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;
018
019 import org.apache.camel.Exchange;
020 import org.apache.camel.LoggingLevel;
021
022 /**
023 * Strategy for acquiring exclusive read locks for files to be consumed. After
024 * granting the read lock it is released, we just want to make sure that when
025 * we start consuming the file its not currently in progress of being written by
026 * third party.
027 * <p/>
028 * Camel supports out of the box the following strategies:
029 * <ul>
030 * <li>FileRenameExclusiveReadLockStrategy waiting until its possible to rename the file.</li>
031 * <li>FileLockExclusiveReadLockStrategy acquiring a RW file lock for the duration of the processing.</li>
032 * <li>MarkerFileExclusiveReadLockStrategy using a marker file for acquiring read lock.</li>
033 * <li>FileChangedExclusiveReadLockStrategy using a file changed detection for acquiring read lock.</li>
034 * </ul>
035 */
036 public interface GenericFileExclusiveReadLockStrategy<T> {
037
038 /**
039 * Allows custom logic to be run on startup preparing the strategy, such as removing old lock files etc.
040 *
041 * @param operations generic file operations
042 * @param endpoint the endpoint
043 * @throws Exception can be thrown in case of errors
044 */
045 void prepareOnStartup(GenericFileOperations<T> operations, GenericFileEndpoint<T> endpoint) throws Exception;
046
047 /**
048 * Acquires exclusive read lock to the file.
049 *
050 * @param operations generic file operations
051 * @param file the file
052 * @param exchange the exchange
053 * @return <tt>true</tt> if read lock was acquired. If <tt>false</tt> Camel
054 * will skip the file and try it on the next poll
055 * @throws Exception can be thrown in case of errors
056 */
057 boolean acquireExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file, Exchange exchange) throws Exception;
058
059 /**
060 * Releases the exclusive read lock granted by the <tt>acquireExclusiveReadLock</tt> method.
061 *
062 * @param operations generic file operations
063 * @param file the file
064 * @param exchange the exchange
065 * @throws Exception can be thrown in case of errors
066 */
067 void releaseExclusiveReadLock(GenericFileOperations<T> operations, GenericFile<T> file, Exchange exchange) throws Exception;
068
069 /**
070 * Sets an optional timeout period.
071 * <p/>
072 * If the readlock could not be granted within the time period then the wait is stopped and the
073 * <tt>acquireExclusiveReadLock</tt> method returns <tt>false</tt>.
074 *
075 * @param timeout period in millis
076 */
077 void setTimeout(long timeout);
078
079
080 /**
081 * Sets the check interval period.
082 * <p/>
083 * The check interval is used for sleeping between attempts to acquire read lock.
084 * Setting a high value allows to cater for <i>slow writes</i> in case the producer
085 * of the file is slow.
086 * <p/>
087 * The default period is 1000 millis.
088 *
089 * @param checkInterval interval in millis
090 */
091 void setCheckInterval(long checkInterval);
092
093 /**
094 * Sets logging level used when a read lock could not be acquired.
095 * <p/>
096 * Logging level used when a read lock could not be acquired.
097 * <p/>
098 * The default logging level is WARN
099 * @param readLockLoggingLevel LoggingLevel
100 */
101 void setReadLockLoggingLevel(LoggingLevel readLockLoggingLevel);
102
103
104 }