001/** 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018package org.apache.oozie.service; 019 020import org.apache.oozie.util.Instrumentable; 021import org.apache.oozie.util.Instrumentation; 022import org.apache.oozie.lock.LockToken; 023import org.apache.oozie.lock.MemoryLocks; 024 025/** 026 * Service that provides in-memory locks. Assumes no other Oozie servers are using the database. 027 */ 028public class MemoryLocksService implements Service, Instrumentable { 029 protected static final String INSTRUMENTATION_GROUP = "locks"; 030 private MemoryLocks locks; 031 032 /** 033 * Initialize the memory locks service 034 * 035 * @param services services instance. 036 */ 037 @Override 038 public void init(Services services) throws ServiceException { 039 locks = new MemoryLocks(); 040 } 041 042 /** 043 * Destroy the memory locks service. 044 */ 045 @Override 046 public void destroy() { 047 locks = null; 048 } 049 050 /** 051 * Return the public interface for the memory locks services 052 * 053 * @return {@link MemoryLocksService}. 054 */ 055 @Override 056 public Class<? extends Service> getInterface() { 057 return MemoryLocksService.class; 058 } 059 060 /** 061 * Instruments the memory locks service. 062 * 063 * @param instr instance to instrument the memory locks service to. 064 */ 065 public void instrument(Instrumentation instr) { 066 final MemoryLocks finalLocks = this.locks; 067 instr.addVariable(INSTRUMENTATION_GROUP, "locks", new Instrumentation.Variable<Long>() { 068 public Long getValue() { 069 return (long) finalLocks.size(); 070 } 071 }); 072 } 073 074 /** 075 * Obtain a READ lock for a source. 076 * 077 * @param resource resource name. 078 * @param wait time out in milliseconds to wait for the lock, -1 means no timeout and 0 no wait. 079 * @return the lock token for the resource, or <code>null</code> if the lock could not be obtained. 080 * @throws InterruptedException thrown if the thread was interrupted while waiting. 081 */ 082 public LockToken getReadLock(String resource, long wait) throws InterruptedException { 083 return locks.getReadLock(resource, wait); 084 } 085 086 /** 087 * Obtain a WRITE lock for a source. 088 * 089 * @param resource resource name. 090 * @param wait time out in milliseconds to wait for the lock, -1 means no timeout and 0 no wait. 091 * @return the lock token for the resource, or <code>null</code> if the lock could not be obtained. 092 * @throws InterruptedException thrown if the thread was interrupted while waiting. 093 */ 094 public LockToken getWriteLock(String resource, long wait) throws InterruptedException { 095 return locks.getWriteLock(resource, wait); 096 } 097}