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Posted to dev@tomcat.apache.org by bu...@apache.org on 2014/06/24 00:05:40 UTC
[Bug 56660] New: Resource leak in FairBlockingQueue::poll method
https://issues.apache.org/bugzilla/show_bug.cgi?id=56660
Bug ID: 56660
Summary: Resource leak in FairBlockingQueue::poll method
Product: Tomcat Modules
Version: unspecified
Hardware: All
OS: All
Status: NEW
Severity: major
Priority: P2
Component: jdbc-pool
Assignee: dev@tomcat.apache.org
Reporter: alex-pub.apache-ant@reflexion.net
tomcat-jdbc version: 7.0.54
In this code fragment from FairBlockingQueue::poll method
Line 144
//the queue is empty we will wait for an object
ExchangeCountDownLatch<E> c = new ExchangeCountDownLatch<E>(1);
//add to the bottom of the wait list
waiters.addLast(c);
//unlock the global lock
lock.unlock();
//wait for the specified timeout
if (!c.await(timeout, unit)) {
//if we timed out, remove ourselves from the waitlist
lock.lock();
waiters.remove(c);
lock.unlock();
}
//return the item we received, can be null if we timed out
result = c.getItem();
When the 'c.await' is interrupted, the Latch is not removed from 'waiters'.
As I understand, it can hold on to the connection object.
Thus the pool is leaking connections, and at some time, all new requests just
hang on the c.await indefinitely.
The fix is pretty simple. Catch InterruptedException (and any other non-checked
exception) and do a cleanup there.
boolean needsWaitersCleanup = false;
try
{
if (!c.await(timeout, unit)) {
needsWaitersCleanup = true;
}
}
catch ( InterruptedException | RuntimeException | Error e )
{
needsWaitersCleanup = true;
throw e;
}
finally
{
if ( needsWaitersCleanup )
{
//if we timed out, remove ourselves from the waitlist
lock.lock();
try
{
waiters.remove(c);
}
finally
{
lock.unlock();
}
}
}
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[Bug 56660] Resource leak in FairBlockingQueue::poll method
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=56660
--- Comment #1 from Alexander Pogrebnyak <al...@reflexion.net> ---
I've encountered this bug in production, under a heavy load. The problem here
is that it's manifestation is pretty random.
One workaround, until this bug is fixed, is to turn off 'fairQueue' property of
PoolProperties.
When 'fairQueue' is off, current implementation falls back to
'java.util.concurrent.ArrayBlockingQueue', which does not have this issue.
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[Bug 56660] Resource leak in FairBlockingQueue::poll method
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=56660
Patric Rufflar <pa...@rufflar.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |patric@rufflar.com
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