Collecting metrics with Kubernetes

Kubernetes has a Metrics API. It supports node and pod metrics out of the box. You can also define your own custom metrics.

A metric contains a timestamp, a usage field, and the time range in which the metric was collected (many metrics are accumulated over a time period). Here is the API definition for node metrics:

type NodeMetrics struct {
    metav1.TypeMeta
    metav1.ObjectMeta
    Timestamp metav1.Time
    Window    metav1.Duration
    Usage corev1.ResourceList
}
// NodeMetricsList is a list of NodeMetrics.
type NodeMetricsList struct {
    metav1.TypeMeta
    // Standard list metadata.
    // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds
    metav1.ListMeta
    // List of node metrics.
    Items []NodeMetrics
}

The usage field type is ResourceList, but it’s actually a map of a resource name to a quantity:

// ResourceList is a set of (resource name, quantity...