| /** |
| * 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.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.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 transient Logger LOG = LoggerFactory.getLogger(GenericFileRenameExclusiveReadLockStrategy.class); |
| private long timeout; |
| private long checkInterval; |
| |
| public void prepareOnStartup(GenericFileOperations<T> operations, GenericFileEndpoint<T> endpoint) throws Exception { |
| // noop |
| } |
| |
| public boolean acquireExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file, |
| Exchange exchange) throws Exception { |
| if (LOG.isTraceEnabled()) { |
| 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) { |
| LOG.warn("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) { |
| if (LOG.isTraceEnabled()) { |
| 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; |
| } |
| |
| public void releaseExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file, |
| Exchange exchange) throws Exception { |
| // noop |
| } |
| |
| private boolean sleep() { |
| if (LOG.isTraceEnabled()) { |
| LOG.trace("Exclusive read lock not granted. Sleeping for " + checkInterval + " millis."); |
| } |
| 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; |
| } |
| |
| public void setTimeout(long timeout) { |
| this.timeout = timeout; |
| } |
| |
| public void setCheckInterval(long checkInterval) { |
| this.checkInterval = checkInterval; |
| } |
| } |