cadonna commented on a change in pull request #9695:
URL: https://github.com/apache/kafka/pull/9695#discussion_r540857996
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File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
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@@ -924,25 +924,64 @@ private StreamThread createStreamThread(final long
cacheSizePerThread, final int
* @return name of the added stream thread or empty if a new stream thread
could not be added
*/
public Optional<String> addStreamThread() {
- synchronized (changeThreadCount) {
- if (isRunningOrRebalancing()) {
- final int threadIdx = getNextThreadIndex();
- final long cacheSizePerThread =
getCacheSizePerThread(threads.size() + 1);
+ if (isRunningOrRebalancing()) {
+ final int threadIdx;
+ final long cacheSizePerThread;
+ synchronized (changeThreadCount) {
+ threadIdx = getNextThreadIndex();
+ cacheSizePerThread = getCacheSizePerThread(threads.size() + 1);
resizeThreadCache(cacheSizePerThread);
- final StreamThread streamThread =
createStreamThread(cacheSizePerThread, threadIdx);
- synchronized (stateLock) {
- if (isRunningOrRebalancing()) {
- streamThread.start();
- return Optional.of(streamThread.getName());
- } else {
- streamThread.shutdown();
+ }
+ final StreamThread streamThread =
createStreamThread(cacheSizePerThread, threadIdx);
+
+ synchronized (stateLock) {
+ if (isRunningOrRebalancing()) {
+ streamThread.start();
+ return Optional.of(streamThread.getName());
+ } else {
+ streamThread.shutdown();
+ threads.remove(streamThread);
+ resizeThreadCache(getCacheSizePerThread(threads.size()));
+ log.warn("Cannot add a stream thread in state " + state());
+ return Optional.empty();
+ }
+ }
+ }
+ log.warn("Cannot add a stream thread in state " + state());
+ return Optional.empty();
+ }
+
+ /**
+ * Removes one stream thread out of the running stream threads from this
Kafka Streams client.
+ * <p>
+ * The removed stream thread is gracefully shut down. This method does not
specify which stream
+ * thread is shut down.
+ * <p>
+ * Since the number of stream threads decreases, the sizes of the caches
in the remaining stream
+ * threads are adapted so that the sum of the cache sizes over all stream
threads equals the total
+ * cache size specified in configuration {@link
StreamsConfig#CACHE_MAX_BYTES_BUFFERING_CONFIG}.
+ *
+ * @return name of the removed stream thread or empty if a stream thread
could not be removed because
+ * no stream threads are alive
+ */
+ public Optional<String> removeStreamThread() {
+ if (isRunningOrRebalancing()) {
+ for (final StreamThread streamThread : threads) {
+ if (streamThread.isAlive()) {
Review comment:
Good point about not removing stream threads in `PENDING_SHUTDOWN`.
> There should not be any dead threads, this check is to make sure another
call the removeThread is not removing the same thread.
Right! Thanks to the new uncaught exception handler!
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