Let's create a docker-compose.yml file :

touch docker-compose.yml

Inside this file we'll add the following (click on Copy to Editor):

version: '3'
services:
  ouroboros:
    container_name: ouroboros
    hostname: ouroboros
    image: pyouroboros/ouroboros
    environment:
      - CLEANUP=true
      - INTERVAL=45
      - LOG_LEVEL=info
      - SELF_UPDATE=true
      - TZ=Africa/Nairobi
    restart: unless-stopped
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock

Tips:

Let's verif that docker-compose.yml file.

docker-compose config

Details

In this configuration, we're pulling Ouroboros image from the official repo. image: pyouroboros/ouroboros

Next, we configure each update to remove old images CLEANUP=true.

We have configured updates to run after every 45 seconds INTERVAL=45

Timezone is set to Nairobi.

The variable SELF_UPDATE=true ensures that Ouroboros updates itself as well.

In the next session we'll try and spin up this image.

Read On!! :)

Let's start the container.

docker-compose up

Press CTRL+c twice to exit once it's up.

To run the container in the background, add the -d flag.

docker-compose up -d

Let's clean-up that file and start up a project.

Let's quickly clone a cool application that counts page views.

Let's clean up first rm -fr *

Close all open editors first to see the new changes.

git clone https://github.com/TheBeachMaster/updating-with-ouroboros.git .

Our cool application uses redis to store browser user agents and IPs.

Now let's start our application and view the app.

docker-compose up -d

Click on the View Page tab to see our application.

The application is visible here :

https://[[HOST_SUBDOMAIN]]-3080-[[KATACODA_HOST]].environments.katacoda.com

Open the app with different browsers and refresh to see the numbers change.

Now let's proceed and update our ouroboros.env to get Slack notifications after every update

Now, let's open ouroboros.env, remember that Slack token in the format https://hooks.slack.com/service/<TOKENA>/<TOKENB>/<TOKENC> ? yeah, that one, add the following line under line 27 :

NOTIFIERS="slack://TOKENA/TOKENB/TOKENC/#CHANNEL , replace the placeholders TOKENA,TOKENB,TOKENC,CHANNEL with their appropriate values.

Unfortunately, I will not be updating arthurkenotieno/site-counter-app as regularly, feel free to fork the repo like so to see changes.

However, we can bring down the instances to and bring them back up to simulate the update.

Let do that.

docker-compose down

Then bring them back up. Ensure you have updated the ouroboros.env file to see the changes.

docker-compose up -d

Head over to you configured Slack channel to see the update.

Now everytime any of the images are updated in the Docker registry, Ouroboros will update the runnig instances and send a notification to your Slack channel.