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Posted to dev@tomcat.apache.org by bu...@apache.org on 2010/06/09 16:11:14 UTC
DO NOT REPLY [Bug 49414] New: Wrong memory leak detection: executor
thread reported as web app thread
https://issues.apache.org/bugzilla/show_bug.cgi?id=49414
Summary: Wrong memory leak detection: executor thread reported
as web app thread
Product: Tomcat 7
Version: trunk
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P2
Component: Catalina
AssignedTo: dev@tomcat.apache.org
ReportedBy: mguillemot@yahoo.fr
Created an attachment (id=25566)
--> (https://issues.apache.org/bugzilla/attachment.cgi?id=25566)
Unit test allowing to generate the wrong log message (but doesn't catpure the
log to really test it)
At Tomcat shutdown I have quite often following message
SEVERE: The web application [/] appears to have started a thread named
[http-8001-exec-1] but has failed to stop it. This is very likely to create a
memory leak.
Looking into the details it appears that a request is still being processed.
The thread that is detected as leak is not a user thread but Tomcat's executor
thread.
I'm not sure what would be the right behaviour here: complain about a request
that is still being processed or to wait for it. In any case, Tomcat shouldn't
complain with current message as it is too misleading and leads to ignoring
real memory leak messages.
The root cause of the problem is the strategy used to detect threads started by
a web app which isn't able to correctly identify threads started by Tomcat
itself (contextClassLoader is changed at each request). A solution could be to
use a ThreadGroup to identify "Tomcat threads". If you see this as a good
solution, I can try to prepare a patch.
Same problem occurs in Tomcat 6.
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DO NOT REPLY [Bug 49414] Wrong memory leak detection: executor
thread reported as web app thread
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=49414
--- Comment #2 from Marc Guillemot <mg...@yahoo.fr> 2010-06-14 03:20:42 EDT ---
(In reply to comment #1)
> Tomcat already waits (I think 20s is the default) for requests to complete
> before shutting down the webapp.
???
If you run the provided unit test, you will see that Tomcat doesn't wait 20
secondes for requests to complete.
> A still running request, particularly if deadlocked, would trigger a memory
> leak so I think this is something that the leak detection should be reporting.
> I agree a better message is required to make clear the correct root cause in
> this scenario. I don't have any strong feelings at this point as to the best
> way to go. At first glance a ThreadGroup looks reasonable.
Thinking at it again, it would surely not be bad to have a "Tomcat ThreadGroup"
but it wouldn't solve the problem here: user Threads started from a webapp
without a specified ThreadGroup would belong to the Tomcat ThreadGroup too. In
this case it wouldn't help to distinguish "Tomcat threads" from "user threads".
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DO NOT REPLY [Bug 49414] Wrong memory leak detection: executor
thread reported as web app thread
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=49414
Mark Thomas <ma...@apache.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|Catalina |Catalina
Version|trunk |6.0.26
Product|Tomcat 7 |Tomcat 6
Target Milestone|--- |default
--- Comment #3 from Mark Thomas <ma...@apache.org> 2010-06-25 03:57:05 EDT ---
Tomcat does wait for requests to complete, I just got the default wait period
wrong by an order of magnitude. It waits 2 seconds, not 20 by default. The
unloadDelay attribute of the context controls this.
I have fixed this issue by examining the stack trace of threads with issues. I
decided to use the presence - or not - of the CoyoteAdator.service() call to
determine if this was a request thread. It is unlikely (but not impossible)
that even a customised Tomcat would have re-written that code.
This has been fixed in trunk and will be included in 7.0.1 onwards.
I have proposed the same fix for Tomcat 6.
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DO NOT REPLY [Bug 49414] Wrong memory leak detection: executor
thread reported as web app thread
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=49414
Mark Thomas <ma...@apache.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |FIXED
--- Comment #4 from Mark Thomas <ma...@apache.org> 2010-06-29 07:32:51 EDT ---
Fixed in 6.0.x and will be included in 6.0.28 onwards.
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DO NOT REPLY [Bug 49414] Wrong memory leak detection: executor
thread reported as web app thread
Posted by bu...@apache.org.
https://issues.apache.org/bugzilla/show_bug.cgi?id=49414
--- Comment #1 from Mark Thomas <ma...@apache.org> 2010-06-13 16:28:45 EDT ---
Tomcat already waits (I think 20s is the default) for requests to complete
before shutting down the webapp.
A still running request, particularly if deadlocked, would trigger a memory
leak so I think this is something that the leak detection should be reporting.
I agree a better message is required to make clear the correct root cause in
this scenario. I don't have any strong feelings at this point as to the best
way to go. At first glance a ThreadGroup looks reasonable.
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