Feature Implementation Request: WaitForFirstConsumer

[ChrisPiece]

Our customer thinks that everyone would benefit from this feature WaitForFirstConsumer that help in having the compute aligned with the storage. This feature would be useful for almost anything that pulls from a DB (mongo, cassandra, elastic ...), which are generally managed by StateFulSets.

Currently, StateFulSets allows us to share computation across distributed AZs, however its PVCs always fall on the same AZ. Therefore, if that particular AZ needs maintenance or experiences an issue, the application would go down.

With WaitForFirstConsumer, the StorageClassName would be assigned based on the topology, selectors, anti-affinity policies, etc. etc. and would allow a more flexible management.
This feature is available on AWS, GCP and Azure that heavily use multi-AZs, but it would be useful for our customer environment too (and many others).

[gnarl]

Does your customer have multiple on-prem NetApp backends in different AZs?

Also, from the document you linked, the volumeBindingMode is a field in the StorageClass configuration. It doesn't appear that theStorageClassName can be assigned by Trident based on topology.

[ChrisPiece]

Customer is trying to move to a Multi-AZ infrastructure with multiple NetApp backends, correct.
That document lists some plugins that support WaitForFirstConsumer and they would like to implement that functionality.
Currently they use code like this:

    storageSpec:
      volumeClaimTemplate:
        spec:
          storageClassName: sc-dev-az1           <----- here goes the AZ, it is hardcoded.
          accessModes: ["ReadWriteMany"]
          resources:
            requests:
              storage: 40Gi

The goal would be to have a dynamic storageClassName option so that if that AZ fails, automatically the storage class could automatically switch.
They are using OpenShift 4.3 and wonder if this functionality could be integrated with Trident.

[gnarl]

@ChrisPiece thanks for the additional information!

[adkerr]

Added in df73a8d

[gnarl]

This feature will be available in the Trident 20.10.0 release.