mirror of
https://github.com/tailscale/tailscale.git
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eefee6f149
I left a few out where writing it explicitly was better for various reasons. Updates #8296 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
368 lines
12 KiB
Go
368 lines
12 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Package varz contains code to export metrics in Prometheus format.
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package varz
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import (
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"expvar"
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"fmt"
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"io"
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"net/http"
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_ "net/http/pprof"
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"reflect"
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"runtime"
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"sort"
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"strings"
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"sync"
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"time"
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"tailscale.com/metrics"
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"tailscale.com/util/cmpx"
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"tailscale.com/version"
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)
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func init() {
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expvar.Publish("process_start_unix_time", expvar.Func(func() any { return timeStart.Unix() }))
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expvar.Publish("version", expvar.Func(func() any { return version.Long() }))
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expvar.Publish("go_version", expvar.Func(func() any { return runtime.Version() }))
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expvar.Publish("counter_uptime_sec", expvar.Func(func() any { return int64(Uptime().Seconds()) }))
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expvar.Publish("gauge_goroutines", expvar.Func(func() any { return runtime.NumGoroutine() }))
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}
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const (
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gaugePrefix = "gauge_"
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counterPrefix = "counter_"
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labelMapPrefix = "labelmap_"
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)
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// prefixesToTrim contains key prefixes to remove when exporting and sorting metrics.
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var prefixesToTrim = []string{gaugePrefix, counterPrefix, labelMapPrefix}
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var timeStart = time.Now()
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func Uptime() time.Duration { return time.Since(timeStart).Round(time.Second) }
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// WritePrometheusExpvar writes kv to w in Prometheus metrics format.
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//
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// See VarzHandler for conventions. This is exported primarily for
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// people to test their varz.
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func WritePrometheusExpvar(w io.Writer, kv expvar.KeyValue) {
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writePromExpVar(w, "", kv)
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}
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type prometheusMetricDetails struct {
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Name string
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Type string
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Label string
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}
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var prometheusMetricCache sync.Map // string => *prometheusMetricDetails
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func prometheusMetric(prefix string, key string) (string, string, string) {
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cachekey := prefix + key
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if v, ok := prometheusMetricCache.Load(cachekey); ok {
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d := v.(*prometheusMetricDetails)
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return d.Name, d.Type, d.Label
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}
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var typ string
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var label string
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switch {
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case strings.HasPrefix(key, gaugePrefix):
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typ = "gauge"
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key = strings.TrimPrefix(key, gaugePrefix)
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case strings.HasPrefix(key, counterPrefix):
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typ = "counter"
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key = strings.TrimPrefix(key, counterPrefix)
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}
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if strings.HasPrefix(key, labelMapPrefix) {
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key = strings.TrimPrefix(key, labelMapPrefix)
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if a, b, ok := strings.Cut(key, "_"); ok {
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label, key = a, b
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}
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}
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d := &prometheusMetricDetails{
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Name: strings.ReplaceAll(prefix+key, "-", "_"),
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Type: typ,
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Label: label,
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}
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prometheusMetricCache.Store(cachekey, d)
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return d.Name, d.Type, d.Label
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}
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func writePromExpVar(w io.Writer, prefix string, kv expvar.KeyValue) {
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key := kv.Key
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name, typ, label := prometheusMetric(prefix, key)
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switch v := kv.Value.(type) {
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case *expvar.Int:
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fmt.Fprintf(w, "# TYPE %s %s\n%s %v\n", name, cmpx.Or(typ, "counter"), name, v.Value())
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return
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case *expvar.Float:
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fmt.Fprintf(w, "# TYPE %s %s\n%s %v\n", name, cmpx.Or(typ, "gauge"), name, v.Value())
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return
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case *metrics.Set:
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v.Do(func(kv expvar.KeyValue) {
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writePromExpVar(w, name+"_", kv)
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})
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return
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case PrometheusMetricsReflectRooter:
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root := v.PrometheusMetricsReflectRoot()
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rv := reflect.ValueOf(root)
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if rv.Type().Kind() == reflect.Ptr {
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if rv.IsNil() {
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return
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}
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rv = rv.Elem()
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}
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if rv.Type().Kind() != reflect.Struct {
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fmt.Fprintf(w, "# skipping expvar %q; unknown root type\n", name)
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return
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}
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foreachExportedStructField(rv, func(fieldOrJSONName, metricType string, rv reflect.Value) {
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mname := name + "_" + fieldOrJSONName
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switch rv.Kind() {
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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fmt.Fprintf(w, "# TYPE %s %s\n%s %v\n", mname, metricType, mname, rv.Int())
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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fmt.Fprintf(w, "# TYPE %s %s\n%s %v\n", mname, metricType, mname, rv.Uint())
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case reflect.Float32, reflect.Float64:
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fmt.Fprintf(w, "# TYPE %s %s\n%s %v\n", mname, metricType, mname, rv.Float())
