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ActiveMQ example source code file (TransactDatabaseLocker.java)
The ActiveMQ TransactDatabaseLocker.java source code/** * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.activemq.store.jdbc.adapter; import java.io.IOException; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import org.apache.activemq.store.jdbc.DefaultDatabaseLocker; import org.apache.activemq.store.jdbc.JDBCPersistenceAdapter; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * Represents an exclusive lock on a database to avoid multiple brokers running * against the same logical database. * * @org.apache.xbean.XBean element="transact-database-locker" * */ public class TransactDatabaseLocker extends DefaultDatabaseLocker { private static final Logger LOG = LoggerFactory.getLogger(TransactDatabaseLocker.class); public TransactDatabaseLocker() { } public TransactDatabaseLocker(JDBCPersistenceAdapter persistenceAdapter) throws IOException { setPersistenceAdapter(persistenceAdapter); } @Override public void start() throws Exception { stopping = false; LOG.info("Attempting to acquire the exclusive lock to become the Master broker"); PreparedStatement statement = null; while (true) { try { connection = dataSource.getConnection(); connection.setAutoCommit(false); String sql = statements.getLockCreateStatement(); statement = connection.prepareStatement(sql); if (statement.getMetaData() != null) { ResultSet rs = statement.executeQuery(); // if not already locked the statement below blocks until lock acquired rs.next(); } else { statement.execute(); } break; } catch (Exception e) { if (stopping) { throw new Exception("Cannot start broker as being asked to shut down. Interrupted attempt to acquire lock: " + e, e); } if (exceptionHandler != null) { try { exceptionHandler.handle(e); } catch (Throwable handlerException) { LOG.error("The exception handler " + exceptionHandler.getClass().getCanonicalName() + " threw this exception: " + handlerException + " while trying to handle this excpetion: " + e, handlerException); } } else { LOG.error("Failed to acquire lock: " + e, e); } } finally { if (null != statement) { try { statement.close(); } catch (SQLException e1) { LOG.warn("Caught while closing statement: " + e1, e1); } statement = null; } } LOG.debug("Sleeping for " + lockAcquireSleepInterval + " milli(s) before trying again to get the lock..."); try { Thread.sleep(lockAcquireSleepInterval); } catch (InterruptedException ie) { LOG.warn("Master lock retry sleep interrupted", ie); } } LOG.info("Becoming the master on dataSource: " + dataSource); } } Other ActiveMQ examples (source code examples)Here is a short list of links related to this ActiveMQ TransactDatabaseLocker.java source code file: |
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