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 */ 017 package org.apache.camel.component.file.strategy; 018 019 import java.io.File; 020 021 import org.apache.camel.Exchange; 022 import org.apache.camel.component.file.GenericFile; 023 import org.apache.camel.component.file.GenericFileOperations; 024 import org.apache.camel.util.StopWatch; 025 import org.slf4j.Logger; 026 import org.slf4j.LoggerFactory; 027 028 /** 029 * Acquires exclusive read lock to the given file by checking whether the file is being 030 * changed by scanning the file at different intervals (to detect changes). 031 */ 032 public class FileChangedExclusiveReadLockStrategy extends MarkerFileExclusiveReadLockStrategy { 033 private static final transient Logger LOG = LoggerFactory.getLogger(FileChangedExclusiveReadLockStrategy.class); 034 private long timeout; 035 private long checkInterval = 1000; 036 private long minLength = 1; 037 038 public boolean acquireExclusiveReadLock(GenericFileOperations<File> operations, GenericFile<File> file, Exchange exchange) throws Exception { 039 // must call super 040 if (!super.acquireExclusiveReadLock(operations, file, exchange)) { 041 return false; 042 } 043 044 File target = new File(file.getAbsoluteFilePath()); 045 boolean exclusive = false; 046 047 LOG.trace("Waiting for exclusive read lock to file: {}", file); 048 049 long lastModified = Long.MIN_VALUE; 050 long length = Long.MIN_VALUE; 051 StopWatch watch = new StopWatch(); 052 053 while (!exclusive) { 054 // timeout check 055 if (timeout > 0) { 056 long delta = watch.taken(); 057 if (delta > timeout) { 058 LOG.warn("Cannot acquire read lock within " + timeout + " millis. Will skip the file: " + file); 059 // we could not get the lock within the timeout period, so return false 060 return false; 061 } 062 } 063 064 long newLastModified = target.lastModified(); 065 long newLength = target.length(); 066 067 LOG.trace("Previous last modified: {}, new last modified: {}", lastModified, newLastModified); 068 LOG.trace("Previous length: {}, new length: {}", length, newLength); 069 070 if (length >= minLength && (newLastModified == lastModified && newLength == length)) { 071 LOG.trace("Read lock acquired."); 072 exclusive = true; 073 } else { 074 // set new base file change information 075 lastModified = newLastModified; 076 length = newLength; 077 078 boolean interrupted = sleep(); 079 if (interrupted) { 080 // we were interrupted while sleeping, we are likely being shutdown so return false 081 return false; 082 } 083 } 084 } 085 086 return exclusive; 087 } 088 089 private boolean sleep() { 090 LOG.trace("Exclusive read lock not granted. Sleeping for {} millis.", checkInterval); 091 try { 092 Thread.sleep(checkInterval); 093 return false; 094 } catch (InterruptedException e) { 095 LOG.debug("Sleep interrupted while waiting for exclusive read lock, so breaking out"); 096 return true; 097 } 098 } 099 100 public long getTimeout() { 101 return timeout; 102 } 103 104 public void setTimeout(long timeout) { 105 this.timeout = timeout; 106 } 107 108 public long getCheckInterval() { 109 return checkInterval; 110 } 111 112 public void setCheckInterval(long checkInterval) { 113 this.checkInterval = checkInterval; 114 } 115 116 public long getMinLength() { 117 return minLength; 118 } 119 120 public void setMinLength(long minLength) { 121 this.minLength = minLength; 122 } 123 }