/**
* 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 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.GenericFileExclusiveReadLockStrategy;
import org.apache.camel.component.file.GenericFileOperations;
import org.apache.camel.util.CamelLogger;
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 GenericFileRenameExclusiveReadLockStrategy<T> implements GenericFileExclusiveReadLockStrategy<T> {
private static final Logger LOG = LoggerFactory.getLogger(GenericFileRenameExclusiveReadLockStrategy.class);
private long timeout;
private long checkInterval;
private LoggingLevel readLockLoggingLevel = LoggingLevel.WARN;
@Override
public void prepareOnStartup(GenericFileOperations<T> operations, GenericFileEndpoint<T> endpoint) throws Exception {
// noop
}
@Override
public boolean acquireExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file,
Exchange exchange) throws Exception {
LOG.trace("Waiting for exclusive read lock to file: {}", file);
// the trick is to try to rename the file, if we can rename then we have exclusive read
// since its a Generic file we cannot use java.nio to get a RW lock
String newName = file.getFileName() + ".camelExclusiveReadLock";
// make a copy as result and change its file name
GenericFile<T> newFile = file.copyFrom(file);
newFile.changeFileName(newName);
StopWatch watch = new StopWatch();
boolean exclusive = false;
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: " + file);
// we could not get the lock within the timeout period, so return false
return false;
}
}
exclusive = operations.renameFile(file.getAbsoluteFilePath(), newFile.getAbsoluteFilePath());
if (exclusive) {
LOG.trace("Acquired exclusive read lock to file: {}", file);
// rename it back so we can read it
operations.renameFile(newFile.getAbsoluteFilePath(), file.getAbsoluteFilePath());
} else {
boolean interrupted = sleep();
if (interrupted) {
// we were interrupted while sleeping, we are likely being shutdown so return false
return false;
}
}
}
return true;
}
@Override
public void releaseExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file,
Exchange exchange) throws Exception {
// noop
}
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;
}
}