[GitHub] [kafka] cadonna commented on a change in pull request #9615: KAFKA-10500: Add thread option

[GitBox]

cadonna commented on a change in pull request #9615:
URL: https://github.com/apache/kafka/pull/9615#discussion_r535383909



##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -870,43 +900,75 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 cacheSizePerThread,
 stateDirectory,
 delegatingStateRestoreListener,
-i + 1,
+threadIdx,
 KafkaStreams.this::closeToError,
-this::defaultStreamsUncaughtExceptionHandler
-);
-threads.add(streamThread);
-threadState.put(streamThread.getId(), streamThread.state());
-storeProviders.add(new 
StreamThreadStateStoreProvider(streamThread));
-}
+streamsUncaughtExceptionHandler

Review comment:
   nit: If it happens that you need to push another commit, could you fix 
the indentation here? Sorry that I haven't noticed this before.

##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -870,43 +900,75 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 cacheSizePerThread,
 stateDirectory,
 delegatingStateRestoreListener,
-i + 1,
+threadIdx,
 KafkaStreams.this::closeToError,
-this::defaultStreamsUncaughtExceptionHandler
-);
-threads.add(streamThread);
-threadState.put(streamThread.getId(), streamThread.state());
-storeProviders.add(new 
StreamThreadStateStoreProvider(streamThread));
-}
+streamsUncaughtExceptionHandler
+);
+streamThread.setStateListener(streamStateListener);
+threads.add(streamThread);
+threadState.put(streamThread.getId(), streamThread.state());
+storeProviders.add(new StreamThreadStateStoreProvider(streamThread));
+return streamThread;
+}
 
-ClientMetrics.addNumAliveStreamThreadMetric(streamsMetrics, 
(metricsConfig, now) ->
-Math.toIntExact(threads.stream().filter(thread -> 
thread.state().isAlive()).count()));
+/**
+ * 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
+ * {@link StreamsConfig#CACHE_MAX_BYTES_BUFFERING_CONFIG}.
+ * 
+ * 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 addStreamThread() {
+synchronized (newThread) {
+if (isRunningOrRebalancing()) {
+final int threadIdx = getNextThreadIndex();
+final long 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();
+threads.remove(streamThread);
+
resizeThreadCache(getCacheSizePerThread(threads.size()));
+return Optional.empty();
+}
+}
+}
+}
+return Optional.empty();
+}
 
-final StreamStateListener streamStateListener = new 
StreamStateListener(threadState, globalThreadState);
-if (hasGlobalTopology) {
-globalStreamThread.setStateListener(streamStateListener);
+private int getNextThreadIndex() {
+final HashSet names = new HashSet<>();
+for (final StreamThread streamThread: threads) {
+names.add(streamThread.getName());
 }
-for (final StreamThread thread : threads) {
-thread.setStateListener(streamStateListener);
+final String baseName = clientId + "-StreamThread-";
+for (int i = 0; i < threads.size(); i++) {

Review comment:
   Shouldn't that be `int i = 1; i <= threads.size(); i++`? Otherwise, we 
would look up `*-StreamThread-0"` and we would not look up `"*-StreamThread-" + 
threads.size()`.
   
   Could you add some tests that check the correct naming as @mjsax suggested? 

##

[GitHub] [kafka] cadonna commented on a change in pull request #9615: KAFKA-10500: Add thread option

[GitBox]

cadonna commented on a change in pull request #9615:
URL: https://github.com/apache/kafka/pull/9615#discussion_r534319500



##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -870,43 +899,73 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 cacheSizePerThread,
 stateDirectory,
 delegatingStateRestoreListener,
-i + 1,
+threadIdx,
 KafkaStreams.this::closeToError,
-this::defaultStreamsUncaughtExceptionHandler
-);
-threads.add(streamThread);
-threadState.put(streamThread.getId(), streamThread.state());
-storeProviders.add(new 
StreamThreadStateStoreProvider(streamThread));
-}
+streamsUncaughtExceptionHandler
+);
+streamThread.setStateListener(streamStateListener);
+threads.add(streamThread);
+threadState.put(streamThread.getId(), streamThread.state());
+storeProviders.add(new StreamThreadStateStoreProvider(streamThread));
+return streamThread;
+}
 
-ClientMetrics.addNumAliveStreamThreadMetric(streamsMetrics, 
(metricsConfig, now) ->
-Math.toIntExact(threads.stream().filter(thread -> 
thread.state().isAlive()).count()));
+/**
+ * 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
+ * {@link StreamsConfig#CACHE_MAX_BYTES_BUFFERING_CONFIG}.
+ * 
+ * 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 addStreamThread() {
+if (isRunningOrRebalancing()) {
+final int threadIdx = getNextThreadIndex();
+final long 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 {
+threads.remove(streamThread);

Review comment:
   > Unfortunately I don't think we can shutdown a thread until we have 
started it.
   
