[GitHub] [incubator-dubbo] chickenlj commented on issue #2541: Lack of HealthCheck ,we need it

["chickenlj (GitHub)" <gi...@apache.org>]

1. In what condition would we consider a service is ready for use?
Currently, we have a serial of model[https://github.com/apache/incubator-dubbo/tree/master/dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/model] artifacts which store all the services consumed and provided by one application. Some telnet commands, for example, ls, online and offline rely on this model to retrieve service status and update the service status if it's a write command. 
But the service status in these models on reflects whether a service has been published to the registry. It cannot meet @stoneapple's requirements:

> we know dubbo have the delay exposed ability, sometimes delay time is not easy to figure out. Also we may want to check other resources like db,cache before we exposed our service to meet the business trade.

To meet this customized requirement, I think we should add a hook mechainism in the export/unexport process and let the users to register callbacks, once the export/unexport process finished Dubbo will trigger all these callbacks. And still, besides callbacks, we need a place to store the status of all services, and I think model artifacts can be a good choice.

A step further, what about the abnormal scenarios, e.g., connection broken, resource exhausted, should we also update the service status, these will mostly happens at runtime, while the scenario @stoneapple cares is focused on starup phase.

2. How to export the health check service to end users, monitor systems or peer Dubbo Consumers? http, telnet or Dubbo?

I think http is more general and more convenience to use for end users and monitor systems, but for peer Dubbo Conumers it maybe not the the case.

[ Full content available at: https://github.com/apache/incubator-dubbo/issues/2541 ]
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