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From "Freeman Fang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CXF-7122) Infinite loop due to AsyncHTTPConduit read timeout with exhausted connection pool
Date Fri, 04 Nov 2016 06:09:58 GMT

    [ https://issues.apache.org/jira/browse/CXF-7122?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15635387#comment-15635387
] 

Freeman Fang commented on CXF-7122:
-----------------------------------

Hi  William,

Thanks for the patch, however it can't resolve the problem you describe.
For the sync, your final patch didn't change anything, it still wait the receivedtimeout and
shutdown the SharedOutputBuffer. 
For the async, when the code run into getHttpResponse method, this means the client can hold
a connection and send out request and the response is back already, so wait there doesn't
make sense.

What we need to do is that tell the ahc IOReactor don't repeat the message write process when
the SharedOutputBuffer is shutdown due to timeout for both sync and async, we can do it in
SharedOutputBuffer, using encoder.complete(); when SharedOutputBuffer is shutdown.

I will commit soon

Best Regards
Freeman



> Infinite loop due to AsyncHTTPConduit read timeout with exhausted connection pool
> ---------------------------------------------------------------------------------
>
>                 Key: CXF-7122
>                 URL: https://issues.apache.org/jira/browse/CXF-7122
>             Project: CXF
>          Issue Type: Bug
>          Components: Transports
>            Reporter: William Montaz
>            Assignee: Freeman Fang
>            Priority: Critical
>
> Using AsyncHTTPConduit, when the underlying connection pool gets exhausted, requests
waiting for a connection will lead to an infinite loop if they reach receive timeout.
> The problem occured on all versions of CXF above 3.0.5 (we did not tested other ones).

> Let's imagine a backend that's broken and leads to timeout for all requests.
> When handling requests, the cxf worker thread will eventually go in wait state (AsyncHTTPConduit:618),
with a timeout that matches the HTTPClientPolicy.setReceiveTimeout() value, waiting for the
NIO stack to complete and call notifyAll via responseCallback (AsyncHTTPConduit:455). 
> The timeout on the wait is the big problem :
> With our broken backend, the connection pool is exhausted waiting for other requests
to timeout. When a new request is made by cxf against this backend, after timeout time this
will happen :
>  - on the one side the reactor threads will get a connection from the pool and try to
write to the output stream. Waiting in the pool is not considered as receive timeout.
>  - on the other side the cxf worker thread will wake up (because of the timedout wait),
and shutdown SharedOutputBuffer and SharedInputBuffer (AsyncHTTPClient:624)
>  - reactor threads will go to infinite loop because they will try to produceContent from
a shutdown buffer (SharedOutputBuffer:120)
>  
>  From there, application recovery is compromised.
>   
>  To fix that, timeout should be handled only via the client callback (AsyncHTTPConduit:463).



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