   Have a look at 
https://github.com/apache/kafka/blob/aeeb7b2f9a9abe8f49543a2278757722e5974cb3/streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamThread.java#L976-L983





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[GitHub] [kafka] cadonna commented on a change in pull request #9615: KAFKA-10500: Add thread option

[GitBox]

cadonna commented on a change in pull request #9615:
URL: https://github.com/apache/kafka/pull/9615#discussion_r534263746



##
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 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:
   See my other comment 
https://github.com/apache/kafka/pull/9615#discussion_r534261843





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[GitHub] [kafka] cadonna commented on a change in pull request #9615: KAFKA-10500: Add thread option

[GitBox]

cadonna commented on a change in pull request #9615:
URL: https://github.com/apache/kafka/pull/9615#discussion_r534261843



##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -870,43 +899,73 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 cacheSizePerThread,
 stateDirectory,
 delegatingStateRestoreListener,
-i + 1,
+threadIdx,
 KafkaStreams.this::closeToError,
-this::defaultStreamsUncaughtExceptionHandler
-);
-threads.add(streamThread);
-threadState.put(streamThread.getId(), streamThread.state());
-storeProviders.add(new 
StreamThreadStateStoreProvider(streamThread));
-}
+streamsUncaughtExceptionHandler
+);
+streamThread.setStateListener(streamStateListener);
+threads.add(streamThread);
+threadState.put(streamThread.getId(), streamThread.state());
+storeProviders.add(new StreamThreadStateStoreProvider(streamThread));
+return streamThread;
+}
 
-ClientMetrics.addNumAliveStreamThreadMetric(streamsMetrics, 
(metricsConfig, now) ->
-Math.toIntExact(threads.stream().filter(thread -> 
thread.state().isAlive()).count()));
+/**
+ * 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
+ * {@link StreamsConfig#CACHE_MAX_BYTES_BUFFERING_CONFIG}.
+ * 
+ * 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 addStreamThread() {
+if (isRunningOrRebalancing()) {
+final int threadIdx = getNextThreadIndex();
+final long 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 {
+threads.remove(streamThread);

Review comment:
   Good point about the shutdown of the stream thread!
   
   Actually, I did not want to have everything in the synchronized block 
because I thought blocking the client state more than needed was not a good 
idea. I thought decreasing the size of the cache might be costly if the evicted 
records are forwarded downstream. 
   Now that you mention to synchronize on a separate lock, I noticed that we 
probably need to put resize, start, and cleanup in the same synchronized block. 
The reason is that if two threads call `addStreamThread()` one after the other 
and the later thread passes
   
   ```
   final long cacheSizePerThread = getCacheSizePerThread(threads.size() + 1);
   ```
   
   before the earlier thread adds the new stream thread to `threads` in 
`createStreamThread()`, the later thread would compute the wrong cache size.
   
   So, I am in favor of having a separate lock that just synchronizes the 
threads calling `addStreamThread()`. Maybe we can simply synchronize the whole 
method (which means to synchronize with `start()` and `close()`).
   
   Still a minor issue seems to be the synchronization 
between`isRunningOrRebalancing()` and `streamThread.start()`. If between these 
two calls the Streams client transits to `ERROR` (the global stream thread 
died) an `IllegalStateException` would be thrown from the `StreamStateListener` 
because the Streams client would try to transit from `ERROR` to `REBALANCING`. 
But I guess that would also happen if the Streams client transits to `ERROR` 
before the new stream thread transits to `PARTITION_ASSIGNED` and calls the 
`StreamStateListener` that would transit the Streams client to `REBALANCING`. 
So it needs to be fixed somewhere else.
   
   Did I miss something? 





