grpc_pass nginx configuration

When I do the same with resolver and set grpc_pass it fails:

    `server {
        listen 443 http2:
        server _name opc.org.com;
        ssl....;
        location / {
            resolver 127.0.0.11 valid=30s;
            set $https_webui https://dev_webui;
            proxy_pass $https_webui;
        }  
        location /App.Room.Api.Contract.ApiService/UpdateOpcDaTags {
            resolver 127.0.0.11 valid=30s;
            set $grpc_webui grpcs://dev_webui;
            grpc_pass $grpc_webui;
        }`

The error I'm getting on grpc-client is:

    `[Microsoft.Extensions.Hosting.Internal.Host)
    [BackgroundServiceFaulted status   BackgroundServledGrpc.Co.RpcException
    (StatusCode="Unknown", Detail="Bad gRPC response. HTTP status code: 500")`

When you have a configuration similar to this (example) it works

        `location /App.Room.Api.Contract.ApiService/UpdateOpcDaTags {
         grpc_pass grpcs://dev_webui;
         }`

Version nginx; nginx version: nginx/1.23.2

After a long review of the materials and tests, the error was discovered.

If we are using variables in the configuration, grpc_pass should have a port on which this grpc can be listened, in this example https and grpcs will use port 443.

So the working configuration for me is:

`server {
    listen 443 http2:
    server _name opc.org.com;
    ssl....;
    location / {
        resolver 127.0.0.11 valid=30s;
        set $https_webui https://dev_webui;
        proxy_pass $https_webui;
    }  
    location /App.Room.Api.Contract.ApiService/UpdateOpcDaTags {
        resolver 127.0.0.11 valid=30s;
        set $grpc_webui grpcs://dev_webui:443;
        grpc_pass $grpc_webui;
    }`

Interestingly, for proxy_pass port is not necessary to specify, I think due to the indication of https://

With this configuration, any stack that nginx maintains can be wiped out of the available stacks, and nginx will not send host not found in upstream message when restarted