internal/lsp: add prometheus exporting of all metrics

Change-Id: I1e7ce371d8abd2eb80aad70935695f61b6374ff8
Reviewed-on: https://go-review.googlesource.com/c/tools/+/185347
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/lsp/debug/prometheus.go

@@ -0,0 +1,111 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package debug
+
+import (
+	"bytes"
+	"fmt"
+	"net/http"
+	"sort"
+
+	"golang.org/x/tools/internal/lsp/telemetry/metric"
+	"golang.org/x/tools/internal/lsp/telemetry/tag"
+	"golang.org/x/tools/internal/lsp/telemetry/worker"
+)
+
+type prometheus struct {
+	metrics []metric.Data
+}
+
+func (p *prometheus) observeMetric(data metric.Data) {
+	name := data.Handle().Name()
+	index := sort.Search(len(p.metrics), func(i int) bool {
+		return p.metrics[i].Handle().Name() >= name
+	})
+	if index >= len(p.metrics) || p.metrics[index].Handle().Name() != name {
+		old := p.metrics
+		p.metrics = make([]metric.Data, len(old)+1)
+		copy(p.metrics, old[:index])
+		copy(p.metrics[index+1:], old[index:])
+	}
+	p.metrics[index] = data
+}
+
+func (p *prometheus) header(w http.ResponseWriter, name, description string, isGauge, isHistogram bool) {
+	kind := "counter"
+	if isGauge {
+		kind = "gauge"
+	}
+	if isHistogram {
+		kind = "histogram"
+	}
+	fmt.Fprintf(w, "# HELP %s %s\n", name, description)
+	fmt.Fprintf(w, "# TYPE %s %s\n", name, kind)
+}
+
+func (p *prometheus) row(w http.ResponseWriter, name string, group tag.List, extra string, value interface{}) {
+	fmt.Fprint(w, name)
+	buf := &bytes.Buffer{}
+	fmt.Fprint(buf, group)
+	if extra != "" {
+		if buf.Len() > 0 {
+			fmt.Fprint(buf, ",")
+		}
+		fmt.Fprint(buf, extra)
+	}
+	if buf.Len() > 0 {
+		fmt.Fprint(w, "{")
+		buf.WriteTo(w)
+		fmt.Fprint(w, "}")
+	}
+	fmt.Fprintf(w, " %v\n", value)
+}
+
+func (p *prometheus) serve(w http.ResponseWriter, r *http.Request) {
+	done := make(chan struct{})
+	worker.Do(func() {
+		defer close(done)
+		for _, data := range p.metrics {
+			switch data := data.(type) {
+			case *metric.Int64Data:
+				p.header(w, data.Info.Name, data.Info.Description, data.IsGauge, false)
+				for i, group := range data.Groups() {
+					p.row(w, data.Info.Name, group, "", data.Rows[i])
+				}
+
+			case *metric.Float64Data:
+				p.header(w, data.Info.Name, data.Info.Description, data.IsGauge, false)
+				for i, group := range data.Groups() {
+					p.row(w, data.Info.Name, group, "", data.Rows[i])
+				}
+
+			case *metric.HistogramInt64Data:
+				p.header(w, data.Info.Name, data.Info.Description, false, true)
+				for i, group := range data.Groups() {
+					row := data.Rows[i]
+					for j, b := range data.Info.Buckets {
+						p.row(w, data.Info.Name+"_bucket", group, fmt.Sprintf(`le="%v"`, b), row.Values[j])
+					}
+					p.row(w, data.Info.Name+"_bucket", group, `le="+Inf"`, row.Count)
+					p.row(w, data.Info.Name+"_count", group, "", row.Count)
+					p.row(w, data.Info.Name+"_sum", group, "", row.Sum)
+				}
+
+			case *metric.HistogramFloat64Data:
+				p.header(w, data.Info.Name, data.Info.Description, false, true)
+				for i, group := range data.Groups() {
+					row := data.Rows[i]
+					for j, b := range data.Info.Buckets {
+						p.row(w, data.Info.Name+"_bucket", group, fmt.Sprintf(`le="%v"`, b), row.Values[j])
+					}
+					p.row(w, data.Info.Name+"_bucket", group, `le="+Inf"`, row.Count)
+					p.row(w, data.Info.Name+"_count", group, "", row.Count)
+					p.row(w, data.Info.Name+"_sum", group, "", row.Sum)
+				}
+			}
+		}
+	})
+	<-done
+}

internal/lsp/debug/serve.go

@@ -19,6 +19,7 @@ import (
 	"strconv"
 	"sync"
 
+	"golang.org/x/tools/internal/lsp/telemetry/metric"
 	"golang.org/x/tools/internal/span"
 )
 
@@ -212,6 +213,8 @@ func Serve(ctx context.Context, addr string) error {
 		return err
 	}
 	log.Printf("Debug serving on port: %d", listener.Addr().(*net.TCPAddr).Port)
+	prometheus := prometheus{}
+	metric.RegisterObservers(prometheus.observeMetric)
 	go func() {
 		mux := http.NewServeMux()
 		mux.HandleFunc("/", Render(mainTmpl, func(*http.Request) interface{} { return data }))
@@ -221,6 +224,7 @@ func Serve(ctx context.Context, addr string) error {
 		mux.HandleFunc("/debug/pprof/profile", pprof.Profile)
 		mux.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
 		mux.HandleFunc("/debug/pprof/trace", pprof.Trace)
+		mux.HandleFunc("/metrics/", prometheus.serve)
 		mux.HandleFunc("/cache/", Render(cacheTmpl, getCache))
 		mux.HandleFunc("/session/", Render(sessionTmpl, getSession))
 		mux.HandleFunc("/view/", Render(viewTmpl, getView))
@@ -283,7 +287,7 @@ td.value {
 <a href="/">Main</a>
 <a href="/info">Info</a>
 <a href="/memory">Memory</a>
-<a href="/debug/">Debug</a>
+<a href="/metrics">Metrics</a>
 <hr>
 <h1>{{template "title" .}}</h1>
 {{block "body" .}}