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From André Warnier (tomcat)>
Subject Re: Strange wait time in my application - Tomcat 7.0.67
Date Mon, 17 Oct 2016 16:01:51 GMT
On 17.10.2016 17:52, Tullio Bettinazzi wrote:
> I didn't find any solution to my problem.
> Could someone provide suggestions or a strategy to find the solution ?

"I don't see relevant garbage collection : heap size and permgen have correct dimentions."

Define "correct".  Are you really *logging* the JVM Garbage Collection, and do you *know*

that this is not the issue ?

(Note that 4 seconds seems an awfully long time for a GC; but one would want to eliminate

this with certainty, before looking any further).

> ________________________________
> Da: Martijn Bos <>
> Inviato: lunedì 3 ottobre 2016 21.05
> A: Tomcat Users List
> Oggetto: Re: Strange wait time in my application - Tomcat 7.0.67
> On 2016-10-03 07:56:34, Tullio Bettinazzi wrote:
>> I've an application under tomcat.
>> When only a one or two users works on it everithing is ok.
>> When the number of users grows the application slows down.
>> Is not a memory nor a cpu problem : using top I see the system resources quite free.
>> I don't see relevant garbage collection : heap size and permgen have correct dimentions.
>> No other applications are running on the system.
>> I log more or less every relevant operation in my system (db query and so on) and
I see that every slowdown is concentered in a single operation.
>> I mean all operations take "normal" time but one or two of them take 4 seconds more.
>> The "slowing" operations are not the same in different executions, and theydo not
have a specific type (not only DB query, not only DB stored procedures, not only.....).
>> It seems like if the thread is frozen for a fixed amount fo time (4 seconds more
or less) and then it restarts.
>> I don't think it's a "queue" problem because otherwise the wait time would be unperdictable
and not a "fixed" 4 seconds time.
>> I don't know any parameter impacting on that behaviour.
>> I use Tomcat 7.0.32 with JVM on a Linux server.
>> Could someone suggest a solution for my problem or, at least, an investigation strategy.
>> Tks
>> Tullio
> The few examples that you mention are all database related (query/stored procedure).
> Can it be that your connection pool (if used) combined with not closing connections is
part of the problem.
> I can imagine :
> 1)
> Maybe you run out of conenctions, because connections are not properly closed.
> And also the connection pool teminates connections when they are not used for 4 seconds.
> After 4 seconds the pool can recreate connections again.
> or 2)
> Maybe your connection pool has very limited connections.
> With one or two users this limited number of connections in the pool will suffice.
> If there are more users, the max. number of connections isn't enough.
> The pool then has to wait for connections to become fee again.
> (uhh....I'm not an expert at all, but the above came immediately to my mind)
> --
> Met vriendelijke groet,
> Martijn Bos
> +31 6 39477001
> (Public pgp-key :
> -----BEGIN PGP PUBLIC KEY BLOCK----- Version: GnuPG v1 mQENBFJ6LpgBCADL9w2eicatZKiw4xijCVC8WZpcPOr2So6jFfQ6nWk3bTXoVsHk
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