Managing multiple instances of ACK with leader election

In a Kubernetes cluster, you may want to run multiple instances of any ACK controller - configured for different accounts or regions, or for fail state rollover. However, to avoid conflicts and ensure proper resource management, it’s necessary to designate one instance as the leader, which takes responsibility for executing certain operations while the other instances remain passive. In the event that the leader instance fails, leader election ensures the seamless transition of leadership to another healthy instance.

By default, leader election is disabled in the ACK Helm charts. However, once enabled, you gain the flexibility to scale the default deployment of ACK controllers from a single replica (1) to a higher number.

Enabling Leader Election for ACK Controllers

To enable leader election when installing an ACK controller, set the leaderElection.enabled to true in the helm chart values.yaml like:

    enabled: true

You also have the flexibility to scale the number of controller replicas. Edit the deployment.replicas configuration in the same values.yaml file and adjust it to your desired count, such as:

    replicas: 3

Configuring Leader Election Namespace

The leader election namespace is a controller configuration setting that determines the namespace where controllers manage leader election. Under the hood it is used for storing objects, which help controllers reach consensus and choose a leader. If not specified, the system will use the namespace from the service account’s configuration by default.

If you would like to set leader election namespace for your ACK controllers, you need to set leaderElection.namespace, like below:

    enabled: true
    namespace: "ack-leader-election-ns"

Verifying Leader Election

To confirm that leader election is active, you can perform the following checks:

  • Log Messages: Examine the logs of your ACK controller pods for any messages indicating the successful execution of leader election.
  • Objects: You can also inspect the objects within the configured leader election namespace. Using kubectl you can retrieve information about these objects, allowing you to verify leadership status.
  • Kubernetes Events: Another method is to monitor Kubernetes events related to your controllers. Execute kubectl get events to view events that might provide insights into leader election and controller behavior.

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