Hi friends, and well wishes to anyone reading this post. I'm currently working to instrument some kind of logging / tracing on the client side for our GRPC requests.
I've been reading this proposal <https://github.com/grpc/proposal/blob/master/L5-node-client-interceptors.md> and would like to level set some of my understandings so far. So first-- the nature of a *client unary interceptor*, as I understand it, is that we can add modifications such as injecting client metadata before the request is sent to the server. The proposal mentions such things as "inbound" and "outbound" operations. *Question 1*: When a GRPC call is being made, are there two streams being opened? Outbound being the stream opened because of the request sent BY the client, and Inbound being the stream opened to *return* the result by the server? So, the listener methods such as `onReceiveMetadata(metadata, next)` are "inbound" in that sense? And it is correct to say that by the time we receive these inbound operations, whatever processing that is done within the function call is "done", and we are just intercepting the entirety of the response as it comes in? *Question 2:* At the time of a call being made by the client, we can pass in interceptors like so: ``` client.myCall(message, { interceptors: [interceptor] }); ``` Is there a practical example for how someone might want to pass in a list of interceptors when a call is made? *Question 3:* In a scenario where the client thinks it sent a message, but the server never receives / acknowledges the request, what happens? (Maybe network went down because of network gremlins), would the pipe close with a stream timeout of `DEADLINE_EXCEEDED` error code? *Question 4:* Similar to this question, <https://github.com/grpc/grpc-go/issues/3492> in the scenario where the stream is not closed but the message is never received by the client- a way to "triage" this would be to add timers earlier in the interceptor stack, and see that the listener method "onRecieveMessage()" for example, was never called. Feedback, pointers, and links towards any extra reading would all be appreciated! Thanks, Rachel -- You received this message because you are subscribed to the Google Groups "grpc.io" group. To unsubscribe from this group and stop receiving emails from it, send an email to grpc-io+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/grpc-io/f739dff2-c37d-478a-a499-ff79a8640c05n%40googlegroups.com.
