Spring Cloud Eureka源码解析之服务续约（四）

àì夳堔傛蜴生んèń 2022-09-16 04:55 238阅读 0赞

## EurekaClient ##

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  
![在这里插入图片描述][a659420b26144de60a994ce3dacb0759.png_pic_center]  
![在这里插入图片描述][53a0e2e01324b39914128991759ed84e.png_pic_center]  
![在这里插入图片描述][5cfc2e24e6672a79c583875f18309d77.png_pic_center]  
如果续约的响应状态码是404，则需要重新去注册

## Eureka Server接收续约请求 ##

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<Application> 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<String, Lease<InstanceInfo>> gMap = registry.get(appName);
        Lease<InstanceInfo> 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。

[a659420b26144de60a994ce3dacb0759.png_pic_center]: /images/20220828/ed3afcb11eed4b2fac3568911bbb0795.png
[53a0e2e01324b39914128991759ed84e.png_pic_center]: /images/20220828/3e3280d3296b4f07a4bbc518a9639693.png
[5cfc2e24e6672a79c583875f18309d77.png_pic_center]: /images/20220828/b6fd0647a8f549c7ac2c408549414fc4.png