Running multiple MongoDBCommunity resources across different namespaces: single operator vs multiple operators

[iilrgmv]

Description
Hi,

I’m currently working on a Kubernetes setup where we need to deploy multiple independent MongoDB replica sets, each one managed as a MongoDBCommunity resource, and isolated per application using different namespaces.

We are using the MongoDB Community Operator, and I would like to better understand the recommended and supported way to handle this scenario.

Current situation

• We have the MongoDBCommunity CRD installed cluster-wide.

• We have deployed one MongoDB Community Operator using Helm.

• We want to create multiple MongoDBCommunity resources, for example:

• MongoDBCommunity in namespace app-a

• MongoDBCommunity in namespace app-b

• Each resource represents a separate replica set, used by a different application.

• We do not want those MongoDB instances to interact with each other.

However, we’ve observed that:

• MongoDBCommunity resources created outside the operator’s namespace are not reconciled
• The CR appears “Active”, but:
• .status.phase is not populated
• no StatefulSets / Pods are created

This suggests that the operator may be watching only a single namespace, or that additional configuration is required.

Questios

1. Is it supported to manage multiple MongoDBCommunity resources across different namespaces using a single operator instance?

If yes:

• How should the operator be configured to watch multiple namespaces (or all namespaces)?
• Is there a recommended Helm value or operator flag for this (WATCH_NAMESPACE, --watch-namespace, etc.)?

2. If a single operator watching multiple namespaces is not recommended:
   Is it supported to deploy multiple instances of the MongoDB Community Operator, each scoped to a specific namespace?

Are there any caveats regarding:

• CRD ownership
• leader election
• resource conflicts

3. What is the recommended best practice for this use case:

• Multiple applications
• Multiple namespaces
• One MongoDB replica set per application
• Strong isolation, but minimal operational overhead

Thanks in advance!

[oskapt]

You can have it watch other namespaces when you install the operator, with something like --set operator.watchNamespace="*".

The documentation here leaves a lot to be desired, pointing to the main mongodb docs, which in turn point back to the Github docs, and between the two there's no information on how to do anything with the community version.

I found this medium article that does a much better job of walking you through everything.

[iilrgmv]

You can have it watch other namespaces when you install the operator, with something like --set operator.watchNamespace="*".

The documentation here leaves a lot to be desired, pointing to the main mongodb docs, which in turn point back to the Github docs, and between the two there's no information on how to do anything with the community version.

I found this medium article that does a much better job of walking you through everything.

I can't find the operator.watchNamespace="*" option inside the values.yaml file, is it a bug or should I just set it as the Medium post you said?

thanks

[KrisJohnstone]

You can have it watch other namespaces when you install the operator, with something like --set operator.watchNamespace="*".
The documentation here leaves a lot to be desired, pointing to the main mongodb docs, which in turn point back to the Github docs, and between the two there's no information on how to do anything with the community version.
I found this medium article that does a much better job of walking you through everything.

I can't find the operator.watchNamespace="*" option inside the values.yaml file, is it a bug or should I just set it as the Medium post you said?

thanks

Or you could have checked the code:
https://github.com/mongodb/helm-charts/blob/22a6dc73ac77a3559b12bce22ae96c0da1059648/charts/mongodb-kubernetes/templates/operator.yaml#L108