eureka client服务续约源码分析

必备知识：

1.定时任务 ScheduledExecutorService

public class demo {
    public static void main(String[] args){
        ScheduledExecutorService ses = Executors.newScheduledThreadPool(5);

        //初始化时间
        int initDelay = 10;
        //线程间隔的时间
        long period1 = 1;
        long period5 = 5;
        long period10 = 10;
        ses.scheduleAtFixedRate(new MyScheduledExcutor("job1"),initDelay,period1, TimeUnit.SECONDS);
        ses.scheduleAtFixedRate(new MyScheduledExcutor("job2"),initDelay,period5, TimeUnit.SECONDS);
        ses.scheduleAtFixedRate(new MyScheduledExcutor("job3"),initDelay,period10, TimeUnit.SECONDS);
    }
}

public class MyScheduledExcutor implements Runnable {
    private String job;

    public MyScheduledExcutor(String job){
        this.job = job;
    }

    @Override
    public void run() {
        System.out.println("execute job name:" + job);
    }
}

简单的说明，实现runnable接口在建立对象的时候启动一个新的线程，建立线程池包含五个线程。

进入正题 initScheduledTasks()

@Singleton
public class DiscoveryClient implements EurekaClient {

    @Inject
    DiscoveryClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args, Provider<BackupRegistry> backupRegistryProvider) {
        //设置定时器
        this.initScheduledTasks();
    }
}

private void initScheduledTasks() {
        int renewalIntervalInSecs;
        int expBackOffBound;
        //shouldFetchRegistry默认是true 第一次启动，本地缓存为空
        if (this.clientConfig.shouldFetchRegistry()) {
            //默认是30秒 每30秒刷新一次  看下面的application.properties
            renewalIntervalInSecs = this.clientConfig.getRegistryFetchIntervalSeconds();
            expBackOffBound = this.clientConfig.getCacheRefreshExecutorExponentialBackOffBound();
            this.scheduler.schedule(new TimedSupervisorTask("cacheRefresh", this.scheduler, this.cacheRefreshExecutor, renewalIntervalInSecs, TimeUnit.SECONDS, expBackOffBound, new DiscoveryClient.CacheRefreshThread()), (long)renewalIntervalInSecs, TimeUnit.SECONDS);
        }

        if (this.clientConfig.shouldRegisterWithEureka()) {
            renewalIntervalInSecs = this.instanceInfo.getLeaseInfo().getRenewalIntervalInSecs();
            expBackOffBound = this.clientConfig.getHeartbeatExecutorExponentialBackOffBound();
            logger.info("Starting heartbeat executor: renew interval is: {}", renewalIntervalInSecs);
            this.scheduler.schedule(new TimedSupervisorTask("heartbeat", this.scheduler, this.heartbeatExecutor, renewalIntervalInSecs, TimeUnit.SECONDS, expBackOffBound, new DiscoveryClient.HeartbeatThread()), (long)renewalIntervalInSecs, TimeUnit.SECONDS);
            this.instanceInfoReplicator = new InstanceInfoReplicator(this, this.instanceInfo, this.clientConfig.getInstanceInfoReplicationIntervalSeconds(), 2);
            this.statusChangeListener = new StatusChangeListener() {
                public String getId() {
                    return "statusChangeListener";
                }

                public void notify(StatusChangeEvent statusChangeEvent) {
                    if (InstanceStatus.DOWN != statusChangeEvent.getStatus() && InstanceStatus.DOWN != statusChangeEvent.getPreviousStatus()) {
                        DiscoveryClient.logger.info("Saw local status change event {}", statusChangeEvent);
                    } else {
                        DiscoveryClient.logger.warn("Saw local status change event {}", statusChangeEvent);
                    }

                    DiscoveryClient.this.instanceInfoReplicator.onDemandUpdate();
                }
            };
            if (this.clientConfig.shouldOnDemandUpdateStatusChange()) {
                this.applicationInfoManager.registerStatusChangeListener(this.statusChangeListener);
            }

            this.instanceInfoReplicator.start(this.clientConfig.getInitialInstanceInfoReplicationIntervalSeconds());
        } else {
            logger.info("Not registering with Eureka server per configuration");
        }

    }

application.properties

#配置服务中心注册地址
eureka.client.service-url.defaultZone=http://localhost:8091/eureka/
#每隔30秒发送一次，证明自己的存在
eureka.instance.lease-renewal-interval-in-seconds=30