ElasticJob是基于Quartz实现的弹性分布式任务调度框架，整个任务触发的底层是Quartz来触发。LiteJob框架触发任务执行的开始，下面来分析任务的执行过程。
public final class LiteJob implements Job {
@Override
public void execute(final JobExecutionContext context) throws JobExecutionException {
//根据任务类型获取执行器，SimpleJobExecutor
JobExecutorFactory.getJobExecutor(elasticJob, jobFacade).execute();
}
}
ElasticJob根据任务的作业类型，获取不同的作业执行器，这里以SimpleJobExecutor为例。它继承了AbstractElasticJobExecutor，它是所有任务执行流程的模板类。
protected AbstractElasticJobExecutor(final JobFacade jobFacade) {
this.jobFacade = jobFacade;
jobRootConfig = jobFacade.loadJobRootConfiguration(true);
jobName = jobRootConfig.getTypeConfig().getCoreConfig().getJobName();
executorService = ExecutorServiceHandlerRegistry.getExecutorServiceHandler(jobName, (ExecutorServiceHandler) getHandler(JobProperties.JobPropertiesEnum.EXECUTOR_SERVICE_HANDLER));
jobExceptionHandler = (JobExceptionHandler) getHandler(JobProperties.JobPropertiesEnum.JOB_EXCEPTION_HANDLER);
itemErrorMessages = new ConcurrentHashMap<>(jobRootConfig.getTypeConfig().getCoreConfig().getShardingTotalCount(), 1);
}
在构造方法里面，是根据JobName为每个Job实例初始化了一个任务执行线程池，就是一个普通的ThreadPoolExecutor封装。下面分析下任务执行的流程：
public void execute() {
try {
//TODO 检验作业服务器和zk服务器系统时差是否可忍受，默认是不开启检查的
jobFacade.checkJobExecutionEnvironment();
} catch (final JobExecutionEnvironmentException cause) {
jobErrorHandler.handleException(jobConfig.getJobName(), cause);
}
//TODO 获取分片的上下文信息
ShardingContexts shardingContexts = jobFacade.getShardingContexts();
jobFacade.postJobStatusTraceEvent(shardingContexts.getTaskId(), State.TASK_STAGING, String.format("Job '%s' execute begin.", jobConfig.getJobName()));
//TODO 查看当前任务是否有分片正在执行，就创建节点/sharding/{item}/misfire
if (jobFacade.misfireIfRunning(shardingContexts.getShardingItemParameters().keySet())) {
jobFacade.postJobStatusTraceEvent(shardingContexts.getTaskId(), State.TASK_FINISHED, String.format(
"Previous job '%s' - shardingItems '%s' is still running, misfired job will start after previous job completed.", jobConfig.getJobName(),
shardingContexts.getShardingItemParameters().keySet()));
return;
}
try {
//TODO 任务开始执行，这里会去执行业务配置的监听器ElasticJobListener
jobFacade.beforeJobExecuted(shardingContexts);
//CHECKSTYLE:OFF
} catch (final Throwable cause) {
//CHECKSTYLE:ON
jobErrorHandler.handleException(jobConfig.getJobName(), cause);
}
//TODO 任务的执行处理
execute(shardingContexts, ExecutionSource.NORMAL_TRIGGER);
//TODO 任务是否有错过执行，重新出发调度一次
while (jobFacade.isExecuteMisfired(shardingContexts.getShardingItemParameters().keySet())) {
jobFacade.clearMisfire(shardingContexts.getShardingItemParameters().keySet());
execute(shardingContexts, ExecutionSource.MISFIRE);
}
//TODO 执行故障转移，防止未及时故障转移吧，其实有个listener在监控，为什么这里还要手动执行下 故障转移
jobFacade.failoverIfNecessary();
try {
//TODO 任务执行完成，这里是去触发业务配置的监听器的执行
jobFacade.afterJobExecuted(shardingContexts);
//CHECKSTYLE:OFF
} catch (final Throwable cause) {
//CHECKSTYLE:ON
jobErrorHandler.handleException(jobConfig.getJobName(), cause);
}
}
- Job节点服务器和zookeeper时钟差校验，对应的是Job的maxTimeDiffSeconds最大始终差配置，默认是-1不检查
try {
//TODO 检验作业服务器和zk服务器系统时差是否可忍受，默认是不开启检查的
jobFacade.checkJobExecutionEnvironment();
} catch (final JobExecutionEnvironmentException cause) {
