/*
* 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.ExecutionEdge;
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.util.FlinkException;
import org.apache.flink.util.FlinkRuntimeException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.IdentityHashMap;
import java.util.List;
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 */
private final ExecutionGraph executionGraph;
/** The executor used for future actions */
private final Executor executor;
/** Fast lookup from vertex to failover region */
private final HashMap<ExecutionVertex, FailoverRegion> vertexToRegion;
/**
* 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
*/
public RestartPipelinedRegionStrategy(ExecutionGraph executionGraph) {
this(executionGraph, executionGraph.getFutureExecutor());
}
/**
* 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
*/
public RestartPipelinedRegionStrategy(ExecutionGraph executionGraph, Executor executor) {
this.executionGraph = checkNotNull(executionGraph);
this.executor = checkNotNull(executor);
this.vertexToRegion = new HashMap<>();
}
// ------------------------------------------------------------------------
// failover implementation
// ------------------------------------------------------------------------
@Override
public void onTaskFailure(Execution taskExecution, Throwable cause) {
final ExecutionVertex ev = taskExecution.getVertex();
final FailoverRegion failoverRegion = vertexToRegion.get(ev);
if (failoverRegion == null) {
executionGraph.failGlobal(new FlinkException(
"Can not find a failover region for the execution " + ev.getTaskNameWithSubtaskIndex(), cause));
}
else {
LOG.info("Recovering task failure for {} #{} ({}) via restart of failover region",
taskExecution.getVertex().getTaskNameWithSubtaskIndex(),
taskExecution.getAttemptNumber(),
taskExecution.getAttemptId());
failoverRegion.onExecutionFail(taskExecution, cause);
}
}
@Override
public void notifyNewVertices(List<ExecutionJobVertex> newJobVerticesTopological) {
generateAllFailoverRegion(newJobVerticesTopological);
}
@Override
public String getStrategyName() {
return "Pipelined Region Failover";
}
/**
* Generate all the FailoverRegion from the new added job vertexes
*/
private void generateAllFailoverRegion(List<ExecutionJobVertex> newJobVerticesTopological) {
final IdentityHashMap<ExecutionVertex, ArrayList<ExecutionVertex>> vertexToRegion = new IdentityHashMap<>();
// we use the map (list -> null) to imitate an IdentityHashSet (which does not exist)
final IdentityHashMap<ArrayList<ExecutionVertex>, 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<IntermediateResult> 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<ExecutionVertex> thisRegion = null;
for (int inputNum = 0; inputNum < numInputs; inputNum++) {
if (inputs.get(inputNum).getResultType().isPipelined()) {
for (ExecutionEdge edge : ev.getInputEdges(inputNum)) {
final ExecutionVertex predecessor = edge.getSource().getProducer();
final ArrayList<ExecutionVertex> 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
thisRegion.addAll(predecessorRegion);
distinctRegions.remove(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<ExecutionVertex> 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 {} ({})",
executionGraph.getJobName(), executionGraph.getJobID());
for (List<ExecutionVertex> region : distinctRegions.keySet()) {
final FailoverRegion failoverRegion = new FailoverRegion(executionGraph, executor, region);
for (ExecutionVertex ev : region) {
this.vertexToRegion.put(ev, failoverRegion);
}
}
}
private void makeAllOneRegion(List<ExecutionJobVertex> 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<ExecutionVertex> 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);
for (ExecutionVertex ev : allVertices) {
vertexToRegion.put(ev, singleRegion);
}
}
// ------------------------------------------------------------------------
// testing
// ------------------------------------------------------------------------
/**
* Finds the failover region that contains the given execution vertex.
*/
@VisibleForTesting
public FailoverRegion getFailoverRegion(ExecutionVertex ev) {
return vertexToRegion.get(ev);
}
// ------------------------------------------------------------------------
// factory
// ------------------------------------------------------------------------
/**
* Factory that instantiates the RestartPipelinedRegionStrategy.
*/
public static class Factory implements FailoverStrategy.Factory {
@Override
public FailoverStrategy create(ExecutionGraph executionGraph) {
return new RestartPipelinedRegionStrategy(executionGraph);
}
}
}