[
https://issues.apache.org/jira/browse/HIVE-21469?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
David Mollitor updated HIVE-21469:
----------------------------------
Description:
A lot of sins in this class to resolve:
{code:java}
@Override
public void setContext(HiveLockManagerCtx ctx) throws LockException {
try {
curatorFramework = CuratorFrameworkSingleton.getInstance(conf);
parent = conf.getVar(HiveConf.ConfVars.HIVE_ZOOKEEPER_NAMESPACE);
try{
curatorFramework.create().withMode(CreateMode.PERSISTENT).forPath("/" +
parent, new byte[0]);
} catch (Exception e) {
// ignore if the parent already exists
if (!(e instanceof KeeperException) || ((KeeperException)e).code() !=
KeeperException.Code.NODEEXISTS) {
LOG.warn("Unexpected ZK exception when creating parent node /" +
parent, e);
}
}
{code}
Every time a new session is created and this {{setContext}} method is called,
it attempts to create the root node. I have seen that, even though the root
node exists, an create node action is written to the ZK logs. Check first if
the node exists before trying to create it.
{code:java}
try {
curatorFramework.delete().forPath(zLock.getPath());
} catch (InterruptedException ie) {
curatorFramework.delete().forPath(zLock.getPath());
}
{code}
There has historically been a quite a few bugs regarding leaked locks. The
Driver will signal the session {{Thread}} by performing an interrupt. That
interrupt can happen any time and it can kill a create/delete action within the
ZK framework. We can see one example of workaround for this. If the ZK action
is interrupted, simply do it again. Well, what if it's interrupted yet again?
The lock will be leaked. Also, when the {{InterruptedException}} is caught in
the try block, the thread's interrupted flag is cleared. The flag is not reset
in this code and therefore we lose the fact that this thread has been
interrupted. This flag should be preserved so that other code paths will know
that it's time to exit.
{code:java}
if (tryNum > 1) {
Thread.sleep(sleepTime);
}
unlockPrimitive(hiveLock, parent, curatorFramework);
break;
} catch (Exception e) {
if (tryNum >= numRetriesForUnLock) {
String name = ((ZooKeeperHiveLock)hiveLock).getPath();
throw new LockException("Node " + name + " can not be deleted after "
+ numRetriesForUnLock + " attempts.",
e);
}
}
{code}
... related... the sleep here may be interrupted, but we still need to delete
the lock (again, for fear of leaking it). This sleep should be
uninterruptible. If we need to get the lock deleted, and there's a problem,
interrupting the sleep will cause the code to eventually exit and locks will be
leaked.
It also requires a bunch more TLC.
was:
A lot of sins in this class to resolve:
{code:java}
@Override
public void setContext(HiveLockManagerCtx ctx) throws LockException {
try {
curatorFramework = CuratorFrameworkSingleton.getInstance(conf);
parent = conf.getVar(HiveConf.ConfVars.HIVE_ZOOKEEPER_NAMESPACE);
try{
curatorFramework.create().withMode(CreateMode.PERSISTENT).forPath("/" +
parent, new byte[0]);
} catch (Exception e) {
// ignore if the parent already exists
if (!(e instanceof KeeperException) || ((KeeperException)e).code() !=
KeeperException.Code.NODEEXISTS) {
LOG.warn("Unexpected ZK exception when creating parent node /" +
parent, e);
}
}
{code}
Every time a new session is created and this {{setContext}} method is called,
it attempts to create the root node. I have seen that, even though the root
node exists, an create node action is written to the ZK logs. Check first if
the node exists before trying to create it.
{code:java}
try {
curatorFramework.delete().forPath(zLock.getPath());
} catch (InterruptedException ie) {
curatorFramework.delete().forPath(zLock.getPath());
}
{code}
There has historically been a quite a few bugs regarding leaked locks. The
Driver will signal the session {{Thread}} by performing an interrupt. That
interrupt can happen any time and it can kill a create/delete action within the
ZK framework. We can see one example of workaround for this. If the ZK action
is interrupted, simply do it again. Well, what if it's interrupted yet again?