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[GitHub] [kafka] cadonna commented on a change in pull request #9615: KAFKA-10500: Add thread option

[GitBox]

cadonna commented on a change in pull request #9615:
URL: https://github.com/apache/kafka/pull/9615#discussion_r533687031



##
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 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:
   Yes, currently this assumption is correct, but if the state transitions 
change in future, we would be safe if we do the cleanup.
   On a second thought, we are probably not 100% safe because if a transition 
from `NOT_RUNNING` to `RUNNING` is added (or any other transition that goes 
from the above mentioned states to `RUNNING` or `REBALANCING`), we would still 
not do the clean up. 





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[GitHub] [kafka] cadonna commented on a change in pull request #9615: KAFKA-10500: Add thread option

[GitBox]

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 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.   





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[GitHub] [kafka] cadonna commented on a change in pull request #9615: KAFKA-10500: Add thread option

[GitBox]

cadonna commented on a change in pull request #9615:
URL: https://github.com/apache/kafka/pull/9615#discussion_r529858401



##
File path: 
streams/src/test/java/org/apache/kafka/streams/integration/AdjustStreamThreadCountTest.java
##
@@ -0,0 +1,104 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.integration;
+
+import org.apache.kafka.common.serialization.Serdes;
+import org.apache.kafka.streams.KafkaStreams;
+import org.apache.kafka.streams.StreamsBuilder;
+import org.apache.kafka.streams.StreamsConfig;
+import org.apache.kafka.streams.integration.utils.EmbeddedKafkaCluster;
+import org.apache.kafka.streams.integration.utils.IntegrationTestUtils;
+import org.apache.kafka.streams.processor.ThreadMetadata;
+import org.apache.kafka.test.IntegrationTest;
+import org.apache.kafka.test.StreamsTestUtils;
+import org.apache.kafka.test.TestUtils;
+import org.hamcrest.CoreMatchers;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+import org.junit.rules.TestName;
+
+import java.io.IOException;
+import java.util.Optional;
+import java.util.Properties;
+
+import static org.apache.kafka.common.utils.Utils.mkEntry;
+import static org.apache.kafka.common.utils.Utils.mkMap;
+import static org.apache.kafka.common.utils.Utils.mkObjectProperties;
+import static 
org.apache.kafka.streams.integration.utils.IntegrationTestUtils.purgeLocalStreamsState;
+import static 
org.apache.kafka.streams.integration.utils.IntegrationTestUtils.safeUniqueTestName;
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+@Category(IntegrationTest.class)
+public class AdjustStreamThreadCountTest {
+
+@ClassRule
+public static final EmbeddedKafkaCluster CLUSTER = new 
EmbeddedKafkaCluster(1);
+
+@Rule
+public TestName testName = new TestName();
+
+private static String inputTopic;
+private static StreamsBuilder builder;
+private static Properties properties;
+private static String appId = "";
+
+@Before
+public void setup() {
+final String testId = safeUniqueTestName(getClass(), testName);
+appId = "appId_" + testId;
+inputTopic = "input" + testId;
+IntegrationTestUtils.cleanStateBeforeTest(CLUSTER, inputTopic);
+
+builder  = new StreamsBuilder();
+builder.stream(inputTopic);
+
+properties  = mkObjectProperties(
+mkMap(
+mkEntry(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, 
CLUSTER.bootstrapServers()),
+mkEntry(StreamsConfig.APPLICATION_ID_CONFIG, appId),
+mkEntry(StreamsConfig.STATE_DIR_CONFIG, 
TestUtils.tempDirectory().getPath()),
+mkEntry(StreamsConfig.NUM_STREAM_THREADS_CONFIG, 2),
+mkEntry(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, 
Serdes.StringSerde.class),
+mkEntry(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, 
Serdes.StringSerde.class)
+)
+);
+}
+
+@After
+public void teardown() throws IOException {
+purgeLocalStreamsState(properties);
+}
+
+@Test
+public void shouldAddStreamThread() throws Exception {
+try (final KafkaStreams kafkaStreams = new 
KafkaStreams(builder.build(), properties)) {
+
StreamsTestUtils.startKafkaStreamsAndWaitForRunningState(kafkaStreams);
+final int oldThreadCount = 
kafkaStreams.localThreadsMetadata().size();
+
+final Optional name = kafkaStreams.addStreamThread();
+assertThat(name, CoreMatchers.not(Optional.empty()));
+TestUtils.waitForCondition(() -> 
kafkaStreams.localThreadsMetadata().stream().sequential().map(ThreadMetadata::threadName).anyMatch(t
 -> t.equals(name.orElse(""))),
+"Wait for the thread to be added");
+assertThat(kafkaStreams.localThreadsMetadata().size(), 
equalTo(oldThreadCount + 1));

