feat: support autoscaling on broker and bookie

[ericsyh]

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[ericsyh]

Example

bookkeeper:
  autoScaling:
    enabled: true
    minReplicas: 1
    maxReplicas: 4
    metrics:
     - pods:
        metric:
          name: cpu_usage
        target:
          averageValue: "75"
          type: AverageValue
      type: Pods

broker:
  autoScaling:
    enabled: true
    minReplicas: 1
    maxReplicas: 4
    metrics:
     - pods:
        metric:
          name: cpu_usage
        target:
          averageValue: "75"
          type: AverageValue
      type: Pods

[ignacioli]

what are the available metrics here?

[ignacioli]

It would be great if there is a list of the metric names that can be used for pulsar auto-scaling.

[ericsyh]

what are the available metrics here?
It depends on the metrics backend service used. If users deploy the Metrics Server then only resource metrics could be used. But with prometheus and prometheus adapter, all metrics from the prometheus could be used by the auto-scaling.

[ignacioli]

The cpu_usage here is a custom metric implemented by prometheus-adapter other than the general prometheus metric, the user should know the catalog of the supported metrics of broker autoScaling.