org.apache.flink.runtime.taskexecutor.BackPressureSampleService Maven / Gradle / Ivy
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* distributed with this work for additional information
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* 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
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*/
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 back pressures 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);
}
/**
* Schedules to sample the task back pressure and returns a future that completes
* with the back pressure ratio.
*
* @param task The task to be sampled.
* @return A future containing the task back pressure ratio.
*/
public CompletableFuture sampleTaskBackPressure(BackPressureSampleableTask task) {
if (!task.isRunning()) {
throw new IllegalStateException(
String.format("Cannot sample task. Because the sampled task %s is not running.", task));
}
return sampleTaskBackPressure(
checkNotNull(task),
numSamples,
new ArrayList<>(numSamples),
new CompletableFuture<>());
}
private CompletableFuture sampleTaskBackPressure(
BackPressureSampleableTask task,
int remainingNumSamples,
List taskBackPressureSamples,
CompletableFuture resultFuture) {
taskBackPressureSamples.add(task.isBackPressured());
if (task.isRunning() && remainingNumSamples > 1) {
scheduledExecutor.schedule(
() -> sampleTaskBackPressure(
task,
remainingNumSamples - 1,
taskBackPressureSamples,
resultFuture),
delayBetweenSamples.getSize(),
delayBetweenSamples.getUnit());
} else {
resultFuture.complete(calculateTaskBackPressureRatio(taskBackPressureSamples));
}
return resultFuture;
}
private double calculateTaskBackPressureRatio(final List taskBackPressureSamples) {
double backPressureCount = 0.0;
for (Boolean isBackPressured: taskBackPressureSamples) {
if (isBackPressured) {
++backPressureCount;
}
}
return taskBackPressureSamples.isEmpty() ? 0.0 : backPressureCount / taskBackPressureSamples.size();
}
}