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ASF GitHub Bot commented on FLINK-8360: --------------------------------------- Github user tillrohrmann commented on a diff in the pull request: https://github.com/apache/flink/pull/5239#discussion_r168477978 --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/state/LocalRecoveryDirectoryProvider.java --- @@ -0,0 +1,112 @@ +/* + * 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.state; + +import org.apache.flink.util.Preconditions; + +import java.io.File; +import java.io.Serializable; +import java.util.Arrays; +import java.util.UUID; +import java.util.concurrent.atomic.AtomicInteger; + +/** + * Provides root directories and the subtask-specific path to build directories for file-based local recovery. Calls + * to {@link #nextRootDirectory()} rotate over all available root directories. this class is thread-safe. + */ +public class LocalRecoveryDirectoryProvider implements Serializable { + + private static final long serialVersionUID = 1L; + + /** All available root directories that this can potentially deliver. */ + private final File[] rootDirectories; + + /** A subtask-specific string that describes a path to it's local state from a given checkpoint root. */ + private final String subtaskSpecificPath; + + /** Current index for rotational selection of delivered root dirs. */ + private AtomicInteger idx; + + public LocalRecoveryDirectoryProvider(File rootDir, String subtaskSpecificPath) { + this(new File[]{rootDir}, subtaskSpecificPath); + } + + public LocalRecoveryDirectoryProvider(File[] rootDirectories, String subtaskSpecificPath) { + + this.rootDirectories = Preconditions.checkNotNull(rootDirectories); + this.subtaskSpecificPath = Preconditions.checkNotNull(subtaskSpecificPath); + Preconditions.checkArgument(rootDirectories.length > 0); + + for (File directory : rootDirectories) { + Preconditions.checkNotNull(directory); + if (!directory.isDirectory()) { + throw new IllegalStateException("Local recovery root directory " + directory + " does not exist!"); + } + } + + this.idx = new AtomicInteger(-1); + } + + /** + * Returns the next root directory w.r.t. our rotation over all available root dirs. + */ + public File nextRootDirectory() { + return rootDirectories[(idx.incrementAndGet() & Integer.MAX_VALUE) % rootDirectories.length]; --- End diff -- Nice trick :-) > Implement task-local state recovery > ----------------------------------- > > Key: FLINK-8360 > URL: https://issues.apache.org/jira/browse/FLINK-8360 > Project: Flink > Issue Type: New Feature > Components: State Backends, Checkpointing > Reporter: Stefan Richter > Assignee: Stefan Richter > Priority: Major > Fix For: 1.5.0 > > > This issue tracks the development of recovery from task-local state. The main > idea is to have a secondary, local copy of the checkpointed state, while > there is still a primary copy in DFS that we report to the checkpoint > coordinator. > Recovery can attempt to restore from the secondary local copy, if available, > to save network bandwidth. This requires that the assignment from tasks to > slots is as sticky is possible. > For starters, we will implement this feature for all managed keyed states and > can easily enhance it to all other state types (e.g. operator state) later. -- This message was sent by Atlassian JIRA (v7.6.3#76005)