聊聊eureka instance的overriddenstatus

序

本文主要研究一下eureka instance的overriddenstatus

overriddenstatus

eureka-client-1.8.8-sources.jar!/com/netflix/appinfo/InstanceInfo.java

        /**
         * Sets the status overridden by some other external process.This is
         * mostly used in putting an instance out of service to block traffic to
         * it.
         *
         * @param status the overridden {@link InstanceStatus} of the instance.
         * @return @return the {@link InstanceInfo} builder.
         */
        public Builder setOverriddenStatus(InstanceStatus status) {
            result.overriddenstatus = status;
            return this;
        }

通過註釋可以看到，這個overriddenstatus的意思就是用於外部的一些操作，在netflix裏頭就是用於red/black部署的時候，先把指定服務設置爲OUT_OF_SERVICE來故意關閉請求流量。

    public enum InstanceStatus {
        UP, // Ready to receive traffic
        DOWN, // Do not send traffic- healthcheck callback failed
        STARTING, // Just about starting- initializations to be done - do not
        // send traffic
        OUT_OF_SERVICE, // Intentionally shutdown for traffic
        UNKNOWN;

        public static InstanceStatus toEnum(String s) {
            if (s != null) {
                try {
                    return InstanceStatus.valueOf(s.toUpperCase());
                } catch (IllegalArgumentException e) {
                    // ignore and fall through to unknown
                    logger.debug("illegal argument supplied to InstanceStatus.valueOf: {}, defaulting to {}", s, UNKNOWN);
                }
            }
            return UNKNOWN;
        }
    }

操作

設置OUT_OF_SERVICE

curl -i -X PUT http://localhost:8761/eureka/apps/client1/127.0.0.1:client1:8081/status?value=OUT_OF_SERVICE
HTTP/1.1 200
Content-Type: application/xml
Content-Length: 0
Date: Wed, 16 May 2018 06:52:29 GMT

刪除OUT_OF_SERVICE

curl -i -X DELETE http://localhost:8761/eureka/apps/client1/127.0.0.1:client1:8081/status
HTTP/1.1 200
Content-Type: application/xml
Content-Length: 0
Date: Wed, 16 May 2018 06:54:30 GM

小結

eureka instance的overriddenstatus對於部署來說非常好用，比如red/black升級，將部分原服務先設置爲OUT_OF_SERVICE，停止接收請求，即變爲black，之後新部署的服務啓動起來，即爲red。如果新服務正常，就可以關閉舊服務了，假設新服務出現問題，則立馬刪除掉新服務，將原有服務的overriddenstatus刪除掉，恢復UP，恢復接收流量。

doc

• 聊聊Eureka Server的REST API
• 聊聊eureka server的instance註冊及元數據變更接口
• Deploying the Netflix API
• The Mystery of Eureka Health Monitoring
• The Mystery of Eureka self-preservation
• Unable to return status to UP after overridden status was set to OUT_OF_SERVICE #955
• Eureka 1.x - there is no mechanism provided to remove overridden status #389
• Provide an API to remove all overridden status #89
• Support DELETE operation for instance status override.