Java tutorial
/** * Copyright 1999-2011 Alibaba Group * * Licensed 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 com.alibaba.cobar.client.datasources.ha; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.SQLException; import java.util.concurrent.Callable; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Future; import java.util.concurrent.TimeUnit; import java.util.concurrent.TimeoutException; import javax.sql.DataSource; import org.apache.commons.lang.Validate; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.aop.target.HotSwappableTargetSource; /** * The standard to switch in this job is vague, because usually we will figure * out different SQLException type with error code to decide whether current * SQLException indicates a connection failure or something else. but as per * Hexianmao's statement, it's not necessary to be so, because sometimes, DBA or * someone will cause SQLException with some operations on purpose so that the * data source can be switched out to be maintained.<br> * So we adapt the failover checking logic from current Cobar's HAPool with some * code structure adjustment.<br> * * @author fujohnwang * @since 1.0 */ public class FailoverMonitorJob implements Runnable { private transient final Logger logger = LoggerFactory.getLogger(FailoverMonitorJob.class); private String detectingSQL; /** * time unit in milliseconds */ private long detectingRequestTimeout; private long recheckInterval; private int recheckTimes; private HotSwappableTargetSource hotSwapTargetSource; private DataSource masterDataSource; private DataSource standbyDataSource; private DataSource masterDetectorDataSource; private DataSource standbyDetectorDataSource; /** * first time it should be referenced to masterDetectorDataSource. */ private DataSource currentDetectorDataSource; /** * Since {@link FailoverMonitorJob} will be scheduled to run in sequence, * One executor as instance field is ok.<br> * This executor will be used to execute detecting logic asynchronously, if * the execution exceeds given timeout threshold, we will check again before * switching to standby data source. */ private ExecutorService executor; public FailoverMonitorJob(ExecutorService es) { Validate.notNull(es); this.executor = es; } public void run() { Future<Integer> future = executor.submit(new Callable<Integer>() { public Integer call() throws Exception { Integer result = -1; for (int i = 0; i < getRecheckTimes(); i++) { Connection conn = null; try { conn = getCurrentDetectorDataSource().getConnection(); PreparedStatement pstmt = conn.prepareStatement(getDetectingSQL()); pstmt.execute(); if (pstmt != null) { pstmt.close(); } result = 0; break; } catch (Exception e) { logger.warn("(" + (i + 1) + ") check with failure. sleep (" + getRecheckInterval() + ") for next round check."); try { TimeUnit.MILLISECONDS.sleep(getRecheckInterval()); } catch (InterruptedException e1) { logger.warn("interrupted when waiting for next round rechecking."); } continue; } finally { if (conn != null) { try { conn.close(); } catch (SQLException e) { logger.warn("failed to close checking connection:\n", e); } } } } return result; } }); try { Integer result = future.get(getDetectingRequestTimeout(), TimeUnit.MILLISECONDS); if (result == -1) { doSwap(); } } catch (InterruptedException e) { logger.warn("interrupted when getting query result in FailoverMonitorJob."); } catch (ExecutionException e) { logger.warn("exception occured when checking failover status in FailoverMonitorJob"); } catch (TimeoutException e) { logger.warn("exceed DetectingRequestTimeout threshold. Switch to standby data source."); doSwap(); } } private void doSwap() { synchronized (hotSwapTargetSource) { DataSource target = (DataSource) getHotSwapTargetSource().getTarget(); if (target == masterDataSource) { getHotSwapTargetSource().swap(standbyDataSource); currentDetectorDataSource = standbyDetectorDataSource; } else { getHotSwapTargetSource().swap(masterDataSource); currentDetectorDataSource = masterDetectorDataSource; } } } public String getDetectingSQL() { return detectingSQL; } public void setDetectingSQL(String detectingSQL) { this.detectingSQL = detectingSQL; } public long getDetectingRequestTimeout() { return detectingRequestTimeout; } public void setDetectingRequestTimeout(long detectingRequestTimeout) { this.detectingRequestTimeout = detectingRequestTimeout; } public HotSwappableTargetSource getHotSwapTargetSource() { return hotSwapTargetSource; } public void setHotSwapTargetSource(HotSwappableTargetSource hotSwapTargetSource) { this.hotSwapTargetSource = hotSwapTargetSource; } public DataSource getMasterDataSource() { return masterDataSource; } public void setMasterDataSource(DataSource masterDataSource) { this.masterDataSource = masterDataSource; } public DataSource getStandbyDataSource() { return standbyDataSource; } public void setStandbyDataSource(DataSource standbyDataSource) { this.standbyDataSource = standbyDataSource; } public void setRecheckInterval(long recheckInterval) { this.recheckInterval = recheckInterval; } public long getRecheckInterval() { return recheckInterval; } public void setRecheckTimes(int recheckTimes) { this.recheckTimes = recheckTimes; } public int getRecheckTimes() { return recheckTimes; } public void setMasterDetectorDataSource(DataSource masterDetectorDataSource) { this.masterDetectorDataSource = masterDetectorDataSource; } public DataSource getMasterDetectorDataSource() { return masterDetectorDataSource; } public void setStandbyDetectorDataSource(DataSource standbyDetectorDataSource) { this.standbyDetectorDataSource = standbyDetectorDataSource; } public DataSource getStandbyDetectorDataSource() { return standbyDetectorDataSource; } public void setCurrentDetectorDataSource(DataSource currentDetectorDataSource) { this.currentDetectorDataSource = currentDetectorDataSource; } public DataSource getCurrentDetectorDataSource() { return currentDetectorDataSource; } }