Allow concurrent deploys about kamal

[djmb]

We should also add the destination to the lock_dir.

Yes that seems sensible 👍

[igor-alexandrov]

@dorianmariecom I wrote about concurrent deploys in this article: https://igor.works/blog/evolution-of-github-action-for-kamal.

TL; DR; concurrency can be (and should be) achieved by using GitHub deployment groups with cancel-in-progress: true and if: ${{ cancelled() }} options.

[fredrikburmester]

We should also add the destination to the lock_dir.

Yes, I agree.

@igor-alexandrov

[wenderjean]

@dorianmariecom Just for the sake of curiosity, do you have a real use case for concurrent deploys? I can just imagine deploying different environments at the same time

[dorianmariecom]

For instance I deploy a first fix and it's deployed while the second fix is building then deployed

[morgoth]

that could get messed up. Imagine having long migration in the first one. It could happen that the second one finishes before the first one, which wouldn't be something you expect.

I think it would be better for you to cancel the first deploy and deploy only the next one.

[dorianmariecom]

I tried that but then if I make too many commits only the last one will get deployed

[djmb]

Just to confirm, is the issue that you are deploying from CI and the second deploy fails because the first is in progress?

Maybe we could add a setting to wait for the lock (with a timeout). Also relevant here is #455. If we remove the lock while building, then the lock won't be held for as long.

[dorianmariecom]

What's the issue with releasing the lock while a deploy is in progress? It seems like it works fine

[djmb]

Kamal deployments are not designed to work concurrently. There are many things that could go wrong if you ran two at the same time. If it works ok, that's by luck and not design!

[igor-alexandrov]

@djmb seems like the issue can be closed.

[fredrikburmester]

One use case would be two environments like -d staging and -d production. It would be nice to be able deploy these at the same time.

[igor-alexandrov]

@fredrikburmester, what is the use case for the simultaneous deployment of two environments?

[fredrikburmester]

@igor-alexandrov I have a production and staging environment, they have completely separate containers but run on the same server. Sometimes I have a change that I want to push to both branches, but then it'll run both my develop and main git workflows, triggering kamal deploy for both production and develop.

[igor-alexandrov]

@fredrikburmester OK, now I understand. Currently, Kamal includes only the service name in the lock file name: https://github.com/basecamp/kamal/blob/main/lib/kamal/commands/lock.rb#L44. This allows you to deploy different services to the same host simultaneously.

We should also add the destination to the lock_dir.

@djmb do you agree?