Eureka源码之服务注册中心处理

Eureka所有的交互处理都是通过REST请求发起的，下面看看服务注册中心对这些请求的处理。Eureka Server对各类REST请求的定义都是位于com.netflix.eurek.resource包中。

以“服务注册”请求为例：

@POST
    @Consumes({"application/json", "application/xml"})
    public Response addInstance(InstanceInfo info,
                                @HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication) {
        logger.debug("Registering instance {} (replication={})", info.getId(), isReplication);
        // validate that the instanceinfo contains all the necessary required fields
      ......

        // handle cases where clients may be registering with bad DataCenterInfo with missing data
        DataCenterInfo dataCenterInfo = info.getDataCenterInfo();
        if (dataCenterInfo instanceof UniqueIdentifier) {
            String dataCenterInfoId = ((UniqueIdentifier) dataCenterInfo).getId();
            if (isBlank(dataCenterInfoId)) {
                boolean experimental = "true".equalsIgnoreCase(serverConfig.getExperimental("registration.validation.dataCenterInfoId"));
                if (experimental) {
                    String entity = "DataCenterInfo of type " + dataCenterInfo.getClass() + " must contain a valid id";
                    return Response.status(400).entity(entity).build();
                } else if (dataCenterInfo instanceof AmazonInfo) {
                    AmazonInfo amazonInfo = (AmazonInfo) dataCenterInfo;
                    String effectiveId = amazonInfo.get(AmazonInfo.MetaDataKey.instanceId);
                    if (effectiveId == null) {
                        amazonInfo.getMetadata().put(AmazonInfo.MetaDataKey.instanceId.getName(), info.getId());
                    }
                } else {
                    logger.warn("Registering DataCenterInfo of type {} without an appropriate id", dataCenterInfo.getClass());
                }
            }
        }

        registry.register(info, "true".equals(isReplication));
        return Response.status(204).build();  // 204 to be backwards compatible
    }

在对注册信息进行了一堆校验之后，会调用org.springframework.cloud.netflix.eureka.server.InstanceRegistry对象的register(InstanceInfo info, int leaseDuration, boolean isReplication)函数进行服务注册。

    public void register(InstanceInfo info, int leaseDuration, boolean isReplication) {
        handleRegistration(info, leaseDuration, isReplication);
        super.register(info, leaseDuration, isReplication);
    }

    private void handleRegistration(InstanceInfo info, int leaseDuration,
            boolean isReplication) {
        log("register " + info.getAppName() + ", vip " + info.getVIPAddress()
                + ", leaseDuration " + leaseDuration + ", isReplication "
                + isReplication);
        publishEvent(new EurekaInstanceRegisteredEvent(this, info, leaseDuration,
                isReplication));
    }

相关调用如上面代码：

在注册函数中，先调用publishEvent函数，将该新服务注册的事件传播出去，然后调用AbstractInstanceRegistry中的注册实现，将InstanceInfo中的元数据信息存储在一个ConcurrentHashMap对象中，注册中心存储了两层Map结构，第一层的key存储服务名：InstanceInfo中的appName属性，第二层的key存储实例名：InstanceInfo中的instanceId属性。