一、状态机库概述
一)简介
状态机由一组状态组成:
【初始状态 -> 中间状态 -> 最终状态】。
在一个状态机中,每个状态会接收一组特定的事件,根据事件类型进行处理,并转换到下一个状态。当转换到最终状态时则退出。
二)状态转换方式
状态间转换会有下面这三种类型
三)Yarn 状态机类
在 Yarn 中提供了一个工厂类 StateMachineFactory
来帮助定义状态机。如何使用,我们直接写个 demo。
一)状态机实现
状态机实现,可以直接嵌入到上篇文章中的 AsyncDispatcher
使用。
这里仅给出状态机JobStateMachine
以及各种事件处理的代码。完整的代码项目执行,请到 github demo 中查看。
import com.shuofxz.event.JobEvent;
import com.shuofxz.event.JobEventType;
import org.apache.hadoop.yarn.event.EventHandler;
import org.apache.hadoop.yarn.state.*;
import java.util.EnumSet;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/*
* 可参考 Yarn 中实现的状态机对象:
* ResourceManager 中的 RMAppImpl、RMApp- AttemptImpl、RMContainerImpl 和 RMNodeImpl,
* NodeManager 中 的 ApplicationImpl、 ContainerImpl 和 LocalizedResource,
* MRAppMaster 中的 JobImpl、TaskImpl 和 TaskAttemptImpl 等
* */
@SuppressWarnings({"rawtypes", "unchecked"})
public class JobStateMachine implements EventHandler<JobEvent> {
private final String jobID;
private EventHandler eventHandler;
private final Lock writeLock;
private final Lock readLock;
// 定义状态机
protected static final StateMachineFactory<JobStateMachine, JobStateInternal,
JobEventType, JobEvent>
stateMachineFactory = new StateMachineFactory<JobStateMachine, JobStateInternal, JobEventType, JobEvent>(JobStateInternal.NEW)
.addTransition(JobStateInternal.NEW, JobStateInternal.INITED, JobEventType.JOB_INIT, new InitTransition())
.addTransition(JobStateInternal.INITED, JobStateInternal.SETUP, JobEventType.JOB_START, new StartTransition())
.addTransition(JobStateInternal.SETUP, JobStateInternal.RUNNING, JobEventType.JOB_SETUP_COMPLETED, new SetupCompletedTransition())
.addTransition(JobStateInternal.RUNNING, EnumSet.of(JobStateInternal.KILLED, JobStateInternal.SUCCEEDED), JobEventType.JOB_COMPLETED, new JobTasksCompletedTransition())
.installTopology();
private final StateMachine<JobStateInternal, JobEventType, JobEvent> stateMachine;
public JobStateMachine(String jobID, EventHandler eventHandler) {
this.jobID = jobID;
// 多线程异步处理,state 有可能被同时读写,使用读写锁来避免竞争
ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
this.readLock = readWriteLock.readLock();
this.writeLock = readWriteLock.writeLock();
this.eventHandler = eventHandler;
stateMachine = stateMachineFactory.make(this);
}
protected StateMachine<JobStateInternal, JobEventType, JobEvent> getStateMachine() {
return stateMachine;
}
public static class InitTransition implements SingleArcTransition<JobStateMachine, JobEvent> {
@Override
public void transition(JobStateMachine jobStateMachine, JobEvent jobEvent) {
System.out.println("Receiving event " + jobEvent);
// do something...
// 完成后发送新的 Event —— JOB_START
jobStateMachine.eventHandler.handle(new JobEvent(jobStateMachine.jobID, JobEventType.JOB_START));
}
}
public static class StartTransition implements SingleArcTransition<JobStateMachine, JobEvent> {
@Override
public void transition(JobStateMachine jobStateMachine, JobEvent jobEvent) {
System.out.println("Receiving event " + jobEvent);
jobStateMachine.eventHandler.handle(new JobEvent(jobStateMachine.jobID, JobEventType.JOB_SETUP_COMPLETED));
}
}
public static class SetupCompletedTransition implements SingleArcTransition<JobStateMachine, JobEvent> {
@Override
public void transition(JobStateMachine jobStateMachine, JobEvent jobEvent) {
System.out.println("Receiving event " + jobEvent);
jobStateMachine.eventHandler.handle(new JobEvent(jobStateMachine.jobID, JobEventType.JOB_COMPLETED));
}
}
public static class JobTasksCompletedTransition implements MultipleArcTransition<JobStateMachine, JobEvent, JobStateInternal> {
@Override
public JobStateInternal transition(JobStateMachine jobStateMachine, JobEvent jobEvent) {
System.out.println("Receiving event " + jobEvent);
// 这是多结果状态部分,因此需要人为制定后续状态
// 这里整个流程结束,设置一下对应的状态
boolean flag = true;
if (flag) {
return JobStateInternal.SUCCEEDED;
} else {
return JobStateInternal.KILLED;
}
}
}
@Override
public void handle(JobEvent jobEvent) {
try {
// 注意这里为了避免静态条件,使用了读写锁
writeLock.lock();
JobStateInternal oldState = getInternalState();
try {
getStateMachine().doTransition(jobEvent.getType(), jobEvent);
} catch (InvalidStateTransitionException e) {
System.out.println("Can't handle this event at current state!");
}
if (oldState != getInternalState()) {
System.out.println("Job Transitioned from " + oldState + " to " + getInternalState());
}
} finally {
writeLock.unlock();
}
}
public JobStateInternal getInternalState() {
readLock.lock();
try {
return getStateMachine().getCurrentState();
} finally {
readLock.unlock();
}
}
public enum JobStateInternal {
NEW,
SETUP,
INITED,
RUNNING,
SUCCEEDED,
KILLED
}
}
二)状态机可视化
hadoop 中提供了状态机可视化的工具类 VisualizeStateMachine.java
,可以拷贝到我们的工程中使用。
根据提示,运行需要三个参数
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