[NATS JetStream] Allow dynamically pull AccountID from a secret

[martin31821]

Proposal

I propose a change to the Nats JetStream scaler, where the account ID can be specified from an external resource, such as a secret.

Use-Case

I'm running a NATS Cluster with several (dynamically created) tenants, running with a self-designed authentication server (github.com/deinstapel/nats-jwt-operator), where the Account IDs are not known in advance. My Operator dynamically creates NATS tenants and accounts with a kubernetes CRD and writes the account IDs into the .status of the CRD as well as to a secret.

I would like to be able to tell KEDA to scale based on these accounts, so I can include KEDA in my CD pipeline.

Is this a feature you are interested in implementing yourself?

Yes

Anything else?

Example:

Currently existing code:

triggers:
- type: nats-jetstream
  metadata:
    natsServerMonitoringEndpoint: "nats.nats.svc.cluster.local:8222"
    account: "$G"

Possible new implementation:

triggers:
- type: nats-jetstream
  metadata:
    natsServerMonitoringEndpoint: "nats.nats.svc.cluster.local:8222"
    accountRef:
      secretName: "my-accountSecret"
      secretKey: "account-id"

[JorTurFer]

Hi,
This is almost ready 😄
From KEDA pov, this is already implemented through TriggerAuthentication/ClusterTriggerAuthentication. Using one of them, you can read a secret and get the key.

Right now, NATS JetStream scaler doesn't read that value from TriggerAuthentication/ClusterTriggerAuthentication but it can be done changing this code:

	if config.TriggerMetadata["account"] == "" {
		return meta, errors.New("no account name given")
	}
	meta.account = config.TriggerMetadata["account"]

with this:

	account, err := GetFromAuthOrMeta(config, "account")
	if err != nil {
		return meta, err
	}
	meta.account = account

and obviously adding at least a unit test. From documentation pov, we should update it too

Are you willing to contribute with the feature?

[martin31821]

Sounds good, will prepare a PR.