org.apache.flink.streaming.api.functions.source.ContinuousFileReaderOperator Maven / Gradle / Ivy
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* 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
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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package org.apache.flink.streaming.api.functions.source;
import org.apache.flink.annotation.Internal;
import org.apache.flink.api.common.ExecutionConfig;
import org.apache.flink.api.common.io.CheckpointableInputFormat;
import org.apache.flink.api.common.io.FileInputFormat;
import org.apache.flink.api.common.state.ListState;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.metrics.Counter;
import org.apache.flink.runtime.state.StateInitializationContext;
import org.apache.flink.runtime.state.StateSnapshotContext;
import org.apache.flink.streaming.api.TimeCharacteristic;
import org.apache.flink.streaming.api.operators.AbstractStreamOperator;
import org.apache.flink.streaming.api.operators.OneInputStreamOperator;
import org.apache.flink.streaming.api.operators.OutputTypeConfigurable;
import org.apache.flink.streaming.api.operators.StreamSourceContexts;
import org.apache.flink.streaming.api.watermark.Watermark;
import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Queue;
import static org.apache.flink.util.Preconditions.checkNotNull;
import static org.apache.flink.util.Preconditions.checkState;
/**
* The operator that reads the {@link TimestampedFileInputSplit splits} received from the preceding
* {@link ContinuousFileMonitoringFunction}. Contrary to the {@link ContinuousFileMonitoringFunction}
* which has a parallelism of 1, this operator can have DOP > 1.
*
* As soon as a split descriptor is received, it is put in a queue, and have another
* thread read the actual data of the split. This architecture allows the separation of the
* reading thread from the one emitting the checkpoint barriers, thus removing any potential
* back-pressure.
*/
@Internal
public class ContinuousFileReaderOperator extends AbstractStreamOperator
implements OneInputStreamOperator, OutputTypeConfigurable {
private static final long serialVersionUID = 1L;
private static final Logger LOG = LoggerFactory.getLogger(ContinuousFileReaderOperator.class);
private FileInputFormat format;
private TypeSerializer serializer;
private transient Object checkpointLock;
private transient SplitReader reader;
private transient SourceFunction.SourceContext readerContext;
private transient ListState checkpointedState;
private transient List restoredReaderState;
public ContinuousFileReaderOperator(FileInputFormat format) {
this.format = checkNotNull(format);
}
@Override
public void setOutputType(TypeInformation outTypeInfo, ExecutionConfig executionConfig) {
this.serializer = outTypeInfo.createSerializer(executionConfig);
}
@Override
public void initializeState(StateInitializationContext context) throws Exception {
super.initializeState(context);
checkState(checkpointedState == null, "The reader state has already been initialized.");
checkpointedState = context.getOperatorStateStore().getSerializableListState("splits");
int subtaskIdx = getRuntimeContext().getIndexOfThisSubtask();
if (context.isRestored()) {
LOG.info("Restoring state for the {} (taskIdx={}).", getClass().getSimpleName(), subtaskIdx);
// this may not be null in case we migrate from a previous Flink version.
if (restoredReaderState == null) {
restoredReaderState = new ArrayList<>();
for (TimestampedFileInputSplit split : checkpointedState.get()) {
restoredReaderState.add(split);
}
if (LOG.isDebugEnabled()) {
LOG.debug("{} (taskIdx={}) restored {}.", getClass().getSimpleName(), subtaskIdx, restoredReaderState);
}
}
} else {
LOG.info("No state to restore for the {} (taskIdx={}).", getClass().getSimpleName(), subtaskIdx);
}
}
@Override
public void open() throws Exception {
super.open();
checkState(this.reader == null, "The reader is already initialized.");
checkState(this.serializer != null, "The serializer has not been set. " +
"Probably the setOutputType() was not called. Please report it.");
this.format.setRuntimeContext(getRuntimeContext());
this.format.configure(new Configuration());
this.checkpointLock = getContainingTask().getCheckpointLock();
// set the reader context based on the time characteristic
final TimeCharacteristic timeCharacteristic = getOperatorConfig().getTimeCharacteristic();
final long watermarkInterval = getRuntimeContext().getExecutionConfig().getAutoWatermarkInterval();
this.readerContext = StreamSourceContexts.getSourceContext(
timeCharacteristic,
getProcessingTimeService(),
checkpointLock,
getContainingTask().getStreamStatusMaintainer(),
output,
watermarkInterval,
-1);
// and initialize the split reading thread
this.reader = new SplitReader<>(format, serializer, readerContext, checkpointLock, restoredReaderState);
this.restoredReaderState = null;
this.reader.start();
}
@Override
public void processElement(StreamRecord element) throws Exception {
reader.addSplit(element.getValue());
}
@Override
public void processWatermark(Watermark mark) throws Exception {
// we do nothing because we emit our own watermarks if needed.
}
@Override
public void dispose() throws Exception {
super.dispose();
// first try to cancel it properly and
// give it some time until it finishes
reader.cancel();
try {
reader.join(200);
} catch (InterruptedException e) {
// we can ignore this
}
// if the above did not work, then interrupt the thread repeatedly
while (reader.isAlive()) {
StringBuilder bld = new StringBuilder();
StackTraceElement[] stack = reader.getStackTrace();
for (StackTraceElement e : stack) {
bld.append(e).append('\n');
}
LOG.warn("The reader is stuck in method:\n {}", bld.toString());
reader.interrupt();
try {
reader.join(50);
} catch (InterruptedException e) {
// we can ignore this
}
}
reader = null;
readerContext = null;
restoredReaderState = null;
format = null;
serializer = null;
}
@Override
public void close() throws Exception {
super.close();
// make sure that we hold the checkpointing lock
Thread.holdsLock(checkpointLock);
// close the reader to signal that no more splits will come. By doing this,
// the reader will exit as soon as it finishes processing the already pending splits.
