kafka FileLock 源码
kafka FileLock 代码
文件路径：/core/src/main/scala/kafka/utils/FileLock.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 kafka.utils
import java.io._
import java.nio.channels._
import java.nio.file.StandardOpenOption
/**
* A file lock a la flock/funlock
*
* The given path will be created and opened if it doesn't exist.
*/
class FileLock(val file: File) extends Logging {
private val channel = FileChannel.open(file.toPath, StandardOpenOption.CREATE, StandardOpenOption.READ,
StandardOpenOption.WRITE)
private var flock: java.nio.channels.FileLock = _
/**
* Lock the file or throw an exception if the lock is already held
*/
def lock(): Unit = {
this synchronized {
trace(s"Acquiring lock on ${file.getAbsolutePath}")
flock = channel.lock()
}
}
/**
* Try to lock the file and return true if the locking succeeds
*/
def tryLock(): Boolean = {
this synchronized {
trace(s"Acquiring lock on ${file.getAbsolutePath}")
try {
// weirdly this method will return null if the lock is held by another
// process, but will throw an exception if the lock is held by this process
// so we have to handle both cases
flock = channel.tryLock()
flock != null
} catch {
case _: OverlappingFileLockException => false
}
}
}
/**
* Unlock the lock if it is held
*/
def unlock(): Unit = {
this synchronized {
trace(s"Releasing lock on ${file.getAbsolutePath}")
if(flock != null)
flock.release()
}
}
/**
* Destroy this lock, closing the associated FileChannel
*/
def destroy(): Unit = {
this synchronized {
unlock()
channel.close()
}
}
}
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