Docker

spider new writes a Dockerfile and a .dockerignore at the root of the project.

Build and run

bash

docker build -t myapp .
docker run -p 3000:3000 myapp

The app listens on port 3000 inside the container.

.env is not copied into the image, so the settings in it have to be given when the container starts:

bash

docker run -p 3000:3000 --env-file .env myapp

An app with a login needs this: a release build refuses to sign anyone in without JWT_SECRET.

What the Dockerfile does

It has two stages.

The first builds the app. It downloads the official Zig release and checks it against its published checksum, installs the spider command, copies the project and runs:

bash

zig build -Doptimize=ReleaseSmall

The second is the image you run. It holds two things: the binary and the public folder. Templates are not copied, because a release build keeps them inside the binary.

What stays out of the image

The .dockerignore keeps .env, the SQLite database and your local build out of the build. Tailwind, the icons, htmx and Alpine are not in git either: the build downloads them again, for the image's own system.

Another port

The app reads the PORT variable:

bash

docker run -p 8080:8080 -e PORT=8080 myapp

The database

The app applies its migrations when it starts, so a new container has its tables on the first request.

With SQLite the data is a file inside the container, and it goes away with the container. To keep it, put the file in a volume:

bash

docker run -p 3000:3000 -v myapp-data:/data -e SQLITE_PATH=/data/db.sqlite myapp

PostgreSQL

A project created with --pg also gets a docker-compose.yml. It does not run the app: it starts a PostgreSQL server for development, on the port written in .env.

bash

docker compose up -d

A PostgreSQL project migrates when it starts, like any other. The same image can also migrate as a step of its own, before the new version starts: with SPIDER_MIGRATE set, the app applies the migrations and exits.

bash

docker run --rm --env-file .env -e SPIDER_MIGRATE=1 myapp

Migrations in production says when that is worth doing.