divijvaidya commented on code in PR #13820: URL: https://github.com/apache/kafka/pull/13820#discussion_r1223073346
########## server-common/src/main/java/org/apache/kafka/server/util/timer/SystemTimer.java: ########## @@ -0,0 +1,112 @@ +/* + * 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.server.util.timer; + +import org.apache.kafka.common.utils.KafkaThread; +import org.apache.kafka.common.utils.Time; + +import java.util.concurrent.DelayQueue; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Executors; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicInteger; +import java.util.concurrent.locks.ReentrantReadWriteLock; + +public class SystemTimer implements Timer { + // timeout timer + private final ExecutorService taskExecutor; + private final DelayQueue<TimerTaskList> delayQueue; + private final AtomicInteger taskCounter; + private final TimingWheel timingWheel; + + // Locks used to protect data structures while ticking + private final ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock(); + private final ReentrantReadWriteLock.ReadLock readLock = readWriteLock.readLock(); + private final ReentrantReadWriteLock.WriteLock writeLock = readWriteLock.writeLock(); + + public SystemTimer(String executorName) { + this(executorName, 1, 20, Time.SYSTEM.hiResClockMs()); + } + + public SystemTimer( + String executorName, + long tickMs, + int wheelSize, + long startMs + ) { + this.taskExecutor = Executors.newFixedThreadPool(1, + runnable -> KafkaThread.nonDaemon("executor-" + executorName, runnable)); + this.delayQueue = new DelayQueue<>(); + this.taskCounter = new AtomicInteger(0); + this.timingWheel = new TimingWheel( + tickMs, + wheelSize, + startMs, + taskCounter, + delayQueue + ); + } + + public void add(TimerTask timerTask) { + readLock.lock(); Review Comment: we are using this pattern of locking very often now (also used in TS related code for leader epoch snapshot). Could we perhaps extract this out into a utility which takes incoming lambda and executes it in a lock, similar to https://github.com/apache/kafka/blob/513e1c641d63c5e15144f9fcdafa1b56c5e5ba09/core/src/main/scala/kafka/utils/CoreUtils.scala#L182 ########## server-common/src/main/java/org/apache/kafka/server/util/timer/TimerTask.java: ########## @@ -0,0 +1,50 @@ +/* + * 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.server.util.timer; + +public abstract class TimerTask implements Runnable { + private volatile TimerTaskEntry timerTaskEntry; + // timestamp in millisecond + public final long delayMs; + + public TimerTask(long delayMs) { + this.delayMs = delayMs; + } + + public void cancel() { + synchronized (this) { Review Comment: you can move `synchronized` to the method signature above? ``` public synchronized a() { } ``` is equivalent to ``` public a() { synchronized(this) { } } ``` ########## server-common/src/main/java/org/apache/kafka/server/util/timer/TimerTask.java: ########## @@ -0,0 +1,50 @@ +/* + * 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.server.util.timer; + +public abstract class TimerTask implements Runnable { + private volatile TimerTaskEntry timerTaskEntry; Review Comment: Perhaps we can use AtomicReference here and remove the synchronized blocks since we just need to protect concurrent access to timerTaskEntry? ########## server-common/src/main/java/org/apache/kafka/server/util/timer/SystemTimer.java: ########## @@ -0,0 +1,112 @@ +/* + * 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.server.util.timer; + +import org.apache.kafka.common.utils.KafkaThread; +import org.apache.kafka.common.utils.Time; + +import java.util.concurrent.DelayQueue; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Executors; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicInteger; +import java.util.concurrent.locks.ReentrantReadWriteLock; + +public class SystemTimer implements Timer { Review Comment: maybe add an additional implements autoCloseable where we can call shutdown? -- This is an automated message from the Apache Git Service. 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