Drop the DataChain install flags from the Studio chart

[0x2b3bfa0]

Companion to https://github.com/datachain-ai/studio/pull/13122, itself a follow-up to https://github.com/datachain-ai/studio/pull/13096#issuecomment-5138512887. Being released in parallel.

The ConfigMap keys

DATACHAIN_ENABLED has had no reader since datachain-ai/studio#13096 merged. datachain-ai/studio#13122 removes the last reader of DATACHAIN_UDF_ENABLED. Both go, along with the $datachain / $datachainClickhouse locals that became unused once they did — secret-studio.yaml keeps its own copies for clickHouse.dsn.

Why no replacement flag

global.datachain.udfEnabled gated nothing's existence. It was purely a replica-count override in two spots:

# deployment-studio-datachain-worker.yaml   (only inside the non-autoscaling branch)
{{- if ((.Values.global.datachain).udfEnabled) }}
replicas: {{ .Values.studioDatachainWorker.replicaCount }}   # honour the value
{{- else }}
replicas: 0                                                  # override it
{{- end }}

The Deployment itself, configmap-studio-datachain-worker, the ServiceAccount, Role/RoleBinding, ClusterRole/ClusterRoleBinding, the PVC, the ResourceQuota and the suspended CronJob Job template all rendered regardless. udfEnabled: false never meant "no worker component" — it meant "scale the worker to zero".

So there's no replacement knob, because the knob already exists: studioDatachainWorker.replicaCount and studioDatachainWorker.autoscaling.minReplicas / maxReplicas say exactly what udfEnabled: false said. udfEnabled was a second, chart-global spelling that silently won over the documented per-component values.

A studioDatachainWorker.enabled flag would have been wrong twice over — this chart's enabled idiom means render or don't render (studioPypiCache.enabled gates its Deployment/Service/PVC at line 1; studioBackend.datachainApi.enabled gates the Service and Ingress backend), which is a strictly bigger hammer than what's being removed, and it would duplicate replicaCount.

global.datachain itself stays — clickHouse.dsn still lives under it.

⚠️ Behaviour change

udfEnabled defaulted to false, so a stock install declared replicaCount: 1 but rendered replicas: 0. It now renders 1. This deletes an override that contradicted the value it sat on top of.

Anyone who wants no DataChain workers sets studioDatachainWorker.replicaCount: 0 (or autoscaling.minReplicas/maxReplicas: 0). Chart minor-bumped to 0.21.0 accordingly.

dev and prod both set udfEnabled: true today, so neither environment changes — see the companion platform PR.

Testing

helm lint passes. helm template diffed against main:

With the real prod values (platform/k8s/prod/studio/studio-values{,-env}.yaml) — the only non-cosmetic change is the two ConfigMap keys disappearing. No replica or HPA change. Remaining diff is the helm.sh/chart label and the ConfigMap/Secret checksum annotations, both expected.

Stock defaults — the two ConfigMap keys, plus the intended replicas: 0 → replicas: 1.

HPA branch, exercised explicitly since prod doesn't autoscale this worker:

	old	new
autoscaling.enabled=true, udfEnabled unset	0 / 0	1 / 5
autoscaling.enabled=true, udfEnabled=true	1 / 5	1 / 5

i.e. identical wherever udfEnabled was set, and honouring the declared values where it wasn't.

https://claude.ai/code/session_01Eb5QaLhxciBiarrZDdJ1ks