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).