Review comment:
   nit: If not all parameters fit on one line, we put each of them on a new 
line. Additionally we put also the closing parenthesis on a new line.
   
   

[GitHub] [kafka] cadonna commented on a change in pull request #9615: KAFKA-10500: Add thread option

[GitBox]

cadonna commented on a change in pull request #9615:
URL: https://github.com/apache/kafka/pull/9615#discussion_r529461975



##
File path: 
streams/src/test/java/org/apache/kafka/streams/integration/AdjustStreamThreadCountTest.java
##
@@ -0,0 +1,115 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.kafka.streams.integration;
+
+import org.apache.kafka.common.serialization.Serdes;
+import org.apache.kafka.common.serialization.StringSerializer;
+import org.apache.kafka.streams.KafkaStreams;
+import org.apache.kafka.streams.KeyValue;
+import org.apache.kafka.streams.StreamsBuilder;
+import org.apache.kafka.streams.StreamsConfig;
+import org.apache.kafka.streams.integration.utils.EmbeddedKafkaCluster;
+import org.apache.kafka.streams.integration.utils.IntegrationTestUtils;
+import org.apache.kafka.test.IntegrationTest;
+import org.apache.kafka.test.StreamsTestUtils;
+import org.apache.kafka.test.TestUtils;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.ClassRule;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+import org.junit.rules.TestName;
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.Properties;
+
+import static org.apache.kafka.common.utils.Utils.mkEntry;
+import static org.apache.kafka.common.utils.Utils.mkMap;
+import static org.apache.kafka.common.utils.Utils.mkObjectProperties;
+import static 
org.apache.kafka.streams.integration.utils.IntegrationTestUtils.purgeLocalStreamsState;
+import static 
org.apache.kafka.streams.integration.utils.IntegrationTestUtils.safeUniqueTestName;
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+@Category(IntegrationTest.class)
+public class AdjustStreamThreadCountTest {
+
+@ClassRule
+public static final EmbeddedKafkaCluster CLUSTER = new 
EmbeddedKafkaCluster(1);
+
+@Rule
+public TestName testName = new TestName();
+
+private static String inputTopic;
+private static StreamsBuilder builder;
+private static Properties properties;
+private static String appId = "";
+
+@Before
+public void setup() {
+final String testId = safeUniqueTestName(getClass(), testName);
+appId = "appId_" + testId;
+inputTopic = "input" + testId;
+IntegrationTestUtils.cleanStateBeforeTest(CLUSTER, inputTopic);
+
+builder  = new StreamsBuilder();
+builder.stream(inputTopic);
+
+properties  = mkObjectProperties(
+mkMap(
+mkEntry(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, 
CLUSTER.bootstrapServers()),
+mkEntry(StreamsConfig.APPLICATION_ID_CONFIG, appId),
+mkEntry(StreamsConfig.STATE_DIR_CONFIG, 
TestUtils.tempDirectory().getPath()),
+mkEntry(StreamsConfig.NUM_STREAM_THREADS_CONFIG, 2),
+mkEntry(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, 
Serdes.StringSerde.class),
+
mkEntry(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, 
Serdes.StringSerde.class)
+)
+);
+}
+
+@After
+public void teardown() throws IOException {
+purgeLocalStreamsState(properties);
+}
+
+private void produceMessages(final long timestamp, final String 
streamOneInput, final String msg) {
+IntegrationTestUtils.produceKeyValuesSynchronouslyWithTimestamp(
+streamOneInput,
+Collections.singletonList(new KeyValue<>("1", msg)),
+TestUtils.producerConfig(
+CLUSTER.bootstrapServers(),
+StringSerializer.class,
+StringSerializer.class,
+new Properties()),
+timestamp);

