`arbiter.enabled` documented on helmforge.dev is not implemented in the mongodb chart (v1.7.17)

[bslpzk]

Chart

mongodb

Chart Version

1.7.17

Kubernetes Version

No response

Helm Version

No response

Deployment Method

None

Steps to Reproduce

The word "arbiter" does not appear anywhere in the chart source: not in values.yaml, not in values.schema.json, not in any file under templates/, and not in README.md, DESIGN.md, docs/*.md, ci/*.yaml, examples/*.yaml, or tests/*.yaml of the mongodb chart at version 1.7.17 (appVersion 8.3.8) in https://github.com/helmforgedev/charts.

Expected Behavior

No response

Actual Behavior

The chart can only provision data-bearing replica set members — the StatefulSet replica count is driven entirely by replicaSet.members, with no separate workload type for a lightweight, non-data-bearing member. So the only way to reach 3 replica set members is 3 full data-bearing instances; there is no way to get 2 data-bearing members plus a 3rd, storage-free arbiter as the site documentation implies. This contradicts the "With Arbiter" example and the arbiter.enabled row in the Architecture reference table on the chart's own documentation page.

Values (relevant snippet)

Error Output

Additional Context

• Docs: https://helmforge.dev/docs/charts/mongodb/ — "Deployment Examples — With Arbiter" and the arbiter.enabled row in the Architecture table.
• Source: https://github.com/helmforgedev/charts/tree/main/charts/mongodb (values.yaml, templates/_helpers.tpl, templates/statefulset.yaml).
• Related: docs/replicaset.md in the same chart lists running only 2 members as a risk and recommends 3 as the minimum — the documented arbiter example is meant to avoid exactly that, but silently doesn't.

[mberlofa]

@bslpzk Thank you for the precise report and for cross-checking the chart source against the site documentation. You are correct: arbiter.enabled is currently documented, but the chart does not render or register an arbiter, so the value is silently ignored. We will implement opt-in arbiter support using the official MongoDB image, including a dedicated workload, schema coverage, idempotent replica-set initialization, chart tests, and synchronized chart/site documentation. We will also validate the Primary-Secondary-Arbiter scenario end to end on the local k3d environment, including replica-set membership and election behavior. We will link the corresponding chart and site pull requests here once they are ready.

[mberlofa]

@bslpzk, thank you again for reporting this and for identifying the documentation/runtime mismatch.

The complete fix is now available for review:

• fix(mongodb): add arbiter support #1076 implements the arbiter StatefulSet and Service, install/upgrade reconciliation, schema, tests, examples, and runtime validation.
• docs(mongodb): document arbiter support site#541 synchronizes the MongoDB documentation and playground configuration.

The chart passed the full 20-layer validation gate, including the new arbiter scenario on k3d. I also validated enabling, disabling, and re-enabling the arbiter while a non-zero ordinal was primary, including a successful write/read after reconfiguration.

[mberlofa]

@bslpzk, the complete fix has now been merged. Thank you again for reporting the mismatch and helping improve the MongoDB chart.

• fix(mongodb): add arbiter support #1076 added the arbiter workload, lifecycle reconciliation, write concern safeguards, tests, examples, and runtime validation.
• docs(mongodb): document arbiter support site#541 updated the documentation and prevents unsupported arbiter combinations in the playground.

Both PRs passed their complete CI suites and all review threads were resolved. This issue is now completed and closed.

Post-merge publication is complete:

• MongoDB chart 1.7.18: https://github.com/helmforgedev/charts/releases/tag/mongodb-v1.7.18
• OCI artifact: oci://ghcr.io/helmforgedev/helm/mongodb --version 1.7.18
• Documentation: https://helmforge.dev/docs/charts/mongodb