I'm using C3P0 as a connection pool in Tomcat, and I'm seeing very worrying errors:
2010-09-16 13:25:00,160 [Timer-0] WARN com.mchange.v2.async.ThreadPoolAsynchronousRunner - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@43502400 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
2010-09-16 13:25:01,407 [Timer-0] WARN com.mchange.v2.async.ThreadPoolAsynchronousRunner - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@43502400 -- APPARENT DEADLOCK!!! Complete Status:
Managed Threads: 10
Active Threads: 0
Active Tasks:
Pending Tasks:
com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask@6e4151a7
Pool thread stack traces:
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#6,5,main]
java.lang.Object.wait(Native Method)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]
java.lang.Object.wait(Native Method)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main]
java.lang.Object.wait(Native Method)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main]
java.lang.Object.wait(Native Method)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#5,5,main]
java.lang.Object.wait(Native Method)
com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:534)
Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#4,5,main]
java.lang.Object.wait(Native Method)
... many more, exact same stack trace
Line 534 is:
while (true) {
Runnable myTask;
synchronized ( ThreadPoolAsynchronousRunner.this ) {
while ( !should_stop && pendingTasks.size() == 0 )
ThreadPoolAsynchronousRunner.this.wait( POLL_FOR_STOP_INTERVAL ); // <- here
if (should_stop) ...
It looks very much like all the threads are idle. They're waiting for work. 0 active threads, and only 1 task to complete. Any clues on what's going wrong?
Here's the configuration:
ds.setUser(userName);
ds.setPassword(password);
ds.setMaxPoolSize(16);
ds.setMaxConnectionAge(1800);
ds.setAcquireRetryAttempts(4);
ds.setMaxIdleTime(900);
ds.setNumHelperThreads(10);
ds.setCheckoutTimeout(1000);
Best Answer
I just experienced a similar issue against an Oracle database, but in my case
Managed ThreadandActive Threadcounts were the same.For me it was actually an authentication error but appeared as the
APPARENT DEADLOCKerror because of the way I was doing login auditing.