ervinb/blue-green-traefik-compose

Blue/Green Deployment POC with Traefik and Docker Compose

• Setup
  • Host
  • Toolchain
• Start
• Deployment
• Testing
• Troubleshooting
  • Proxy doesn't get updated

Setup

The scripts in this repository rely on the following tools being present in the environment:

• curl
• jq
• docker
• docker-compose
• ab
• envsubst

Set up the tools on the host or use the included toolchain Docker image.

Host

Install the required tools on the host machine:

$ apt update -qq
$ apt install apache2-utils curl jq gettext-base docker docker-compose

Toolchain

Alternatively, use a Docker container to run the scripts:

$ docker build -t bg-toolchain -f Dockerfile.toolchain .
$ docker run --rm --net host -ti -v /var/run/docker.sock:/var/run/docker.sock -v $(pwd):/workspace bg-toolchain
$$ <run scripts>

Start

$ docker-compose up -d

NOTE: This should be executed on the host and not in the toolchain container. Otherwise, the command will fail with traefik error: read /etc/traefik/traefik.yml: is a directory because the source path is on the host and not in the toolchain container, so it mounts it as a directory.

The command will start up the proxy (traefik) and 2 instances of the sample application (blue, green). Initially both versions have the same content and use the same Docker image.

---

Traefik dashboard: http://localhost:8080

Query the application endpoint:

$ curl -L -H 'Host: docker.localhost' http://localhost:8090
> INITIAL STATE

Deployment

• Change the application content in app/index.html:

  $ date > app/index.html
  

• Deploy the change:

  $ ./deploy.sh
  

  Running the deployment process:

  • builds a new application image (including the change from the previous step)
  • recreates the inactive (blue or green) container using the new image
  • updates the proxy to route to this new instance

• Query the application endpoint:

  $ curl -L -H 'Host: docker.localhost' http://localhost:8090
  > Tue Feb 20 11:36:33 CET 2022
  

Testing

To verify a no-downtime deployment process, run:

$ ./test.sh

This will:

• make a GET request to the application endpoint and print the result
• start the ab benchmark, hitting the application endpoint
• introduce a change in the application
• build and deploy the new container
• perform another GET request to show the updated content
• print the report

Troubleshooting

Proxy doesn't get updated

The update process (and traefik's file provider) relies on inotofy events. Running the components where Docker is in a VM (like on a Mac, Docker Desktop for Mac is an exception) does not properly propagate inotify events. See: moby/moby#18246

The proposed solution is to use https://github.com/sillypog/inotify-proxy