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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.
*/
package org.apache.flink.runtime.executiongraph.failover;
import org.apache.flink.annotation.VisibleForTesting;
import org.apache.flink.runtime.executiongraph.Execution;
import org.apache.flink.runtime.executiongraph.ExecutionJobVertex;
import org.apache.flink.runtime.executiongraph.ExecutionVertex;
import org.apache.flink.runtime.executiongraph.ExecutionGraph;
import org.apache.flink.runtime.executiongraph.IntermediateResult;
import org.apache.flink.runtime.executiongraph.IntermediateResultPartition;
import org.apache.flink.runtime.io.network.partition.DataConsumptionException;
import org.apache.flink.runtime.io.network.partition.ResultPartitionID;
import org.apache.flink.util.ExceptionUtils;
import org.apache.flink.util.FlinkRuntimeException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Optional;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.Executor;
import static org.apache.flink.util.Preconditions.checkNotNull;
/**
* A failover strategy that restarts regions of the ExecutionGraph. A region is defined
* by this strategy as the weakly connected component of tasks that communicate via pipelined
* data exchange.
*/
public class RestartPipelinedRegionStrategy extends FailoverStrategy {
/** The log object used for debugging. */
private static final Logger LOG = LoggerFactory.getLogger(RestartPipelinedRegionStrategy.class);
/** The execution graph on which this FailoverStrategy works. */
protected final ExecutionGraph executionGraph;
/** The executor used for future actions. */
private final Executor executor;
/** Fast lookup from vertex to failover region. */
protected final HashMap vertexToRegion;
/** Regions topologically sorted. */
protected final List sortedRegions;
/** The max number a region can fail. */
private int regionFailLimit;
/** The checker helps to check whether the given partition is failed. */
protected final ResultPartitionFailureChecker resultPartitionFailureChecker;
/**
* Creates a new failover strategy to restart pipelined regions that works on the given
* execution graph and uses the execution graph's future executor to call restart actions.
*
* @param executionGraph The execution graph on which this FailoverStrategy will work
* @param regionFailLimit The max number a region can fail
*/
public RestartPipelinedRegionStrategy(ExecutionGraph executionGraph, int regionFailLimit) {
this(executionGraph, executionGraph.getFutureExecutor(), regionFailLimit);
}
/**
* Creates a new failover strategy to restart pipelined regions that works on the given
* execution graph and uses the given executor to call restart actions.
*
* @param executionGraph The execution graph on which this FailoverStrategy will work
* @param executor The executor used for future actions
* @param regionFailLimit The max number a region can fail
*/
public RestartPipelinedRegionStrategy(ExecutionGraph executionGraph, Executor executor, int regionFailLimit) {
this(executionGraph, executor, executionGraph.getResultPartitionFailureChecker(), regionFailLimit);
}
@VisibleForTesting
public RestartPipelinedRegionStrategy(
ExecutionGraph executionGraph,
Executor executor,
ResultPartitionFailureChecker resultPartitionFailureChecker,
int regionFailLimit) {
this.executionGraph = checkNotNull(executionGraph);
this.executor = checkNotNull(executor);
this.vertexToRegion = new HashMap<>();
this.sortedRegions = new ArrayList<>();
this.regionFailLimit = regionFailLimit;
this.resultPartitionFailureChecker = checkNotNull(resultPartitionFailureChecker);
}
// ------------------------------------------------------------------------
// failover implementation
// ------------------------------------------------------------------------
@Override
public void onTaskFailure(Execution taskExecution, Throwable cause) {
List sortedRegionsToRestart = sortRegionsTopologically(
getRegionsToRestart(taskExecution.getVertex(), cause));
// Cancel and restart the region of the target vertex
LOG.info("Recovering task failure for {} #{} ({}) via restarting {} failover regions",
taskExecution.getVertex().getTaskNameWithSubtaskIndex(),
taskExecution.getAttemptNumber(),
taskExecution.getAttemptId(),
sortedRegionsToRestart.size());
for (FailoverRegion regionToRestart : sortedRegionsToRestart) {
regionToRestart.onExecutionFail(taskExecution.getGlobalModVersion(), cause);
}
}
/**
* All 'involved' regions are proposed to be restarted.