Review comment:
   wrong indentation

##
File path: 
streams/src/test/java/org/apache/kafka/streams/integration/AdjustStreamThreadCountTest.java
##
@@ -0,0 +1,115 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for 

[GitHub] [kafka] cadonna commented on a change in pull request #9615: KAFKA-10500: Add thread option

[GitBox]

cadonna commented on a change in pull request #9615:
URL: https://github.com/apache/kafka/pull/9615#discussion_r527530444



##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -894,11 +885,77 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 queryableStoreProvider = new QueryableStoreProvider(storeProviders, 
globalStateStoreProvider);
 
 stateDirCleaner = setupStateDirCleaner();
-oldHandler = false;
 maybeWarnAboutCodeInRocksDBConfigSetter(log, config);
 rocksDBMetricsRecordingService = 
maybeCreateRocksDBMetricsRecordingService(clientId, config);
 }
 
+private StreamThread makeThread(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 addStreamThread() {
+synchronized (stateLock) {
+if (isRunningOrRebalancing()) {
+final int threadIdx = getNextThreadIndex();
+final long cacheSizePerThread = 
getCacheSizePerThread(threads.size() + 1);
+resizeThreadCache(threads.size() + 1);

Review comment:
   I think it would be cleaner to pass `cacheSizePerThread` to 
`resizeThreadCache()` instead of the number of stream threads. We would then 
just call `getCacheSizePerThread()` once instead of once in `addStreamThread()` 
and once in `resizeThreadCache()`. We would also just need to compute 
`threads.size() + 1` once.

##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -894,11 +885,77 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 queryableStoreProvider = new QueryableStoreProvider(storeProviders, 
globalStateStoreProvider);
 
 stateDirCleaner = setupStateDirCleaner();
-oldHandler = false;
 maybeWarnAboutCodeInRocksDBConfigSetter(log, config);
 rocksDBMetricsRecordingService = 
maybeCreateRocksDBMetricsRecordingService(clientId, config);
 }
 
+private StreamThread makeThread(final long cacheSizePerThread, final int 
threadIdx) {

Review comment:
   IMO, `createStreamThread()` would describe the behavior better.

##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -894,11 +904,72 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 queryableStoreProvider = new QueryableStoreProvider(storeProviders, 
globalStateStoreProvider);
 
 stateDirCleaner = setupStateDirCleaner();
-oldHandler = false;
 maybeWarnAboutCodeInRocksDBConfigSetter(log, config);
 rocksDBMetricsRecordingService = 
maybeCreateRocksDBMetricsRecordingService(clientId, config);
 }
 
+/**
+ * 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 

[GitHub] [kafka] cadonna commented on a change in pull request #9615: KAFKA-10500: Add thread option

[GitBox]

cadonna commented on a change in pull request #9615:
URL: https://github.com/apache/kafka/pull/9615#discussion_r527145996



##
File path: streams/src/test/java/org/apache/kafka/streams/KafkaStreamsTest.java
##
@@ -588,6 +592,29 @@ public void testCloseIsIdempotent() {
 closeCount, MockMetricsReporter.CLOSE_COUNT.get());
 }
 
+@Test
+public void testAddThread() {
+props.put(StreamsConfig.NUM_STREAM_THREADS_CONFIG, 1);
+final KafkaStreams streams = new 
KafkaStreams(getBuilderWithSource().build(), props, supplier, time);
+streams.start();
+final int oldSize = streams.threads.size();
+try {
+TestUtils.waitForCondition(() -> streams.state() == 
KafkaStreams.State.RUNNING, 15L, "wait until running");
+} catch (final InterruptedException e) {
+e.printStackTrace();
+}

Review comment:
   You should not use `try-catch` here but just add `throws 
InterruptedException` to the method signature.

##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -894,11 +904,72 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 queryableStoreProvider = new QueryableStoreProvider(storeProviders, 
globalStateStoreProvider);
 
 stateDirCleaner = setupStateDirCleaner();
-oldHandler = false;
 maybeWarnAboutCodeInRocksDBConfigSetter(log, config);
 rocksDBMetricsRecordingService = 
maybeCreateRocksDBMetricsRecordingService(clientId, config);
 }
 
+/**
+ * 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 addStreamThread() {
+synchronized (stateLock) {

Review comment:
   Why do we need to synchronize the whole method on `stateLock`?

