On Monday, November 15, 2021 at 11:30:52 AM UTC-5 Mansfield Mark wrote:
> Hi all, I'm trying to build an auth flow (email + OTP -> JWT) between a > grpc-web client and a grpc-java server, with an Envoy proxy between the > two. Just to make sure I'm not missing anything big, this is my mental > image of how I think RPC calls are handled on the server, with a > ServerInterceptor attached. > > 1. ServerInterceptor#interceptCall to wrap the real call in a > CustomServerCall > 2. CustomServerCall#sendHeaders to build and return response headers > 3. CustomServerCall#sendMessage to build and return response body > 4. CustomServerCall#close to set final status, response trailers, etc. > 5. Response headers are converted to HTTP response headers when sent > back to the gRPC web client. Response trailers look like they are only > part > of the gRPC payload, but they don't get handled by the browser. > > I'm under the impression that with this pattern, the response headers are > always built and sent before the RPC call actually starts. This makes me > think there's no access to the request body when constructing response > headers. > > My workaround is: > > 1. Attach a username + password as request *headers*, instead of in > the request body. > 2. Convert username + password into a JWT in > CustomServerCall#sendHeaders, and include a set-cookie header > 3. The actual body of the server call is a no-op. > > I recently ran up against a similar problem as well, so I'm also curious about the answer. Last week, I was trying to attach a metadata header in a ClientInterceptor that was a function of the message body -- but, also ran into the similar problem that the start callback (where headers can be manipulated and are transmitted) are handled before the message is. The best I can tell is that this is done to support the streaming API internally (even if performing a unary call) where, the sendMessage function, will be executed multiple times for each transmitted message, after the headers are sent. Presumably, this is the same for the ServerInterceptor, where the headers will be sent before the response. Christopher -- 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/a6cbc746-3b2d-4011-8c78-12fd1a929090n%40googlegroups.com.
