Configuration

All configuration comes from environment variables, read once at startup by internal/config. Invalid configuration stops the process with a message listing every problem.

Variable	Required	Default	Description
`BASE_URL`	yes		Public URL of this service. Used to build links in emails. Trailing slash is trimmed
`SITE_URL`	yes		Origin of the static site, for example `https://example.com`. Used as the CORS origin and as the redirect target. No path
`TOKEN_SECRET`	yes		HMAC key, at least 32 bytes. Generate with `openssl rand -hex 32`
`PORT`	no	`8080`	Listen port. Cloud Run sets this for you
`LISTS`	no	`newsletter`	Comma-separated allow-list of list names
`FIRESTORE_PROJECT`	no		GCP project ID. Unset means an in-memory store (data lost on restart)
`SMTP_HOST`	no		SMTP server. Unset means emails are only logged
`SMTP_PORT`	no	`587`	SMTP port (STARTTLS)
`SMTP_USER`	with `SMTP_HOST`		SMTP username, usually the mailbox address
`SMTP_PASSWORD`	with `SMTP_HOST`		SMTP password or app password
`MAIL_FROM`	with `SMTP_HOST`		From address, for example `news@example.com`

Behaviour by combination

`FIRESTORE_PROJECT`	`SMTP_HOST`	Result
unset	unset	Local development: in-memory data, emails in the log
set	unset	Real storage, emails still only logged (useful for staging)
unset	set	Real emails, data lost on restart (do not use in production)
set	set	Production

Firestore credentials come from Application Default Credentials: the Cloud Run service account in production, or gcloud auth application-default login on a workstation. FIRESTORE_EMULATOR_HOST redirects the client to the emulator.

Secrets

Treat TOKEN_SECRET and SMTP_PASSWORD as secrets: keep them out of the image, the repository and shell history. In production use Secret Manager (see Deployment).

Example

BASE_URL=https://api.example.com
SITE_URL=https://example.com
LISTS=newsletter,events
FIRESTORE_PROJECT=my-gcp-project
SMTP_HOST=smtp.gmail.com
SMTP_USER=news@example.com
MAIL_FROM=news@example.com
# TOKEN_SECRET and SMTP_PASSWORD come from Secret Manager