Ouroboros is an automation engine that updates running Docker containers with the latest image from a specified contaner registry.

The updated containers will preserve all parameters and tags as the previously run container.

version: '3'
services:
  ouroboros:
    container_name: ouroboros
    hostname: ouroboros
    image: pyouroboros/ouroboros
    environment:
      - CLEANUP=true
      - INTERVAL=300
      - LOG_LEVEL=info
      - SELF_UPDATE=true
      - IGNORE=mongo influxdb postgres mariadb
      - TZ=America/Chicago
    restart: unless-stopped
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock

Ouroboros is no longer maintained, see more

Benefits

Updating containers enables :

quick and easy patching of security vulnerabilities
quick update running applications
customization of images to suit business needs

Getting Started with Ouroboros

Scenario

In this post we have built a simple site visit counter , that saves unique page visits in Redis under the key visits.

The visits key contains the browser user agent and the ip .

The visits counter can be reset by going to the /reset route of the application.

Architecture

The application architecure is as shown below.

graph LR subgraph docker subgraph app logic-->keys end subgraph redis keys-.->db end subgraph ouroboros update-->notify update-.->logic end end subgraph webhook notify-.->message message end

Configuration

Slack

We’ll be using Slack to manage notifications. Anytime a container is updated we’ll receive a notification in a specified channel.

In this case we’ll configure an incoming webhook. To do so create a free workspace, or use an existing workspace.

Use this link to create a webhook.

Create incoming webhook

Next assign a workspace channel that will be receiving the messages.

Add channel “Assign a channel

You’ll get a webhook channel in the format https://hooks.slack.com/service/<TOKENA>/<TOKENB>/<TOKENC> .

Webhook URL

That’s it.

You can add an icon if you need to.

Ouroboros

As we’ll be running Ourboros as a Docker container we’ll pass all the environment variables in an ouroboros.env file.

Possible Env variables can be found here

	# Auto Update Ourbororos see -> https://github.com/pyouroboros/ouroboros/wiki/Usage#self-update
	SELF_UPDATE=true

	# Update the Application only works like Ignore
	#MONITOR="arthurkenotieno/site-counter-app"

	# Set Update interval seconds
	INTERVAL=180

	# Ignore Redis
	IGNORE="redis"

	# Remove old images after update
	CLEANUP=true

	# Use the latest tag
	LATEST=true

	# If pulling from a secure repository :
	#REPO_USER=myusername
	#REPO_PASS=mypass

	# Send notitifcations to Slack
	# See Apprise options -> https://github.com/caronc/apprise
	# Slack -> https://github.com/caronc/apprise/wiki/Notify_slack
	# Create an Incoming webhook -> https://my.slack.com/services/new/incoming-webhook/
	##NOTIFIERS="slack://{TOKENA}/{TOKENB}/{TOKENC}/#{CHANNEL}"

view raw .env hosted with ❤ by GitHub

Deploying

In this sample we’ll be using docker-compose to deploy our service therefore we wrote a docker-compose.yml to deploy our application, and bring up Ouroboros with our desired configurations.

	version: '2.1'

	services:
	site-counter-app:
	container_name: sitecounter
	image: arthurkenotieno/site-counter-app
	environment:
	NODE_ENV: production
	REDIS_URL: redis://cache
	ports:
	- 3080:3080
	depends_on:
	- redis

	redis:
	image: redis:latest
	container_name: redisdb
	ports:
	- 6379:6379

	ouroboros:
	container_name: ouroboros
	image: pyouroboros/ouroboros
	env_file: ./ouroboros.env
	volumes:
	- /var/run/docker.sock:/var/run/docker.sock

view raw docker-compose.yml hosted with ❤ by GitHub

For multiple sockets/hosts set a space separated list of DOCKER_SOCKETS in your environment file. Learn More

Learn how to push your images to Docker registry {% post_link devops-with-bitbucket-pipelines ‘using Bitbucket pipelines’ %}.

Every update will push a notification to Slack, you can disable startup notifcations by setting SKIP_STARTUP_NOTIFICATIONS in the environment file to True.

Slack Notifications

Katacoda

Here’s an interactive tutorial to get you up and running with Ouroboros :

Katacoda scenario

References

Use this example application hosted on github
Refer to Ouroboros wiki

Updating Docker Containers With Ouroboros