* The 'involved' regions are calculated with rules below:
* 1. The region containing the failed task is always involved
* 2. If an input result partition of an involved region is not available, i.e. Missing or Corrupted,
* the region containing the partition producer task is involved
*/
@VisibleForTesting
public Set getRegionsToRestart(ExecutionVertex failedVertex, Throwable cause) {
IdentityHashMap regionsToRestart = new IdentityHashMap<>();
IdentityHashMap visitedRegions = new IdentityHashMap<>();
Queue regionsToVisit = new ArrayDeque<>();
FailoverRegion failedRegion = getFailoverRegion(failedVertex);
regionsToVisit.add(failedRegion);
visitedRegions.put(failedRegion, null);
// get root failed region.
Optional rootFailedRegion = getRootFailedRegion(failedVertex, cause);
if (rootFailedRegion.isPresent() && rootFailedRegion.get() != failedRegion) {
regionsToVisit.add(rootFailedRegion.get());
visitedRegions.put(rootFailedRegion.get(), null);
}
// start from the failed region to visit all involved regions
while (!regionsToVisit.isEmpty()) {
FailoverRegion regionToRestart = regionsToVisit.poll();
// an involved region should be restarted
regionsToRestart.put(regionToRestart, null);
// if a needed input result partition is not available, its producer region is involved
for (ExecutionVertex vertex : regionToRestart.getAllExecutionVertices()) {
for (int i = 0; i < vertex.getNumberOfInputs(); ++i) {
for (IntermediateResultPartition consumedPartition : vertex.getConsumedPartitions(i)) {
if (resultPartitionFailureChecker.isFailed(consumedPartition.getPartitionId())) {
FailoverRegion producerRegion = getFailoverRegion(consumedPartition.getProducer());
if (!visitedRegions.containsKey(producerRegion)) {
visitedRegions.put(producerRegion, null);
regionsToVisit.add(producerRegion);
}
}
}
}
}
}
return regionsToRestart.keySet();
}
protected Optional getRootFailedRegion(ExecutionVertex failedVertex, Throwable cause) {
Optional dataConsumptionException = ExceptionUtils.findThrowable(
cause, DataConsumptionException.class);
if (dataConsumptionException.isPresent()) {
LOG.info("Try restarting producer of {} due to DataConsumptionException", failedVertex);
ResultPartitionID predecessorResultPartition = dataConsumptionException.get().getResultPartitionId();
Execution producer = executionGraph.getRegisteredExecutions().get(predecessorResultPartition.getProducerId());
if (producer == null) {
// If the producer has finished, it is removed from registeredExecutions and we need to locate it via the
// ResultPartitionID and the down-stream task.
for (IntermediateResult intermediateResult : failedVertex.getJobVertex().getInputs()) {
IntermediateResultPartition resultPartition = intermediateResult.getPartitionOrNullById(
predecessorResultPartition.getPartitionId());
if (resultPartition != null) {
Execution producerVertexCurrentAttempt = resultPartition.getProducer().getCurrentExecutionAttempt();
if (producerVertexCurrentAttempt.getAttemptId().equals(predecessorResultPartition.getProducerId())) {
producer = producerVertexCurrentAttempt;
} else {
LOG.warn("partition {} has already been disposed, skip restarting the producer.",
predecessorResultPartition);
}
break;
}
}
}
if (producer != null) {
return Optional.of(getFailoverRegion(producer.getVertex()));
} else {
return Optional.empty();
}
} else {
return Optional.of(getFailoverRegion(failedVertex));
}
}
private List sortRegionsTopologically(Set regions) {
final List regionsSorted = new ArrayList<>();
for (FailoverRegion region : sortedRegions) {
if (regions.contains(region)) {
regionsSorted.add(region);
}
}
return regionsSorted;
}
@Override
public void notifyNewVertices(List newJobVerticesTopological) {
generateAllFailoverRegion(newJobVerticesTopological);
sortRegions();
}
@Override
public String getStrategyName() {
return "Pipelined Region Failover";
}
/**
* Generate all the FailoverRegion from the new added job vertexes
*/
private void generateAllFailoverRegion(List newJobVerticesTopological) {
final IdentityHashMap> vertexToRegion = new IdentityHashMap<>();
// we use the map (list -> null) to imitate an IdentityHashSet (which does not exist)
final IdentityHashMap, Object> distinctRegions = new IdentityHashMap<>();
// this loop will worst case iterate over every edge in the graph (complexity is O(#edges))
for (ExecutionJobVertex ejv : newJobVerticesTopological) {
// currently, jobs with a co-location constraint fail as one
// we want to improve that in the future (or get rid of co-location constraints)
if (ejv.getCoLocationGroup() != null) {
