kylemeow commented on a change in pull request #11639: [FLINK-16626][runtime]
Prevent REST handler from being closed more than once
URL: https://github.com/apache/flink/pull/11639#discussion_r404755577
##########
File path:
flink-runtime/src/main/java/org/apache/flink/runtime/rest/handler/AbstractHandler.java
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@@ -221,7 +227,12 @@ private void finalizeRequestProcessing(FileUploads
uploadedFiles) {
@Override
public final CompletableFuture<Void> closeAsync() {
- return FutureUtils.composeAfterwards(closeHandlerAsync(),
inFlightRequestTracker::awaitAsync);
+ if (isHandlerClosed.compareAndSet(false, true)) {
+ return
FutureUtils.composeAfterwards(closeHandlerAsync(),
inFlightRequestTracker::awaitAsync);
+ } else {
+ log.warn("The handler instance for {} had already been
closed, but another attempt at closing it was made.",
untypedResponseMessageHeaders.getTargetRestEndpointURL());
+ return CompletableFuture.completedFuture(null);
Review comment:
> I don't think we should return a completed future if the handle has
received "close" message. It is possible that the handle is still closing.
Possibly we alter `inFlightRequestTracker::awaitAsync` to return the terminate
future if it is closed, without deregister the phaser party.
>
> cc @zentol @GJL
Hi @TisonKun , thanks for your review.
My original thought was that a completed ComplatableFuture
*CompletableFuture.completedFuture(null)* would indicate that this invocation
has finished without any longer effect, as it has nothing to do with the
previous call from the user's perspective.
To my understanding, if the REST handler was previously requested to be
closed, then the corresponding CompletableFuture would have already been sent
to the user, and if that CompletedFuture is still not finished,
org.apache.flink.runtime.rest.RestServerEndpoint#closeHandlersAsync would wait
for its completion, so it would not cause the RestServerEndpoint to shutdown
earlier.
Or else maybe we could just throw an *Exception* if the handler is being
closed more than once? This would make the design simpler.
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