从之前的 Xxl Job Helloworld 中学会了简单的使用 Xxl-Job 进行分步式任务调度。并且可以知道当我使用 Xxl-Job时。我们核心基本需要以下三个步骤：
- 启动调度中心(xxl-job-admin)
- 启动执行器(引用xxl-job-core 的业务代码)
- 调度中心添加任务并执行任务
经过以上的三个步骤，然后添加的任务就可以执行了。下面我们就来从源码的角度分析一下：上面 3 个步骤都做了什么事，使得任务可以定时调度的。所以我决定分为三篇 blog 来分析 xxl-job 的源码实现。
启动调度中心除了添加 com.xxl.job.admin.controller 目录下的 XXXcontroller 支持通过Web页面对任务进行CRUD操作和对用户以及用户相关的权限管理之后，最核心的其实是 XxlJobAdminConfig 这个类的初始化。它实现了 spring 中的 InitializingBean 接口，所以在这个对象初始化的时候会调用 XxlJobAdminConfig#afterPropertiesSet
public void afterPropertiesSet() throws Exception {
adminConfig = this;
xxlJobScheduler = new XxlJobScheduler();
xxlJobScheduler.init();
}
下面我们来看一下 XxlJobScheduler 里面主要作了哪些事：
public void init() throws Exception {
// init i18n
initI18n();
// admin registry monitor run
JobRegistryMonitorHelper.getInstance().start();
// admin monitor run
JobFailMonitorHelper.getInstance().start();
// admin trigger pool start
JobTriggerPoolHelper.toStart();
// admin log report start
JobLogReportHelper.getInstance().start();
// start-schedule
JobScheduleHelper.getInstance().start();
logger.info(">>>>>>>>> init xxl-job admin success.");
}
1、initI18n
private void initI18n(){
for (ExecutorBlockStrategyEnum item:ExecutorBlockStrategyEnum.values()) {
item.setTitle(I18nUtil.getString("jobconf_block_".concat(item.name())));
}
}
它的功能比较简单，就是初始化新增任务页面中的阻塞处理策略相关的国际化信息。国际化提供中文、英文两种可选语言，默认为中文。
2、JobRegistryMonitorHelper
JobRegistryMonitorHelper 的作用是开启一个 Daemon 线程主要管理 xxl-job-core 注册的任务调用地址。里面的代码比较简单，它的核心功能是以下三点：
JobRegistryMonitorHelper#start
public void start(){
registryThread = new Thread(new Runnable() {
@Override
public void run() {
while (!toStop) {
try {
// auto registry group
List<XxlJobGroup> groupList = XxlJobAdminConfig.getAdminConfig().getXxlJobGroupDao().findByAddressType(0);
if (groupList!=null && !groupList.isEmpty()) {
// remove dead address (admin/executor)
List<Integer> ids = XxlJobAdminConfig.getAdminConfig().getXxlJobRegistryDao().findDead(RegistryConfig.DEAD_TIMEOUT, new Date());
if (ids!=null && ids.size()>0) {
XxlJobAdminConfig.getAdminConfig().getXxlJobRegistryDao().removeDead(ids);
}
// fresh online address (admin/executor)
HashMap<String, List<String>> appAddressMap = new HashMap<String, List<String>>();
List<XxlJobRegistry> list = XxlJobAdminConfig.getAdminConfig().getXxlJobRegistryDao().findAll(RegistryConfig.DEAD_TIMEOUT, new Date());
if (list != null) {
for (XxlJobRegistry item: list) {
if (RegistryConfig.RegistType.EXECUTOR.name().equals(item.getRegistryGroup())) {
String appName = item.getRegistryKey();
List<String> registryList = appAddressMap.get(appName);
if (registryList == null) {
registryList = new ArrayList<String>();
}
if (!registryList.contains(item.getRegistryValue())) {
registryList.add(item.getRegistryValue());
}
appAddressMap.put(appName, registryList);
}
}
}
// fresh group address
for (XxlJobGroup group: groupList) {
