Calabash, thread-local variables and memory leaks from Florent Georges on 2013-09-18 (xproc-dev@w3.org from September 2013)

From: Florent Georges <fgeorges@fgeorges.org>
Date: Wed, 18 Sep 2013 19:05:30 +0200
To: XProc Dev <xproc-dev@w3.org>
Message-ID: <CADyR_r0EOt_v8+Pb9E9yCEMzQcfpa3t1-Po7hCiRr9VREMA=sg@mail.gmail.com>

  Hi,

  I use Calabash in Tomcat.  Tomcat tells me that there is a memory
leak related to ThreadLocal variables never released (and with keys
and values from Calabash packages).  I saw that the class
XProcExtensionFunctionDefinition uses a ThreadLocal variable. I added
log statements and was able to find that an object of the following
classes exists and its thread-local variable is set() once per thread:

    com.xmlcalabash.functions.Cwd
    com.xmlcalabash.functions.BaseURI
    com.xmlcalabash.functions.ResolveURI
    com.xmlcalabash.functions.SystemProperty
    com.xmlcalabash.functions.StepAvailable
    com.xmlcalabash.functions.IterationSize
    com.xmlcalabash.functions.IterationPosition
    com.xmlcalabash.functions.ValueAvailable
    com.xmlcalabash.functions.VersionAvailable
    com.xmlcalabash.functions.XPathVersionAvailable

  So every time Tomcat receives a request served by Calabash, the
thread-local variable gets a new value.  The problem is, they are
never released.  Given that the value is the Calabash engine itself
(AKA XProcRuntime), it grows rapidely.

  Because this is Calabash internals, I can't release them myself.
I am not sure how we can solve this one.  Maybe by adding a method
to release (or close) the runtime object itself, that throws away
everything it does not need anymore, recursively, including releasing
the thread-local variables?

  Or maybe simply by removing the thread-local variable?  I am not
sure what it is used for.

  Regards,

-- 
Florent Georges
http://fgeorges.org/
http://h2oconsulting.be/

Received on Wednesday, 18 September 2013 17:06:18 UTC