Github user aljoscha commented on a diff in the pull request:
https://github.com/apache/flink/pull/1929#discussion_r61403602
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/functions/source/FileSplitReadOperator.java
---
@@ -0,0 +1,184 @@
+/*
+ * 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.streaming.api.functions.source;
+
+import org.apache.flink.api.common.io.FileInputFormat;
+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.core.fs.FileInputSplit;
+import org.apache.flink.streaming.api.operators.AbstractStreamOperator;
+import org.apache.flink.streaming.api.operators.ChainingStrategy;
+import org.apache.flink.streaming.api.operators.OneInputStreamOperator;
+import org.apache.flink.streaming.api.operators.TimestampedCollector;
+import org.apache.flink.streaming.api.watermark.Watermark;
+import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
+import org.apache.flink.util.Preconditions;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Queue;
+import java.util.concurrent.ConcurrentLinkedQueue;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
+
+/**
+ * This is the operator that reads the splits received from {@link
FileSplitMonitoringFunction}.
+ * This operator will receive just the split descriptors and then read and
emit records. This may lead
+ * to backpressure. To avoid this, we will have another thread actually
reading the splits and
+ * another forwarding the checkpoint barriers. The two should sync so that
the checkpoints reflect the
+ * current state.
+ * */
+public class FileSplitReadOperator<OUT> extends
AbstractStreamOperator<OUT> implements OneInputStreamOperator<FileInputSplit,
OUT> {
+
+ private static final Logger LOG =
LoggerFactory.getLogger(FileSplitMonitoringFunction.class);
+
+ private transient SplitReader<OUT> reader;
+ private transient TimestampedCollector<OUT> collector;
+
+ private Configuration configuration;
+ private FileInputFormat<OUT> format;
+ private TypeInformation<OUT> typeInfo;
+
+ public FileSplitReadOperator(FileInputFormat<OUT> format,
TypeInformation<OUT> typeInfo, Configuration configuration) {
+ this.format = format;
+ this.typeInfo = typeInfo;
+ this.configuration = configuration;
+
+ // this is for the extra thread that is reading,
+ // the tests were not terminating because the success
+ // exception was caught by the extra thread, and never
+ // forwarded.
+
+ // for now, and to keep the extra thread to avoid backpressure,
+ // we just disable chaining for the operator, so that it runs on
+ // another thread. This will change later for a cleaner design.
+ setChainingStrategy(ChainingStrategy.NEVER);
+ }
+
+ @Override
+ public void open() throws Exception {
+ super.open();
+
+ this.format.configure(configuration);
+ this.collector = new TimestampedCollector<>(output);
+
+ TypeSerializer<OUT> serializer =
typeInfo.createSerializer(getRuntimeContext().getExecutionConfig());
+ Object checkpointLock = getContainingTask().getCheckpointLock();
+
+ this.reader = new SplitReader<>(format, serializer, collector,
checkpointLock);
+ this.reader.start();
+ }
+
+ @Override
+ public void processElement(StreamRecord<FileInputSplit> element) throws
Exception {
+ this.reader.addSplit(element.getValue());
+ }
+
+ @Override
+ public void processWatermark(Watermark mark) throws Exception {
+ output.emitWatermark(mark);
+ }
+
+ @Override
+ public void close() throws Exception {
+ super.close();
+ this.reader.cancel();
+ this.reader.interrupt();
+ this.collector.close();
+ }
+
+ private class SplitReader<OT> extends Thread {
+
+ private boolean isRunning;
+
+ private final Queue<FileInputSplit> pendingSplits;
+
+ private final FileInputFormat<OT> format;
+ private final TypeSerializer<OT> serializer;
+
+ private final Object checkpointLock;
+ private final TimestampedCollector<OT> collector;
+
+ SplitReader(FileInputFormat<OT> format,
+ TypeSerializer<OT> serializer,
+ TimestampedCollector<OT> collector,
+ Object checkpointLock) {
+ this.format = checkNotNull(format, "Unspecified
FileInputFormat.");
+ this.serializer = checkNotNull(serializer, "Unspecified
Serialized.");
+
+ this.pendingSplits = new ConcurrentLinkedQueue<>();
+ this.collector = collector;
+ this.checkpointLock = checkpointLock;
+ this.isRunning = true;
+ }
+
+ void addSplit(FileInputSplit split) {
+ Preconditions.checkNotNull(split);
+ LOG.info("Adding split to read queue: " + split);
+ this.pendingSplits.add(split);
+ }
+
+ @Override
+ public void run() {
+ FileInputSplit split = null;
+
+ try {
+ while(this.isRunning) {
+
+ // get the next split to read
+ split = this.pendingSplits.poll();
+ if (split == null) {
+ Thread.sleep(50);
+ continue;
+ }
+
+ boolean isOpen = false;
+ try {
+ this.format.open(split);
+ isOpen = true;
+ OT nextElement =
serializer.createInstance();
+ do {
+ nextElement =
format.nextRecord(nextElement);
+ if (nextElement !=
null) {
+ synchronized
(checkpointLock) {
+
collector.collect(nextElement);
+ //
checkpointing should be here.
+ }
+ }
+ } while (nextElement != null &&
!format.reachedEnd());
+ } finally {
+ if (isOpen) {
+ this.format.close();
+ }
+ }
+ }
+
+ LOG.info("Split Reader terminated, and exiting
normally.");
+ } catch (IOException e) {
+ throw new RuntimeException("Unable to open
split: " + split, e.getCause());
--- End diff --
We should wrap this in an `AsyncException` and store it, so that
`processElement` can rethrow it. Please have a look at
`StreamTask.asyncException`, we can basically copy the stuff from there.
This is not completely fool-proof, since we only recognize the exception if
new data arrives in `processElement` but it is better than nothing.
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