLOSS);
}
} catch (InterruptedException e) {
@ -1041,29 +1037,18 @@ public class ActiveStandbyElector implements StatCallback, StringCallback {
}
}
private synchronized void setZooKeeperRef(ZooKeeper zk) {
private void setZooKeeperRef(ZooKeeper zk) {
Preconditions.checkState(this.zk == null,
"zk already set -- must be set exactly once");
this.zk = zk;
for (WatchedEvent e : queuedEvents) {
forwardEvent(e);
}
queuedEvents.clear();
hasSetZooKeeper.countDown();
}
@Override
public synchronized void process(WatchedEvent event) {
if (zk != null) {
forwardEvent(event);
} else {
queuedEvents.add(event);
}
}
private void forwardEvent(WatchedEvent event) {
public void process(WatchedEvent event) {
hasReceivedEvent.countDown();
try {
hasSetZooKeeper.await(zkSessionTimeout, TimeUnit.MILLISECONDS);
ActiveStandbyElector.this.processWatchEvent(
zk, event);
} catch (Throwable t) {