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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.spark.storage
import java.io.{FileOutputStream, File, OutputStream}
import java.nio.channels.FileChannel
import it.unimi.dsi.fastutil.io.FastBufferedOutputStream
import org.apache.spark.Logging
import org.apache.spark.serializer.{SerializationStream, Serializer}
/**
* An interface for writing JVM objects to some underlying storage. This interface allows
* appending data to an existing block, and can guarantee atomicity in the case of faults
* as it allows the caller to revert partial writes.
*
* This interface does not support concurrent writes.
*/
abstract class BlockObjectWriter(val blockId: BlockId) {
def open(): BlockObjectWriter
def close()
def isOpen: Boolean
/**
* Flush the partial writes and commit them as a single atomic block. Return the
* number of bytes written for this commit.
*/
def commit(): Long
/**
* Reverts writes that haven't been flushed yet. Callers should invoke this function
* when there are runtime exceptions.
*/
def revertPartialWrites()
/**
* Writes an object.
*/
def write(value: Any)
/**
* Returns the file segment of committed data that this Writer has written.
*/
def fileSegment(): FileSegment
/**
* Cumulative time spent performing blocking writes, in ns.
*/
def timeWriting(): Long
}
/** BlockObjectWriter which writes directly to a file on disk. Appends to the given file. */
class DiskBlockObjectWriter(
blockId: BlockId,
file: File,
serializer: Serializer,
bufferSize: Int,
compressStream: OutputStream => OutputStream)
extends BlockObjectWriter(blockId)
with Logging
{
/** Intercepts write calls and tracks total time spent writing. Not thread safe. */
private class TimeTrackingOutputStream(out: OutputStream) extends OutputStream {
def timeWriting = _timeWriting
private var _timeWriting = 0L
private def callWithTiming(f: => Unit) = {
val start = System.nanoTime()
f
_timeWriting += (System.nanoTime() - start)
}
def write(i: Int): Unit = callWithTiming(out.write(i))
override def write(b: Array[Byte]) = callWithTiming(out.write(b))
override def write(b: Array[Byte], off: Int, len: Int) = callWithTiming(out.write(b, off, len))
}
private val syncWrites = System.getProperty("spark.shuffle.sync", "false").toBoolean
/** The file channel, used for repositioning / truncating the file. */
private var channel: FileChannel = null
private var bs: OutputStream = null
private var fos: FileOutputStream = null
private var ts: TimeTrackingOutputStream = null
private var objOut: SerializationStream = null
private val initialPosition = file.length()
private var lastValidPosition = initialPosition
private var initialized = false
private var _timeWriting = 0L
override def open(): BlockObjectWriter = {
fos = new FileOutputStream(file, true)
ts = new TimeTrackingOutputStream(fos)
channel = fos.getChannel()
lastValidPosition = initialPosition
bs = compressStream(new FastBufferedOutputStream(ts, bufferSize))
objOut = serializer.newInstance().serializeStream(bs)
initialized = true
this
}
override def close() {
if (initialized) {
if (syncWrites) {
// Force outstanding writes to disk and track how long it takes
objOut.flush()
val start = System.nanoTime()
fos.getFD.sync()
_timeWriting += System.nanoTime() - start
}
objOut.close()
_timeWriting += ts.timeWriting
channel = null
bs = null
fos = null
ts = null
objOut = null
}
}
override def isOpen: Boolean = objOut != null
override def commit(): Long = {
if (initialized) {
// NOTE: Flush the serializer first and then the compressed/buffered output stream
objOut.flush()
bs.flush()
val prevPos = lastValidPosition
lastValidPosition = channel.position()
lastValidPosition - prevPos
} else {
// lastValidPosition is zero if stream is uninitialized
lastValidPosition
}
}
override def revertPartialWrites() {
if (initialized) {
// Discard current writes. We do this by flushing the outstanding writes and
// truncate the file to the last valid position.
objOut.flush()
bs.flush()
channel.truncate(lastValidPosition)
}
}
override def write(value: Any) {
if (!initialized) {
open()
}
objOut.writeObject(value)
}
override def fileSegment(): FileSegment = {
val bytesWritten = lastValidPosition - initialPosition
new FileSegment(file, initialPosition, bytesWritten)
}
// Only valid if called after close()
override def timeWriting() = _timeWriting
}
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