List<String> registryList = appAddressMap.get(group.getAppName());
String addressListStr = null;
if (registryList!=null && !registryList.isEmpty()) {
Collections.sort(registryList);
addressListStr = "";
for (String item:registryList) {
addressListStr += item + ",";
}
addressListStr = addressListStr.substring(0, addressListStr.length()-1);
}
group.setAddressList(addressListStr);
XxlJobAdminConfig.getAdminConfig().getXxlJobGroupDao().update(group);
}
}
} catch (Exception e) {
if (!toStop) {
logger.error(">>>>>>>>>>> xxl-job, job registry monitor thread error:{}", e);
}
}
try {
TimeUnit.SECONDS.sleep(RegistryConfig.BEAT_TIMEOUT);
} catch (InterruptedException e) {
if (!toStop) {
logger.error(">>>>>>>>>>> xxl-job, job registry monitor thread error:{}", e);
}
}
}
logger.info(">>>>>>>>>>> xxl-job, job registry monitor thread stop");
}
});
registryThread.setDaemon(true);
registryThread.setName("xxl-job, admin JobRegistryMonitorHelper");
registryThread.start();
}
}
- 删除无效注册地址，服务自动下线
- 刷新有效注册地址，服务自动上线
- 刷新执行器里的注册地址,这样在远程调用 job 的时候就可以调用到最新的有效的服务
3、JobFailMonitorHelper
JobFailMonitorHelper#start
public void start(){
monitorThread = new Thread(new Runnable() {
@Override
public void run() {
// monitor
while (!toStop) {
try {
List<Long> failLogIds = XxlJobAdminConfig.getAdminConfig().getXxlJobLogDao().findFailJobLogIds(1000);
if (failLogIds!=null && !failLogIds.isEmpty()) {
for (long failLogId: failLogIds) {
// lock log
int lockRet = XxlJobAdminConfig.getAdminConfig().getXxlJobLogDao().updateAlarmStatus(failLogId, 0, -1);
if (lockRet < 1) {
continue;
}
XxlJobLog log = XxlJobAdminConfig.getAdminConfig().getXxlJobLogDao().load(failLogId);
XxlJobInfo info = XxlJobAdminConfig.getAdminConfig().getXxlJobInfoDao().loadById(log.getJobId());
// 1、fail retry monitor
if (log.getExecutorFailRetryCount() > 0) {
JobTriggerPoolHelper.trigger(log.getJobId(), TriggerTypeEnum.RETRY, (log.getExecutorFailRetryCount()-1), log.getExecutorShardingParam(), log.getExecutorParam());
String retryMsg = "<br><br><span style=\"color:#F39C12;\" > >>>>>>>>>>>"+ I18nUtil.getString("jobconf_trigger_type_retry") +"<<<<<<<<<<< </span><br>";
log.setTriggerMsg(log.getTriggerMsg() + retryMsg);
XxlJobAdminConfig.getAdminConfig().getXxlJobLogDao().updateTriggerInfo(log);
}
// 2、fail alarm monitor
int newAlarmStatus = 0; // 告警状态：0-默认、-1=锁定状态、1-无需告警、2-告警成功、3-告警失败
if (info!=null && info.getAlarmEmail()!=null && info.getAlarmEmail().trim().length()>0) {
boolean alarmResult = true;
try {
alarmResult = failAlarm(info, log);
} catch (Exception e) {
alarmResult = false;
logger.error(e.getMessage(), e);
}
newAlarmStatus = alarmResult?2:3;
} else {
newAlarmStatus = 1;
}
XxlJobAdminConfig.getAdminConfig().getXxlJobLogDao().updateAlarmStatus(failLogId, -1, newAlarmStatus);
}
}
} catch (Exception e) {
if (!toStop) {
