Deploy services by dependency tree order instead of lexicographical order

[vladkucherov]

Hey,

The documentation states:

Services are updated in lexicographical order (by Unicode code point),
regardless of dependencies.

I see this is intentional, but could you please add an ability to deploy containers by dependency order.

For example, for the following docker-compose file:

services:
  website-frontend-react:
    ...
  website-backend-tasks:
    ...
  website-backend-service:
    ...
    deploy:
      replicas: 2
      update_config:
        parallelism: 1
        order: start-first
        failure_action: rollback
        delay: 20s
    depends_on:
      - website-backend-tasks

The deploy order if in lexicographic order would be:

1. website-frontend-react
2. website-backend-service
3. website-backend-tasks

In my case, it's an issue because the thing website-backend-tasks do is run db migrations. So it prepares the DB before the new website-backend-service can boot, because if it would boot before the migrations, it would run on new queries but the db is not prepared.

Also, as a side effect of the new website-backend-service container running new queries without migrations, it's not healthy, so the deployment fails, which prevents it from continuing to the next service, which in my case is the one they would fix everything, but the deployment stopped.

So without Kerek considering the depends_on, it's harder to make it work with this kind of architecture.

Can someone please add this ability?

[evolutics]

Thanks for reporting this issue. Yeah, this is an intentional simplification.

Unfortunately, I currently don't have much capacity to work on respecting dependencies.

As a workaround, you could rename your services to match the desired order.

[vladkucherov]

Thank you!

If we could have an option to pass service names manually, and the order of the names would be used, that could be useful and not very complicated.

for example:

kerek deploy website-frontend-service website-backend-tasks website-backend-service --no-deps

WDYT?

[evolutics]

You could do one separate call per service like so:

kerek deploy website-frontend-service --no-deps
kerek deploy website-backend-tasks --no-deps
kerek deploy website-backend-service --no-deps

I know it's clumsy, I'm sorry, but that's your best best for now.

[vladkucherov]

That could work, but Kerek doesn't support docker-compose flag --no-deps. It throws this error:

error: unexpected argument '--no-deps' found

  tip: to pass '--no-deps' as a value, use '-- --no-deps'

Usage: kerek deploy <--all-resources|--ansi <ANSI>|--compatibility|--env-file <ENV_FILE>|--file <FILE>|--parallel <PARALLEL>|--profile <PROFILE>|--progress <PROGRESS>|--project-directory <PROJECT_DIRECTORY>|--project-name <PROJECT_NAME>> <--build|--force-recreate|--no-build|--no-start|--pull <PULL>|--quiet-pull|--remove-orphans|--renew-anon-volumes|--timeout <TIMEOUT>|--wait|--wait-timeout <WAIT_TIMEOUT>> <SERVICE_NAMES>...

For more information, try '--help'.

[evolutics]

You're right, of course, option --no-deps doesn't exist as services are updated without dependencies anyway. It works without options.

[vladkucherov]

Yes it doesn't support --no-deps, but I am not sure you're right, deploying a single service would also deploy it's dependencies

for this docker compose:

services:
  mysql:
    ...
  rabbitmq:
    ...
  website-frontend-react:
    ...
  website-backend-tasks:
    ...
  website-backend-service:
    ...
    deploy:
      replicas: 2
      update_config:
        parallelism: 1
        order: start-first
        failure_action: rollback
        delay: 20s
    depends_on:
      - website-backend-tasks
      - mysql
      - rabbitmq

kerek deploy website-backend-service`

kerek deploys:

• website-backend-tasks
• db
• rabbitmq
• website-backend-service

instead of only website-backend-service

[evolutics]

Oh, that's a bug indeed.

I've just fixed that: --no-deps is now supported to ignore any dependencies. It's available in the latest version 2.1.0.

Please try again using --no-deps. Thanks.

[vladkucherov]

@evolutics Thanks! --no-deps works great.

Now I can deploy a single container (with its replicas) with my order.

📖 How I manually control the deploy order

For the above docker-compose yaml

I run:

####
# Run kerek for only the services that should be gradually deployed
####
kerek deploy -f $FILE website-backend-tasks --no-deps --wait
kerek deploy -f $FILE website-backend-service --no-deps --wait
kerek deploy -f $FILE website-frontend-service --no-deps --wait

####
# Finally run docker compose to make sure all the other services are up and aligned to latest version/config
####
docker compose -f $FILE up -d --no-deps