Spring Cloud Eureka源码解析之服务续约（四）

Eureka Client启动时会创建一个每隔30s向Eureka Server发送心跳的定时任务



如果续约的响应状态码是404，则需要重新去注册

处理续约请求的是InstanceResource#renewLease方法

@PUT
public Response renewLease(
    @HeaderParam(PeerEurekaNode.HEADER_REPLICATION) String isReplication,
    @QueryParam("overriddenstatus") String overriddenStatus,
    @QueryParam("status") String status,
    @QueryParam("lastDirtyTimestamp") String lastDirtyTimestamp) {
    boolean isFromReplicaNode = "true".equals(isReplication);
    // 服务续约
    boolean isSuccess = registry.renew(app.getName(), id, isFromReplicaNode);

    // 没续约成功，client需要立即发起一次注册
    if (!isSuccess) {
        logger.warn("Not Found (Renew): {} - {}", app.getName(), id);
        return Response.status(Status.NOT_FOUND).build();
    }
    // Check if we need to sync based on dirty time stamp, the client
    // instance might have changed some value
    Response response = null;
    if (lastDirtyTimestamp != null && serverConfig.shouldSyncWhenTimestampDiffers()) {
        response = this.validateDirtyTimestamp(Long.valueOf(lastDirtyTimestamp), isFromReplicaNode);
        // Store the overridden status since the validation found out the node that replicates wins
        if (response.getStatus() == Response.Status.NOT_FOUND.getStatusCode()
            && (overriddenStatus != null)
            && !(InstanceStatus.UNKNOWN.name().equals(overriddenStatus))
            && isFromReplicaNode) {
            registry.storeOverriddenStatusIfRequired(app.getAppName(), id, InstanceStatus.valueOf(overriddenStatus));
        }
    } else {
        response = Response.ok().build();
    }
    logger.debug("Found (Renew): {} - {}; reply status={}", app.getName(), id, response.getStatus());
    return response;
}

InstanceRegistry#renew

@Override
public boolean renew(final String appName, final String serverId,
                     boolean isReplication) {
    log("renew " + appName + " serverId " + serverId + ", isReplication {}"
        + isReplication);
    List applications = getSortedApplications();
    for (Application input : applications) {
        if (input.getName().equals(appName)) {
            InstanceInfo instance = null;
            for (InstanceInfo info : input.getInstances()) {
                if (info.getId().equals(serverId)) {
                    instance = info;
                    break;
                }
            }
            // 获取server上的实例发布事件
            publishEvent(new EurekaInstanceRenewedEvent(this, appName, serverId,
                                                        instance, isReplication));
            break;
        }
    }
    // 主要续约逻辑在父类
    return super.renew(appName, serverId, isReplication);
}

PeerAwareInstanceRegistryImpl#renew

public boolean renew(final String appName, final String id, final boolean isReplication) {
    // 续约成功，则需要同步到其它Server
    if (super.renew(appName, id, isReplication)) {
        replicateToPeers(Action.Heartbeat, appName, id, null, null, isReplication);
        return true;
    }
    return false;
}

AbstractInstanceRegistry#renew

public boolean renew(String appName, String id, boolean isReplication) {
    RENEW.increment(isReplication);
    Map> gMap = registry.get(appName);
    Lease leaseToRenew = null;
    if (gMap != null) {
        // 服务端上的续约信息
        leaseToRenew = gMap.get(id);
    }
    if (leaseToRenew == null) {
        RENEW_NOT_FOUND.increment(isReplication);
        logger.warn("DS: Registry: lease doesn't exist, registering resource: {} - {}", appName, id);
        return false;
    } else {
        // 服务端上的实例信息
        InstanceInfo instanceInfo = leaseToRenew.getHolder();
        if (instanceInfo != null) {
            // touchASGCache(instanceInfo.getASGName());
            InstanceStatus overriddenInstanceStatus = this.getOverriddenInstanceStatus(
                instanceInfo, leaseToRenew, isReplication);
            if (overriddenInstanceStatus == InstanceStatus.UNKNOWN) {
                logger.info("Instance status UNKNOWN possibly due to deleted override for instance {}"
                            + "; re-register required", instanceInfo.getId());
                RENEW_NOT_FOUND.increment(isReplication);
                return false;
            }
            if (!instanceInfo.getStatus().equals(overriddenInstanceStatus)) {
                logger.info(
                    "The instance status {} is different from overridden instance status {} for instance {}. "
                    + "Hence setting the status to overridden status", instanceInfo.getStatus().name(),
                    instanceInfo.getOverriddenStatus().name(),
                    instanceInfo.getId());
                instanceInfo.setStatusWithoutDirty(overriddenInstanceStatus);

            }
        }
        // 最近一分钟续约数+1，用于在后面判断服务过期剔除用的
        renewsLastMin.increment();
        // 更新时间
        leaseToRenew.renew();
        return true;
    }
}

public void renew() {
    lastUpdateTimestamp = System.currentTimeMillis() + duration;
}

续约最终的操作就是更新一下最近更新时间lastUpdateTimestamp，这里有一个问题，多加了一个duration，导致后面服务过期时间变长了。