Support AAD Pod Identity

[joclegg]

Add support for using pod identity binding to access the cosmos db via account endpoint only.

Use-Case

Our cosmos dbs are set up to only use AD for access. We would like to create a role with the access that this scaler will need and use that and the account endpoint for access. We would then not need to have connection strings in configuration.

[karpikpl]

Hey,
is there any update on this issue?
the comment about TriggerAuthentication is 3 years old.
The external scaler example now references secrets? https://keda.sh/docs/2.14/scalers/external/#authentication-parameters

[karpikpl]

I've been trying to understand if I can deploy the scaler with TriggerAuthentication since I cannot find anything in KEDA docs that would say it's not supported for external scalers.

# Create KEDA scaled object to scale order processor application.
apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
  name: azure-cosmosdb-auth
spec:
  podIdentity:
    provider: azure-workload
---    
apiVersion: keda.sh/v1alpha1
kind: ScaledObject
metadata:
  name: cosmosdb-order-processor-scaledobject
  namespace: cosmosdb-order-processor
spec:
  pollingInterval: 20
  scaleTargetRef:
    name: cosmosdb-order-processor
  triggers:
    - type: external
      authenticationRef:
        name: azure-cosmosdb-auth # authenticationRef would need either podIdentity or define a connection parameter
      metadata:
        scalerAddress: external-scaler-azure-cosmos-db.cosmosdb-order-processor:4050
        endpoint: https://{Cosmos DB Account Name}.documents.azure.com:443/ # update as per your environment
        databaseId: StoreDatabase
        containerId: OrderContainer
        LeaseEndpoint: https://{Cosmos DB Account Name}.documents.azure.com:443/ # update as per your environment
        leaseDatabaseId: StoreDatabase
        leaseContainerId: OrderProcessorLeases
        processorName: OrderProcessor

It looks like Azure Workload Identity is supported in KEDA. The only thing missing is the actual support in code that I tried adding in #68.

State of the code is little confusing though:

1. There's a new sample that has support for Identity, developed 1 year ago: https://github.com/Azure-Samples/cosmos-aks-keda which looks like a fork of this repo, but it was never merged into this one.
2. Even though this repo gets updates, keda chart hasn't been updated in a while: https://github.com/kedacore/charts/blob/43b0f516e0d101c18830d06126700916c029712b/external-scaler-azure-cosmos-db/values.yaml#L10
3. Container image is built in this repo but latest tag is not moved and there are no new releases ("experimental" tag is used instead.