StephanEwen commented on a change in pull request #13401: URL: https://github.com/apache/flink/pull/13401#discussion_r491699660
########## File path: flink-connectors/flink-connector-files/src/main/java/org/apache/flink/connector/file/src/impl/ContinuousFileSplitEnumerator.java ########## @@ -0,0 +1,156 @@ +/* + * 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.connector.file.src.impl; + +import org.apache.flink.api.connector.source.SourceEvent; +import org.apache.flink.api.connector.source.SplitEnumerator; +import org.apache.flink.api.connector.source.SplitEnumeratorContext; +import org.apache.flink.connector.base.source.event.RequestSplitEvent; +import org.apache.flink.connector.file.src.FileSourceSplit; +import org.apache.flink.connector.file.src.PendingSplitsCheckpoint; +import org.apache.flink.connector.file.src.assigners.FileSplitAssigner; +import org.apache.flink.connector.file.src.enumerate.FileEnumerator; +import org.apache.flink.core.fs.Path; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.io.IOException; +import java.util.Collection; +import java.util.HashSet; +import java.util.Iterator; +import java.util.List; +import java.util.Optional; +import java.util.stream.Collectors; + +import static org.apache.flink.util.Preconditions.checkArgument; +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * A continuously monitoring enumerator. + */ +public class ContinuousFileSplitEnumerator implements SplitEnumerator<FileSourceSplit, PendingSplitsCheckpoint> { + + private static final Logger LOG = LoggerFactory.getLogger(ContinuousFileSplitEnumerator.class); + + private final SplitEnumeratorContext<FileSourceSplit> context; + + private final FileSplitAssigner splitAssigner; + + private final FileEnumerator enumerator; + + private final HashSet<Path> pathsAlreadyProcessed; + + private final HashSet<Integer> readersAwaitingSplit; + + private final Path[] paths; + + private final long discoveryInterval; + + // ------------------------------------------------------------------------ + + public ContinuousFileSplitEnumerator( + SplitEnumeratorContext<FileSourceSplit> context, + FileEnumerator enumerator, + FileSplitAssigner splitAssigner, + Path[] paths, + Collection<Path> alreadyDiscoveredPaths, + long discoveryInterval) { + + checkArgument(discoveryInterval > 0L); + this.context = checkNotNull(context); + this.enumerator = checkNotNull(enumerator); + this.splitAssigner = checkNotNull(splitAssigner); + this.paths = paths; + this.discoveryInterval = discoveryInterval; + this.pathsAlreadyProcessed = new HashSet<>(alreadyDiscoveredPaths); + this.readersAwaitingSplit = new HashSet<>(); + } + + @Override + public void start() { + context.callAsync( + () -> enumerator.enumerateSplits(paths, 1), + this::processDiscoveredSplits, + discoveryInterval, discoveryInterval); + } + + @Override + public void close() throws IOException { + // no resources to close + } + + @Override + public void addReader(int subtaskId) { + // this source is purely lazy-pull-based, nothing to do upon registration + } + + @Override + public void handleSourceEvent(int subtaskId, SourceEvent sourceEvent) { + if (sourceEvent instanceof RequestSplitEvent) { + readersAwaitingSplit.add(subtaskId); + assignSplits(); + } + else { + LOG.error("Received unrecognized event: {}", sourceEvent); + } + } + + @Override + public void addSplitsBack(List<FileSourceSplit> splits, int subtaskId) { + LOG.debug("File Source Enumerator adds splits back: {}", splits); + splitAssigner.addSplits(splits); + } + + @Override + public PendingSplitsCheckpoint snapshotState() throws Exception { + return PendingSplitsCheckpoint.fromCollectionSnapshot(splitAssigner.remainingSplits(), pathsAlreadyProcessed); + } + + // ------------------------------------------------------------------------ + + private void processDiscoveredSplits(Collection<FileSourceSplit> splits, Throwable error) { + if (error != null) { + LOG.error("Failed to enumerate files", error); + return; + } + + final Collection<FileSourceSplit> newSplits = splits.stream() + .filter((split) -> pathsAlreadyProcessed.add(split.path())) + .collect(Collectors.toList()); + splitAssigner.addSplits(newSplits); + + assignSplits(); + } + + private void assignSplits() { + final Iterator<Integer> awaitingReader = readersAwaitingSplit.iterator(); + + while (awaitingReader.hasNext()) { + final int awaitingSubtask = awaitingReader.next(); + final Optional<FileSourceSplit> nextSplit = splitAssigner.getNext(null); Review comment: Good catch. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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