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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: Application hanging on Tomcat 7.0.54
Date Wed, 26 Sep 2018 23:29:32 GMT
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Louis,

On 9/26/18 15:56, Louis Zipes wrote:
> Problem just re-occurred and so I was able to at least get a JSTACK
> (I assume it was Tomcat since it was the Java using the most memory
> on the machine).  Here is the reoccurring message.  I get more hits
> on but haven't dug through all of the Google hits yet (due to
> multi-tasking) so apologies up front if there is a simple answer to
> this.
> 
> "Event_Manager_1413" daemon prio=6 tid=0x0000000024856000
> nid=0x40c4 waiting on condition [0x0000000042dae000] 
> java.lang.Thread.State: TIMED_WAITING (parking) at
> sun.misc.Unsafe.park(Native Method) - parking to wait for
> <0x00000005ab45f7b8> (a
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
>
> 
at java.util.concurrent.locks.LockSupport.parkNanos(Unknown Source)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.
awaitNanos(Unknown
> Source) at java.util.concurrent.LinkedBlockingQueue.poll(Unknown
> Source) at java.util.concurrent.ThreadPoolExecutor.getTask(Unknown
> Source) at
> java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) 
> at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown
> Source) at java.lang.Thread.run(Unknown Source)

This thread is waiting for a task, and is essentially idle. You will
have many of these on a non-busy system.

What are the other threads doing?

> Locked ownable synchronizers: - None
> 
>> Any comments/suggestions are appreciated!
> 
> Your most likely problem is database connection pool
> mismanagement: connections aren't properly released and the pool
> empties. All threads are left waiting on available database
> connections which will never be replenished.
> 
> I'm using the ojdbc6.jar if that is what you are referring to or is
> there a better setting somewhere.

ODBC? What is your database?

- -chris


> -----Original Message----- From: Christopher Schultz
> [mailto:chris@christopherschultz.net] Sent: Wednesday, September
> 26, 2018 3:46 PM To: users@tomcat.apache.org Subject: Re:
> Application hanging on Tomcat 7.0.54
> 
> - - - external message, proceed with caution - - -
> 
> 
> Louis,
> 
> On 9/26/18 14:42, Louis Zipes wrote:
>> Hi all, Tomcat 7.0.54 running on Windows 2012
> 
>> We are running a third party application on Tomcat and today we 
>> have intermittently run in issues where the application stops 
>> working.  The big changes in our system is that we have added
>> more end users and we are at year end so of course everyone is
>> hitting the system hard. Even if we force a log out of all users
>> and stop all background jobs then the application doesn't
>> recover.
> 
>> We see no active sessions on the database (our application is 
>> connecting to an Oracle database) and I see no clear error
>> messages in either our third party application logs or the Tomcat
>> logs (ex. OutofMemory).  When we go to the Windows Task Manager
>> we did not see the machine's Memory max'd out but admittedly I
>> didn't look at the Java session to see if was reaching its Heap
>> Max.  The only thing that we noticed was that TCP connections
>> went down right after the restart.  I did open up Jconsole under
>> Java and I did force a garbage collection but that didn't seem to
>> help.
> 
>> We do have an Oracle Grid Control and we did get an alert in 
>> regards to Metric: [HTTP Transaction] Perceived Time per Page
>> going past thresholds but not sure if that was just an old alert
>> with and old range that was set up a long time ago or is a really
>> valid clue.    Since this is PRD we had to get it back up and
>> running so all I did was increase the Tomcat Xmx Heap size and
>> restarted.  I'm not really confident that is the solution since
>> as mentioned you tend to see a clear out of memory error if it
>> was too small.
> 
>> So a few questions:
> 
> 
>> 1)     Does this sound like a known issue with this earlier
>> version of Tomcat?
> 
> No.
> 
>> 2)     Should I turn up any logging on Tomcat and if so which 
>> ones?
> 
> Not yet.
> 
>> 3)     We didn't do a JSTACK dump while it was happening.  Would 
>> that have been useful?
> 
> Absolutely.
> 
>> 4)     Do we need to play around with MaxThreads and/or 
>> MaxConnections.  We do have maxThreads in our server.mxl but in
>> DEV when we turned it down to a value = 5  hoping to overwhelm
>> it nothing bad happened.
> 
> Don't change anything, yet.
> 
>> Once again, we are limited to what we could do and collect since
>> it was PRD and we needed to restart it.  We restarted the Tomcat 
>> service and everything is processing fine for right now.  I will 
>> note that that we did have that bad Windows patch that prevented
>> it from stopping and starting cleanly 
>> (https://stackoverflow.com/questions/51498291/tomcat-lockup-on-shutdo
w
>
>> 
n)
>> but we have taken the break fix patch and the daily restarts
>> seem to be fine since then.
> 
>> Any comments/suggestions are appreciated!
> 
> Your most likely problem is database connection pool
> mismanagement: connections aren't properly released and the pool
> empties. All threads are left waiting on available database
> connections which will never be replenished.
> 
> -chris
> 
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