The lock will be leaked anyway. Also, when the {{InterruptedException}} is
caught in the try block, the thread's interrupted flag is cleared. The flag is
not reset in this code and therefore we lose the fact that this thread has been
interrupted.
{code:java}
if (tryNum > 1) {
Thread.sleep(sleepTime);
}
unlockPrimitive(hiveLock, parent, curatorFramework);
break;
} catch (Exception e) {
if (tryNum >= numRetriesForUnLock) {
String name = ((ZooKeeperHiveLock)hiveLock).getPath();
throw new LockException("Node " + name + " can not be deleted after "
+ numRetriesForUnLock + " attempts.",
e);
}
}
{code}
... related... the sleep here may be interrupted, but we still need to delete
the lock (again, for fear of leaking it). This sleep should be
uninterruptible. If we need to get the lock deleted, and there's a problem,
interrupting the sleep will cause the code to eventually exit and locks will be
leaked.
It also requires a bunch more TLC.
> Review of ZooKeeperHiveLockManager
> ----------------------------------
>
> Key: HIVE-21469
> URL: https://issues.apache.org/jira/browse/HIVE-21469
> Project: Hive
> Issue Type: Improvement
> Components: Locking
> Affects Versions: 4.0.0, 3.2.0
> Reporter: David Mollitor
> Assignee: David Mollitor
> Priority: Major
> Attachments: HIVE-21469.1.patch
>
>
> A lot of sins in this class to resolve:
> {code:java}
> @Override
> public void setContext(HiveLockManagerCtx ctx) throws LockException {
> try {
> curatorFramework = CuratorFrameworkSingleton.getInstance(conf);
> parent = conf.getVar(HiveConf.ConfVars.HIVE_ZOOKEEPER_NAMESPACE);
> try{
> curatorFramework.create().withMode(CreateMode.PERSISTENT).forPath("/"
> + parent, new byte[0]);
> } catch (Exception e) {
> // ignore if the parent already exists
> if (!(e instanceof KeeperException) || ((KeeperException)e).code() !=
> KeeperException.Code.NODEEXISTS) {
> LOG.warn("Unexpected ZK exception when creating parent node /" +
> parent, e);
> }
> }
> {code}
> Every time a new session is created and this {{setContext}} method is called,
> it attempts to create the root node. I have seen that, even though the root
> node exists, an create node action is written to the ZK logs. Check first if
> the node exists before trying to create it.
> {code:java}
> try {
> curatorFramework.delete().forPath(zLock.getPath());
> } catch (InterruptedException ie) {
> curatorFramework.delete().forPath(zLock.getPath());
> }
> {code}
> There has historically been a quite a few bugs regarding leaked locks. The
> Driver will signal the session {{Thread}} by performing an interrupt. That
> interrupt can happen any time and it can kill a create/delete action within
> the ZK framework. We can see one example of workaround for this. If the ZK
> action is interrupted, simply do it again. Well, what if it's interrupted
> yet again? The lock will be leaked. Also, when the {{InterruptedException}}
> is caught in the try block, the thread's interrupted flag is cleared. The
> flag is not reset in this code and therefore we lose the fact that this
> thread has been interrupted. This flag should be preserved so that other
> code paths will know that it's time to exit.
> {code:java}
> if (tryNum > 1) {
> Thread.sleep(sleepTime);
> }
> unlockPrimitive(hiveLock, parent, curatorFramework);
> break;
> } catch (Exception e) {
> if (tryNum >= numRetriesForUnLock) {
> String name = ((ZooKeeperHiveLock)hiveLock).getPath();
> throw new LockException("Node " + name + " can not be deleted after
> " + numRetriesForUnLock + " attempts.",
> e);
> }
> }
> {code}
> ... related... the sleep here may be interrupted, but we still need to delete
> the lock (again, for fear of leaking it). This sleep should be
> uninterruptible. If we need to get the lock deleted, and there's a problem,
> interrupting the sleep will cause the code to eventually exit and locks will
> be leaked.
> It also requires a bunch more TLC.
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