CC @envoyproxy/api-shepherds: Your approval is needed for changes made to api/envoy/.
CC @envoyproxy/api-watchers: FYI only for changes made to api/envoy/.

I don't understand why this is needed. There's already a way to match on the node ID field in the NodeMatcher message:

As per offline discussion, it seems like what you want here is not a way to select the data that you want CSDS to return but rather a way to identify the CSDS client to the CSDS server. In that case, I suspect the right way to do it is to add a Node message, not just a single string id field.

That having been said, I'm not actually all that familiar with how CSDS is used, so I'm going to defer to @htuch or one of the other API shephards to review this.

Yes, I think this probably belongs in the Node ID or metadata.

@markdroth @htuch Just want to make sure that what you suggested is replacing the string id field by a Node filed just like which in DiscoveryRequest, right?

Yes, exactly.

Yeah, it seems reasonable to re-use this structure if we consider nodes to be Envoy/gRPC clients, intermediaries such as proxies, CSDS, etc.

@markdroth @htuch Thanks for the suggestion! I've modified the csds request by adding a node field to it and also edited the commit message.

/cc @fuqianggao

LGTM