Configure base URL for API schema

[machristie]

Provide a setting in settings.py that can be specified with an environment variable that will set the base URL for the API schema. This is needed when the API is behind a proxying web server that changes its path prefix, for example, for launch.usegalaxy.org.

See http://www.django-rest-framework.org/api-guide/schemas/#url

See also CloudVE/cloudlaunch-cli#6 which depends on this issue.

See also DRF issue: https://github.com/encode/django-rest-framework/issues/5788. DRF doesn't take SCRIPT_NAME into account when generating schema urls, it's expected behavior however and one needs to pass the base URL to the schema generator.

[machristie]

@nuwang Is it okay if I work on this one, or have you already started on this?

[nuwang]

@machristie Sure, that'd be great!

[machristie]

Tested this with following nginx.conf config running locally on my laptop:

# user  nginx;
worker_processes  1;

# error_log  /var/log/nginx/error.log warn;
# pid        /var/run/nginx.pid;


events {
    worker_connections  1024;
}



http {
    # include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    # access_log  /var/log/nginx/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

    #gzip  on;

    # include /etc/nginx/conf.d/*.conf;

    upstream cloudlaunch_server {
      # fail_timeout=0 means we always retry an upstream even if it failed
      # to return a good HTTP response (in case the Unicorn master nukes a
      # single worker for timing out).
      server 127.0.0.1:8000 fail_timeout=0;
    }
    
    server {
        listen *:8888;
        server_name localhost;
        
        location /cloudlaunch {
            # an HTTP header important enough to have its own Wikipedia entry:
            #   http://en.wikipedia.org/wiki/X-Forwarded-For
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header SCRIPT_NAME /cloudlaunch;

            # enable this if and only if you use HTTPS, this helps Rack
            # set the proper protocol for doing redirects:
            # proxy_set_header X-Forwarded-Proto https;

            # pass the Host: header from the client right along so redirects
            # can be set properly within the Rack application
            proxy_set_header Host $http_host;

            # we don't want nginx trying to do something clever with
            # redirects, we set the Host: header above already.
            proxy_redirect off;

            # set "proxy_buffering off" *only* for Rainbows! when doing
            # Comet/long-poll stuff.  It's also safe to set if you're
            # using only serving fast clients with Unicorn + nginx.
            # Otherwise you _want_ nginx to buffer responses to slow
            # clients, really.
            # proxy_buffering off;

            # Try to serve static files from nginx, no point in making an
            # *application* server like Unicorn/Rainbows! serve static files.

            if (!-f $request_filename) {
                proxy_pass http://cloudlaunch_server;
                break;
            }
        }
    }
}

Then I ran it with:

nginx -c $PWD/nginx/nginx-local.conf -g "daemon off;"

I then started cloudlaunch locally with

CLOUDLAUNCH_PATH_PREFIX='/cloudlaunch' python manage.py runserver

And now I get the desired effect when I browse the schema.