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: [email protected]
Reporter: [email protected]
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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