jobErrorHandler.handleException(jobConfig.getJobName(), cause);
}
public void checkMaxTimeDiffSecondsTolerable() throws JobExecutionEnvironmentException {
int maxTimeDiffSeconds = load(true).getMaxTimeDiffSeconds();
if (-1 == maxTimeDiffSeconds) {
return;
}
long timeDiff = Math.abs(timeService.getCurrentMillis() - jobNodeStorage.getRegistryCenterTime());
if (timeDiff > maxTimeDiffSeconds * 1000L) {
throw new JobExecutionEnvironmentException(
"Time different between job server and register center exceed '%s' seconds, max time different is '%s' seconds.", timeDiff / 1000, maxTimeDiffSeconds);
}
}
- 获取当前节点服务器的分片信息，这里是分片的关键，在分片那节再细说，这里大概说下做的事情。如果Job配置了故障转移并且存在故障转移分片，优先执行从其它故障节点转移到当前节点服务器的分片。如果需要重新分片，则执行重新分片逻辑，获取分配到当前节点的分片信息。
public ShardingContexts getShardingContexts() {
boolean isFailover = configService.load(true).isFailover();
if (isFailover) {
//TODO 获取故障转移到当前节点的分片信息
List<Integer> failoverShardingItems = failoverService.getLocalFailoverItems();
if (!failoverShardingItems.isEmpty()) {
//TODO 获取故障转移分片信息
return executionContextService.getJobShardingContext(failoverShardingItems);
}
}
shardingService.shardingIfNecessary();
List<Integer> shardingItems = shardingService.getLocalShardingItems();
if (isFailover) {
//TODO 删除本节点被故障转移的分片信息
shardingItems.removeAll(failoverService.getLocalTakeOffItems());
}
shardingItems.removeAll(executionService.getDisabledItems(shardingItems));
return executionContextService.getJobShardingContext(shardingItems);
}
- 当前节点服务器该job对应的所有分片，是否有执行中的分片，只要有一个执行中的分片，则对应的所有分片都会被设置为misfire错失执行，然后退出。就是上次触发的执行没有完成，本次触发不会执行，会等待上次执行完成，防止任务分片在当前节点被重复执行。
//TODO 查看当前任务是否有分片正在执行，就创建节点/sharding/{item}/misfire
if (jobFacade.misfireIfRunning(shardingContexts.getShardingItemParameters().keySet())) {
jobFacade.postJobStatusTraceEvent(shardingContexts.getTaskId(), State.TASK_FINISHED, String.format(
"Previous job '%s' - shardingItems '%s' is still running, misfired job will start after previous job completed.", jobConfig.getJobName(),
shardingContexts.getShardingItemParameters().keySet()));
return;
}
public boolean misfireIfHasRunningItems(final Collection<Integer> items) {
if (!hasRunningItems(items)) {
return false;
}
//TODO 只要其中一个分片没有执行完成，就会设置misfire
setMisfire(items);
return true;
}
public boolean hasRunningItems(final Collection<Integer> items) {
JobConfiguration jobConfig = configService.load(true);
if (!jobConfig.isMonitorExecution()) {
return false;
}
for (int each : items) {
//TODO 只要其中一个分片没有执行完成，就会设置misfire
if (jobNodeStorage.isJobNodeExisted(ShardingNode.getRunningNode(each))) {
return true;
}
}
return false;
}
- 执行任务之前对应的ElasticJobListener，这个是之前在配置Job任务时对应的ElasticJobListener。
try {
//TODO 任务开始执行，这里会去执行业务配置的监听器ElasticJobListener
jobFacade.beforeJobExecuted(shardingContexts);
//CHECKSTYLE:OFF
} catch (final Throwable cause) {
//CHECKSTYLE:ON
jobErrorHandler.handleException(jobConfig.getJobName(), cause);
}
- 具体任务分片的调度执行，在分片任务执行前，在当前节点服务器把任务在内存中设置为running状态，如果配置了幂等机制，同时也会在zookeeper中创建/sharding/{item}/running临时节点，在服务器宕机该节点就会自动删除了。然后就是把所有的分片任务提交到ThreadPoolExecutor中执行。这里使用的CountDownLatch控制并发等待所有的分片任务都完成，然后就删除任务执行钱创建的/sharding/{item}/running节点。同时如果开启了故障转移机制，就会删除之前创建的故障转移节点/sharding/{item}/failover
