How to handle initial & trailing metadata for clients and servers (Python)

[Jens Troeger]

Hello,

I’m looking into the details of accessing request and response metadata on both client and server side, including from a chain of client and server interceptors. There’s some documentation here and a Python example here, but I still have a few questions.

In the linked Python example, a client sends initial metadata with the request (code) and then reads trailing metadata with the response (code). Likewise, a server reads the initial metadata from a request (code) and then sends trailing metadata with the response (code).

But given the ServicerContext.send_initial_metadata() function (docs) it seems to me that a server can also send initial metadata with a response? How would a client read that, using the Call.initial_metadata()function (docs)?

More interestingly, in a chain of server interceptors, how can one server interceptor read the initial/trailing response metadata sent by another downstream interceptor or the method handler itself? The docs list a ServicerContext.set_trailing_metadata() function (docs) and a ServicerContext.trailing_metadata() function (code), but they do not show an equivalent to access the initial metadata for a response?

And likewise with client interceptors?

Much thanks!

Jens