cadonna commented on a change in pull request #9615: URL: https://github.com/apache/kafka/pull/9615#discussion_r533675429
########## File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java ########## @@ -894,19 +885,88 @@ private KafkaStreams(final InternalTopologyBuilder internalTopologyBuilder, queryableStoreProvider = new QueryableStoreProvider(storeProviders, globalStateStoreProvider); stateDirCleaner = setupStateDirCleaner(); - oldHandler = false; maybeWarnAboutCodeInRocksDBConfigSetter(log, config); rocksDBMetricsRecordingService = maybeCreateRocksDBMetricsRecordingService(clientId, config); } + private StreamThread createStreamThread(final long cacheSizePerThread, final int threadIdx) { + final StreamThread streamThread = StreamThread.create( + internalTopologyBuilder, + config, + clientSupplier, + adminClient, + processId, + clientId, + streamsMetrics, + time, + streamsMetadataState, + cacheSizePerThread, + stateDirectory, + delegatingStateRestoreListener, + threadIdx, + KafkaStreams.this::closeToError, + streamsUncaughtExceptionHandler + ); + threads.add(streamThread); + threadState.put(streamThread.getId(), streamThread.state()); + storeProviders.add(new StreamThreadStateStoreProvider(streamThread)); + return streamThread; + } + + /** + * Adds and starts a stream thread in addition to the stream threads that are already running in this + * Kafka Streams client. + * + * Since the number of stream threads increases, the sizes of the caches in the new stream thread + * and the existing stream threads are adapted so that the sum of the cache sizes over all stream + * threads does not exceed the total cache size specified in configuration + * {@code cache.max.bytes.buffering}. + * + * Stream threads can only be added if this Kafka Streams client is in state RUNNING or REBALANCING. + * + * @return name of the added stream thread or empty if a new stream thread could not be added + */ + public Optional<String> addStreamThread() { + if (isRunningOrRebalancing()) { + final int threadIdx = getNextThreadIndex(); + final long cacheSizePerThread = getCacheSizePerThread(threads.size() + 1); + resizeThreadCache(cacheSizePerThread); + final StreamThread streamThread = createStreamThread(cacheSizePerThread, threadIdx); + streamThread.setStateListener(streamStateListener); + synchronized (stateLock) { + if (isRunningOrRebalancing()) { + streamThread.start(); Review comment: What about checking for the state and do the clean-up only if the state is not `PENDING_SHUTDOWN` and not `ERROR` and not `NOT_RUNNING`? In this way we are safe for future changes that break our assumption on state transitions and we make sure not to do unnecessary stuff when we are shutting down. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org