001/** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.camel.component.file.strategy; 018 019import org.apache.camel.Exchange; 020import org.apache.camel.LoggingLevel; 021import org.apache.camel.component.file.GenericFile; 022import org.apache.camel.component.file.GenericFileEndpoint; 023import org.apache.camel.component.file.GenericFileExclusiveReadLockStrategy; 024import org.apache.camel.component.file.GenericFileOperations; 025import org.apache.camel.util.CamelLogger; 026import org.apache.camel.util.StopWatch; 027import org.slf4j.Logger; 028import org.slf4j.LoggerFactory; 029 030/** 031 * Acquires exclusive read lock to the given file. Will wait until the lock is granted. 032 * After granting the read lock it is released, we just want to make sure that when we start 033 * consuming the file its not currently in progress of being written by third party. 034 */ 035public class GenericFileRenameExclusiveReadLockStrategy<T> implements GenericFileExclusiveReadLockStrategy<T> { 036 private static final Logger LOG = LoggerFactory.getLogger(GenericFileRenameExclusiveReadLockStrategy.class); 037 private long timeout; 038 private long checkInterval; 039 private LoggingLevel readLockLoggingLevel = LoggingLevel.WARN; 040 041 @Override 042 public void prepareOnStartup(GenericFileOperations<T> operations, GenericFileEndpoint<T> endpoint) throws Exception { 043 // noop 044 } 045 046 @Override 047 public boolean acquireExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file, 048 Exchange exchange) throws Exception { 049 LOG.trace("Waiting for exclusive read lock to file: {}", file); 050 051 // the trick is to try to rename the file, if we can rename then we have exclusive read 052 // since its a Generic file we cannot use java.nio to get a RW lock 053 String newName = file.getFileName() + ".camelExclusiveReadLock"; 054 055 // make a copy as result and change its file name 056 GenericFile<T> newFile = file.copyFrom(file); 057 newFile.changeFileName(newName); 058 StopWatch watch = new StopWatch(); 059 060 boolean exclusive = false; 061 while (!exclusive) { 062 // timeout check 063 if (timeout > 0) { 064 long delta = watch.taken(); 065 if (delta > timeout) { 066 CamelLogger.log(LOG, readLockLoggingLevel, 067 "Cannot acquire read lock within " + timeout + " millis. Will skip the file: " + file); 068 // we could not get the lock within the timeout period, so return false 069 return false; 070 } 071 } 072 073 exclusive = operations.renameFile(file.getAbsoluteFilePath(), newFile.getAbsoluteFilePath()); 074 if (exclusive) { 075 LOG.trace("Acquired exclusive read lock to file: {}", file); 076 // rename it back so we can read it 077 operations.renameFile(newFile.getAbsoluteFilePath(), file.getAbsoluteFilePath()); 078 } else { 079 boolean interrupted = sleep(); 080 if (interrupted) { 081 // we were interrupted while sleeping, we are likely being shutdown so return false 082 return false; 083 } 084 } 085 } 086 087 return true; 088 } 089 090 @Override 091 public void releaseExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file, 092 Exchange exchange) throws Exception { 093 // noop 094 } 095 096 private boolean sleep() { 097 LOG.trace("Exclusive read lock not granted. Sleeping for {} millis.", checkInterval); 098 try { 099 Thread.sleep(checkInterval); 100 return false; 101 } catch (InterruptedException e) { 102 LOG.debug("Sleep interrupted while waiting for exclusive read lock, so breaking out"); 103 return true; 104 } 105 } 106 107 public long getTimeout() { 108 return timeout; 109 } 110 111 @Override 112 public void setTimeout(long timeout) { 113 this.timeout = timeout; 114 } 115 116 @Override 117 public void setCheckInterval(long checkInterval) { 118 this.checkInterval = checkInterval; 119 } 120 121 @Override 122 public void setReadLockLoggingLevel(LoggingLevel readLockLoggingLevel) { 123 this.readLockLoggingLevel = readLockLoggingLevel; 124 } 125 126 @Override 127 public void setMarkerFiler(boolean markerFile) { 128 // noop - we do not use marker file with the rename strategy 129 } 130}