/**
* 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.camel.component.file.strategy;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.Channel;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import org.apache.camel.Exchange;
import org.apache.camel.LoggingLevel;
import org.apache.camel.component.file.GenericFile;
import org.apache.camel.component.file.GenericFileEndpoint;
import org.apache.camel.component.file.GenericFileOperations;
import org.apache.camel.util.CamelLogger;
import org.apache.camel.util.IOHelper;
import org.apache.camel.util.StopWatch;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Acquires exclusive read lock to the given file. Will wait until the lock is granted.
* After granting the read lock it is released, we just want to make sure that when we start
* consuming the file its not currently in progress of being written by third party.
*/
public class FileLockExclusiveReadLockStrategy extends MarkerFileExclusiveReadLockStrategy {
private static final Logger LOG = LoggerFactory.getLogger(FileLockExclusiveReadLockStrategy.class);
private long timeout;
private long checkInterval = 1000;
private FileLock lock;
private String lockFileName;
private LoggingLevel readLockLoggingLevel = LoggingLevel.WARN;
@Override
public void prepareOnStartup(GenericFileOperations<File> operations, GenericFileEndpoint<File> endpoint) {
// noop
}
@Override
public boolean acquireExclusiveReadLock(GenericFileOperations<File> operations, GenericFile<File> file, Exchange exchange) throws Exception {
// must call super
if (!super.acquireExclusiveReadLock(operations, file, exchange)) {
return false;
}
File target = new File(file.getAbsoluteFilePath());
LOG.trace("Waiting for exclusive read lock to file: {}", target);
FileChannel channel = null;
RandomAccessFile randomAccessFile = null;
try {
randomAccessFile = new RandomAccessFile(target, "rw");
// try to acquire rw lock on the file before we can consume it
channel = randomAccessFile.getChannel();
boolean exclusive = false;
StopWatch watch = new StopWatch();
while (!exclusive) {
// timeout check
if (timeout > 0) {
long delta = watch.taken();
if (delta > timeout) {
CamelLogger.log(LOG, readLockLoggingLevel,
"Cannot acquire read lock within " + timeout + " millis. Will skip the file: " + target);
// we could not get the lock within the timeout period, so return false
return false;
}
}
// get the lock using either try lock or not depending on if we are using timeout or not
try {
lock = timeout > 0 ? channel.tryLock() : channel.lock();
} catch (IllegalStateException ex) {
// Also catch the OverlappingFileLockException here. Do nothing here
}
if (lock != null) {
LOG.trace("Acquired exclusive read lock: {} to file: {}", lock, target);
lockFileName = target.getName();
exclusive = true;
} else {
boolean interrupted = sleep();
if (interrupted) {
// we were interrupted while sleeping, we are likely being shutdown so return false
return false;
}
}
}
} catch (IOException e) {
// must handle IOException as some apps on Windows etc. will still somehow hold a lock to a file
// such as AntiVirus or MS Office that has special locks for it's supported files
if (timeout == 0) {
// if not using timeout, then we cant retry, so return false
return false;
}
LOG.debug("Cannot acquire read lock. Will try again.", e);
boolean interrupted = sleep();
if (interrupted) {
// we were interrupted while sleeping, we are likely being shutdown so return false
return false;
}
} finally {
IOHelper.close(channel, "while acquiring exclusive read lock for file: " + lockFileName, LOG);
IOHelper.close(randomAccessFile, "while acquiring exclusive read lock for file: " + lockFileName, LOG);
}
return true;
}
@Override
public void releaseExclusiveReadLock(GenericFileOperations<File> operations,
GenericFile<File> file, Exchange exchange) throws Exception {
// must call super
super.releaseExclusiveReadLock(operations, file, exchange);
if (lock != null) {
Channel channel = lock.channel();
try {
lock.release();
} finally {
// must close channel first
IOHelper.close(channel, "while releasing exclusive read lock for file: " + lockFileName, LOG);
}
}
}
private boolean sleep() {
LOG.trace("Exclusive read lock not granted. Sleeping for {} millis.", checkInterval);
try {
Thread.sleep(checkInterval);
return false;
} catch (InterruptedException e) {
LOG.debug("Sleep interrupted while waiting for exclusive read lock, so breaking out");
return true;
}
}
public long getTimeout() {
return timeout;
}
@Override
public void setTimeout(long timeout) {
this.timeout = timeout;
}
@Override
public void setCheckInterval(long checkInterval) {
this.checkInterval = checkInterval;
}
@Override
public void setReadLockLoggingLevel(LoggingLevel readLockLoggingLevel) {
this.readLockLoggingLevel = readLockLoggingLevel;
}
}