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

[Paul Malolepsy (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-2481?page=comments#action_26436 ] 

Paul Malolepsy commented on HHH-2481:
-------------------------------------

For those who want to fix this issue without waiting for this fix, or making a custom build of hibernate, here is a workaround you can implement in your own code.  This code should go after you create a Configuration object and before you create the SessionFactory:

{code:title=Bar.java|borderStyle=solid}

        //assumes an instantiated Configuration variable called cfg
        cfg.setListeners("load", new LoadEventListener [] {new DefaultLoadEventListener(), new LoadEventListener() {
            public void onLoad(LoadEvent event, LoadType loadType) throws HibernateException {
                Object obj = event.getResult();
                if (obj instanceof HibernateProxy) {
                    Enhancer.registerCallbacks(obj.getClass(),null);
                }
            }
        }});


{code}

> 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
>     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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