varz

Documentation

Overview

Package varz contains code to export metrics in Prometheus format.

Index

• func ExpvarDoHandler(expvarDoFunc func(f func(expvar.KeyValue))) func(http.ResponseWriter, *http.Request)
• func Handler(w http.ResponseWriter, r *http.Request)
• func StaticStringVar(s string) expvar.Var
• func Uptime() time.Duration
• func WritePrometheusExpvar(w io.Writer, kv expvar.KeyValue)
• type PrometheusMetricsReflectRooter
• type PrometheusWriter

Functions

func ExpvarDoHandler

func ExpvarDoHandler(expvarDoFunc func(f func(expvar.KeyValue))) func(http.ResponseWriter, *http.Request)

ExpvarDoHandler handler returns a Handler like above, but takes an optional expvar.Do func allow the usage of alternative containers of metrics, other than the global expvar.Map.

func Handler

func Handler(w http.ResponseWriter, r *http.Request)

Handler is an HTTP handler to write expvar values into the prometheus export format:

https://github.com/prometheus/docs/blob/master/content/docs/instrumenting/exposition_formats.md

It makes the following assumptions:

• *expvar.Int are counters (unless marked as a gauge_; see below)
• a *tailscale/metrics.Set is descended into, joining keys with underscores. So use underscores as your metric names.
• an expvar named starting with "gauge_" or "counter_" is of that Prometheus type, and has that prefix stripped.
• anything else is untyped and thus not exported.
• expvar.Func can return an int or int64 (for now) and anything else is not exported.

This will evolve over time, or perhaps be replaced.

func StaticStringVar

func StaticStringVar(s string) expvar.Var

StaticStringVar returns a new expvar.Var that always returns s.

func Uptime

func Uptime() time.Duration

func WritePrometheusExpvar

func WritePrometheusExpvar(w io.Writer, kv expvar.KeyValue)

WritePrometheusExpvar writes kv to w in Prometheus metrics format.

See VarzHandler for conventions. This is exported primarily for people to test their varz.

Types

type PrometheusMetricsReflectRooter

type PrometheusMetricsReflectRooter interface {
	expvar.Var

	// PrometheusMetricsReflectRoot returns the struct or struct pointer to walk.
	PrometheusMetricsReflectRoot() any
}

PrometheusMetricsReflectRooter is an optional interface that expvar.Var implementations can implement to indicate that they should be walked recursively with reflect to find sets of fields to export.

type PrometheusWriter

type PrometheusWriter interface {
	WritePrometheus(w io.Writer, name string)
}

PrometheusWriter is the interface implemented by metrics that can write themselves into Prometheus exposition format.

As of 2024-03-25, this is only *metrics.MultiLabelMap.