[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-2481) Big memory leak in the use of CGLIB

[Scott Marlow (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-2481?page=comments#action_26474 ] 

Scott Marlow commented on HHH-2481:
-----------------------------------

The fix looks good (except we use hard tabs instead of spaces but no big deal).

We used to pass in the callback directly until we hit HHH-1293.  Registering the callback, works around HHH-1293, but not clearing the TLS caused this Jira.

I'll check the fix into trunk and the 3_2 branch soon.

> Big memory leak in the use of CGLIB
> -----------------------------------
>
>          Key: HHH-2481
>          URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2481
>      Project: Hibernate3
>         Type: Bug

>   Components: core
>     Versions: 3.2.2
>  Environment: Hibernate 3.2.2
> MySQL 5.1
>     Reporter: Paul Malolepsy
>     Assignee: Scott Marlow
>     Priority: Critical
>  Attachments: fix.diff
>
> Original Estimate: 5 minutes
>         Remaining: 5 minutes
>
> The way CGLIBLazyInitializer is creating proxies is resulting in a potentially massive memory leak.
> In CGLIBLazyInitializer.getProxy() just before the proxy is instantiated, a call is made to Enhancer.registerCallbacks() passing in the instance of CGLIBLazyInitializer that will manage the proxy.  This variable is stored in a static ThreadLocal on the CGLIB created persistentClass so that any subsequent objects instantiated will get this callback class.  
> The problem is that once this ThreadLocal is set, it is never cleared, so it will stay around (together with the object it's managing, and whatever object graph it may be connected to) until the next time a proxy is created for that type on that thread.  
> For our application we have about 150 different proxy types, and our app can have over 100 threads.  This results in potentially 15,000 proxy objects and their graphs stuck in memory.
> The fix for this is simple.  Just make another call the Enhancer.registerCallbacks() with a null callback arg, right after the proxy class is instantiated:
> Enhancer.registerCallbacks(factory, null);

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