// This method will wait until then. Further cleaning up is handled by the dispose().
while (reader != null && reader.isAlive() && reader.isRunning()) {
reader.close();
checkpointLock.wait();
}
// finally if we are operating on event or ingestion time,
// emit the long-max watermark indicating the end of the stream,
// like a normal source would do.
if (readerContext != null) {
readerContext.emitWatermark(Watermark.MAX_WATERMARK);
readerContext.close();
}
output.close();
}
private class SplitReader extends Thread {
private volatile boolean shouldClose;
private volatile boolean isRunning;
private final FileInputFormat format;
private final TypeSerializer serializer;
private final Object checkpointLock;
private final SourceFunction.SourceContext readerContext;
private final Queue pendingSplits;
private TimestampedFileInputSplit currentSplit;
private volatile boolean isSplitOpen;
private SplitReader(FileInputFormat format,
TypeSerializer serializer,
SourceFunction.SourceContext readerContext,
Object checkpointLock,
List restoredState) {
this.format = checkNotNull(format, "Unspecified FileInputFormat.");
this.serializer = checkNotNull(serializer, "Unspecified Serializer.");
this.readerContext = checkNotNull(readerContext, "Unspecified Reader Context.");
this.checkpointLock = checkNotNull(checkpointLock, "Unspecified checkpoint lock.");
this.shouldClose = false;
this.isRunning = true;
this.pendingSplits = new PriorityQueue<>();
// this is the case where a task recovers from a previous failed attempt
if (restoredState != null) {
this.pendingSplits.addAll(restoredState);
}
}
private void addSplit(TimestampedFileInputSplit split) {
checkNotNull(split, "Cannot insert a null value in the pending splits queue.");
synchronized (checkpointLock) {
this.pendingSplits.add(split);
}
}
public boolean isRunning() {
return this.isRunning;
}
@Override
public void run() {
try {
Counter completedSplitsCounter = getMetricGroup().counter("numSplitsProcessed");
this.format.openInputFormat();
while (this.isRunning) {
synchronized (checkpointLock) {
if (currentSplit == null) {
currentSplit = this.pendingSplits.poll();
// if the list of pending splits is empty (currentSplit == null) then:
// 1) if close() was called on the operator then exit the while loop
// 2) if not wait 50 ms and try again to fetch a new split to read
if (currentSplit == null) {
if (this.shouldClose) {
isRunning = false;
} else {
checkpointLock.wait(50);
}
continue;
}
}
if (this.format instanceof CheckpointableInputFormat && currentSplit.getSplitState() != null) {
// recovering after a node failure with an input
// format that supports resetting the offset
((CheckpointableInputFormat) this.format).
reopen(currentSplit, currentSplit.getSplitState());
} else {
// we either have a new split, or we recovered from a node
// failure but the input format does not support resetting the offset.
this.format.open(currentSplit);
}
// reset the restored state to null for the next iteration
this.currentSplit.resetSplitState();
this.isSplitOpen = true;
}
LOG.debug("Reading split: " + currentSplit);
try {
OT nextElement = serializer.createInstance();
while (!format.reachedEnd()) {
synchronized (checkpointLock) {
nextElement = format.nextRecord(nextElement);
if (nextElement != null) {
readerContext.collect(nextElement);
} else {
break;
}
}
}
completedSplitsCounter.inc();
} finally {
// close and prepare for the next iteration
synchronized (checkpointLock) {
this.format.close();
this.isSplitOpen = false;
this.currentSplit = null;
}
}
}
} catch (Throwable e) {
getContainingTask().handleAsyncException("Caught exception when processing split: " + currentSplit, e);
} finally {
synchronized (checkpointLock) {
LOG.debug("Reader terminated, and exiting...");
try {
this.format.closeInputFormat();
} catch (IOException e) {
getContainingTask().handleAsyncException(
"Caught exception from " + this.format.getClass().getName() + ".closeInputFormat() : " + e.getMessage(), e);
}
this.isSplitOpen = false;
this.currentSplit = null;
this.isRunning = false;
checkpointLock.notifyAll();
}
}
}
private List getReaderState() throws IOException {
List snapshot = new ArrayList<>(this.pendingSplits.size());
if (currentSplit != null) {
if (this.format instanceof CheckpointableInputFormat && this.isSplitOpen) {
Serializable formatState =
((CheckpointableInputFormat) this.format).getCurrentState();
this.currentSplit.setSplitState(formatState);
}
snapshot.add(this.currentSplit);
}
snapshot.addAll(this.pendingSplits);
return snapshot;
}
public void cancel() {
this.isRunning = false;
}
public void close() {
this.shouldClose = true;
}
}
// --------------------- Checkpointing --------------------------
@Override
public void snapshotState(StateSnapshotContext context) throws Exception {
super.snapshotState(context);
checkState(checkpointedState != null,
"The operator state has not been properly initialized.");
int subtaskIdx = getRuntimeContext().getIndexOfThisSubtask();
checkpointedState.clear();
List readerState = reader.getReaderState();
try {
for (TimestampedFileInputSplit split : readerState) {
// create a new partition for each entry.
checkpointedState.add(split);
}
} catch (Exception e) {
checkpointedState.clear();
throw new Exception("Could not add timestamped file input splits to to operator " +
"state backend of operator " + getOperatorName() + '.', e);
}
if (LOG.isDebugEnabled()) {
LOG.debug("{} (taskIdx={}) checkpointed {} splits: {}.",
getClass().getSimpleName(), subtaskIdx, readerState.size(), readerState);
}
}
}