[GitHub] [flink] tillrohrmann commented on a change in pull request #8922: [FLINK-12876][runtime] Add an adapter of region failover NG for legacy scheduler

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tillrohrmann commented on a change in pull request #8922: [FLINK-12876][runtime] Add an adapter of region failover NG for legacy scheduler
URL: https://github.com/apache/flink/pull/8922#discussion_r299514990
 
 

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 File path: flink-runtime/src/main/java/org/apache/flink/runtime/executiongraph/failover/AdaptedRestartPipelinedRegionStrategyNG.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.
+ */
+
+package org.apache.flink.runtime.executiongraph.failover;
+
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.runtime.JobException;
+import org.apache.flink.runtime.checkpoint.CheckpointException;
+import org.apache.flink.runtime.checkpoint.CheckpointFailureReason;
+import org.apache.flink.runtime.concurrent.FutureUtils;
+import org.apache.flink.runtime.executiongraph.Execution;
+import org.apache.flink.runtime.executiongraph.ExecutionGraph;
+import org.apache.flink.runtime.executiongraph.ExecutionJobVertex;
+import org.apache.flink.runtime.executiongraph.ExecutionVertex;
+import org.apache.flink.runtime.executiongraph.GlobalModVersionMismatch;
+import org.apache.flink.runtime.executiongraph.SchedulingUtils;
+import org.apache.flink.runtime.executiongraph.failover.adapter.DefaultFailoverTopology;
+import org.apache.flink.runtime.executiongraph.failover.flip1.RestartPipelinedRegionStrategy;
+import org.apache.flink.runtime.jobgraph.JobStatus;
+import org.apache.flink.runtime.jobgraph.JobVertexID;
+import org.apache.flink.runtime.jobmanager.scheduler.CoLocationGroup;
+import org.apache.flink.runtime.scheduler.ExecutionVertexVersion;
+import org.apache.flink.runtime.scheduler.ExecutionVertexVersioner;
+import org.apache.flink.runtime.scheduler.strategy.ExecutionVertexID;
+import org.apache.flink.util.ExceptionUtils;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.CancellationException;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+import java.util.function.BiFunction;
+import java.util.stream.Collectors;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
+import static org.apache.flink.util.Preconditions.checkState;
+
+/**
+ * This failover strategy uses flip1.RestartPipelinedRegionStrategy to make task failover decisions.
+ */
+public class AdaptedRestartPipelinedRegionStrategyNG extends FailoverStrategy {
+
+	private static final Logger LOG = LoggerFactory.getLogger(AdaptedRestartPipelinedRegionStrategyNG.class);
+
+	/** The execution graph on which this FailoverStrategy works. */
+	private final ExecutionGraph executionGraph;
+
+	/** The versioner helps to maintain execution vertex versions. */
+	private final ExecutionVertexVersioner executionVertexVersioner;
+
+	/** The underlying new generation region failover strategy. */
+	private RestartPipelinedRegionStrategy restartPipelinedRegionStrategy;
+
+	public AdaptedRestartPipelinedRegionStrategyNG(final ExecutionGraph executionGraph) {
+		this.executionGraph = checkNotNull(executionGraph);
+		this.executionVertexVersioner = new ExecutionVertexVersioner();
+	}
+
+	@Override
+	public void onTaskFailure(final Execution taskExecution, final Throwable cause) {
+		if (!executionGraph.getRestartStrategy().canRestart()) {
+			// delegate the failure to a global fail that will check the restart strategy and not restart
+			LOG.info("Fail to pass the restart strategy validation in region failover. Fallback to fail global.");
+			failGlobal(cause);
+			return;
+		}
+
+		if (!isLocalFailoverValid(executionGraph.getGlobalModVersion())) {
+			LOG.info("Skip current region failover as a global failover is ongoing.");
+			return;
+		}
+
+		final ExecutionVertexID vertexID = getExecutionVertexID(taskExecution.getVertex());
+
+		final Set<ExecutionVertexID> tasksToRestart = restartPipelinedRegionStrategy.getTasksNeedingRestart(vertexID, cause);
+		restartTasks(tasksToRestart);
+	}
+
+	@VisibleForTesting
+	protected void restartTasks(final Set<ExecutionVertexID> verticesToRestart) {
+		final long globalModVersion = executionGraph.getGlobalModVersion();
+		final Set<ExecutionVertexVersion> vertexVersions = new HashSet<>(
+			executionVertexVersioner.recordVertexModifications(verticesToRestart).values());
+
+		FutureUtils.assertNoException(
+			cancelTasks(verticesToRestart)
+				.thenRunAsync(resetAndRescheduleTasks(globalModVersion, vertexVersions), executionGraph.getJobMasterMainThreadExecutor())
+				.handle(failGlobalOnError()));
+	}
+
+	private Runnable resetAndRescheduleTasks(final long globalModVersion, final Set<ExecutionVertexVersion> vertexVersions) {
+		return () -> {
+			if (!isLocalFailoverValid(globalModVersion)) {
+				LOG.info("Skip current region failover as a global failover is ongoing.");
+				return;
+			}
+
+			// found out vertices which are still valid to restart.
+			// some vertices involved in this failover may be modified if another region
+			// failover happens during the cancellation stage of this failover.
+			// Will ignore the modified vertices as the other failover will deal with them.
+			final Set<ExecutionVertex> unmodifiedVertices = executionVertexVersioner
+				.getUnmodifiedExecutionVertices(vertexVersions)
+				.stream()
+				.map(this::getExecutionVertex)
+				.collect(Collectors.toSet());
+
+			try {
+				LOG.info("Finally restart {} tasks to recover from task failure.", unmodifiedVertices.size());
+
+				// reset tasks to CREATED state and reload state
+				resetTasks(unmodifiedVertices, globalModVersion);
+
+				// re-schedule tasks
+				rescheduleTasks(unmodifiedVertices, globalModVersion);
+			} catch (GlobalModVersionMismatch e) {
+				// happens when a global recovery happens concurrently to the regional recovery
+				// just stop this local failover
 
 Review comment:
   Technically this should not be possible since we check the global mod version in `isLocalFailoverValid` and there should not be any concurrency in the EG. I guess we can revisit the `GlobalModVersionMismatch` exception and replace it with explicit checks and an `IllegalStateException` if resets happen with a different version.

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