go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/server/pprof/internal/pprof.go

// Copyright 2010 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 internal

// This code is copied from go/src/net/http/pprof/pprof.go at revision
// 01c144c410b09d8b56d40e7e9c54fface204aa29 of the official Golang repo.
//
// Modifications:
//  * Different package name, no package doc.
//  * Removed init() section, since we don't want to autoregister routes in the
//    default router (that's the main reason we are copy-pasting code instead of
//    importing the package).
//  * Modified Index() to put '&tok=...' into URLs.

import (
	"bufio"
	"bytes"
	"fmt"
	"html/template"
	"io"
	"log"
	"net/http"
	"os"
	"runtime"
	"runtime/pprof"
	"runtime/trace"
	"strconv"
	"strings"
	"time"
)

// Cmdline responds with the running program's
// command line, with arguments separated by NUL bytes.
// The package initialization registers it as /debug/pprof/cmdline.
func Cmdline(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	fmt.Fprintf(w, strings.Join(os.Args, "\x00"))
}

func sleep(w http.ResponseWriter, d time.Duration) {
	var clientGone <-chan bool
	if cn, ok := w.(http.CloseNotifier); ok {
		clientGone = cn.CloseNotify()
	}
	select {
	case <-time.After(d):
	case <-clientGone:
	}
}

func durationExceedsWriteTimeout(r *http.Request, seconds float64) bool {
	srv, ok := r.Context().Value(http.ServerContextKey).(*http.Server)
	return ok && srv.WriteTimeout != 0 && seconds >= srv.WriteTimeout.Seconds()
}

// Profile responds with the pprof-formatted cpu profile.
// The package initialization registers it as /debug/pprof/profile.
func Profile(w http.ResponseWriter, r *http.Request) {
	sec, _ := strconv.ParseInt(r.FormValue("seconds"), 10, 64)
	if sec == 0 {
		sec = 30
	}

	if durationExceedsWriteTimeout(r, float64(sec)) {
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		w.Header().Set("X-Go-Pprof", "1")
		w.WriteHeader(http.StatusBadRequest)
		fmt.Fprintln(w, "profile duration exceeds server's WriteTimeout")
		return
	}

	// Set Content Type assuming StartCPUProfile will work,
	// because if it does it starts writing.
	w.Header().Set("Content-Type", "application/octet-stream")
	if err := pprof.StartCPUProfile(w); err != nil {
		// StartCPUProfile failed, so no writes yet.
		// Can change header back to text content
		// and send error code.
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		w.Header().Set("X-Go-Pprof", "1")
		w.WriteHeader(http.StatusInternalServerError)
		fmt.Fprintf(w, "Could not enable CPU profiling: %s\n", err)
		return
	}
	sleep(w, time.Duration(sec)*time.Second)
	pprof.StopCPUProfile()
}

// Trace responds with the execution trace in binary form.
// Tracing lasts for duration specified in seconds GET parameter, or for 1 second if not specified.
// The package initialization registers it as /debug/pprof/trace.
func Trace(w http.ResponseWriter, r *http.Request) {
	sec, err := strconv.ParseFloat(r.FormValue("seconds"), 64)
	if sec <= 0 || err != nil {
		sec = 1
	}

	if durationExceedsWriteTimeout(r, sec) {
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		w.Header().Set("X-Go-Pprof", "1")
		w.WriteHeader(http.StatusBadRequest)
		fmt.Fprintln(w, "profile duration exceeds server's WriteTimeout")
		return
	}

	// Set Content Type assuming trace.Start will work,
	// because if it does it starts writing.
	w.Header().Set("Content-Type", "application/octet-stream")
	if err := trace.Start(w); err != nil {
		// trace.Start failed, so no writes yet.
		// Can change header back to text content and send error code.
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		w.Header().Set("X-Go-Pprof", "1")
		w.WriteHeader(http.StatusInternalServerError)
		fmt.Fprintf(w, "Could not enable tracing: %s\n", err)
		return
	}
	sleep(w, time.Duration(sec*float64(time.Second)))
	trace.Stop()
}

// Symbol looks up the program counters listed in the request,
// responding with a table mapping program counters to function names.
// The package initialization registers it as /debug/pprof/symbol.
func Symbol(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")

	// We have to read the whole POST body before
	// writing any output. Buffer the output here.
	var buf bytes.Buffer

	// We don't know how many symbols we have, but we
	// do have symbol information. Pprof only cares whether
	// this number is 0 (no symbols available) or > 0.
	fmt.Fprintf(&buf, "num_symbols: 1\n")

	var b *bufio.Reader
	if r.Method == "POST" {
		b = bufio.NewReader(r.Body)
	} else {
		b = bufio.NewReader(strings.NewReader(r.URL.RawQuery))
	}

	for {
		word, err := b.ReadSlice('+')
		if err == nil {
			word = word[0 : len(word)-1] // trim +
		}
		pc, _ := strconv.ParseUint(string(word), 0, 64)
		if pc != 0 {
			f := runtime.FuncForPC(uintptr(pc))
			if f != nil {
				fmt.Fprintf(&buf, "%#x %s\n", pc, f.Name())
			}
		}

		// Wait until here to check for err; the last
		// symbol will have an err because it doesn't end in +.
		if err != nil {
			if err != io.EOF {
				fmt.Fprintf(&buf, "reading request: %v\n", err)
			}
			break
		}
	}

	w.Write(buf.Bytes())
}

// Handler returns an HTTP handler that serves the named profile.
func Handler(name string) http.Handler {
	return handler(name)
}

type handler string

func (name handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	debug, _ := strconv.Atoi(r.FormValue("debug"))
	p := pprof.Lookup(string(name))
	if p == nil {
		w.WriteHeader(404)
		fmt.Fprintf(w, "Unknown profile: %s\n", name)
		return
	}
	gc, _ := strconv.Atoi(r.FormValue("gc"))
	if name == "heap" && gc > 0 {
		runtime.GC()
	}
	p.WriteTo(w, debug)
}

// Index responds with the pprof-formatted profile named by the request.
// For example, "/debug/pprof/heap" serves the "heap" profile.
// Index responds to a request for "/debug/pprof/" with an HTML page
// listing the available profiles.
func Index(w http.ResponseWriter, r *http.Request) {
	if strings.HasPrefix(r.URL.Path, "/debug/pprof/") {
		name := strings.TrimPrefix(r.URL.Path, "/debug/pprof/")
		if name != "" {
			handler(name).ServeHTTP(w, r)
			return
		}
	}

	// [BEGIN modification]
	err := indexTmpl.Execute(w, map[string]any{
		"Tok":      r.FormValue("tok"),
		"Profiles": pprof.Profiles(),
	})
	if err != nil {
		log.Print(err)
	}
	// [END modification]
}

var indexTmpl = template.Must(template.New("index").Parse(`<html>
<head>
<title>/debug/pprof/</title>
</head>
<body>
/debug/pprof/<br>
<br>
profiles:<br>
<table>
{{/* [BEGIN modification] */}}
{{range .Profiles}}
<tr><td align=right>{{.Count}}<td><a href="{{.Name}}?debug=1&tok={{$.Tok}}">{{.Name}}</a>
{{end}}
</table>
<br>
<a href="goroutine?debug=2&tok={{.Tok}}">full goroutine stack dump</a><br>
{{/* [END modification] */}}
</body>
</html>
`))