//TODO 任务的执行处理
execute(shardingContexts, ExecutionSource.NORMAL_TRIGGER);
private void execute(final ShardingContexts shardingContexts, final ExecutionSource executionSource) {
if (shardingContexts.getShardingItemParameters().isEmpty()) {
jobFacade.postJobStatusTraceEvent(shardingContexts.getTaskId(), State.TASK_FINISHED, String.format("Sharding item for job '%s' is empty.", jobConfig.getJobName()));
return;
}
//TODO 将当前任务设置为运行中Running的状态，分为内存状态和zk状态，在zk中创建一个临时节点
jobFacade.registerJobBegin(shardingContexts);
String taskId = shardingContexts.getTaskId();
jobFacade.postJobStatusTraceEvent(taskId, State.TASK_RUNNING, "");
try {
process(shardingContexts, executionSource);
} finally {
// TODO Consider increasing the status of job failure, and how to handle the overall loop of job failure
//TODO 清除job的running状态和删除故障转移节点/sharding/{item}/failover
jobFacade.registerJobCompleted(shardingContexts);
if (itemErrorMessages.isEmpty()) {
jobFacade.postJobStatusTraceEvent(taskId, State.TASK_FINISHED, "");
} else {
jobFacade.postJobStatusTraceEvent(taskId, State.TASK_ERROR, itemErrorMessages.toString());
}
}
}
private void process(final ShardingContexts shardingContexts, final ExecutionSource executionSource) {
Collection<Integer> items = shardingContexts.getShardingItemParameters().keySet();
if (1 == items.size()) {
int item = shardingContexts.getShardingItemParameters().keySet().iterator().next();
JobExecutionEvent jobExecutionEvent = new JobExecutionEvent(IpUtils.getHostName(), IpUtils.getIp(), shardingContexts.getTaskId(), jobConfig.getJobName(), executionSource, item);
process(shardingContexts, item, jobExecutionEvent);
return;
}
CountDownLatch latch = new CountDownLatch(items.size());
for (int each : items) {
JobExecutionEvent jobExecutionEvent = new JobExecutionEvent(IpUtils.getHostName(), IpUtils.getIp(), shardingContexts.getTaskId(), jobConfig.getJobName(), executionSource, each);
if (executorService.isShutdown()) {
return;
}
executorService.submit(() -> {
try {
process(shardingContexts, each, jobExecutionEvent);
} finally {
latch.countDown();
}
});
}
try {
latch.await();
} catch (final InterruptedException ex) {
Thread.currentThread().interrupt();
}
}
- 检查是否有任务分片错过执行，这里的判断是开启了misfire任务错过机制并且分片存在/sharding/{item}/misfire节点。如果开启了任务错过机制，并且有任务错过执行，这里会重新执行一次分片节点任务。任务执行之前清除了/sharding/{item}/misfire节点。
//TODO 任务是否有错过执行，重新出发调度一次
while (jobFacade.isExecuteMisfired(shardingContexts.getShardingItemParameters().keySet())) {
jobFacade.clearMisfire(shardingContexts.getShardingItemParameters().keySet());
execute(shardingContexts, ExecutionSource.MISFIRE);
}
- 在这里再手动执行下故障转移操作，在这里不知道为啥还需要手动执行下故障转移，在故障转移监听器里面就能监听到，为啥这里还要在任务执行的时候再手动触发下？？？没太理解
//TODO 执行故障转移，防止未及时故障转移吧，其实有个listener在监控，为什么这里还要手动执行下 故障转移
jobFacade.failoverIfNecessary();
- 任务分片执行完之后，触发业务给任务配置的监听器的执行
try {
//TODO 任务执行完成，这里是去触发业务配置的监听器的执行
jobFacade.afterJobExecuted(shardingContexts);
//CHECKSTYLE:OFF
} catch (final Throwable cause) {
//CHECKSTYLE:ON
jobErrorHandler.handleException(jobConfig.getJobName(), cause);
}
作业执行流程图:
ElasticJob作业执行流程图
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