[jira] Updated: (CXF-2939) Permgen Leak in JAXB due to recreation of JAXBContexts in CXF

["Stefan Schubert (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CXF-2939?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Stefan Schubert updated CXF-2939:
---------------------------------

    Attachment: removed_weak_hash_maps.patch

This patch just changes WeakHashMaps to HashMaps in two lines. I did not write any tests as testing GC behaviour seemed a little ridiculous to me and the interface to create the JAXBContext is a static. Should I refactor anything that this is testable? Nevertheless testing if the GC doesn't throw away any Map entries sounds funny :-)

But I executed the tests nonetheless. 

> Permgen Leak in JAXB due to recreation of JAXBContexts in CXF
> -------------------------------------------------------------
>
>                 Key: CXF-2939
>                 URL: https://issues.apache.org/jira/browse/CXF-2939
>             Project: CXF
>          Issue Type: Bug
>          Components: JAX-RS
>    Affects Versions: 2.1.5
>            Reporter: Stefan Schubert
>         Attachments: removed_weak_hash_maps.patch
>
>
> From http://cxf.547215.n5.nabble.com/REST-web-service-loading-many-classes-for-each-request-CXF-2-2-6-and-jaxb-impl-2-1-5-td2266472.html#a2266472:
> If a GC occurs, WeakRefs throw away the JAXBContext. So on the next occasion (where occasion could be one of billions of calls to a CXF/JAXB api) the JAXBContext has to be rebuilt from scratch. 
> JAXB (specifically com.sun.xml.bind.v2.runtime.reflect.opt.AccessorInjector) calls com.sun.xml.bind.v2.runtime.reflect.opt.Injector#find to try, if it already created a field or method accessor class. If not it injects a new one into the class loader via com.sun.xml.bind.v2.runtime.reflect.opt.Injector#inject. 
> The problem is now that #inject caches the generated accessor in the Injector and find only looks into the Injector (and never again into the class loader, where it used to define the class). But once a GC occurs the Injector throws itself away, too (caching itself in some weak map). 
> So it happens that each REST api call after a GC occurred a hundred new classes are created by JAXB - because JAXB on low-level forgets the classes it defines (and keeps them on high-level) and CXF forgets the JAXBContext so that the high-level memory of JAXB is erased as well. 
> There are four possible solutions: 
>  - Fix the Injector: Actually very easy and my favorite solution. Just let the Injector look into the class loader as well when it cannot find the class in its own memory. BUT to have a bug fixed in JAXB actually sounds scary, how long would that take to get into a version?) 
>  - Enable CXF to keep only one JAXB context (and not to throw it away) - do not know how to do that 
>  - Use a workaround to disable bytecode generation by JAXB (-Dcom.sun.xml.bind.v2.bytecode.ClassTailor.noOptimize=true) --> disables the whole bytecode magic Injector stuff and just does reflection - probably with a slight performance impact 
>  - Do not use JAXB with CXF on a website with significant load 

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