spring cloud学习--eureka 02

开启eureka client的注解@EnableDiscoveryClient的功能类DiscoveryClient梳理图

获取server url位于类EndpointUtils的getServiceUrlsMapFromConfig方法上

public static Map<String, List<String>> getServiceUrlsMapFromConfig(EurekaClientConfig clientConfig, String instanceZone, boolean preferSameZone) {
        Map<String, List<String>> orderedUrls = new LinkedHashMap();
        //获取regin，一个微服务应用只有一个region
        String region = getRegion(clientConfig);
        //获取zone，一个微服务可以有多个zone
        String[] availZones = clientConfig.getAvailabilityZones(clientConfig.getRegion());
        if (availZones == null || availZones.length == 0) {
            //如果zone为null,就设置为default
            availZones = new String[]{"default"};
        }

        logger.debug("The availability zone for the given region {} are {}", region, Arrays.toString(availZones));
        int myZoneOffset = getZoneOffset(instanceZone, preferSameZone, availZones);
        String zone = availZones[myZoneOffset];
        //根据region和zone得出server url， 并且可以配置多个server url
        List<String> serviceUrls = clientConfig.getEurekaServerServiceUrls(zone);
        if (serviceUrls != null) {
            orderedUrls.put(zone, serviceUrls);
        }

        int currentOffset = myZoneOffset == availZones.length - 1 ? 0 : myZoneOffset + 1;

        while(currentOffset != myZoneOffset) {
            zone = availZones[currentOffset];
            serviceUrls = clientConfig.getEurekaServerServiceUrls(zone);
            if (serviceUrls != null) {
                orderedUrls.put(zone, serviceUrls);
            }

            if (currentOffset == availZones.length - 1) {
                currentOffset = 0;
            } else {
                ++currentOffset;
            }
        }

        if (orderedUrls.size() < 1) {
            throw new IllegalArgumentException("DiscoveryClient: invalid serviceUrl specified!");
        } else {
            return orderedUrls;
        }
    }

服务注册DiscoveryClient initScheduledTasks方法

 private void initScheduledTasks() {
        int renewalIntervalInSecs;
        int expBackOffBound;
        if (this.clientConfig.shouldFetchRegistry()) {
            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);
        }
        
        //配置文件注册服务
        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);
            }
            
            //开启一个任务
            this.instanceInfoReplicator.start(this.clientConfig.getInitialInstanceInfoReplicationIntervalSeconds());
        } else {
            logger.info("Not registering with Eureka server per configuration");
        }

    }

上面代码中 this.instanceInfoReplicator.start(this.clientConfig.getInitialInstanceInfoReplicationIntervalSeconds());开启了一个任务，该任务的代码如下

public void run() {
        boolean var6 = false;

        ScheduledFuture next;
        label53: {
            try {
                var6 = true;
                this.discoveryClient.refreshInstanceInfo();
                Long dirtyTimestamp = this.instanceInfo.isDirtyWithTime();
                if (dirtyTimestamp != null) {
                    //真正触发了注册
                    this.discoveryClient.register();
                    this.instanceInfo.unsetIsDirty(dirtyTimestamp);
                    var6 = false;
                } else {
                    var6 = false;
                }
                break label53;
            } catch (Throwable var7) {
                logger.warn("There was a problem with the instance info replicator", var7);
                var6 = false;
            } finally {
                if (var6) {
                    ScheduledFuture next = this.scheduler.schedule(this, (long)this.replicationIntervalSeconds, TimeUnit.SECONDS);
                    this.scheduledPeriodicRef.set(next);
                }
            }

            next = this.scheduler.schedule(this, (long)this.replicationIntervalSeconds, TimeUnit.SECONDS);
            this.scheduledPeriodicRef.set(next);
            return;
        }

        next = this.scheduler.schedule(this, (long)this.replicationIntervalSeconds, TimeUnit.SECONDS);
        this.scheduledPeriodicRef.set(next);
    }

真正触发了注册的代码为this.discoveryClient.register();
注册的代码为：

boolean register() throws Throwable {
        logger.info("DiscoveryClient_" + this.appPathIdentifier + ": registering service...");

        EurekaHttpResponse httpResponse;
        try {
            //通过REST请求进行注册
            httpResponse = this.eurekaTransport.registrationClient.register(this.instanceInfo);
        } catch (Exception var3) {
            logger.warn("{} - registration failed {}", new Object[]{"DiscoveryClient_" + this.appPathIdentifier, var3.getMessage(), var3});
            throw var3;
        }

        if (logger.isInfoEnabled()) {
            logger.info("{} - registration status: {}", "DiscoveryClient_" + this.appPathIdentifier, httpResponse.getStatusCode());
        }

        return httpResponse.getStatusCode() == 204;
    }