John Bellassai created CXF-7575:
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Summary: @Suspended race condition
Key: CXF-7575
URL: https://issues.apache.org/jira/browse/CXF-7575
Project: CXF
Issue Type: Bug
Components: JAX-RS
Affects Versions: 3.1.14
Reporter: John Bellassai
There appears to be a race condition with the use of AsyncResponseImpl where my
user thread can invoke resume() before initialSuspend is set to false by
suspendContinuationIfNeeded() and therefore the resume() call does not actually
resume the Continuation _and returns true_, indicating that the resume was
successful even though it wasn't.
I've spent all day trying to make sense of this problem and my understanding of
how all of this works together is still a bit spotty, but it seems to me that
AsyncResponseImpl.suspendContinuationIfNeeded() (or something similar) should
be called _before_ invoking the JAXRS method. Right now, that method is only
called after the JAXRS method is invoked by JAXRSInvoker so the instance of
AsyncResponse passed into the JAXRS method appears to not actually get
suspended (or perhaps _marked_ internally as suspended) until after the JAXRS
method returns. If my async task happens to get finished very quickly and
calls resume() before that happens, it fails silently.
I seem to be able to circumvent this problem by running the following at the
start of my JAXRS method (pseudo code):
{code}
@POST
@Path(....)
void myJaxrsMethod(@Suspended AsyncResponse asyncResponse, ...) {
if(asyncResponse instanceof AsyncResponseImpl) {
((AsyncResponseImpl)asyncResponse).suspendContinuationIfNeeded()
}
Runnable asyncTask = createAsyncTask(asyncResponse)
submitAsyncTask(asyncTask)
}
{code}
which is why I suspect suspendContinuationIfNeeded() should be called before
JAXRSInvoker invokes the JAXRS method.
One of the things that made this really difficult to track down was that
AsyncResponseImpl.resume() returns true even if the Continuation was not
resumed! If you make it into doResumeFinal(), like was happening in my case,
the return is always true even if cont.resume() is not called. So from user
code, it looks like everything is ok, but the response never gets sent to the
client.
This seems somewhat related to the problems reported in CXF-7037
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