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case reflect.Struct:
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if rv.CanAddr() {
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// Slight optimization, not copying big structs if they're addressable:
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writePromExpVar(w, name+"_", expvar.KeyValue{Key: fieldOrJSONName, Value: expVarPromStructRoot{rv.Addr().Interface()}})
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} else {
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writePromExpVar(w, name+"_", expvar.KeyValue{Key: fieldOrJSONName, Value: expVarPromStructRoot{rv.Interface()}})
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}
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}
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return
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})
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return
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}
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if typ == "" {
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var funcRet string
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if f, ok := kv.Value.(expvar.Func); ok {
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v := f()
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if ms, ok := v.(runtime.MemStats); ok && name == "memstats" {
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writeMemstats(w, &ms)
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return
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}
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if vs, ok := v.(string); ok && strings.HasSuffix(name, "version") {
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fmt.Fprintf(w, "%s{version=%q} 1\n", name, vs)
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return
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}
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switch v := v.(type) {
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case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64, uintptr, float32, float64:
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fmt.Fprintf(w, "%s %v\n", name, v)
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return
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}
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funcRet = fmt.Sprintf(" returning %T", v)
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}
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switch kv.Value.(type) {
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default:
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fmt.Fprintf(w, "# skipping expvar %q (Go type %T%s) with undeclared Prometheus type\n", name, kv.Value, funcRet)
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return
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case *metrics.LabelMap, *expvar.Map:
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// Permit typeless LabelMap and expvar.Map for
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// compatibility with old expvar-registered
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// metrics.LabelMap.
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}
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}
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switch v := kv.Value.(type) {
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case expvar.Func:
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val := v()
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switch val.(type) {
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case float64, int64, int:
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fmt.Fprintf(w, "# TYPE %s %s\n%s %v\n", name, typ, name, val)
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default:
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fmt.Fprintf(w, "# skipping expvar func %q returning unknown type %T\n", name, val)
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}
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case *metrics.LabelMap:
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if typ != "" {
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fmt.Fprintf(w, "# TYPE %s %s\n", name, typ)
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}
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// IntMap uses expvar.Map on the inside, which presorts
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// keys. The output ordering is deterministic.
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v.Do(func(kv expvar.KeyValue) {
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fmt.Fprintf(w, "%s{%s=%q} %v\n", name, v.Label, kv.Key, kv.Value)
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})
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case *expvar.Map:
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if label != "" && typ != "" {
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fmt.Fprintf(w, "# TYPE %s %s\n", name, typ)
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v.Do(func(kv expvar.KeyValue) {
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fmt.Fprintf(w, "%s{%s=%q} %v\n", name, label, kv.Key, kv.Value)
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})
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} else {
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v.Do(func(kv expvar.KeyValue) {
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fmt.Fprintf(w, "%s_%s %v\n", name, kv.Key, kv.Value)
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})
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}
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}
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}
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var sortedKVsPool = &sync.Pool{New: func() any { return new(sortedKVs) }}
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// sortedKV is a KeyValue with a sort key.
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type sortedKV struct {
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expvar.KeyValue
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sortKey string // KeyValue.Key with type prefix removed
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}
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type sortedKVs struct {
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kvs []sortedKV
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}
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// Handler is an HTTP handler to write expvar values into the
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// prometheus export format:
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//
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// https://github.com/prometheus/docs/blob/master/content/docs/instrumenting/exposition_formats.md
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//
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// It makes the following assumptions:
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//
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// - *expvar.Int are counters (unless marked as a gauge_; see below)
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// - a *tailscale/metrics.Set is descended into, joining keys with
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// underscores. So use underscores as your metric names.
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// - an expvar named starting with "gauge_" or "counter_" is of that
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// Prometheus type, and has that prefix stripped.
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// - anything else is untyped and thus not exported.
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// - expvar.Func can return an int or int64 (for now) and anything else
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// is not exported.
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//
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// This will evolve over time, or perhaps be replaced.
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func Handler(w http.ResponseWriter, r *http.Request) {
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w.Header().Set("Content-Type", "text/plain; version=0.0.4")
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s := sortedKVsPool.Get().(*sortedKVs)
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defer sortedKVsPool.Put(s)
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s.kvs = s.kvs[:0]
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expvarDo(func(kv expvar.KeyValue) {
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s.kvs = append(s.kvs, sortedKV{kv, removeTypePrefixes(kv.Key)})
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})
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sort.Slice(s.kvs, func(i, j int) bool {
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return s.kvs[i].sortKey < s.kvs[j].sortKey
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})
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for _, e := range s.kvs {
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writePromExpVar(w, "", e.KeyValue)
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}
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}
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// PrometheusMetricsReflectRooter is an optional interface that expvar.Var implementations
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// can implement to indicate that they should be walked recursively with reflect to find
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// sets of fields to export.
