A small agent deploys apps

Context

The dashboard on the ops server has to start, update and remove apps on the apps server. Alternatives were SSH from the dashboard (a compromised dashboard is root on the apps server) and GitOps through GitHub Actions (slower, and the dashboard needs a GitHub token).

Decision

A small HTTP service, the agent, runs on the apps server, listens only on the private network and requires a token. It writes each app's compose file and Caddy site block and runs docker. The dashboard never holds SSH credentials.

Consequences

• The agent mounts the Docker socket, so it is effectively root on the apps server; the private-network binding and the token are what protect it.
• The agent's API is the one place that defines what a deploy is.