zhijiangW commented on a change in pull request #10083: [FLINK-14472][runtime]Implement back-pressure monitor with non-blocking outputs. URL: https://github.com/apache/flink/pull/10083#discussion_r344009866
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/taskexecutor/BackPressureSampleService.java ########## @@ -0,0 +1,116 @@ +/* + * 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.flink.runtime.taskexecutor; + +import org.apache.flink.api.common.time.Time; +import org.apache.flink.runtime.concurrent.ScheduledExecutor; + +import java.util.ArrayList; +import java.util.List; +import java.util.concurrent.CompletableFuture; + +import static org.apache.flink.util.Preconditions.checkArgument; +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * Samples whether a task is back pressured multi times. The total number of samples + * divided by the number of back pressure samples reaches the back pressure ratio. + */ +public class BackPressureSampleService { + + /** Number of samples to take when determining the back pressure of a task. */ + private final int numSamples; + + /** Time to wait between samples when determining the back pressure of a task. */ + private final Time delayBetweenSamples; + + /** Executor to run sample tasks. */ + private final ScheduledExecutor scheduledExecutor; + + BackPressureSampleService( + int numSamples, + Time delayBetweenSamples, + ScheduledExecutor scheduledExecutor) { + + checkArgument(numSamples >= 1, "Illegal number of samples: " + numSamples); + + this.numSamples = numSamples; + this.delayBetweenSamples = checkNotNull(delayBetweenSamples); + this.scheduledExecutor = checkNotNull(scheduledExecutor, "The scheduledExecutor must not be null."); + } + + /** + * Returns a future that completes with the back pressure ratio of a task. + * + * @param task The task to be sampled. + * @return A future of the task back pressure ratio. + */ + public CompletableFuture<Double> sampleTaskBackPressure(BackPressureSampleableTask task) { + return sampleTaskBackPressure( + checkNotNull(task), + numSamples, + delayBetweenSamples, + new ArrayList<>(numSamples), + new CompletableFuture<>()); + } + + private CompletableFuture<Double> sampleTaskBackPressure( + final BackPressureSampleableTask task, + final int remainingNumSamples, + final Time delayBetweenSamples, + final List<Boolean> taskBackPressureSamples, + final CompletableFuture<Double> resultFuture) { + + if (task.isRunning()) { + taskBackPressureSamples.add(task.isBackPressured()); + } else if (!taskBackPressureSamples.isEmpty()) { + resultFuture.complete(calculateTaskBackPressureRatio(taskBackPressureSamples)); Review comment: There seems some logic bug here. If the `remainingNumSamples` has not reached 0, then we should not complete the future, otherwise the results would not be accurate? ---------------------------------------------------------------- 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 With regards, Apache Git Services