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type PrometheusMetricsReflectRooter interface {
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expvar.Var
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// PrometheusMetricsReflectRoot returns the struct or struct pointer to walk.
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PrometheusMetricsReflectRoot() any
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}
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var expvarDo = expvar.Do // pulled out for tests
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func writeMemstats(w io.Writer, ms *runtime.MemStats) {
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out := func(name, typ string, v uint64, help string) {
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if help != "" {
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fmt.Fprintf(w, "# HELP memstats_%s %s\n", name, help)
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}
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fmt.Fprintf(w, "# TYPE memstats_%s %s\nmemstats_%s %v\n", name, typ, name, v)
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}
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g := func(name string, v uint64, help string) { out(name, "gauge", v, help) }
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c := func(name string, v uint64, help string) { out(name, "counter", v, help) }
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g("heap_alloc", ms.HeapAlloc, "current bytes of allocated heap objects (up/down smoothly)")
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c("total_alloc", ms.TotalAlloc, "cumulative bytes allocated for heap objects")
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g("sys", ms.Sys, "total bytes of memory obtained from the OS")
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c("mallocs", ms.Mallocs, "cumulative count of heap objects allocated")
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c("frees", ms.Frees, "cumulative count of heap objects freed")
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c("num_gc", uint64(ms.NumGC), "number of completed GC cycles")
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}
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// sortedStructField is metadata about a struct field used both for sorting once
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// (by structTypeSortedFields) and at serving time (by
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// foreachExportedStructField).
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type sortedStructField struct {
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Index int // index of struct field in struct
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Name string // struct field name, or "json" name
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SortName string // Name with "foo_" type prefixes removed
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MetricType string // the "metrictype" struct tag
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StructFieldType *reflect.StructField
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}
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var structSortedFieldsCache sync.Map // reflect.Type => []sortedStructField
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// structTypeSortedFields returns the sorted fields of t, caching as needed.
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func structTypeSortedFields(t reflect.Type) []sortedStructField {
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if v, ok := structSortedFieldsCache.Load(t); ok {
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return v.([]sortedStructField)
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}
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fields := make([]sortedStructField, 0, t.NumField())
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for i, n := 0, t.NumField(); i < n; i++ {
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sf := t.Field(i)
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name := sf.Name
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if v := sf.Tag.Get("json"); v != "" {
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v, _, _ = strings.Cut(v, ",")
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if v == "-" {
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// Skip it, regardless of its metrictype.
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continue
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}
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if v != "" {
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name = v
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}
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}
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fields = append(fields, sortedStructField{
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Index: i,
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Name: name,
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SortName: removeTypePrefixes(name),
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MetricType: sf.Tag.Get("metrictype"),
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StructFieldType: &sf,
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})
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}
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sort.Slice(fields, func(i, j int) bool {
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return fields[i].SortName < fields[j].SortName
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})
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structSortedFieldsCache.Store(t, fields)
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return fields
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}
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// removeTypePrefixes returns s with the first "foo_" prefix in prefixesToTrim
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// removed.
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func removeTypePrefixes(s string) string {
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for _, prefix := range prefixesToTrim {
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if trimmed, ok := strings.CutPrefix(s, prefix); ok {
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return trimmed
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}
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}
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return s
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}
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// foreachExportedStructField iterates over the fields in sorted order of
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// their name, after removing metric prefixes. This is not necessarily the
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// order they were declared in the struct
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func foreachExportedStructField(rv reflect.Value, f func(fieldOrJSONName, metricType string, rv reflect.Value)) {
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t := rv.Type()
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for _, ssf := range structTypeSortedFields(t) {
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sf := ssf.StructFieldType
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if ssf.MetricType != "" || sf.Type.Kind() == reflect.Struct {
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f(ssf.Name, ssf.MetricType, rv.Field(ssf.Index))
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} else if sf.Type.Kind() == reflect.Ptr && sf.Type.Elem().Kind() == reflect.Struct {
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fv := rv.Field(ssf.Index)
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if !fv.IsNil() {
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f(ssf.Name, ssf.MetricType, fv.Elem())
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}
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}
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}
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}
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type expVarPromStructRoot struct{ v any }
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func (r expVarPromStructRoot) PrometheusMetricsReflectRoot() any { return r.v }
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func (r expVarPromStructRoot) String() string { panic("unused") }
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var (
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_ PrometheusMetricsReflectRooter = expVarPromStructRoot{}
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_ expvar.Var = expVarPromStructRoot{}
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)
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