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jsonnet-libs / k8s

Code generator for Jsonnet Kubernetes libraries.

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Can't create a deployment without specifying replicas

hairyhenderson opened this issue · comments

commented

Currently if we create a deployment with this lib we're forced to have the replicas field set to 1 by default (or a specified integer), because of this line: https://github.com/jsonnet-libs/k8s-libsonnet/blob/main/1.21/_custom/apps.libsonnet#L37

However, when using an HPA and Flux, we're ending up with Flux constantly resetting our replica count back to this setting every time the HPA decides to scale out. See this FAQ in the Flux docs for some details.

I'm not entirely sure how to fix this in a non-breaking way, but it seems that being able to set a null value might be reasonable...

commented

Currently if we create a deployment with this lib we're forced to have the replicas field set to 1 by default (or a specified integer), because of this line: https://github.com/jsonnet-libs/k8s-libsonnet/blob/main/1.21/_custom/apps.libsonnet#L37

However, when using an HPA and Flux, we're ending up with Flux constantly resetting our replica count back to this setting every time the HPA decides to scale out. See this FAQ in the Flux docs for some details.

I'm not entirely sure how to fix this in a non-breaking way, but it seems that being able to set a null value might be reasonable...

From what I remember, if using an HPA, you have to hide the replicas. Example:

deployment.new(...) + {
    spec+: {
      // Hide the replica attribute so it's not output anymore
      replicas:: super.replicas,
   }
}

This is not supported in the lib obviously, but it's a workaround

commented

Ah, interesting. Thanks @julienduchesne! It'd obviously be nice to bake this into the lib somehow too...

commented

@hairyhenderson we are doing the same as @julienduchesne suggested. Do you have suggestions for the UX workflow?

commented

Do you have suggestions for the UX workflow?

Just what I suggested in the description:

it seems that being able to set a null value might be reasonable...

commented

actually makes sense for me. @hairyhenderson feel free to create a PR!