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/*
* 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.runtime.state;
import org.apache.flink.annotation.VisibleForTesting;
import org.apache.flink.util.ExceptionUtils;
import org.apache.flink.util.Preconditions;
import javax.annotation.Nullable;
import java.io.IOException;
/**
* A CheckpointStateOutputStream that wraps a primary and a secondary CheckpointStateOutputStream and duplicates
* all writes into both streams. This stream applies buffering to reduce the amount of dual-method calling. Furthermore,
* exceptions that happen in interactions with the secondary stream are not exposed, until the user calls
* {@link #closeAndGetSecondaryHandle()}. In contrast to that, exceptions from interactions with the primary stream
* are immediately returned to the user. This class is used to write state for local recovery as a local (secondary)
* copy of the (primary) state snapshot that is written to a (slower but highly-available) remote filesystem.
*/
public class DuplicatingCheckpointOutputStream extends CheckpointStreamFactory.CheckpointStateOutputStream {
/** Default buffer size of 8KB. */
private static final int DEFAULT_BUFFER_SIZER = 8 * 1024;
/** Write buffer. */
private final byte[] buffer;
/** Position in the write buffer. */
private int bufferIdx;
/**
* Primary stream for writing the checkpoint data. Failures from this stream are forwarded.
*/
private final CheckpointStreamFactory.CheckpointStateOutputStream primaryOutputStream;
/**
* Primary stream for writing the checkpoint data. Failures from this stream are not forwarded until
* {@link #closeAndGetSecondaryHandle()}.
*/
private final CheckpointStreamFactory.CheckpointStateOutputStream secondaryOutputStream;
/**
* Stores a potential exception that occurred while interacting with {@link #secondaryOutputStream}
*/
private Exception secondaryStreamException;
public DuplicatingCheckpointOutputStream(
CheckpointStreamFactory.CheckpointStateOutputStream primaryOutputStream,
CheckpointStreamFactory.CheckpointStateOutputStream secondaryOutputStream) throws IOException {
this(primaryOutputStream, secondaryOutputStream, DEFAULT_BUFFER_SIZER);
}
public DuplicatingCheckpointOutputStream(
CheckpointStreamFactory.CheckpointStateOutputStream primaryOutputStream,
CheckpointStreamFactory.CheckpointStateOutputStream secondaryOutputStream,
int bufferSize) throws IOException {
this.primaryOutputStream = Preconditions.checkNotNull(primaryOutputStream);
this.secondaryOutputStream = Preconditions.checkNotNull(secondaryOutputStream);
this.buffer = new byte[bufferSize];
this.bufferIdx = 0;
this.secondaryStreamException = null;
checkForAlignedStreamPositions();
}
@Override
public void write(int b) throws IOException {
if (buffer.length <= bufferIdx) {
flushInternalBuffer();
}
buffer[bufferIdx] = (byte) b;
++bufferIdx;
}
@Override
public void write(byte[] b) throws IOException {
write(b, 0, b.length);
}
@Override
public void write(byte[] b, int off, int len) throws IOException {
if (buffer.length <= len) {
flushInternalBuffer();
writeThroughInternal(b, off, len);
} else {
if (buffer.length < len + bufferIdx) {
flushInternalBuffer();
}
System.arraycopy(b, off, buffer, bufferIdx, len);
bufferIdx += len;
}
}
@Override
public long getPos() throws IOException {
final long referencePos = primaryOutputStream.getPos();
return referencePos + bufferIdx;
}
@Override
public void flush() throws IOException {
flushInternalBuffer();
primaryOutputStream.flush();
if (secondaryStreamException == null) {
try {
secondaryOutputStream.flush();
} catch (Exception flushEx) {
handleSecondaryStreamOnException(flushEx);
}
}
}
@Override
public void sync() throws IOException {
flushInternalBuffer();
primaryOutputStream.sync();
if (secondaryStreamException == null) {
try {
secondaryOutputStream.sync();
} catch (Exception syncEx) {
handleSecondaryStreamOnException(syncEx);
}
}
}
@Override
public void close() throws IOException {
Exception exCollector = null;
try {
flushInternalBuffer();
} catch (Exception flushEx) {
exCollector = flushEx;
}
try {
primaryOutputStream.close();
} catch (Exception closeEx) {
exCollector = ExceptionUtils.firstOrSuppressed(closeEx, exCollector);
}
if (secondaryStreamException == null) {
try {
secondaryOutputStream.close();
} catch (Exception closeEx) {
handleSecondaryStreamOnException(closeEx);
}
}
if (exCollector != null) {
throw new IOException("Exception while closing duplicating stream.", exCollector);
}
}
private void checkForAlignedStreamPositions() throws IOException {
if (secondaryStreamException != null) {
return;
}
final long primaryPos = primaryOutputStream.getPos();
try {
final long secondaryPos = secondaryOutputStream.getPos();
if (primaryPos != secondaryPos) {
handleSecondaryStreamOnException(
new IOException("Stream positions are out of sync between primary stream and secondary stream. " +
"Reported positions are " + primaryPos + " (primary) and " + secondaryPos + " (secondary)."));
}
} catch (Exception posEx) {
handleSecondaryStreamOnException(posEx);
}
}
private void flushInternalBuffer() throws IOException {
if (bufferIdx > 0) {
writeThroughInternal(buffer, 0, bufferIdx);
bufferIdx = 0;
}
}
private void writeThroughInternal(byte[] b, int off, int len) throws IOException {
primaryOutputStream.write(b, off, len);
if (secondaryStreamException == null) {
try {
secondaryOutputStream.write(b, off, len);
} catch (Exception writeEx) {
handleSecondaryStreamOnException(writeEx);
}
}
}
private void handleSecondaryStreamOnException(Exception ex) {
Preconditions.checkState(secondaryStreamException == null,
"Secondary stream already failed from previous exception!");
try {
secondaryOutputStream.close();
} catch (Exception closeEx) {
ex = ExceptionUtils.firstOrSuppressed(closeEx, ex);
}
secondaryStreamException = Preconditions.checkNotNull(ex);
}
@Nullable
@Override
public StreamStateHandle closeAndGetHandle() throws IOException {
return closeAndGetPrimaryHandle();
}
/**
* Returns the state handle from the {@link #primaryOutputStream}.
*/
public StreamStateHandle closeAndGetPrimaryHandle() throws IOException {
flushInternalBuffer();
return primaryOutputStream.closeAndGetHandle();
}
/**
* Returns the state handle from the {@link #secondaryOutputStream}. Also reports suppressed exceptions from earlier
* interactions with that stream.
*/
public StreamStateHandle closeAndGetSecondaryHandle() throws IOException {
if (secondaryStreamException == null) {
flushInternalBuffer();
return secondaryOutputStream.closeAndGetHandle();
} else {
throw new IOException("Secondary stream previously failed exceptionally", secondaryStreamException);
}
}
public Exception getSecondaryStreamException() {
return secondaryStreamException;
}
@VisibleForTesting
CheckpointStreamFactory.CheckpointStateOutputStream getPrimaryOutputStream() {
return primaryOutputStream;
}
@VisibleForTesting
CheckpointStreamFactory.CheckpointStateOutputStream getSecondaryOutputStream() {
return secondaryOutputStream;
}
}
