HTTP Stack

A couple hundred users per host, a few domains each, security headers, HTTPS with let's encrypt, websocket, pass-through, web backends, htaccess.. at some point a web setup reaches a point, when there are too many feature to handle them all with just one web server software. That's why we're employing two of them back-to-back: caddy and Apache httpd.

                 _
               (`  ).
              (     ).                 .-------.        .-------.
             _(       '`.  ----------> | caddy | -----> | httpd |
         .=(`( Internet )              '-------'        '-------'
         ((    (..__.:'-'                  |                => php (via php-fpm)
         `(       ) )                      |                => static files
           ` __.:'   )                     |                => .htaccess
               a:f--'                      |
                                           |            .--------------.
                                           '----------> | Web Backends |
                                                        '--------------'
                                                            => nodejs, python, ruby, ...
                                                            => gogs, mattermost, matrix, ...

caddy

caddy handles all the nitty gritty of accepting requests from browsers, making sure HTTPS works properly and passing requests through to configured web backends to serve apps based on rust, python, ruby, etc. It also connects to apache for more traditional web development needs, like php/wordpress.

Within caddy each user domain gets their very own config block. On a fresh asteroid, it might look like this:

[isabell@moondust ~]# cat /readonly/marie/caddy.conf
# Written by `generator-caddy` for Asteroid `isabell`,
# with these domains: isabell.uber.space.

isabell.uber.space {
  root /var/www/virtual/isabell/html
  import logs isabell

  tls {
    on_demand
  }

  handle `/*` {
    reverse_proxy localhost:81 {}
  }
}

By default, this block only contains a simple reverse_proxy statement processing all requests the same way: send everything to Apache httpd and report back whatever it said.

This configuration can be extended using uberspace web backend set <web-backends> commands.

[isabell@moondust ~]$ uberspace web backend set /etherpad-lite --http --port 51922
Set backend for /etherpad-lite to port 51922; please make sure something is listening!
You can always check the status of your backend using "uberspace web backend list".
[isabell@moondust ~]# cat /readonly/isabell/caddy.conf
# Written by `generator-caddy` for Asteroid `isabell`,
# with these domains: isabell.uber.space.

isabell.uber.space {
  root /var/www/virtual/marie/html
  import logs isabell

  tls {
    on_demand
  }

  handle `/*` {
    reverse_proxy localhost:81 {}
  }

  handle `/etherpad-lite/*` {
    reverse_proxy `100.64.9.2:51922` {}
  }
}

The original configuration has now been extended with a new handle/reverse_proxy section. By default, all requests are still routed to Apache, but requests intended for etherpad are passed onto the service directly. This enables you to get the direct, raw HTTP traffic - including the original headers and WebSocket connections.

The curious 100.64.9.2 IP address above is due to our networking setup. Feel free to read up on it, if you'd like to know more!

Other backend types like --apache or ones specific to a domain work in a very similar way. They are documented over in the web backends article.

Apache httpd

Apache serves requests for more traditional development needs like PHP and applications requiring .htaccess files. As you saw in the above examples, it is reverse proxied using caddy - just like other web backends. Since we try to handle as much as possible within caddy, which makes our httpd configuration rather short:

[isabell@moondust ~]$ cat /etc/httpd/user.d/dbcheck.conf
<Directory /var/www/virtual/dbcheck>
AllowOverride AuthConfig FileInfo Indexes Limit Options=ExecCGI,Includes,Indexes,MultiViews,SymLinksIfOwnerMatch
Options +Includes
</Directory>

<VirtualHost *>
ServerName dbcheck.uber.space
SuexecUserGroup dbcheck dbcheck
DocumentRoot /var/www/virtual/dbcheck/html

(...)

<FilesMatch "\.php$">
    SetHandler  "proxy:unix:/run/php-fpm-dbcheck.sock|fcgi://php-fpm-dbcheck"
</FilesMatch>
<Proxy "fcgi://php-fpm-dbcheck" max=10></Proxy>
</VirtualHost>

As mentioned earlier httpd only handles .htaccess (=> AllowOverride), static files (=> DocumentRoot) and PHP (=> SetHandler). Since all of those are rather ordinary duties for httpd, the configuration is rather simple in this case. Additionally, since everything else is handled within caddy, the only dynamic parts of this configuration is the list of domains in ServerName

• and the username, of course.

Some probably noticed that static files are handled within httpd, instead of caddy. Even though caddy easily outperforms httpd when it comes to serving static files, we need to use httpd in this case. Many applications like wordpress rely on .htaccess files to rewrite URLs or protect certain directories from being accessed. Since those files can only be parsed by httpd, caddy does not qualify for the job.

We may change this in the future in a backwards-compatible way.

Acknowledgements

The ASCII art cloud has been copied from asciiart.eu. The artist goes by the name a:f. Thank you!