what url hostname to use in front-end app downstream from nginx proxy

Question

I'm a newb, don't know much about nginx and how it interacts with frontend. I tried searching SO and Google, but I dont think I know the keywords to get good hits. This site is somewhat related, but couldn't solve my issue from it: basic setup. I have been looking for hours and nothing related to what I am inquiring about. What url string do I need to use in order for the front-end application (shinyR) can reach any of the (flask) back-end API servers? Prior to have 2 API servers, I would simply use the docker container name, like: pyapi:5000/post for post request. Within my nginx.conf file, I set up 2x api servers. So, how can it be load-balanced from the point of view of the front-end app? From host, I can type in localhost:1889 and it will round-robin select from my two API servers. But I want it to do the same from within the front-end app. Here is my nginx.conf I took the example from example:

# declare flask app
upstream pyapi_app {
    least_conn;
    server pyapi1:5000;
    server pyapi2:5000;
}

# declare shiny app
upstream shiny_app {
    server shinyapp:3838;
}

map $http_upgrade $connection_upgrade {
    default upgrade;
    '' close;
}

# shinyapp server
server {
    listen 80 default_server;
    server_name shiny_app;

    client_max_body_size 50M;
    # normal requests go to shiny app
    location / {
        proxy_pass http://shiny_app;
        proxy_redirect off;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Host $server_name;

        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection $connection_upgrade;

        proxy_read_timeout 5d;
        proxy_buffering off;
    }

}

# python api server
server {
    listen 81;
    server_name pyapi_app;

    # pyapi requests go to the flask app
    location / {

        proxy_pass http://pyapi_app;
        proxy_redirect off;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Host $server_name;

    }
}

question from:https://stackoverflow.com/questions/65894105/what-url-hostname-to-use-in-front-end-app-downstream-from-nginx-proxy

Answer 1

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