logger.error(">>>>>>>>>>> xxl-job, job fail monitor thread error:{}", e);
}
}
try {
TimeUnit.SECONDS.sleep(10);
} catch (Exception e) {
if (!toStop) {
logger.error(e.getMessage(), e);
}
}
}
logger.info(">>>>>>>>>>> xxl-job, job fail monitor thread stop");
}
});
monitorThread.setDaemon(true);
monitorThread.setName("xxl-job, admin JobFailMonitorHelper");
monitorThread.start();
}
}
JobFailMonitorHelper 的作用是开启一个 Daemon 线程主要管理异常调用的任务。如果任务调用失败，它会判断这个任务是否配置了失败重试(默认不重试)。如果配置重试次数大于0就会执行失败重试，如果一直失败最大重试次数就是你配置的重试次数。
另外一个作用就是如果你这个任务里面配置了报警邮件信息。这个失败的任务就是发送任务失败的相关信息到配置的邮箱。
4、JobTriggerPoolHelper
public void start(){
fastTriggerPool = new ThreadPoolExecutor(
10,
XxlJobAdminConfig.getAdminConfig().getTriggerPoolFastMax(),
60L,
TimeUnit.SECONDS,
new LinkedBlockingQueue<Runnable>(1000),
new ThreadFactory() {
@Override
public Thread newThread(Runnable r) {
return new Thread(r, "xxl-job, admin JobTriggerPoolHelper-fastTriggerPool-" + r.hashCode());
}
});
slowTriggerPool = new ThreadPoolExecutor(
10,
XxlJobAdminConfig.getAdminConfig().getTriggerPoolSlowMax(),
60L,
TimeUnit.SECONDS,
new LinkedBlockingQueue<Runnable>(2000),
new ThreadFactory() {
@Override
public Thread newThread(Runnable r) {
return new Thread(r, "xxl-job, admin JobTriggerPoolHelper-slowTriggerPool-" + r.hashCode());
}
});
}
它的作用就是初始化快慢两个线程池，当任务开始执行的时候使用快线程池。然后当任务执行失败次数达到阈值的时候就会使用慢线程池来执行任务。使执行任务的线程池隔离：调度线程池进行隔离拆分，慢任务自动降级进入"Slow"线程池，避免耗尽调度线程，提高系统稳定性。
5、JobLogReportHelper
public void start(){
logrThread = new Thread(new Runnable() {
@Override
public void run() {
// last clean log time
long lastCleanLogTime = 0;
while (!toStop) {
// 1、log-report refresh: refresh log report in 3 days
try {
for (int i = 0; i < 3; i++) {
// today
Calendar itemDay = Calendar.getInstance();
itemDay.add(Calendar.DAY_OF_MONTH, -i);
itemDay.set(Calendar.HOUR_OF_DAY, 0);
itemDay.set(Calendar.MINUTE, 0);
itemDay.set(Calendar.SECOND, 0);
itemDay.set(Calendar.MILLISECOND, 0);
Date todayFrom = itemDay.getTime();
itemDay.set(Calendar.HOUR_OF_DAY, 23);
itemDay.set(Calendar.MINUTE, 59);
itemDay.set(Calendar.SECOND, 59);
itemDay.set(Calendar.MILLISECOND, 999);
Date todayTo = itemDay.getTime();
// refresh log-report every minute
XxlJobLogReport xxlJobLogReport = new XxlJobLogReport();
xxlJobLogReport.setTriggerDay(todayFrom);
xxlJobLogReport.setRunningCount(0);
xxlJobLogReport.setSucCount(0);
xxlJobLogReport.setFailCount(0);
Map<String, Object> triggerCountMap = XxlJobAdminConfig.getAdminConfig().getXxlJobLogDao().findLogReport(todayFrom, todayTo);
if (triggerCountMap!=null && triggerCountMap.size()>0) {
int triggerDayCount = triggerCountMap.containsKey("triggerDayCount")?Integer.valueOf(String.valueOf(triggerCountMap.get("triggerDayCount"))):0;
int triggerDayCountRunning = triggerCountMap.containsKey("triggerDayCountRunning")?Integer.valueOf(String.valueOf(triggerCountMap.get("triggerDayCountRunning"))):0;
