Font cacher

With the advancements of HTTP2 it can be beneficial to route all assets, including fonts, through ones own domain. This saves additional round trips to establish new connections to the font hosting. Additionally it allows to initiate a HTTP2 server push directly, reducing the time for all critical CSS to be received by the browser.

This project aims to include just that, by allowing to an internal service which simply proxies (and caches) Google Fonts.

Features

• Exact Google Fonts proxy: Only need to change the domain name in your application
• HTTP2 Push: Directly push the requested font files as part of the stream to further reduce latency
• Configurable cache size: Determine the number of CSS files and font files saved in the cache
• Memory friendly: We have seen cases where with a cache hit ratio of 95%+, only 50MB per instance is required.
• Cloud-friendly: Use Consul to register your instances
• HTTP API: Request memory usage and cache statistics through a HTTP JSON API.

Configuration

The system is configured using environment variables.

Key	Description
MAX_CSS_ENTRIES	The maximum number of CSS entries to cache. Default 10000.
MAX_FONT_ENTRIES	The maximum number of font entries to cache. Default 1000. The same number is used for font kits
CSS_CACHE_CONTROL	The value of the Cache-control header for all CSS responses. If not set, the upstream value will be used.
FONT_CACHE_CONTROL	The value of the Cache-control header for all font responses. If not set, the upstream value will be used. The same value is used for font kits
PUBLIC_URL	Public URL of access the fonts. Default http://localhost:3000/font/.

In the URL you can specify the exact same parameters as Google Fonts. One additional feature is available: by specifying a query param noPush the linked font files will not be pushed to the client.

You can request instance statistic from the following URLs:

• _stats/css: Cache statistics for the CSS cache
• _stats/font: Cache statistics for the font cache
• _stats/fontKit: Cache statistics for the font cache
• _stats/memory: Statistics about the instance memory usage

Quick start

1. Start a Docker container docker run -e PUBLIC_URL="https://yourdomain.com/fonts" -p 3000:3000 rogierslag/font-cacher
2. Configure your application or load balancer to proxy its /fonts directory to the started Docker container.
3. Search for the following line https://fonts.googleapis.com/css and replace it with https://yourdomain.com/fonts/css. Leave the query string untouched.
4. Visit your application: the fonts will have gone through the proxy.

To further improve performance, you can set the following flag in nginx to automatically push the resources as well http2_push_preload on;

Blog

I blogged about this service on https://medium.com/@Rogier.Slag/nailing-ux-with-fast-font-delivery-446693db7a59?sk=d71b6138294620628826f04b141041ac