Markus Heiden created CXF-9257:
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Summary: Client futures never complete if the async callback throws
Key: CXF-9257
URL: https://issues.apache.org/jira/browse/CXF-9257
Project: CXF
Issue Type: Bug
Components: JAX-RS, JAX-WS Runtime
Reporter: Markus Heiden
If the callback passed to an asynchronous client invocation throws an unchecked
exception, the future returned by the invocation is never completed. Threads
blocked in {{Future.get()}} hang forever, and {{get(timeout)}} is the only way
out.
*Affected*
* JAX-RS client: {{JaxrsClientCallback}} invokes
{{InvocationCallback.completed()}} / {{failed()}} before completing its
{{CompletableFuture}}. An exception thrown by the callback propagates out of
{{handleResponse()}} / {{handleException()}}, so the future is never completed.
For {{WebClient}} the call to {{handleResponse()}} in
{{ClientAsyncResponseInterceptor}} is not even inside a try block, so nothing
downstream can recover. The same applies to {{cancel()}} and to the
interruption path of {{JaxrsResponseFuture.get()}}, which both invoke
{{failed()}}.
* JAX-WS client: {{JaxwsClientCallback}} invokes
{{AsyncHandler.handleResponse()}} the same way. In addition, when the exception
escapes, {{ClientImpl}} catches it and calls {{handleException()}}, which
invokes the same {{AsyncHandler}} a second time and may throw again.
*Expected behaviour*
The future completes in every case. If the callback throws while handling a
successful response, the future completes exceptionally with that exception,
which is what the JAX-WS reference implementation does
({{com.sun.xml.ws.client.AsyncResponseImpl.set}}). If the callback throws while
handling a failure, the original failure is kept as the cause and the
callback's exception is attached as a suppressed exception.
*Context*
Observed in the Microsoft Advertising Java SDK, which builds its own futures on
top of the CXF async client: a runtime exception in its handler, e.g. from a
missing response header, left the SDK's future unresolved forever. See
https://github.com/BingAds/BingAds-Java-SDK/issues/166#issuecomment-2016613395
and https://github.com/BingAds/BingAds-Java-SDK/issues/242.
*Fix*
https://github.com/apache/cxf/pull/3565 guards every callback invocation in
both callbacks and adds unit tests, which fail without the fix.
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