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[FLINK-35030][runtime] Introduce Epoch Manager for under async execut…
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flink-runtime/src/main/java/org/apache/flink/runtime/asyncprocessing/EpochManager.java
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| /* | ||
| * 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. | ||
| */ | ||
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| package org.apache.flink.runtime.asyncprocessing; | ||
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| import org.slf4j.Logger; | ||
| import org.slf4j.LoggerFactory; | ||
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| import javax.annotation.Nullable; | ||
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| import java.util.LinkedList; | ||
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| /** | ||
| * Epoch manager segments inputs into distinct epochs, marked by the arrival of non-records(e.g. | ||
| * watermark, record attributes). Records are assigned to a unique epoch based on their arrival, | ||
| * records within an epoch are allowed to be parallelized, while the non-record of an epoch can only | ||
| * be executed when all records in this epoch have finished. | ||
| * | ||
| * <p>For more details please refer to FLIP-425. | ||
| */ | ||
| public class EpochManager { | ||
| private static final Logger LOG = LoggerFactory.getLogger(EpochManager.class); | ||
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| /** | ||
| * This enum defines whether parallel execution between epochs is allowed. We should keep this | ||
| * internal and away from API module for now, until we could see the concrete need for {@link | ||
| * #PARALLEL_BETWEEN_EPOCH} from average users. | ||
| */ | ||
| public enum ParallelMode { | ||
| /** | ||
| * Subsequent epochs must wait until the previous epoch is completed before they can start. | ||
| */ | ||
| SERIAL_BETWEEN_EPOCH, | ||
| /** | ||
| * Subsequent epochs can begin execution even if the previous epoch has not yet completed. | ||
| * Usually performs better than {@link #SERIAL_BETWEEN_EPOCH}. | ||
| */ | ||
| PARALLEL_BETWEEN_EPOCH | ||
| } | ||
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| /** | ||
| * The reference to the {@link AsyncExecutionController}, used for {@link | ||
| * ParallelMode#SERIAL_BETWEEN_EPOCH}. Can be null when testing. | ||
| */ | ||
| final AsyncExecutionController<?> asyncExecutionController; | ||
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| /** The number of epochs that have arrived. */ | ||
| long epochNum; | ||
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| /** The output queue to hold ongoing epochs. */ | ||
| LinkedList<Epoch> outputQueue; | ||
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| /** Current active epoch, only one active epoch at the same time. */ | ||
| Epoch activeEpoch; | ||
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| public EpochManager(AsyncExecutionController<?> aec) { | ||
| this.epochNum = 0; | ||
| this.outputQueue = new LinkedList<>(); | ||
| this.asyncExecutionController = aec; | ||
| // init an empty epoch, the epoch action will be updated when non-record is received. | ||
| this.activeEpoch = new Epoch(epochNum++); | ||
| } | ||
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| /** | ||
| * Add a record to the current epoch and return the current open epoch, the epoch will be | ||
| * associated with the {@link RecordContext} of this record. Must be invoked within task thread. | ||
| * | ||
| * @return the current open epoch. | ||
| */ | ||
| public Epoch onRecord() { | ||
| activeEpoch.ongoingRecordCount++; | ||
| return activeEpoch; | ||
| } | ||
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| /** | ||
| * Add a non-record to the current epoch, close current epoch and open a new epoch. Must be | ||
| * invoked within task thread. | ||
| * | ||
| * @param action the action associated with this non-record. | ||
| * @param parallelMode the parallel mode for this epoch. | ||
| */ | ||
| public void onNonRecord(Runnable action, ParallelMode parallelMode) { | ||
| LOG.trace( | ||
| "on NonRecord, old epoch: {}, outputQueue size: {}", | ||
| activeEpoch, | ||
| outputQueue.size()); | ||
| switchActiveEpoch(action); | ||
| if (parallelMode == ParallelMode.SERIAL_BETWEEN_EPOCH) { | ||
| asyncExecutionController.drainInflightRecords(0); | ||
| } | ||
| } | ||
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| /** | ||
| * Complete one record in the specific epoch. Must be invoked within task thread. | ||
| * | ||
| * @param epoch the specific epoch | ||
| */ | ||
| public void completeOneRecord(Epoch epoch) { | ||
| if (--epoch.ongoingRecordCount == 0) { | ||
| tryFinishInQueue(); | ||
| } | ||
| } | ||
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| private void tryFinishInQueue() { | ||
| // If one epoch has been closed before and all records in | ||
| // this epoch have finished, the epoch will be removed from the output queue. | ||
| while (!outputQueue.isEmpty() && outputQueue.peek().tryFinish()) { | ||
| LOG.trace( | ||
| "Finish epoch: {}, outputQueue size: {}", | ||
| outputQueue.peek(), | ||
| outputQueue.size()); | ||
| outputQueue.pop(); | ||
| } | ||
| } | ||
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| private void switchActiveEpoch(Runnable action) { | ||
| activeEpoch.close(action); | ||
| outputQueue.offer(activeEpoch); | ||
| this.activeEpoch = new Epoch(epochNum++); | ||
| tryFinishInQueue(); | ||
| } | ||
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| /** The status of an epoch, see Fig.6 in FLIP-425 for details. */ | ||
| enum EpochStatus { | ||
| /** | ||
| * The subsequent non-record input has not arrived. So arriving records will be collected | ||
| * into current epoch. | ||
| */ | ||
| OPEN, | ||
| /** | ||
| * The records belong to this epoch is settled since the following non-record input has | ||
| * arrived, the newly arriving records would be collected into the next epoch. | ||
| */ | ||
| CLOSED, | ||
| /** | ||
| * One epoch can only be finished when it meets the following three conditions. 1. The | ||
| * records of this epoch have finished execution. 2. The epoch is closed. 3. The epoch is in | ||
| * the front of outputQueue. | ||
| */ | ||
| FINISHED | ||
| } | ||
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| /** | ||
| * All inputs are segment into distinct epochs, marked by the arrival of non-record inputs. | ||
| * Records are assigned to a unique epoch based on their arrival. | ||
| */ | ||
| public static class Epoch { | ||
| /** The id of this epoch for easy debugging. */ | ||
| long id; | ||
| /** The number of records that are still ongoing in this epoch. */ | ||
| int ongoingRecordCount; | ||
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| /** The action associated with non-record of this epoch(e.g. advance watermark). */ | ||
| @Nullable Runnable action; | ||
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| EpochStatus status; | ||
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| public Epoch(long id) { | ||
| this.id = id; | ||
| this.ongoingRecordCount = 0; | ||
| this.status = EpochStatus.OPEN; | ||
| this.action = null; | ||
| } | ||
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| /** | ||
| * Try to finish this epoch. | ||
| * | ||
| * @return whether this epoch has been finished. | ||
| */ | ||
| boolean tryFinish() { | ||
| if (this.status == EpochStatus.FINISHED) { | ||
| return true; | ||
| } | ||
| if (ongoingRecordCount == 0 && this.status == EpochStatus.CLOSED) { | ||
| this.status = EpochStatus.FINISHED; | ||
| if (action != null) { | ||
| action.run(); | ||
| } | ||
| return true; | ||
| } | ||
| return false; | ||
| } | ||
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| /** Close this epoch. */ | ||
| void close(Runnable action) { | ||
| this.action = action; | ||
| this.status = EpochStatus.CLOSED; | ||
| } | ||
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| public String toString() { | ||
| return String.format( | ||
| "Epoch{id=%d, ongoingRecord=%d, status=%s}", id, ongoingRecordCount, status); | ||
| } | ||
| } | ||
| } |
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