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