pprof.go

Documentation: net/http/pprof

     1  // Copyright 2010 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package pprof serves via its HTTP server runtime profiling data
     6  // in the format expected by the pprof visualization tool.
     7  //
     8  // The package is typically only imported for the side effect of
     9  // registering its HTTP handlers.
    10  // The handled paths all begin with /debug/pprof/.
    11  //
    12  // To use pprof, link this package into your program:
    13  //	import _ "net/http/pprof"
    14  //
    15  // If your application is not already running an http server, you
    16  // need to start one. Add "net/http" and "log" to your imports and
    17  // the following code to your main function:
    18  //
    19  // 	go func() {
    20  // 		log.Println(http.ListenAndServe("localhost:6060", nil))
    21  // 	}()
    22  //
    23  // Then use the pprof tool to look at the heap profile:
    24  //
    25  //	go tool pprof http://localhost:6060/debug/pprof/heap
    26  //
    27  // Or to look at a 30-second CPU profile:
    28  //
    29  //	go tool pprof http://localhost:6060/debug/pprof/profile
    30  //
    31  // Or to look at the goroutine blocking profile, after calling
    32  // runtime.SetBlockProfileRate in your program:
    33  //
    34  //	go tool pprof http://localhost:6060/debug/pprof/block
    35  //
    36  // Or to collect a 5-second execution trace:
    37  //
    38  //	wget http://localhost:6060/debug/pprof/trace?seconds=5
    39  //
    40  // Or to look at the holders of contended mutexes, after calling
    41  // runtime.SetMutexProfileFraction in your program:
    42  //
    43  //	go tool pprof http://localhost:6060/debug/pprof/mutex
    44  //
    45  // To view all available profiles, open http://localhost:6060/debug/pprof/
    46  // in your browser.
    47  //
    48  // For a study of the facility in action, visit
    49  //
    50  //	https://blog.golang.org/2011/06/profiling-go-programs.html
    51  //
    52  package pprof
    53  
    54  import (
    55  	"bufio"
    56  	"bytes"
    57  	"fmt"
    58  	"html/template"
    59  	"io"
    60  	"log"
    61  	"net/http"
    62  	"os"
    63  	"runtime"
    64  	"runtime/pprof"
    65  	"runtime/trace"
    66  	"strconv"
    67  	"strings"
    68  	"time"
    69  )
    70  
    71  func init() {
    72  	http.HandleFunc("/debug/pprof/", Index)
    73  	http.HandleFunc("/debug/pprof/cmdline", Cmdline)
    74  	http.HandleFunc("/debug/pprof/profile", Profile)
    75  	http.HandleFunc("/debug/pprof/symbol", Symbol)
    76  	http.HandleFunc("/debug/pprof/trace", Trace)
    77  }
    78  
    79  // Cmdline responds with the running program's
    80  // command line, with arguments separated by NUL bytes.
    81  // The package initialization registers it as /debug/pprof/cmdline.
    82  func Cmdline(w http.ResponseWriter, r *http.Request) {
    83  	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
    84  	fmt.Fprintf(w, strings.Join(os.Args, "\x00"))
    85  }
    86  
    87  func sleep(w http.ResponseWriter, d time.Duration) {
    88  	var clientGone <-chan bool
    89  	if cn, ok := w.(http.CloseNotifier); ok {
    90  		clientGone = cn.CloseNotify()
    91  	}
    92  	select {
    93  	case <-time.After(d):
    94  	case <-clientGone:
    95  	}
    96  }
    97  
    98  func durationExceedsWriteTimeout(r *http.Request, seconds float64) bool {
    99  	srv, ok := r.Context().Value(http.ServerContextKey).(*http.Server)
   100  	return ok && srv.WriteTimeout != 0 && seconds >= srv.WriteTimeout.Seconds()
   101  }
   102  
   103  // Profile responds with the pprof-formatted cpu profile.
   104  // The package initialization registers it as /debug/pprof/profile.
   105  func Profile(w http.ResponseWriter, r *http.Request) {
   106  	sec, _ := strconv.ParseInt(r.FormValue("seconds"), 10, 64)
   107  	if sec == 0 {
   108  		sec = 30
   109  	}
   110  
   111  	if durationExceedsWriteTimeout(r, float64(sec)) {
   112  		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
   113  		w.Header().Set("X-Go-Pprof", "1")
   114  		w.WriteHeader(http.StatusBadRequest)
   115  		fmt.Fprintln(w, "profile duration exceeds server's WriteTimeout")
   116  		return
   117  	}
   118  
   119  	// Set Content Type assuming StartCPUProfile will work,
   120  	// because if it does it starts writing.
   121  	w.Header().Set("Content-Type", "application/octet-stream")
   122  	if err := pprof.StartCPUProfile(w); err != nil {
   123  		// StartCPUProfile failed, so no writes yet.
   124  		// Can change header back to text content
   125  		// and send error code.
   126  		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
   127  		w.Header().Set("X-Go-Pprof", "1")
   128  		w.WriteHeader(http.StatusInternalServerError)
   129  		fmt.Fprintf(w, "Could not enable CPU profiling: %s\n", err)
   130  		return
   131  	}
   132  	sleep(w, time.Duration(sec)*time.Second)
   133  	pprof.StopCPUProfile()
   134  }
   135  
   136  // Trace responds with the execution trace in binary form.
   137  // Tracing lasts for duration specified in seconds GET parameter, or for 1 second if not specified.
