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    }