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状态机与状态机的设计
状态机就是状态转移图。
关于状态机的一个极度确切的描述是它是一个有向图形，由一组节点和一组相应的转移函数组成。状态机通过响应一系列事件而“运行”。每个事件都在属于“当前” 节点的转移函数的控制范围内，其中函数的范围是节点的一个子集。函数返回“下一个”（也许是同一个）节点。这些节点中至少有一个必须是终态。当到达终态， 状态机停止。
状态机可归纳为4个要素，即现态、条件、动作、次态。这样的归纳，主要是出于对状态机的内在因果关系的考虑。“现态”和“条件”是因，“动作”和“次态”是果。
我们定义一个jobEvent
public class JobEvent extends AbstractEvent<JobEventType> { private String jobID; public JobEvent(JobEventType type,String jobID) { super(type); this.jobID=jobID; } public String getJobID() { return jobID; } }
JobEventType：
package org.apache.hadoop.state;public enum JobEventType { JOB_KILL, JOB_INIT, JOB_START, JOB_SETUP_COMPLETED, JOB_COMPLETED}
作业内部状态JobStateInternal：
package org.apache.hadoop.state;/** * 定义作业内部状态 * @author joqk * */public enum JobStateInternal { NEW, SETUP, INITED, RUNNING, SUCCEEDED, KILLED,}
作业状态机JobStateMachine:
package org.apache.hadoop.state;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReadWriteLock;import java.util.concurrent.locks.ReentrantReadWriteLock;import org.apache.hadoop.event.JobEvent;import org.apache.hadoop.yarn.event.EventHandler;import org.apache.hadoop.yarn.state.SingleArcTransition;import org.apache.hadoop.yarn.state.StateMachine;import org.apache.hadoop.yarn.state.StateMachineFactory;public class JobStateMachine implements EventHandler<JobEvent> { private String jobID; private EventHandler eventHandler; private Lock writeLock=null; private Lock readLock=null; private StateMachine<JobStateInternal,JobEventType,JobEvent> stateMacthie; 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 InitTranstion()) .addTransition(JobStateInternal.INITED, JobStateInternal.SETUP, JobEventType.JOB_START,new StartTransition()) .installTopology(); public static class InitTranstion implements SingleArcTransition<JobStateMachine, JobEvent>{ @Override public void transition(JobStateMachine job, JobEvent event) { System.out.println("receiving event "+event); // job.eventHandler.handle(new JobEvent(JobEventType.JOB_START,job.jobID)); job.eventHandler.handle(new JobEvent(org.apache.hadoop.event.JobEventType.JOB_START, job.jobID)); } } public static class StartTransition implements SingleArcTransition<JobStateMachine, JobEvent>{ @Override public void transition(JobStateMachine job, JobEvent event) { System.out.println("receiving event "+event); // job.eventHandler.handle(new JobEvent(JobEventType.JOB_START,job.jobID));// job.eventHandler.handle(new JobEvent(JobEventType.JOB_SETUP_COMPLETED, job.jobID)); } } public JobStateMachine(String jobID,EventHandler eventHandler){ this.jobID = jobID; ReadWriteLock readWriteLock = new ReentrantReadWriteLock(); this.readLock = readWriteLock.readLock(); this.writeLock = readWriteLock.writeLock(); this.eventHandler =eventHandler; stateMacthie = stateMachineFactory.make(this); } /** * 得到当前状态机 * @return */ protected StateMachine<JobStateInternal,JobEventType,JobEvent> getStateMachine(){ return stateMacthie; } /** * 获取作业内部状态的变化 * @return */ public JobStateInternal getInternalState(){ readLock.lock(); try{ return getStateMachine().getCurrentState(); }finally{ readLock.unlock(); } } @Override public void handle(JobEvent event) { try{ writeLock.lock(); JobStateInternal oldState = getInternalState(); try{ getStateMachine().doTransition(event.getType(), event); }catch(InvalidStateTranstitonException e){ System.out.println("Can‘t handle thi event at current state "); } if(oldState != getInternalState()){ System.out.println("JOb Transtitioned from "+oldState +"to"+getInternalState()); } }finally{ writeLock.unlock(); } }}
这样就完成了一个状态机的定义。
状态机与状态机的设计
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