int triggerDayCountSuc = triggerCountMap.containsKey("triggerDayCountSuc")?Integer.valueOf(String.valueOf(triggerCountMap.get("triggerDayCountSuc"))):0;
int triggerDayCountFail = triggerDayCount - triggerDayCountRunning - triggerDayCountSuc;
xxlJobLogReport.setRunningCount(triggerDayCountRunning);
xxlJobLogReport.setSucCount(triggerDayCountSuc);
xxlJobLogReport.setFailCount(triggerDayCountFail);
}
// do refresh
int ret = XxlJobAdminConfig.getAdminConfig().getXxlJobLogReportDao().update(xxlJobLogReport);
if (ret < 1) {
XxlJobAdminConfig.getAdminConfig().getXxlJobLogReportDao().save(xxlJobLogReport);
}
}
} catch (Exception e) {
if (!toStop) {
logger.error(">>>>>>>>>>> xxl-job, job log report thread error:{}", e);
}
}
// 2、log-clean: switch open & once each day
if (XxlJobAdminConfig.getAdminConfig().getLogretentiondays()>0
&& System.currentTimeMillis() - lastCleanLogTime > 24*60*60*1000) {
// expire-time
Calendar expiredDay = Calendar.getInstance();
expiredDay.add(Calendar.DAY_OF_MONTH, -1 * XxlJobAdminConfig.getAdminConfig().getLogretentiondays());
expiredDay.set(Calendar.HOUR_OF_DAY, 0);
expiredDay.set(Calendar.MINUTE, 0);
expiredDay.set(Calendar.SECOND, 0);
expiredDay.set(Calendar.MILLISECOND, 0);
Date clearBeforeTime = expiredDay.getTime();
// clean expired log
List<Long> logIds = null;
do {
logIds = XxlJobAdminConfig.getAdminConfig().getXxlJobLogDao().findClearLogIds(0, 0, clearBeforeTime, 0, 1000);
if (logIds!=null && logIds.size()>0) {
XxlJobAdminConfig.getAdminConfig().getXxlJobLogDao().clearLog(logIds);
}
} while (logIds!=null && logIds.size()>0);
// update clean time
lastCleanLogTime = System.currentTimeMillis();
}
try {
TimeUnit.MINUTES.sleep(1);
} catch (Exception e) {
if (!toStop) {
logger.error(e.getMessage(), e);
}
}
}
}
});
logrThread.setDaemon(true);
logrThread.setName("xxl-job, admin JobLogReportHelper");
logrThread.start();
}
主要是报表相关的功能，保存任务执行的日志。并且生成日结报表，并且清理过期日志。支持实时查看运行数据，如任务数量、调度次数、执行器数量等；以及调度报表，如调度日期分布图，调度成功分布图等。
6、JobScheduleHelper
它的作用就是死循环从xxl_job_info表中取出未来5秒内要执行的任务，进行调度分发。启动了两个守护线程，先来看scheduleThread。
conn = XxlJobAdminConfig.getAdminConfig().getDataSource().getConnection();
connAutoCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
preparedStatement = conn.prepareStatement( "select * from xxl_job_lock where lock_name = 'schedule_lock' for update" );
preparedStatement.execute();
首先利用for update语句进行获取任务的资格锁定，再去获取未来5秒内即将要执行的任务。任务的逻辑代码，有三个分支。
// 1、pre read
long nowTime = System.currentTimeMillis();
List<XxlJobInfo> scheduleList = XxlJobAdminConfig.getAdminConfig().getXxlJobInfoDao().scheduleJobQuery(nowTime + PRE_READ_MS, preReadCount);
if (scheduleList!=null && scheduleList.size()>0) {
// 2、push time-ring
for (XxlJobInfo jobInfo: scheduleList) {
// time-ring jump
if (nowTime > jobInfo.getTriggerNextTime() + PRE_READ_MS) {
