font-preview-service

A small Rust web service that will render font previews. It currently exposes a health endpoint and ships as a container image with the full Google Fonts and Noto font sets on disk.

Status: early scaffold. The only endpoint is GET /healthz. The font sets are packaged into the image, but the service does not read or render them yet.

Image

Published to Docker Hub as dylanmtaylorartcraft/font-preview-service.

• Built for linux/amd64 and linux/arm64, each on a native Ubuntu 26.04 runner, then merged into one multi-arch manifest.
• Builds on the Docker Hardened Images Rust images (dhi.io/rust). The runtime stage runs as a nonroot user.
• A single ENTRYPOINT runs the binary. Pass configuration through environment variables, not arguments.

Tags:

Trigger	Tags
Push to main	main, latest
Push of v* tag	semver tags (for example 1.2.3, 1.2)
Manual run	branch tag

Configuration

Variable	Default	Purpose
PORT	8000	TCP port the server binds on all interfaces. Keep it above 1024 for the nonroot runtime.
FONTS_DIR	/opt/fonts (image)	Location of the font sets inside the image. Set by the Dockerfile; the app does not read it yet.
FILES_CONCURRENCY	64	File downloads (/v1/files/...) sent at once. Bounds the memory that downloads hold.
FILES_QUEUE	16 × FILES_CONCURRENCY	Downloads that may wait up to 2 s for a slot; beyond that the server answers 503 with Retry-After.

Running

docker run --rm -p 8000:8000 dylanmtaylorartcraft/font-preview-service:latest
curl http://localhost:8000/healthz   # ok

Endpoints

Method	Path	Response
GET	/healthz	200 ok

Development

Requires a recent stable Rust toolchain (edition 2024).

cargo run                 # listens on :8000
cargo test
cargo fmt --check
cargo clippy --all-targets -- -D warnings

Fonts

The image includes these font sets, each with its licence files. CI fetches them at pinned upstream commits, so the repository does not store them.

Source	Pinned commit	Contents	Licence files
google/fonts	e7db6ca	ofl/, apache/, ufl/ families	Per-family licence files in each directory
notofonts/noto-fonts	ffebf8c	unhinted/ fonts	LICENSE
notofonts/noto-cjk	f8d1575	Sans/OTF/ fonts	LICENSE

The sets are large: about 7.3 GB of font files in total, which is why the image is large. Google Fonts families are licensed under the SIL Open Font License, Apache 2.0 and the Ubuntu Font License. Keep the licence files with the fonts when redistributing.

To change a pin, edit the *_SHA variables in the "Fetch font sources (pinned)" step of .github/workflows/docker-publish.yml.

CI

Workflow	Runs on	Does
docker-publish.yml	push to main, v* tags, manual	Fetches fonts, builds both architectures, pushes the multi-arch image.
sonar.yml	push to main, same-repo pull requests	Runs the shared SonarCloud scan from storytold/craft-common-actions.

Required repository secrets: DOCKERHUB_USERNAME, DOCKERHUB_TOKEN, SONAR_TOKEN.

Not yet implemented

• Reading the font files from FONTS_DIR.
• Rendering preview images or any font-related endpoints.
• Subsetting. The idea is to render only the glyphs needed for each preview string; this is not built.