Docker compose image upgrade - docker

Question

I have a docker-compose image running:
version: '2'
services:
db:
image: postgres:commit1
service:
image: service:commit1
ports:
- "3000:3000"
depends_on:
- db
The image has a tag of commit id of git. If anything changes in code, CI/CD pipeline runs and updates the image with latest commit id.
Now let's say I have images as:
postgres:commit2 and service:commit2.
What is the best procedure to update the images given the containers are running using commit1 in the compose file?
Do I need to update the images manually in compose and then:
docker-compose restart
And remove the other containers manually?
Is it the best way?

Answer 1

One way is to templatize your compose file and have a separate CI/CD step to generate a new file with the new image tags on every build.
For ex. -
// docker-compose.yml.template
version: '2'
services:
db:
image: postgres:{{ COMMIT_ID }}
service:
image: service:{{ COMMIT_ID }}
ports:
- "3000:3000"
depends_on:
- db
and a using sed or awk script you can replace {{ COMMIT_ID }} with the latest commit id and generate the new file.
// docker-compose.yml
version: '2'
services:
db:
image: postgres:commit2
service:
image: service:commit2
ports:
- "3000:3000"
depends_on:
- db
Then you can finally pull and use latest images using docker-compose pull && docker-compose up -d

Answer 2

I am assuming you are looking for some option to do rolling update with docker-compose and your service support multiple instances. This can be achieved by, first changing the image id in docker-compose file, you can use your CI/CD tool to create new docker-compose file with updated commit hash.
Then you can use below command add new containers(with new new image) behind the services.
docker-compose up --scale db=1 --scale service=1 --no-recreate
Then next step would be to delete the old containers
docker rm old-container # service
Then the last step would be to scale the services to the number of instances you want.
This is the best I can think of for just docker-compose. If you were using docker swarm or any other system it would have been out of box feature :)