makeAllOneRegion(newJobVerticesTopological);
return;
}
// see if this JobVertex one has pipelined inputs at all
final List inputs = ejv.getInputs();
final int numInputs = inputs.size();
boolean hasPipelinedInputs = false;
for (IntermediateResult input : inputs) {
if (input.getResultType().isPipelined()) {
hasPipelinedInputs = true;
break;
}
}
if (hasPipelinedInputs) {
// build upon the predecessors
for (ExecutionVertex ev : ejv.getTaskVertices()) {
// remember the region in which we are
ArrayList thisRegion = null;
for (int inputNum = 0; inputNum < numInputs; inputNum++) {
if (inputs.get(inputNum).getResultType().isPipelined()) {
for (IntermediateResultPartition consumedPartition : ev.getConsumedPartitions(inputNum)) {
final ExecutionVertex predecessor = consumedPartition.getProducer();
final ArrayList predecessorRegion = vertexToRegion.get(predecessor);
if (thisRegion != null) {
// we already have a region. see if it is the same as the predecessor's region
if (predecessorRegion != thisRegion) {
// we need to merge our region and the predecessor's region
predecessorRegion.addAll(thisRegion);
distinctRegions.remove(thisRegion);
thisRegion = predecessorRegion;
// remap the vertices from that merged region
for (ExecutionVertex inPredRegion: predecessorRegion) {
vertexToRegion.put(inPredRegion, thisRegion);
}
}
}
else if (predecessor != null) {
// first case, make this our region
thisRegion = predecessorRegion;
thisRegion.add(ev);
vertexToRegion.put(ev, thisRegion);
}
else {
// throw an uncaught exception here
// this is a bug and not a recoverable situation
throw new FlinkRuntimeException(
"bug in the logic to construct the pipelined failover regions");
}
}
}
}
}
}
else {
// no pipelined inputs, start a new region
for (ExecutionVertex ev : ejv.getTaskVertices()) {
ArrayList region = new ArrayList<>(1);
region.add(ev);
vertexToRegion.put(ev, region);
distinctRegions.put(region, null);
}
}
}
// now that we have all regions, create the failover region objects
LOG.info("Creating {} individual failover regions for job {} ({})",
distinctRegions.keySet().size(), executionGraph.getJobName(), executionGraph.getJobID());
for (List region : distinctRegions.keySet()) {
final FailoverRegion failoverRegion = new FailoverRegion(executionGraph, executor, region, regionFailLimit);
for (ExecutionVertex ev : region) {
this.vertexToRegion.put(ev, failoverRegion);
}
}
}
private void makeAllOneRegion(List jobVertices) {
LOG.warn("Cannot decompose ExecutionGraph into individual failover regions due to use of " +
"Co-Location constraints (iterations). Job will fail over as one holistic unit.");
final ArrayList allVertices = new ArrayList<>();
for (ExecutionJobVertex ejv : jobVertices) {
// safe some incremental size growing
allVertices.ensureCapacity(allVertices.size() + ejv.getParallelism());
for (ExecutionVertex ev : ejv.getTaskVertices()) {
allVertices.add(ev);
}
}
final FailoverRegion singleRegion = new FailoverRegion(executionGraph, executor, allVertices, regionFailLimit);
for (ExecutionVertex ev : allVertices) {
vertexToRegion.put(ev, singleRegion);
}
}
private void sortRegions() {
final Set sortedRegionSet = new HashSet<>();
sortedRegions.clear();
for (ExecutionJobVertex jobVertex : executionGraph.getVerticesTopologically()) {
for (ExecutionVertex ev : jobVertex.getTaskVertices()) {
FailoverRegion region = getFailoverRegion(ev);
if (!sortedRegionSet.contains(region)) {
sortedRegionSet.add(region);
sortedRegions.add(region);
}
}
}
}
// ------------------------------------------------------------------------
// testing
// ------------------------------------------------------------------------
/**
* Finds the failover region that contains the given execution vertex.
*/
@VisibleForTesting
public FailoverRegion getFailoverRegion(ExecutionVertex ev) {
return checkNotNull(vertexToRegion.get(ev),
"Can not find a failover region for the execution " + ev.getTaskNameWithSubtaskIndex());
}
// ------------------------------------------------------------------------
// factory
// ------------------------------------------------------------------------
/**
* Factory that instantiates the RestartPipelinedRegionStrategy.
*/
public static class Factory implements FailoverStrategy.Factory {
private int regionFailLimit = 100;
@Override
public FailoverStrategy create(ExecutionGraph executionGraph) {
return new RestartPipelinedRegionStrategy(executionGraph, regionFailLimit);
}
public void setRegionFailLimit(int regionFailLimit) {
this.regionFailLimit = regionFailLimit;
}
}
}
