spark FileBasedWriteAheadLogWriter 源码
spark FileBasedWriteAheadLogWriter 代码
文件路径：/streaming/src/main/scala/org/apache/spark/streaming/util/FileBasedWriteAheadLogWriter.scala
/*
* 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.streaming.util
import java.io._
import java.nio.ByteBuffer
import org.apache.hadoop.conf.Configuration
import org.apache.spark.util.Utils
/**
* A writer for writing byte-buffers to a write ahead log file.
*/
private[streaming] class FileBasedWriteAheadLogWriter(path: String, hadoopConf: Configuration)
extends Closeable {
private lazy val stream = HdfsUtils.getOutputStream(path, hadoopConf)
private var nextOffset = stream.getPos()
private var closed = false
/** Write the bytebuffer to the log file */
def write(data: ByteBuffer): FileBasedWriteAheadLogSegment = synchronized {
assertOpen()
data.rewind() // Rewind to ensure all data in the buffer is retrieved
val lengthToWrite = data.remaining()
val segment = new FileBasedWriteAheadLogSegment(path, nextOffset, lengthToWrite)
stream.writeInt(lengthToWrite)
Utils.writeByteBuffer(data, stream: OutputStream)
flush()
nextOffset = stream.getPos()
segment
}
override def close(): Unit = synchronized {
closed = true
stream.close()
}
private def flush(): Unit = {
stream.hflush()
// Useful for local file system where hflush/sync does not work (HADOOP-7844)
stream.getWrappedStream.flush()
}
private def assertOpen(): Unit = {
HdfsUtils.checkState(!closed, "Stream is closed. Create a new Writer to write to file.")
}
}
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