Nginx reverse proxy config for Planka with a URL prefix

planka_snippet.conf

# In your docker-compose.yaml, set 
# - BASE_URL=https://myhost.com
# with no port and no URL prefix.
  
  location ^~ /planka {

    # Set proxy headers
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $host;

    # Define upstream address
    set $upstream_app planka;
    proxy_pass http://$upstream_app:1337; # NO TRAILING SLASH

    # Remove /planka path to pass to the app
    rewrite ^/planka/planka/planka/?(.*)$ /$1 break;
    rewrite ^/planka/planka/?(.*)$ /$1 break;
    rewrite ^/planka/?(.*)$ /$1 break;

    # Sub filters to replace hardcoded paths
    proxy_set_header Accept-Encoding "";
    sub_filter_once off;
    sub_filter_types *;
    sub_filter 'href="/"' 'href="/$upstream_app"';
    sub_filter '/planka/planka/static/' '/$upstream_app/static/';
    sub_filter '/static/' '/$upstream_app/static/';
    sub_filter '://$host' '://$host/planka';
    
    sub_filter '/favicon' '/$upstream_app/favicon';
    sub_filter '/manifest.json' '/$upstream_app/manifest.json';

  }