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_r343983655
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/rest/handler/legacy/backpressure/BackPressureRequestCoordinator.java ########## @@ -0,0 +1,365 @@ +/* + * 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.rest.handler.legacy.backpressure; + +import org.apache.flink.annotation.VisibleForTesting; +import org.apache.flink.api.common.time.Time; +import org.apache.flink.runtime.concurrent.FutureUtils; +import org.apache.flink.runtime.execution.ExecutionState; +import org.apache.flink.runtime.executiongraph.Execution; +import org.apache.flink.runtime.executiongraph.ExecutionAttemptID; +import org.apache.flink.runtime.executiongraph.ExecutionVertex; +import org.apache.flink.runtime.messages.TaskBackPressureResponse; + +import org.apache.flink.shaded.guava18.com.google.common.collect.Maps; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import javax.annotation.Nullable; +import javax.annotation.concurrent.GuardedBy; + +import java.util.ArrayDeque; +import java.util.Arrays; +import java.util.HashMap; +import java.util.HashSet; +import java.util.Map; +import java.util.Set; +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.Executor; + +import static org.apache.flink.util.Preconditions.checkArgument; +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * A coordinator for triggering and collecting back pressure stats + * of running tasks. + */ +public class BackPressureRequestCoordinator { + + private static final Logger LOG = LoggerFactory.getLogger(BackPressureRequestCoordinator.class); + + private static final int NUM_GHOST_REQUEST_IDS = 10; + + private final Object lock = new Object(); + + /** Executor used to run the futures. */ + private final Executor executor; + + /** Request time out of a triggered back pressure request. */ + private final Time requestTimeout; + + /** In progress back pressure requests. */ + @GuardedBy("lock") + private final Map<Integer, PendingBackPressureRequest> pendingRequests = new HashMap<>(); + + /** A list of recent request IDs to identify late messages vs. invalid ones. */ + private final ArrayDeque<Integer> recentPendingRequests = new ArrayDeque<>(NUM_GHOST_REQUEST_IDS); + + /** Request ID counter. */ + @GuardedBy("lock") + private int requestIdCounter; + + /** Flag indicating whether the coordinator is still running. */ + @GuardedBy("lock") + private boolean isShutDown; + + /** + * Creates a new coordinator for the cluster. + * + * @param executor Used to execute the futures. + * @param requestTimeout Request time out of a triggered back pressure request. + */ + public BackPressureRequestCoordinator( + Executor executor, + long requestTimeout) { + + checkArgument(requestTimeout >= 0L, "Illegal request timeout: " + requestTimeout); + + this.executor = checkNotNull(executor); + this.requestTimeout = Time.milliseconds(requestTimeout); + } + + /** + * Triggers a task back pressure stats request to all tasks. + * + * @param tasks Tasks to request. + * @return A future of the completed task back pressure stats. + */ + CompletableFuture<BackPressureStats> triggerBackPressureRequest(ExecutionVertex[] tasks) { + + checkNotNull(tasks, "Tasks to request must not be null."); + checkArgument(tasks.length >= 1, "No tasks to request."); + + // Execution IDs of running tasks + ExecutionAttemptID[] triggerIds = new ExecutionAttemptID[tasks.length]; + Execution[] executions = new Execution[tasks.length]; + + // Check that all tasks are RUNNING before triggering anything. The + // triggering can still fail. + for (int i = 0; i < triggerIds.length; i++) { + Execution execution = tasks[i].getCurrentExecutionAttempt(); + if (execution != null && execution.getState() == ExecutionState.RUNNING) { + executions[i] = execution; + triggerIds[i] = execution.getAttemptId(); + } else { + return FutureUtils.completedExceptionally(new IllegalStateException("Task " + tasks[i] + .getTaskNameWithSubtaskIndex() + " is not running.")); + } + } + + synchronized (lock) { + if (isShutDown) { + return FutureUtils.completedExceptionally(new IllegalStateException("Shut down")); + } + + final int requestId = requestIdCounter++; + + LOG.debug("Triggering task back pressure request {}", requestId); + + final PendingBackPressureRequest pending = new PendingBackPressureRequest(requestId, triggerIds); + + // Add the pending request before scheduling the discard task to + // prevent races with removing it again. + pendingRequests.put(requestId, pending); + + // Trigger all requests. The request will be discarded if it takes + // too long. We don't send cancel messages to the task managers, + // but only wait for the responses and then ignore them. + for (Execution execution: executions) { + final CompletableFuture<TaskBackPressureResponse> taskBackPressureFuture = + execution.requestBackPressure(requestId, requestTimeout); + + taskBackPressureFuture.handleAsync( + (TaskBackPressureResponse taskBackPressureResponse, Throwable throwable) -> { + if (taskBackPressureResponse != null) { + collectTaskBackPressureStat( + taskBackPressureResponse.getRequestId(), + taskBackPressureResponse.getExecutionAttemptID(), + taskBackPressureResponse.getBackPressureRatio()); + } else { + cancelBackPressureRequest(requestId, throwable); + } + + return null; + }, + executor); + } + + return pending.getBackPressureStatsFuture(); + } + } + + /** + * Cancels a pending task back pressure request. + * + * @param requestId ID of the request to cancel. + * @param cause Cause of the cancelling (can be <code>null</code>). + */ + @VisibleForTesting + void cancelBackPressureRequest(int requestId, @Nullable Throwable cause) { + synchronized (lock) { + if (isShutDown) { + return; + } + + PendingBackPressureRequest pendingRequest = pendingRequests.remove(requestId); + if (pendingRequest != null) { + if (cause != null) { + LOG.info("Cancelling back pressure request " + requestId, cause); + } else { + LOG.info("Cancelling back pressure request {}", requestId); + } + + pendingRequest.discard(cause); + rememberRecentRequestId(requestId); + } + } + } + + /** + * Shuts down the coordinator. + * + * <p>After shut down, no further operations are executed. + */ + public void shutDown() { + synchronized (lock) { + if (!isShutDown) { + LOG.info("Shutting down back pressure request coordinator."); + + for (PendingBackPressureRequest pending : pendingRequests.values()) { + pending.discard(new RuntimeException("Shut down.")); + } + + pendingRequests.clear(); Review comment: also clear `recentPendingRequests` ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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