cadonna commented on a change in pull request #9487:
URL: https://github.com/apache/kafka/pull/9487#discussion_r525161434
##########
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##########
@@ -366,6 +374,63 @@ public void setUncaughtExceptionHandler(final
Thread.UncaughtExceptionHandler eh
}
}
+ /**
+ * Set the handler invoked when an {@link
StreamsConfig#NUM_STREAM_THREADS_CONFIG internal thread}
+ * throws an unexpected exception.
+ * These might be exceptions indicating rare bugs in Kafka Streams, or they
+ * might be exceptions thrown by your code, for example a
NullPointerException thrown from your processor
+ * logic.
+ * <p>
+ * Note, this handler must be threadsafe, since it will be shared among
all threads, and invoked from any
+ * thread that encounters such an exception.
+ *
+ * @param streamsUncaughtExceptionHandler the uncaught exception handler
of type {@link StreamsUncaughtExceptionHandler} for all internal threads
+ * @throws IllegalStateException if this {@code KafkaStreams} instance is
not in state {@link State#CREATED CREATED}.
+ * @throws NullPointerException if streamsUncaughtExceptionHandler is null.
+ */
+ public void setUncaughtExceptionHandler(final
StreamsUncaughtExceptionHandler streamsUncaughtExceptionHandler) {
+ final StreamsUncaughtExceptionHandler handler = exception ->
handleStreamsUncaughtException(exception, streamsUncaughtExceptionHandler);
+ synchronized (stateLock) {
+ if (state == State.CREATED) {
+ Objects.requireNonNull(streamsUncaughtExceptionHandler);
+ for (final StreamThread thread : threads) {
+ thread.setStreamsUncaughtExceptionHandler(handler);
+ }
+ if (globalStreamThread != null) {
+ globalStreamThread.setUncaughtExceptionHandler(handler);
+ }
+ } else {
+ throw new IllegalStateException("Can only set
UncaughtExceptionHandler in CREATED state. " +
+ "Current state is: " + state);
+ }
+ }
+ }
+
+ private StreamsUncaughtExceptionHandler.StreamThreadExceptionResponse
handleStreamsUncaughtException(final Throwable e,
+
final StreamsUncaughtExceptionHandler
streamsUncaughtExceptionHandler) {
+ final StreamsUncaughtExceptionHandler.StreamThreadExceptionResponse
action = streamsUncaughtExceptionHandler.handle(e);
+ switch (action) {
+ case SHUTDOWN_CLIENT:
+ log.error("Encountered the following exception during
processing " +
+ "and the registered exception handler opted to \" +
action + \"." +
+ " The streams client is going to shut down now. ", e);
+ close(Duration.ZERO);
Review comment:
> I thought we would still be in danger of deadlock if we use the
blocking close(), since close() will not return until every thread has joined
but the StreamThread that called close() would be stuck in this blocking call
and thus never stop/join
OK, I think you are right. I focused too much on
```
if (!thread.isRunning()) {
thread.join();
}
```
without considering that before the stream threads are shutdown which makes
them not running.
In the meantime, I understood a bit better the motivation of the shutdown
thread in `close()`. The shutdown thread ensures that the timeout is still
consiered in case `close()` is called by a stream thread. I think we should
revisit it. But that is outside the scope of this PR.
To unblock this PR, I am fine with `close(Duration.Zero)`, but I have the
feeling we could do better.
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