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 */ 017package org.apache.activemq.store.jdbc; 018 019import java.io.IOException; 020import java.sql.Connection; 021import java.sql.PreparedStatement; 022import java.sql.SQLException; 023import java.sql.SQLFeatureNotSupportedException; 024 025import javax.sql.DataSource; 026 027import org.apache.activemq.util.Handler; 028import org.slf4j.Logger; 029import org.slf4j.LoggerFactory; 030 031/** 032 * Represents an exclusive lock on a database to avoid multiple brokers running 033 * against the same logical database. 034 * 035 * @org.apache.xbean.XBean element="database-locker" 036 * 037 */ 038public class DefaultDatabaseLocker implements DatabaseLocker { 039 public static final long DEFAULT_LOCK_ACQUIRE_SLEEP_INTERVAL = 1000; 040 private static final Logger LOG = LoggerFactory.getLogger(DefaultDatabaseLocker.class); 041 protected DataSource dataSource; 042 protected Statements statements; 043 protected long lockAcquireSleepInterval = DEFAULT_LOCK_ACQUIRE_SLEEP_INTERVAL; 044 045 protected PreparedStatement lockCreateStatement; 046 protected PreparedStatement lockUpdateStatement; 047 protected Connection connection; 048 protected boolean stopping; 049 protected Handler<Exception> exceptionHandler; 050 protected int queryTimeout = 10; 051 052 public DefaultDatabaseLocker() { 053 } 054 055 public DefaultDatabaseLocker(JDBCPersistenceAdapter persistenceAdapter) throws IOException { 056 setPersistenceAdapter(persistenceAdapter); 057 } 058 059 public void setPersistenceAdapter(JDBCPersistenceAdapter adapter) throws IOException { 060 this.dataSource = adapter.getLockDataSource(); 061 this.statements = adapter.getStatements(); 062 } 063 064 public void start() throws Exception { 065 stopping = false; 066 067 LOG.info("Attempting to acquire the exclusive lock to become the Master broker"); 068 String sql = statements.getLockCreateStatement(); 069 LOG.debug("Locking Query is "+sql); 070 071 while (true) { 072 try { 073 connection = dataSource.getConnection(); 074 connection.setAutoCommit(false); 075 lockCreateStatement = connection.prepareStatement(sql); 076 lockCreateStatement.execute(); 077 break; 078 } catch (Exception e) { 079 try { 080 if (stopping) { 081 throw new Exception( 082 "Cannot start broker as being asked to shut down. " 083 + "Interrupted attempt to acquire lock: " 084 + e, e); 085 } 086 if (exceptionHandler != null) { 087 try { 088 exceptionHandler.handle(e); 089 } catch (Throwable handlerException) { 090 LOG.error( "The exception handler " 091 + exceptionHandler.getClass().getCanonicalName() 092 + " threw this exception: " 093 + handlerException 094 + " while trying to handle this exception: " 095 + e, handlerException); 096 } 097 098 } else { 099 LOG.debug("Lock failure: "+ e, e); 100 } 101 } finally { 102 // Let's make sure the database connection is properly 103 // closed when an error occurs so that we're not leaking 104 // connections 105 if (null != connection) { 106 try { 107 connection.close(); 108 } catch (SQLException e1) { 109 LOG.error("Caught exception while closing connection: " + e1, e1); 110 } 111 112 connection = null; 113 } 114 } 115 } finally { 116 if (null != lockCreateStatement) { 117 try { 118 lockCreateStatement.close(); 119 } catch (SQLException e1) { 120 LOG.debug("Caught while closing statement: " + e1, e1); 121 } 122 lockCreateStatement = null; 123 } 124 } 125 126 LOG.info("Failed to acquire lock. Sleeping for " + lockAcquireSleepInterval + " milli(s) before trying again..."); 127 try { 128 Thread.sleep(lockAcquireSleepInterval); 129 } catch (InterruptedException ie) { 130 LOG.warn("Master lock retry sleep interrupted", ie); 131 } 132 } 133 134 LOG.info("Becoming the master on dataSource: " + dataSource); 135 } 136 137 public void stop() throws Exception { 138 stopping = true; 139 try { 140 if (lockCreateStatement != null) { 141 lockCreateStatement.cancel(); 142 } 143 } catch (SQLFeatureNotSupportedException e) { 144 LOG.warn("Failed to cancel locking query on dataSource" + dataSource, e); 145 } 146 try { 147 if (lockUpdateStatement != null) { 148 lockUpdateStatement.cancel(); 149 } 150 } catch (SQLFeatureNotSupportedException e) { 151 LOG.warn("Failed to cancel locking query on dataSource" + dataSource, e); 152 } 153 try { 154 if (connection != null && !connection.isClosed()) { 155 try { 156 connection.rollback(); 157 } catch (SQLException sqle) { 158 LOG.warn("Exception while rollbacking the connection on shutdown", sqle); 159 } finally { 160 try { 161 connection.close(); 162 } catch (SQLException ignored) { 163 LOG.debug("Exception while closing connection on shutdown", ignored); 164 } 165 lockCreateStatement = null; 166 } 167 } 168 } catch (SQLException sqle) { 169 LOG.warn("Exception while checking close status of connection on shutdown", sqle); 170 } 171 } 172 173 public boolean keepAlive() { 174 boolean result = false; 175 try { 176 lockUpdateStatement = connection.prepareStatement(statements.getLockUpdateStatement()); 177 lockUpdateStatement.setLong(1, System.currentTimeMillis()); 178 if (queryTimeout > 0) { 179 lockUpdateStatement.setQueryTimeout(queryTimeout); 180 } 181 int rows = lockUpdateStatement.executeUpdate(); 182 if (rows == 1) { 183 result=true; 184 } 185 } catch (Exception e) { 186 LOG.error("Failed to update database lock: " + e, e); 187 } finally { 188 if (lockUpdateStatement != null) { 189 try { 190 lockUpdateStatement.close(); 191 } catch (SQLException e) { 192 LOG.error("Failed to close statement",e); 193 } 194 lockUpdateStatement = null; 195 } 196 } 197 return result; 198 } 199 200 public long getLockAcquireSleepInterval() { 201 return lockAcquireSleepInterval; 202 } 203 204 public void setLockAcquireSleepInterval(long lockAcquireSleepInterval) { 205 this.lockAcquireSleepInterval = lockAcquireSleepInterval; 206 } 207 208 public Handler getExceptionHandler() { 209 return exceptionHandler; 210 } 211 212 public void setExceptionHandler(Handler exceptionHandler) { 213 this.exceptionHandler = exceptionHandler; 214 } 215 216 public int getQueryTimeout() { 217 return queryTimeout; 218 } 219 220 public void setQueryTimeout(int queryTimeout) { 221 this.queryTimeout = queryTimeout; 222 } 223}