   138  // The package initialization registers it as /debug/pprof/trace.
   139  func Trace(w http.ResponseWriter, r *http.Request) {
   140  	sec, err := strconv.ParseFloat(r.FormValue("seconds"), 64)
   141  	if sec <= 0 || err != nil {
   142  		sec = 1
   143  	}
   144  
   145  	if durationExceedsWriteTimeout(r, sec) {
   146  		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
   147  		w.Header().Set("X-Go-Pprof", "1")
   148  		w.WriteHeader(http.StatusBadRequest)
   149  		fmt.Fprintln(w, "profile duration exceeds server's WriteTimeout")
   150  		return
   151  	}
   152  
   153  	// Set Content Type assuming trace.Start will work,
   154  	// because if it does it starts writing.
   155  	w.Header().Set("Content-Type", "application/octet-stream")
   156  	if err := trace.Start(w); err != nil {
   157  		// trace.Start failed, so no writes yet.
   158  		// Can change header back to text content and send error code.
   159  		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
   160  		w.Header().Set("X-Go-Pprof", "1")
   161  		w.WriteHeader(http.StatusInternalServerError)
   162  		fmt.Fprintf(w, "Could not enable tracing: %s\n", err)
   163  		return
   164  	}
   165  	sleep(w, time.Duration(sec*float64(time.Second)))
   166  	trace.Stop()
   167  }
   168  
   169  // Symbol looks up the program counters listed in the request,
   170  // responding with a table mapping program counters to function names.
   171  // The package initialization registers it as /debug/pprof/symbol.
   172  func Symbol(w http.ResponseWriter, r *http.Request) {
   173  	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
   174  
   175  	// We have to read the whole POST body before
   176  	// writing any output. Buffer the output here.
   177  	var buf bytes.Buffer
   178  
   179  	// We don't know how many symbols we have, but we
   180  	// do have symbol information. Pprof only cares whether
   181  	// this number is 0 (no symbols available) or > 0.
   182  	fmt.Fprintf(&buf, "num_symbols: 1\n")
   183  
   184  	var b *bufio.Reader
   185  	if r.Method == "POST" {
   186  		b = bufio.NewReader(r.Body)
   187  	} else {
   188  		b = bufio.NewReader(strings.NewReader(r.URL.RawQuery))
   189  	}
   190  
   191  	for {
   192  		word, err := b.ReadSlice('+')
   193  		if err == nil {
   194  			word = word[0 : len(word)-1] // trim +
   195  		}
   196  		pc, _ := strconv.ParseUint(string(word), 0, 64)
   197  		if pc != 0 {
   198  			f := runtime.FuncForPC(uintptr(pc))
   199  			if f != nil {
   200  				fmt.Fprintf(&buf, "%#x %s\n", pc, f.Name())
   201  			}
   202  		}
   203  
   204  		// Wait until here to check for err; the last
   205  		// symbol will have an err because it doesn't end in +.
   206  		if err != nil {
   207  			if err != io.EOF {
   208  				fmt.Fprintf(&buf, "reading request: %v\n", err)
   209  			}
   210  			break
   211  		}
   212  	}
   213  
   214  	w.Write(buf.Bytes())
   215  }
   216  
   217  // Handler returns an HTTP handler that serves the named profile.
   218  func Handler(name string) http.Handler {
   219  	return handler(name)
   220  }
   221  
   222  type handler string
   223  
   224  func (name handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
   225  	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
   226  	debug, _ := strconv.Atoi(r.FormValue("debug"))
   227  	p := pprof.Lookup(string(name))
   228  	if p == nil {
   229  		w.WriteHeader(404)
   230  		fmt.Fprintf(w, "Unknown profile: %s\n", name)
   231  		return
   232  	}
   233  	gc, _ := strconv.Atoi(r.FormValue("gc"))
   234  	if name == "heap" && gc > 0 {
   235  		runtime.GC()
   236  	}
   237  	p.WriteTo(w, debug)
   238  }
   239  
   240  // Index responds with the pprof-formatted profile named by the request.
   241  // For example, "/debug/pprof/heap" serves the "heap" profile.
   242  // Index responds to a request for "/debug/pprof/" with an HTML page
   243  // listing the available profiles.
   244  func Index(w http.ResponseWriter, r *http.Request) {
   245  	if strings.HasPrefix(r.URL.Path, "/debug/pprof/") {
   246  		name := strings.TrimPrefix(r.URL.Path, "/debug/pprof/")
   247  		if name != "" {
   248  			handler(name).ServeHTTP(w, r)
   249  			return
   250  		}
   251  	}
   252  
   253  	profiles := pprof.Profiles()
   254  	if err := indexTmpl.Execute(w, profiles); err != nil {
   255  		log.Print(err)
   256  	}
   257  }
   258  
   259  var indexTmpl = template.Must(template.New("index").Parse(`<html>
   260  <head>
   261  <title>/debug/pprof/</title>
   262  </head>
   263  <body>
   264  /debug/pprof/<br>
   265  <br>
   266  profiles:<br>
   267  <table>
   268  {{range .}}
   269  <tr><td align=right>{{.Count}}<td><a href="{{.Name}}?debug=1">{{.Name}}</a>
   270  {{end}}
   271  </table>
   272  <br>
   273  <a href="goroutine?debug=2">full goroutine stack dump</a><br>
   274  </body>
   275  </html>
   276  `))
   277
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