How do I scale my app (with a volume) to multiple instances?

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I just migrated my app kcd to the V2 platform and now I’m trying to scale things up. I read that fly scale count doesn’t yet work for apps with volumes and that I should use fly machine clone, but then that says that it creates a volume for you if the machine you’re cloning has one, but that:

It’s up to you to decide what to put on the new volume; fly machine clone will not automatically copy the contents of the original Machine’s volume.

This has me scratching my head. I have no idea how to do this. I think I don’t need to put anything in there because I’m using LiteFS which should handle that, but I don’t want to do anything until I’m sure. It’s definitely more work than I want it to be here. Can someone give me direction?

Honestly, I never really liked that with v1 you had to create volumes and then scale up. I would much rather a command that “does it all” with something like:

fly instance add --region ams

And it takes care of creating any necessary volumes etc. That would make the most sense to me.

1 Like
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Hi @kentcdodds

Scaling in in v2 apps should be roughly the same process. Create the volumes first then use the scale command.

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But it doesn’t work that way as I said

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What’s the error you’re getting?

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I’m pretty sure that I had all this working last month :slight_smile:

If I recall correctly, all I had to do was to ensure that I did not run migrations on the second instance.

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@charsleysa and @rubys, here’s what happens when I try to run fly scale count 2 on kcd which is a v2 app with a volume and LiteFS:

~/code/kentcdodds.com (main) 🤠
$ fly scale count 2
App 'kcd' is going to be scaled according to this plan:
  +1 machines for group 'app' on region 'den' with size 'shared-cpu-1x'
Error: 'fly scale count' can't scale up groups with mounts, use 'fly machine clone' to add machines for: app
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That’s what I did. I’m confident that scale with volumes will be supported at some point, but for now, clone the machine and litefs will populate the empty volume.

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That worked for me. Thanks!

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