LakshSingla commented on code in PR #15025: URL: https://github.com/apache/druid/pull/15025#discussion_r1337857801
########## processing/src/main/java/org/apache/druid/java/util/metrics/MergeBufferPoolMonitor.java: ########## @@ -0,0 +1,54 @@ +/* + * 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.druid.java.util.metrics; + +import com.google.inject.Inject; +import org.apache.druid.collections.BlockingPool; +import org.apache.druid.guice.annotations.Merging; +import org.apache.druid.java.util.emitter.service.ServiceEmitter; +import org.apache.druid.java.util.emitter.service.ServiceMetricEvent; + +import java.nio.ByteBuffer; + +public class MergeBufferPoolMonitor extends AbstractMonitor +{ + + private final BlockingPool<ByteBuffer> mergeBufferPool; + + @Inject + public MergeBufferPoolMonitor( + @Merging BlockingPool<ByteBuffer> mergeBufferPoolIn Review Comment: The monitor itself shouldn't care about the actual blocking pool. It should have a "stats provider" (interface) which exposes the method `getPendingQueries`. You can take a look at the example: `QueryCountStatsProvider` and `QueryResource` for the pattern. You will need to wire it up in Guice as well. ########## processing/src/main/java/org/apache/druid/java/util/metrics/MergeBufferPoolMonitor.java: ########## @@ -0,0 +1,54 @@ +/* + * 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.druid.java.util.metrics; + +import com.google.inject.Inject; +import org.apache.druid.collections.BlockingPool; +import org.apache.druid.guice.annotations.Merging; +import org.apache.druid.java.util.emitter.service.ServiceEmitter; +import org.apache.druid.java.util.emitter.service.ServiceMetricEvent; + +import java.nio.ByteBuffer; + +public class MergeBufferPoolMonitor extends AbstractMonitor +{ + + private final BlockingPool<ByteBuffer> mergeBufferPool; + + @Inject + public MergeBufferPoolMonitor( + @Merging BlockingPool<ByteBuffer> mergeBufferPoolIn + ) + { + this.mergeBufferPool = mergeBufferPoolIn; + } + + @Override + public boolean doMonitor(ServiceEmitter emitter) + { + long pendingQueries = this.mergeBufferPool.getPendingQueries(); + + ServiceMetricEvent.Builder builder = ServiceMetricEvent.builder().setFeed("metrics"); + emitter.emit(builder.setMetric("mergebuffer/pendingQueries", pendingQueries)); Review Comment: ```suggestion emitter.emit(builder.setMetric("mergeBuffer/pendingQueries", pendingQueries)); ``` Capitalization since merge buffer is not a single word ########## processing/src/test/java/org/apache/druid/java/util/metrics/MergeBufferPoolMonitorTest.java: ########## @@ -0,0 +1,85 @@ +/* + * 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.druid.java.util.metrics; + +import org.apache.druid.collections.BlockingPool; +import org.apache.druid.collections.DefaultBlockingPool; +import org.junit.After; +import org.junit.Assert; +import org.junit.Before; +import org.junit.Test; + +import java.nio.ByteBuffer; +import java.util.Collections; +import java.util.List; +import java.util.concurrent.CountDownLatch; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Executors; + +public class MergeBufferPoolMonitorTest +{ + private ExecutorService executorService; + + @Before + public void setUp() + { + executorService = Executors.newSingleThreadExecutor(); + } + + @After + public void tearDown() + { + executorService.shutdown(); + } + + @Test + public void testBlockingQueriesCount() + { + BlockingPool<ByteBuffer> pool = new DefaultBlockingPool(() -> ByteBuffer.allocate(1024), 1); + MergeBufferPoolMonitor monitor = new MergeBufferPoolMonitor(pool); + + CountDownLatch latch = new CountDownLatch(1); + executorService.submit(() -> { + latch.countDown(); + pool.takeBatch(10); + }); + + try { + // the latch returns from await() guarantees the above lamda to take buffer from the pool starting to run in the + // executorService thread + latch.await(); + + // give 1 sec for pool.takeBatch to run and blocking at the pool + Thread.sleep(1000); + Review Comment: Tests relying on sleep are slower than necessary and flaky. Can we instead use an already existing implementation to test the monitor? If we do decide to go with the test due to the lack of another method, please add a timeout `@Test(timeout = 2_000L)` just in case it starts running over the sleep value. ########## processing/src/main/java/org/apache/druid/collections/BlockingPool.java: ########## @@ -40,8 +39,14 @@ public interface BlockingPool<T> * Take resources from the pool, waiting if necessary until the elements of the given number become available. * * @param elementNum number of resources to take - * * @return a list of resource holders. An empty list is returned if {@code elementNum} resources aren't available. */ List<ReferenceCountingResourceHolder<T>> takeBatch(int elementNum); + + /** + * Return the count of pending queries blocking in this queue for merge buffers Review Comment: ```suggestion * Return the count of pending queries waiting for merge buffers ``` ########## processing/src/test/java/org/apache/druid/java/util/metrics/MergeBufferPoolMonitorTest.java: ########## @@ -0,0 +1,85 @@ +/* + * 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.druid.java.util.metrics; + +import org.apache.druid.collections.BlockingPool; +import org.apache.druid.collections.DefaultBlockingPool; +import org.junit.After; +import org.junit.Assert; +import org.junit.Before; +import org.junit.Test; + +import java.nio.ByteBuffer; +import java.util.Collections; +import java.util.List; +import java.util.concurrent.CountDownLatch; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Executors; + +public class MergeBufferPoolMonitorTest +{ + private ExecutorService executorService; + + @Before + public void setUp() + { + executorService = Executors.newSingleThreadExecutor(); + } + + @After + public void tearDown() + { + executorService.shutdown(); + } + + @Test + public void testBlockingQueriesCount() + { + BlockingPool<ByteBuffer> pool = new DefaultBlockingPool(() -> ByteBuffer.allocate(1024), 1); + MergeBufferPoolMonitor monitor = new MergeBufferPoolMonitor(pool); + + CountDownLatch latch = new CountDownLatch(1); + executorService.submit(() -> { + latch.countDown(); + pool.takeBatch(10); + }); + + try { + // the latch returns from await() guarantees the above lamda to take buffer from the pool starting to run in the + // executorService thread + latch.await(); + + // give 1 sec for pool.takeBatch to run and blocking at the pool Review Comment: ```suggestion // give 1 sec for pool.takeBatch to run and block the pool ``` -- This is an automated message from the Apache Git Service. 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