##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -894,11 +904,72 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 queryableStoreProvider = new QueryableStoreProvider(storeProviders, 
globalStateStoreProvider);
 
 stateDirCleaner = setupStateDirCleaner();
-oldHandler = false;
 maybeWarnAboutCodeInRocksDBConfigSetter(log, config);
 rocksDBMetricsRecordingService = 
maybeCreateRocksDBMetricsRecordingService(clientId, config);
 }
 
+/**
+ * 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 addStreamThread() {
+synchronized (stateLock) {
+if (state == State.RUNNING || state == State.REBALANCING) {

Review comment:
   Could we also use `isRunningOrRebalancing()` here?

##
File path: streams/src/test/java/org/apache/kafka/streams/KafkaStreamsTest.java
##
@@ -588,6 +592,29 @@ public void testCloseIsIdempotent() {
 closeCount, MockMetricsReporter.CLOSE_COUNT.get());
 }
 
+@Test
+public void testAddThread() {

Review comment:
   I would prefer to use `shouldAddThread()` as name although the pattern 
is different for the other test methods.

##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -894,11 +904,72 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 queryableStoreProvider = new QueryableStoreProvider(storeProviders, 
globalStateStoreProvider);
 
 stateDirCleaner = setupStateDirCleaner();
-oldHandler = false;
 maybeWarnAboutCodeInRocksDBConfigSetter(log, config);
 rocksDBMetricsRecordingService = 
maybeCreateRocksDBMetricsRecordingService(clientId, config);
 }
 
+/**
+ * Adds and starts a stream 

[GitHub] [kafka] cadonna commented on a change in pull request #9615: KAFKA-10500: Add thread option

[GitBox]

cadonna commented on a change in pull request #9615:
URL: https://github.com/apache/kafka/pull/9615#discussion_r527055689



##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -894,11 +904,57 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 queryableStoreProvider = new QueryableStoreProvider(storeProviders, 
globalStateStoreProvider);
 
 stateDirCleaner = setupStateDirCleaner();
-oldHandler = false;
 maybeWarnAboutCodeInRocksDBConfigSetter(log, config);
 rocksDBMetricsRecordingService = 
maybeCreateRocksDBMetricsRecordingService(clientId, config);
 }
 
+/**
+ * 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 addStreamThread() {
+synchronized (stateLock) {
+if (state == State.RUNNING || state == State.REBALANCING) {
+final int threadIdx = threads.size() + 1;
+final long cacheSizePerThread = 
getCacheSizePerThread(threadIdx);

Review comment:
   This should be:
   ```suggestion
   final long cacheSizePerThread = 
getCacheSizePerThread(threads.size() + 1);
   ```

##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -894,11 +904,57 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 queryableStoreProvider = new QueryableStoreProvider(storeProviders, 
globalStateStoreProvider);
 
 stateDirCleaner = setupStateDirCleaner();
-oldHandler = false;
 maybeWarnAboutCodeInRocksDBConfigSetter(log, config);
 rocksDBMetricsRecordingService = 
maybeCreateRocksDBMetricsRecordingService(clientId, config);
 }
 
+/**
+ * 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 addStreamThread() {
+synchronized (stateLock) {
+if (state == State.RUNNING || state == State.REBALANCING) {
+final int threadIdx = threads.size() + 1;

Review comment:
   Assume the following thread list [t2, t3, t4], `threadIdx` would be 4, 
which is already there. You should keep the currently used `threadIdx`s and 
check those to decide on the next `threadIdx`.
   
   

##
File path: streams/src/main/java/org/apache/kafka/streams/KafkaStreams.java
##
@@ -894,11 +904,57 @@ private KafkaStreams(final InternalTopologyBuilder 
internalTopologyBuilder,
 queryableStoreProvider = new QueryableStoreProvider(storeProviders, 
globalStateStoreProvider);
 
 stateDirCleaner = setupStateDirCleaner();
-oldHandler = false;
 maybeWarnAboutCodeInRocksDBConfigSetter(log, config);
 rocksDBMetricsRecordingService = 
maybeCreateRocksDBMetricsRecordingService(clientId, config);
 }
 
+/**
+ * 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 addStreamThread() {
+synchronized (stateLock) {
+if (state == State.RUNNING || state ==