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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;
        }

通过注释可以看到，这个overriddenstatus的意思就是用于外部的一些操作，在netflix里头就是用于red/black部署的时候，先把指定服务设置为OUT_OF_SERVICE来故意关闭请求流量。

1_r6qGvK49cv_9A8b4OCAZZw.png

InstanceStatus枚举定义如下：

    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

设置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

删除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

小结

eureka instance的overriddenstatus对于部署来说非常好用，比如red/black升级，将部分原服务先设置为OUT_OF_SERVICE，停止接收请求，即变为black，之后新部署的服务启动起来，即为red。如果新服务正常，就可以关闭旧服务了，假设新服务出现问题，则立马删除掉新服务，将原有服务的overriddenstatus删除掉，恢复UP，恢复接收流量。

doc

• 聊聊Eureka Server的REST API
• 聊聊eureka server的instance注册及元数据变更接口
• 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.