Github user mxm commented on a diff in the pull request:
https://github.com/apache/flink/pull/2618#discussion_r84288776
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/functions/source/RichFileInputSplit.java
---
@@ -0,0 +1,153 @@
+/*
+ * 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.core.fs.FileInputSplit;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.util.Preconditions;
+
+import java.io.Serializable;
+
+/**
+ * An extended {@link FileInputSplit} that also includes information about:
+ * <ul>
+ * <li>The modification time of the file this split belongs to.</li>
+ * <li>When checkpointing, the state of the split at the moment of the
checkpoint.</li>
+ * </ul>
+ * This class is used by the {@link ContinuousFileMonitoringFunction} and
the
+ * {@link ContinuousFileReaderOperator} to perform continuous file
processing.
+ * */
+public class RichFileInputSplit<S extends Serializable>
+ extends FileInputSplit implements
Comparable<RichFileInputSplit>{
+
+ /** The modification time of the file this split belongs to. */
+ private final long modificationTime;
+
+ /**
+ * The state of the split. This information is used when
+ * restoring from a checkpoint and allows to resume reading the
+ * underlying file from the point we left off.
+ * */
+ private S splitState;
+
+ /** A special {@link RichFileInputSplit} signaling the end of the
stream of splits.*/
+ public static final RichFileInputSplit EOS =
+ new RichFileInputSplit<>(Long.MIN_VALUE, -1, null, -1, -1,
null);
+
+ /**
+ * Creates a {@link RichFileInputSplit} based on the file modification
time and
+ * the rest of the information of the {@link FileInputSplit}, as
returned by the
+ * underlying filesystem.
+ *
+ * @param modificationTime the modification file of the file this
split belongs to
+ * @param split the rest of the information about the split
+ */
+ public RichFileInputSplit(long modificationTime, FileInputSplit split) {
+ this(modificationTime,
+ split.getSplitNumber(),
+ split.getPath(),
+ split.getStart(),
+ split.getLength(),
+ split.getHostnames());
+ }
+
+ /**
+ * Constructor with the raw split information.
+ *
+ * @param modificationTime the modification file of the file this split
belongs to
+ * @param num the number of this input split
+ * @param file the file name
+ * @param start the position of the first byte in the file to process
+ * @param length the number of bytes in the file to process (-1 is flag
for "read whole file")
+ * @param hosts the list of hosts containing the block, possibly
<code>null</code>
+ */
+ private RichFileInputSplit(long modificationTime, int num, Path file,
long start, long length, String[] hosts) {
+ super(num, file, start, length, hosts);
+
+ Preconditions.checkArgument(modificationTime >= 0 ||
modificationTime == Long.MIN_VALUE,
+ "Invalid File Split Modification Time: "+
modificationTime +".");
+
+ this.modificationTime = modificationTime;
+ }
+
+ /**
+ * Sets the state of the split. This information is used when
+ * restoring from a checkpoint and allows to resume reading the
+ * underlying file from the point we left off.
+ * <p>
+ * This is applicable to {@link
org.apache.flink.api.common.io.FileInputFormat FileInputFormats}
+ * that implement the {@link
org.apache.flink.api.common.io.CheckpointableInputFormat
+ * CheckpointableInputFormat} interface.
+ * */
+ public void setSplitState(S state) {
+ this.splitState = state;
+ }
+
+ /**
+ * Sets the state of the split to {@code null}.
+ */
+ public void resetSplitState() {
+ this.setSplitState(null);
+ }
+
+ /** @return the state of the split. */
+ public S getSplitState() {
--- End diff --
```java
public Serializable getSplitState() {
```
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