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From "Alexander Klimetschek (JIRA)" <j...@apache.org>
Subject [jira] Created: (COCOON-2070) Releasing of pooled beans might skip recycle() call on aggregated beans (leading to: "Generator already set"-style exceptions)
Date Tue, 29 May 2007 14:45:15 GMT
Releasing of pooled beans might skip recycle() call on aggregated beans (leading to: "Generator
already set"-style exceptions)
------------------------------------------------------------------------------------------------------------------------------

                 Key: COCOON-2070
                 URL: https://issues.apache.org/jira/browse/COCOON-2070
             Project: Cocoon
          Issue Type: Bug
          Components: - Components: Sitemap
    Affects Versions: 2.2-dev (Current SVN)
            Reporter: Alexander Klimetschek
            Priority: Blocker
             Fix For: 2.2-dev (Current SVN)


There is a serious bug in o.a.c.core.container.spring.avalon.PoolableProxyHandler (and PoolableFactoryBean)
that can lead to exceptions like "Cannot set reader. Generator already set". This is because
the pipeline impl bean is reused from the pool, but was never recycle()d. The recycle() call
is skipped in cases when an exception is thrown by Spring inside PoolableProxyHandler.invoke("putBackIntoAvalonPool")
- this exception is simply swalled by both PoolableProxyHandler.run() and PoolableFactoryBean.putIntoPool().

The typical behaviour is that the first call to the pipeline works, but because the components
are put back into the pool unrecycled, the next call will fail. If there is lots of activity,
you might get a fresh component from the pool and it might work again, so the error seems
quite random.

The problematic exception happens when RequestContextHolder.currentRequestAttributes() is
called when the attributes for the request are null: IllegalStateException("No thread-bound
request found:....."). The call to that method happens in the "putBackIntoAvalonPool" case
in PoolableProxyHandler.invoke(). The problem is that this code will also be called *after*
the request attributes were set to null by the RequestContextListener, because it is registered
as a destruction callback, that gets called by Spring after the attribute reset.

The real chain of calls is as follows:
  RequestContextListener.requestDestroyed()
  RequestContextHolder.setRequestAttributes(null)
  callDestructionCallbacks()
  PoolableProxyHandler.run()   <- which is a destruction callback
  PoolableFactoryBean.putIntoPool()
  PoolableFactoryBean.enteringPool()
  component.recycle()
  AvalonServiceManager/Selector.release(childComponent)   <- component releases its childComponent
  AvalonPoolable.putBackIntoAvalonPool()
  PoolableProxyHandler.invoke()   <- intercepts the putBackIntoAvalonPool() call
  RequestContextHolder.currentRequestAttributes()   <-- Exception !!!


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