Metrics Configuration #

This document walks you through how to configure the Metrics feature.

What is a Metrics? #

The Metrics is a kwok Configuration that allows users to define and simulate metrics endpoints exposed by kubelet.

The YAML below shows all the fields of a Metrics resource:

kind: Metrics
  name: <string>
  path: <string>
  - name: <string>
    help: <string>
    kind: <string>
    dimension: <string>
    - name: <string>
      value: <string>
    value: <string>   # for counter and gauge
    buckets:          # for histogram
    - le: <float64>
      value: <string>
      hidden: <bool>

There are total four metric-related endpoints in kubelet: /metrics, /metrics/resource, /metrics/probe and /metrics/cadvisor, all of which are exposed with a Prometheus style. The Metrics resource is capable of simulating endpoints with such style.

The path field is required and must start with /metrics. To distinguish the metrics of different nodes, the path includes a variable {nodeName} that is replaced by the node name.

The descriptions of each sub-field are available at Metric API. For readers’ convenience, we also mirror the documents here with some additional notes.

metrics is a list of specific configuration items, with each corresponding to a Prometheus style metric:

  • name defines the metric name.
  • labels defines the metric labels, with each item corresponding to a specific metric label.
    • name is a const string that provides the label name.
    • value is represented as a CEL expressions that dynamically determines the label value. For example: you can use to reference the node name as the label value.
  • help defines the help string of a metric.
  • kind defines the type of the metric: counter, gauge, or histogram.
  • dimension defines where the data comes from. It could be node, pod, or container.
  • value is a CEL expressions that defines the metric value if kind is counter or gauge.
  • buckets is exclusively for customizing the data of the metric of kind histogram.
    • le, which defines the histogram bucket’s upper threshold, has the same meaning as the one of Prometheus histogram bucket. That is, each bucket contains values less than or equal to le.
    • value is a CEL expression that provides the value of the bucket.
    • hidden indicates whether to show the bucket in the metric. But the value of the bucket will be calculated and cumulated into the next bucket.

Examples #

Please refer to Metrics for kubelet’s /metrics/resource endpoint for a detailed.