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Sensor High Availability

Sensor controller creates a k8s deployment (replica number defaults to 1) for each Sensor object. HA with Active-Passive strategy can be achieved by setting spec.replicas to a number greater than 1, which means only one Pod serves traffic and the rest ones stand by. One of standby Pods will be automatically elected to be active if the old one is gone.

Please DO NOT manually scale up the replicas, that might cause unexpected behaviors!

Kubernetes Leader Election

By default, Argo Events will use NATS for the HA leader election except when using a Kafka Eventbus, in which case a leader election is not required as a Sensor that uses a Kafka EventBus is capable of horizontally scaling. If using a different EventBus you can opt-in to a Kubernetes native leader election by specifying the following annotation. 

annotations:
  events.argoproj.io/leader-election: k8s

To use Kubernetes leader election the following RBAC rules need to be associated with the Sensor ServiceAccount. 

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: argo-events-leaderelection-role
rules:
- apiGroups: ["coordination.k8s.io"]
  resources: ["leases"]
  verbs:     ["get", "create", "update"]

More

Click here to learn more information about Argo Events DR/HA recommendations.

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