Docker Compose Blue-Green: Health Check, Switch, Drain

Fri, 11 Sep 2026 05:00:00 +0800

A Docker Compose blue-green deployment on one server starts the candidate, waits until the app is ready, validates and switches the Caddy upstream, proves the public hostname, drains old connections, then stops the old version. Do not delete the old container before the candidate is taking traffic.

That sequence can shrink the unavailable window. The host, disk, Docker daemon, and shared database are still single points of failure, so measure the window instead of calling the result zero downtime.

The gateway switch is the only public cutover. Candidate startup and warmup happen before that switch.

Docker Compose blue-green only works under these constraints

Run two app instances on one host only when the service meets all of these conditions:

OneDev Tutorial: Docker Compose, Git, and CI/CD on One Server

Fri, 11 Sep 2026 04:24:00 +0800

A OneDev tutorial starts with one instance that can host Git, review, issues, CI/CD, artifacts, and packages. Keep code on a server you operate, and skip running a separate Git service, CI, and package registry, when that trade-off is worth the ops work. The official single-node baseline is also lower than full GitLab.

The environment is one 64-bit Linux host: OneDev and PostgreSQL run under Docker Compose, and Caddy terminates HTTPS. After the instance is ready, create a Go project and prove push, tests, image build, production deploy, backup, restore, and upgrade. A container in running is not enough. The repository, Git SSH, the pipeline, and restore still have to work.

Docker Compose on StackOnward

Docker Compose Blue-Green: Health Check, Switch, Drain

Docker Compose blue-green only works under these constraints

OneDev Tutorial: Docker Compose, Git, and CI/CD on One Server