Caching assets and media

The Cache-Control header is manually set to merge the values from the configuration and the expires directive to avoid breakage from having two header lines. Header set defaults to onsuccess, so it is also not added to error responses.

Assuming your GtS installation is rooted in /opt/GtS with a storage subdirectory, and the webserver has been given access, add the following section to the vhost:

<Directory /opt/GtS/web/assets>
    Options None
    AllowOverride None
    Require all granted
    ExpiresActive on
    ExpiresDefault A300
    Header set Cache-Control "public, max-age=300"
</Directory>
RewriteRule "^/assets/(.*)$" "/opt/GtS/web/assets/$1" [L]

<Directory /opt/GtS/storage>
    Options None
    AllowOverride None
    Require all granted
    ExpiresActive on
    ExpiresDefault A604800
    Header set Cache-Control "private, immutable, max-age=604800"
</Directory>
RewriteCond "/opt/GtS/storage/$1" -f
RewriteRule "^/fileserver/(.*)$" "/opt/GtS/storage/$1" [L]

The trick here is that, in an Apache 2-based reverse proxy setup…

RewriteEngine On

RewriteCond %{HTTP:Upgrade} websocket [NC]
RewriteCond %{HTTP:Connection} upgrade [NC]
RewriteRule ^/?(.*) "ws://localhost:8980/$1" [P,L]

ProxyIOBufferSize 65536
ProxyTimeout 120

ProxyPreserveHost On
<Location "/">
    ProxyPass http://127.0.0.1:8980/
    ProxyPassReverse http://127.0.0.1:8980/
</Location>

… everything is proxied by default, the RewriteRule bypasses the proxy (by specifying a filesystem path to redirect to) for specific URL præficēs and the RewriteCond ensures to only disable the /fileserver/ proxy if the file is, indeed, present.

Also run the following commands (assuming a Debian-like setup) to enable the modules used:

$ sudo a2enmod expires
$ sudo a2enmod headers
$ sudo a2enmod rewrite

Then (after a configtest), restart Apache.

Here's an example of the three location blocks you'll need to add to your existing configuration in nginx:

server {
server_name social.example.org;

location /assets/ {
    alias web-asset-base-dir/;
    autoindex off;
    expires 5m;
    add_header Cache-Control "public";
}

location @fileserver {
    proxy_pass http://localhost:8080;
    proxy_set_header Host $host;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_set_header X-Forwarded-For $remote_addr;
    proxy_set_header X-Forwarded-Proto $scheme;
}

location /fileserver/ {
    alias storage-local-base-path/;
    autoindex off;
    expires 1w;
    add_header Cache-Control "private, immutable";
    try_files $uri @fileserver;
}
}

The /fileserver location is a bit special. When we fail to fetch the media from disk, we want to proxy the request on to GoToSocial so it can try and fetch it. The try_files directive can't take a proxy_pass itself so instead we created the named @fileserver location that we pass in last to try_files.

The expires directive adds the necessary headers to inform the client how long it may cache the resource:

• For assets, which may change on each release, 5 minutes is used in this example
• For attachments, which should never change once they're created, we currently use one week

For other options, see the nginx documentation on the expires directive.

Nginx does not add cache headers to 4xx or 5xx response codes so a failure to fetch an asset won't get cached by clients. The autoindex off directive tells nginx to not serve a directory listing. This should be the default but it doesn't hurt to be explicit. The added add_header lines set additional options for the Cache-Control header:

• public is used to indicate that anyone may cache this resource
• immutable is used to indicate this resource will never change while it is fresh (it's before the end of the expires) allowing clients to forgo conditional requests to revalidate the resource during that timespan.