org.apache.flink.connector.base.source.reader.fetcher.FetchTask Maven / Gradle / Ivy
/*
* 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.base.source.reader.fetcher;
import org.apache.flink.api.connector.source.SourceSplit;
import org.apache.flink.connector.base.source.reader.RecordsWithSplitIds;
import org.apache.flink.connector.base.source.reader.splitreader.SplitReader;
import org.apache.flink.connector.base.source.reader.synchronization.FutureCompletingBlockingQueue;
import java.io.IOException;
import java.util.Collection;
import java.util.function.Consumer;
/** The default fetch task that fetches the records into the element queue. */
class FetchTask implements SplitFetcherTask {
private final SplitReader splitReader;
private final FutureCompletingBlockingQueue> elementsQueue;
private final Consumer> splitFinishedCallback;
private final int fetcherIndex;
private volatile RecordsWithSplitIds lastRecords;
private volatile boolean wakeup;
FetchTask(
SplitReader splitReader,
FutureCompletingBlockingQueue> elementsQueue,
Consumer> splitFinishedCallback,
int fetcherIndex) {
this.splitReader = splitReader;
this.elementsQueue = elementsQueue;
this.splitFinishedCallback = splitFinishedCallback;
this.lastRecords = null;
this.fetcherIndex = fetcherIndex;
this.wakeup = false;
}
@Override
public boolean run() throws IOException {
try {
if (!isWakenUp() && lastRecords == null) {
lastRecords = splitReader.fetch();
}
if (!isWakenUp()) {
// The order matters here. We must first put the last records into the queue.
// This ensures the handling of the fetched records is atomic to wakeup.
if (elementsQueue.put(fetcherIndex, lastRecords)) {
if (!lastRecords.finishedSplits().isEmpty()) {
// The callback does not throw InterruptedException.
splitFinishedCallback.accept(lastRecords.finishedSplits());
}
lastRecords = null;
}
}
} catch (InterruptedException e) {
// this should only happen on shutdown
throw new IOException("Source fetch execution was interrupted", e);
} finally {
// clean up the potential wakeup effect. It is possible that the fetcher is waken up
// after the clean up. In that case, either the wakeup flag will be set or the
// running thread will be interrupted. The next invocation of run() will see that and
// just skip.
if (isWakenUp()) {
wakeup = false;
}
}
// The return value of fetch task does not matter.
return true;
}
@Override
public void wakeUp() {
// Set the wakeup flag first.
wakeup = true;
if (lastRecords == null) {
// Two possible cases:
// 1. The splitReader is reading or is about to read the records.
// 2. The records has been enqueued and set to null.
// In case 1, we just wakeup the split reader. In case 2, the next run might be skipped.
// In any case, the records won't be enqueued in the ongoing run().
splitReader.wakeUp();
} else {
// The task might be blocking on enqueuing the records, just interrupt.
elementsQueue.wakeUpPuttingThread(fetcherIndex);
}
}
private boolean isWakenUp() {
return wakeup;
}
@Override
public String toString() {
return "FetchTask";
}
}