blue-green-traefik-compose: A Shell repository from ervinb

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

ervinb/blue-green-traefik-compose