martongreber commented on code in PR #8: URL: https://github.com/apache/flink-connector-kudu/pull/8#discussion_r1995453773
########## flink-connector-kudu/src/main/java/org/apache/flink/connector/kudu/source/enumerator/KuduSourceEnumerator.java: ########## @@ -0,0 +1,264 @@ +/* + * 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.kudu.source.enumerator; + +import org.apache.flink.api.connector.source.Boundedness; +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.kudu.connector.KuduTableInfo; +import org.apache.flink.connector.kudu.connector.reader.KuduReaderConfig; +import org.apache.flink.connector.kudu.source.split.KuduSourceSplit; +import org.apache.flink.connector.kudu.source.split.SplitFinishedEvent; +import org.apache.flink.connector.kudu.source.utils.KuduSourceUtils; +import org.apache.flink.connector.kudu.source.utils.KuduSplitGenerator; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import javax.annotation.Nullable; + +import java.io.IOException; +import java.time.Duration; +import java.util.ArrayList; +import java.util.Iterator; +import java.util.List; +import java.util.function.Supplier; + +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * The Kudu source enumerator is responsible for discovering and assigning splits. + * + * <ul> + * <li>If {@code Boundedness.BOUNDED} is set, the enumerator generates splits corresponding to the + * current snapshot time and emits records only for this bounded set. + * <li>If {@code Boundedness.CONTINUOUS_UNBOUNDED} is set, the enumerator follows a CDC-like + * approach as described below. + * </ul> + * + * <p>To provide CDC-like functionality, the enumeration works as follows: Initially, we perform a + * snapshot read of the table and mark the snapshot time as t0. From that point onward, we perform + * differential scans in the time intervals t0 - t1, t1 - t2, and so on. + * + * <p>This approach means that new splits can only be enumerated once the current time range is + * fully processed. + * + * <p>The process is controlled as follows: + * + * <ul> + * <li>Once a set of splits is enumerated for a time range, we track: + * <ul> + * <li><b>Unassigned splits</b>: Discovered but not yet assigned to readers. + * <li><b>Pending splits</b>: Assigned but not yet fully processed. + * </ul> + * <li>A new set of splits is generated only when there are no remaining unassigned or pending + * splits. + * </ul> + */ +public class KuduSourceEnumerator + implements SplitEnumerator<KuduSourceSplit, KuduSourceEnumeratorState> { + private static final Logger LOG = LoggerFactory.getLogger(KuduSourceEnumerator.class); + + private final SplitEnumeratorContext<KuduSourceSplit> context; + private final List<Integer> readersAwaitingSplit; + private final KuduSplitGenerator splitGenerator; + private final Boundedness boundedness; + private final Duration discoveryInterval; + + private long lastEndTimestamp; + private final List<KuduSourceSplit> unassigned; + private final List<KuduSourceSplit> pending; + + public KuduSourceEnumerator( + KuduTableInfo tableInfo, + KuduReaderConfig readerConfig, + Boundedness boundedness, + Duration discoveryInterval, + SplitEnumeratorContext<KuduSourceSplit> context) { + this( + tableInfo, + readerConfig, + boundedness, + discoveryInterval, + context, + KuduSourceEnumeratorState.empty()); + } + + public KuduSourceEnumerator( + KuduTableInfo tableInfo, + KuduReaderConfig readerConfig, + Boundedness boundedness, + Duration discoveryInterval, + SplitEnumeratorContext<KuduSourceSplit> context, + KuduSourceEnumeratorState enumState) { + this.boundedness = checkNotNull(boundedness); + this.discoveryInterval = discoveryInterval; + this.context = checkNotNull(context); + this.readersAwaitingSplit = new ArrayList<>(); + this.unassigned = enumState.getUnassigned(); + this.pending = enumState.getPending(); + this.splitGenerator = new KuduSplitGenerator(readerConfig, tableInfo); + this.lastEndTimestamp = enumState.getLastEndTimestamp(); + + validateConfiguration(); + } + + private void validateConfiguration() { + if (boundedness == Boundedness.CONTINUOUS_UNBOUNDED && discoveryInterval == null) { + throw new IllegalArgumentException( + "discoveryInterval must be set for CONTINUOUS_UNBOUNDED mode."); + } + } + + @Override + public void start() { + if (boundedness == Boundedness.CONTINUOUS_UNBOUNDED) { + context.callAsync( + () -> enumerateNewSplits(this::shouldEnumerateNewSplits), + this::assignSplits, + 0, + discoveryInterval.toMillis()); + } else if (boundedness == Boundedness.BOUNDED) { + List<KuduSourceSplit> splits = enumerateNewSplits(this::shouldEnumerateNewSplits); + assignSplits(splits, null); + } + } + + @Override + public void handleSplitRequest(int subtaskId, @Nullable String requesterHostname) { + readersAwaitingSplit.add(subtaskId); + assignSplitsToReaders(); + } + + @Override + public void addSplitsBack(List<KuduSourceSplit> splits, int subtaskId) { + LOG.debug("Adding splits back: {}", splits); + pending.removeAll(splits); + unassigned.addAll(splits); + if (context.registeredReaders().containsKey(subtaskId)) { + readersAwaitingSplit.add(subtaskId); + } + assignSplitsToReaders(); + } + + @Override + public void addReader(int subtaskId) { + // The source is purely lazy-pull-based, nothing to do upon registration + } + + @Override + public KuduSourceEnumeratorState snapshotState(long checkpointId) throws Exception { + return new KuduSourceEnumeratorState(lastEndTimestamp, unassigned, pending); + } + + @Override + public void close() throws IOException { + try { + splitGenerator.close(); + } catch (Exception e) { + throw new IOException("Error closing split generator", e); + } + } + + @Override + public void handleSourceEvent(int subtaskId, SourceEvent sourceEvent) { + if (sourceEvent instanceof SplitFinishedEvent) { + SplitFinishedEvent splitFinishedEvent = (SplitFinishedEvent) sourceEvent; + LOG.debug( + "Received SplitFinishedEvent from subtask {} for splits: {}", + subtaskId, + splitFinishedEvent.getFinishedSplits()); + pending.removeAll(splitFinishedEvent.getFinishedSplits()); + readersAwaitingSplit.add(subtaskId); + assignSplitsToReaders(); + } + } + + // This function is invoked repeatedly according to this.period if there are no outstanding + // splits. + // Outstanding meaning that there are no pending splits, and no enumerated but not assigned + // splits for the + // current period. + private List<KuduSourceSplit> enumerateNewSplits(Supplier<Boolean> shouldGenerate) { + if (!shouldGenerate.get()) { + return null; + } + List<KuduSourceSplit> newSplits; + + if (isFirstSplitGeneration()) { + lastEndTimestamp = KuduSourceUtils.getCurrentHybridTime(); + newSplits = splitGenerator.generateFullScanSplits(lastEndTimestamp); + } else { + long startHT = lastEndTimestamp; + long endHT = KuduSourceUtils.getCurrentHybridTime(); + newSplits = splitGenerator.generateIncrementalSplits(startHT, endHT); + lastEndTimestamp = endHT; + } + + return newSplits; + } + + private void assignSplits(List<KuduSourceSplit> splits, Throwable error) { + if (error != null) { + LOG.error("Failed to enumerate Kudu splits.", error); + return; Review Comment: done. -- This is an automated message from the Apache Git Service. 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