mirror of
https://github.com/tailscale/tailscale.git
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tsweb: make VarzHandler capable of walking structs with reflect
To be used by control, per linked bug's plan. Updates #2635 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick
committed by
Brad Fitzpatrick
Brad Fitzpatrick
parent
b9bd7dbc5d
commit
5aba620fb9
259
tsweb/tsweb.go
259
tsweb/tsweb.go
@@ -19,6 +19,7 @@ import (
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_ "net/http/pprof"
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"os"
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"path/filepath"
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"reflect"
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"runtime"
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"strings"
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"time"
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@@ -342,6 +343,134 @@ func Error(code int, msg string, err error) HTTPError {
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return HTTPError{Code: code, Msg: msg, Err: err}
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}
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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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func writePromExpVar(w io.Writer, prefix string, kv expvar.KeyValue) {
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key := kv.Key
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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(kv.Key, "gauge_"):
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typ = "gauge"
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key = strings.TrimPrefix(kv.Key, "gauge_")
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case strings.HasPrefix(kv.Key, "counter_"):
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typ = "counter"
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key = strings.TrimPrefix(kv.Key, "counter_")
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}
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if strings.HasPrefix(key, "labelmap_") {
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key = strings.TrimPrefix(key, "labelmap_")
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if i := strings.Index(key, "_"); i != -1 {
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label, key = key[:i], key[i+1:]
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}
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}
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name := prefix + key
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switch v := kv.Value.(type) {
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case *expvar.Int:
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if typ == "" {
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typ = "counter"
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}
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fmt.Fprintf(w, "# TYPE %s %s\n%s %v\n", name, typ, 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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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:
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// Permit typeless LabelMap for compatibility
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// 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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fmt.Fprintf(w, "# skipping expvar.Map %q with incomplete metadata: label %q, Prometheus type %q\n", name, label, typ)
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}
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}
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}
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// VarzHandler 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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@@ -361,90 +490,21 @@ func Error(code int, msg string, err error) HTTPError {
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// This will evolve over time, or perhaps be replaced.
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func VarzHandler(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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var dump func(prefix string, kv expvar.KeyValue)
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dump = func(prefix string, kv expvar.KeyValue) {
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key := kv.Key
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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(kv.Key, "gauge_"):
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typ = "gauge"
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key = strings.TrimPrefix(kv.Key, "gauge_")
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case strings.HasPrefix(kv.Key, "counter_"):
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typ = "counter"
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key = strings.TrimPrefix(kv.Key, "counter_")
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}
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if strings.HasPrefix(key, "labelmap_") {
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key = strings.TrimPrefix(key, "labelmap_")
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if i := strings.Index(key, "_"); i != -1 {
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label, key = key[:i], key[i+1:]
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}
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}
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name := prefix + key
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switch v := kv.Value.(type) {
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case *expvar.Int:
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if typ == "" {
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typ = "counter"
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}
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fmt.Fprintf(w, "# TYPE %s %s\n%s %v\n", name, typ, 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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dump(name+"_", kv)
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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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funcRet = fmt.Sprintf(" returning %T", v)
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}
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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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}
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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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fmt.Fprintf(w, "# TYPE %s %s\n", name, typ)
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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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fmt.Fprintf(w, "# skipping expvar.Map %q with incomplete metadata: label %q, Prometheus type %q\n", name, label, typ)
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}
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}
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}
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expvarDo(func(kv expvar.KeyValue) {
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dump("", kv)
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writePromExpVar(w, "", kv)
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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() interface{}
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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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@@ -463,3 +523,42 @@ func writeMemstats(w io.Writer, ms *runtime.MemStats) {
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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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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 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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if i := strings.Index(v, ","); i != -1 {
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v = v[:i]
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}
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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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metricType := sf.Tag.Get("metrictype")
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if metricType != "" || sf.Type.Kind() == reflect.Struct {
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f(name, metricType, rv.Field(i))
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} else if sf.Type.Kind() == reflect.Ptr && sf.Type.Elem().Kind() == reflect.Struct {
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fv := rv.Field(i)
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if !fv.IsNil() {
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f(name, 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 interface{} }
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func (r expVarPromStructRoot) PrometheusMetricsReflectRoot() interface{} { 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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