// 2.1、trigger-expire > 5s：pass && make next-trigger-time
logger.warn(">>>>>>>>>>> xxl-job, schedule misfire, jobId = " + jobInfo.getId());
// fresh next
refreshNextValidTime(jobInfo, new Date());
} else if (nowTime > jobInfo.getTriggerNextTime()) {
// 2.2、trigger-expire < 5s：direct-trigger && make next-trigger-time
// 1、trigger
JobTriggerPoolHelper.trigger(jobInfo.getId(), TriggerTypeEnum.CRON, -1, null, null);
logger.debug(">>>>>>>>>>> xxl-job, schedule push trigger : jobId = " + jobInfo.getId() );
// 2、fresh next
refreshNextValidTime(jobInfo, new Date());
// next-trigger-time in 5s, pre-read again
if (jobInfo.getTriggerStatus()==1 && nowTime + PRE_READ_MS > jobInfo.getTriggerNextTime()) {
// 1、make ring second
int ringSecond = (int)((jobInfo.getTriggerNextTime()/1000)%60);
// 2、push time ring
pushTimeRing(ringSecond, jobInfo.getId());
// 3、fresh next
refreshNextValidTime(jobInfo, new Date(jobInfo.getTriggerNextTime()));
}
} else {
// 2.3、trigger-pre-read：time-ring trigger && make next-trigger-time
// 1、make ring second
int ringSecond = (int)((jobInfo.getTriggerNextTime()/1000)%60);
// 2、push time ring
pushTimeRing(ringSecond, jobInfo.getId());
// 3、fresh next
refreshNextValidTime(jobInfo, new Date(jobInfo.getTriggerNextTime()));
}
}
// 3、update trigger info
for (XxlJobInfo jobInfo: scheduleList) {
XxlJobAdminConfig.getAdminConfig().getXxlJobInfoDao().scheduleUpdate(jobInfo);
}
} else {
preReadSuc = false;
}
第一个分支当前任务的触发时间已经超时5秒以上了，不在执行，直接计算下一次触发时间。
第二个分支为触发时间已满足，利用JobTriggerPoolHelper这个类进行任务调度，之后判断下一次执行时间如果在5秒内，进行此任务数据的缓存，处理逻辑与第三个分支一样。
第三个分支就是对触发时间秒数进行60取模，跟进pushTimeRing方法。
ringData是以 0 到 59 的整数为key，以jobId集合为value的Map集合。这个集合数据的处理逻辑，就在我们第二个守护线程ringThread中。
while (!ringThreadToStop) {
try {
// second data
List<Integer> ringItemData = new ArrayList<>();
int nowSecond = Calendar.getInstance().get(Calendar.SECOND); // 避免处理耗时太长，跨过刻度，向前校验一个刻度；
for (int i = 0; i < 2; i++) {
List<Integer> tmpData = ringData.remove( (nowSecond+60-i)%60 );
if (tmpData != null) {
ringItemData.addAll(tmpData);
}
}
// ring trigger
logger.debug(">>>>>>>>>>> xxl-job, time-ring beat : " + nowSecond + " = " + Arrays.asList(ringItemData) );
if (ringItemData.size() > 0) {
// do trigger
for (int jobId: ringItemData) {
// do trigger
JobTriggerPoolHelper.trigger(jobId, TriggerTypeEnum.CRON, -1, null, null);
}
// clear
ringItemData.clear();
}
} catch (Exception e) {
if (!ringThreadToStop) {
logger.error(">>>>>>>>>>> xxl-job, JobScheduleHelper#ringThread error:{}", e);
}
}
// next second, align second
try {
TimeUnit.MILLISECONDS.sleep(1000 - System.currentTimeMillis()%1000);
} catch (InterruptedException e) {
if (!ringThreadToStop) {
logger.error(e.getMessage(), e);
}
}
}
根据当前秒数刻度和前一个刻度进行时间轮的任务获取，之后和上文一样，利用JobTriggerPoolHelper进行任务调度。关于如何进行任务调度的在第三篇文章中具体讲解。第二篇就来讲一下执行器在启动的时候都做了哪些事。
参考文章：https://www.cnblogs.com/jiangyang/p/11576931.html