Nginx 502 when serving error page content?

Question

I\'ve been setting up Nginx as a reverse proxy for an app on the server. Part of this includes a maintenance page that has external content (like images). I was able to find a m

Answer 1

You shouldn't need to involve the backend (I.E., shouldn't use proxy pass) since your maintenance page should be a static html file that Nginx can serve directly.

Assuming you have a setup configured as ...

server {
    listen 80;
    server_name example.com;
    root /path/to/webroot;


    # Regular locations etc
    ...
}

Create a folder called "503_status" and put your maintenance page in there as "503.html".

With that in place, create a file called "maintenance.default" under the Nginx directory with the following content ...

error_page 503 /503_status/503.html;

# Candidate for redirection if not ending with one of these extensions.
if ( $request_uri !~ \.(jpg|gif|png|css|js)$ ) {
     set $maint  "Tr";
}
# Candidate for redirection if not a request for the maintenance page 
if ( $request_uri !~ ^/maintenance/$ ) {
    set $maint  "${maint}ue";
}
# Redirect to a location where the status code will be issued 
if ( $maint = True ) {
    rewrite ^ /maintenance/ redirect;
}
# Due to Nginx quirk, issue the status code in a location context.
# Make "internal" to prevent direct browsing.
location /maintenance {
    internal;
    return 503;
}
# 503_status folder as "internal" so no direct browsing 
location 503_status {
    internal;
    alias /server/path/to/503_status/folder;
}

Whenever you put to put the site into maintenance, just include the file as follows ...

server {
    listen 80;
    server_name example.com;
    root /path/to/webroot;

    include /server/path/to/maintenance.default;        

    # Regular locations etc
    ...
}

This will serve your maintenance page as well as any resources it needs (just make sure extension is in the list). The backend server does not come into play at all.