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From j...@apache.org
Subject [jira] Resolved: (AXIS-935) Using ThreadLocal Call objects in a servlet memory leak both on client and server side
Date Thu, 03 Jun 2004 16:58:53 GMT
Message:

   The following issue has been resolved as FIXED.

   Resolver: Davanum Srinivas
       Date: Thu, 3 Jun 2004 9:57 AM

Do you have some sample code to recreate the problem?
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View the issue:
  http://issues.apache.org/jira/browse/AXIS-935

Here is an overview of the issue:
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        Key: AXIS-935
    Summary: Using ThreadLocal Call objects in a servlet memory leak both on client and server
side
       Type: Bug

     Status: Resolved
 Resolution: FIXED

    Project: Axis
 Components: 
             Basic Architecture
   Versions:
             1.1rc2

   Assignee: 
   Reporter: Jennifer Jackson

    Created: Mon, 30 Jun 2003 12:12 PM
    Updated: Thu, 3 Jun 2004 9:57 AM
Environment: Operating System: All
Platform: All

Description:
I discovered using Axis in tomcat causes a memory leak.

It seems using threadlocal in the classes causes a memory leak for each Call 
that is created.  Threadlocal sticks around until the calling thread dies, and 
since tomcat keeps threads alive to answer new calls, the threadlocal data 
never goes away.  The Call object gets stuck in the threadlocal data, which 
contains the entire soap response and all objects.  This is a BIG memory leak.  
I initially cleared it by forcing all Call objects to clean their member vars 
after I was done with a call, then I realized the source was from the thread 
local class.  Here is some info I found about threadlocal:

This is stated in the Sun Javadocs for ThreadLocal:

	Each thread holds an implicit reference to its copy of a
	ThreadLocal as long as the thread is alive and the
	ThreadLocal object is accessible; after a thread goes
	away, all of its copies of ThreadLocal variables are
	subject to garbage collection (unless other references
	to these copies exist).

So, this means that ANY APPLICATION that uses PreparedStatements in a thread
that 1) either does a lot of PreparedStatements or 2) never dies (i.e., a
main thread) will ALWAYS eventually have an out of memory error. Simply put,
this is a MEMORY LEAK. I imagine that the leak is very small, the
ThreadLocal object only contains one member variable, maybe 64 bytes or less
(depending on the VM implementation). So, our 60,000 PreparedStatements of 2
ThreadLocals each times 64 bytes (my wild guess) is 7.5MB.

Ideas?  I've never used threadlocal myself so this is new to me.


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