nginx: Send HTTP User Agent Requests To Specific Backend Server

To send HTTP requests with a specific user agent to a specific backend server in Nginx, you can use the map directive to define a mapping between user agent strings and backend servers. You can then use the $backend variable in the proxy_pass directive to pass the requests to the appropriate backend server.

Here is an example configuration that sends requests with a user agent of MobileBrowser to the backend1 server, and all other requests to the backend2 server:

map $http_user_agent $backend {
    MobileBrowser   backend1;
    default         backend2;
}

server {
    ...
    location / {
        proxy_pass http://$backend;
    }
    ...
}

This configuration defines a mapping between user agent strings and backend servers using the map directive. It then uses the $backend variable in the proxy_pass directive to pass the requests to the appropriate backend server based on the user agent string.

You can add multiple entries to the map directive to send requests with different user agent strings to different backend servers. For example:

map $http_user_agent $backend {
    MobileBrowser   backend1;
    Chrome          backend2;
    Firefox         backend3;
    default         backend4;
}

This configuration sends requests with a user agent of MobileBrowser to the backend1 server, requests with a user agent of Chrome to the backend2 server, requests with a user agent of Firefox to the backend3 server, and all other requests to the backend4 server.

You can refer to the Nginx documentation for more information on the map directive and using variables in the proxy_pass directive.