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// Copyright 2015 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 trace
import (
"bytes"
"fmt"
"html/template"
"io"
"log"
"net/http"
"runtime"
"sort"
"strconv"
"strings"
"sync"
"sync/atomic"
"text/tabwriter"
"time"
)
const maxEventsPerLog = 100
type bucket struct {
MaxErrAge time.Duration
String string
}
var buckets = []bucket{
{0, "total"},
{10 * time.Second, "errs<10s"},
{1 * time.Minute, "errs<1m"},
{10 * time.Minute, "errs<10m"},
{1 * time.Hour, "errs<1h"},
{10 * time.Hour, "errs<10h"},
{24000 * time.Hour, "errors"},
}
// RenderEvents renders the HTML page typically served at /debug/events.
// It does not do any auth checking. The request may be nil.
//
// Most users will use the Events handler.
func RenderEvents(w http.ResponseWriter, req *http.Request, sensitive bool) {
now := time.Now()
data := &struct {
Families []string // family names
Buckets []bucket
Counts [][]int // eventLog count per family/bucket
// Set when a bucket has been selected.
Family string
Bucket int
EventLogs eventLogs
Expanded bool
}{
Buckets: buckets,
}
data.Families = make([]string, 0, len(families))
famMu.RLock()
for name := range families {
data.Families = append(data.Families, name)
}
famMu.RUnlock()
sort.Strings(data.Families)
// Count the number of eventLogs in each family for each error age.
data.Counts = make([][]int, len(data.Families))
for i, name := range data.Families {
// TODO(sameer): move this loop under the family lock.
f := getEventFamily(name)
data.Counts[i] = make([]int, len(data.Buckets))
for j, b := range data.Buckets {
data.Counts[i][j] = f.Count(now, b.MaxErrAge)
}
}
if req != nil {
var ok bool
data.Family, data.Bucket, ok = parseEventsArgs(req)
if !ok {
// No-op
} else {
data.EventLogs = getEventFamily(data.Family).Copy(now, buckets[data.Bucket].MaxErrAge)
}
if data.EventLogs != nil {
defer data.EventLogs.Free()
sort.Sort(data.EventLogs)
}
if exp, err := strconv.ParseBool(req.FormValue("exp")); err == nil {
data.Expanded = exp
}
}
famMu.RLock()
defer famMu.RUnlock()
if err := eventsTmpl().Execute(w, data); err != nil {
log.Printf("net/trace: Failed executing template: %v", err)
}
}
func parseEventsArgs(req *http.Request) (fam string, b int, ok bool) {
fam, bStr := req.FormValue("fam"), req.FormValue("b")
if fam == "" || bStr == "" {
return "", 0, false
}
b, err := strconv.Atoi(bStr)
if err != nil || b < 0 || b >= len(buckets) {
return "", 0, false
}
return fam, b, true
}
// An EventLog provides a log of events associated with a specific object.
type EventLog interface {
// Printf formats its arguments with fmt.Sprintf and adds the
// result to the event log.
Printf(format string, a ...interface{})
// Errorf is like Printf, but it marks this event as an error.
Errorf(format string, a ...interface{})
// Finish declares that this event log is complete.
// The event log should not be used after calling this method.
Finish()
}
// NewEventLog returns a new EventLog with the specified family name
// and title.
func NewEventLog(family, title string) EventLog {
el := newEventLog()
el.ref()
el.Family, el.Title = family, title
el.Start = time.Now()
el.events = make([]logEntry, 0, maxEventsPerLog)
el.stack = make([]uintptr, 32)
n := runtime.Callers(2, el.stack)
el.stack = el.stack[:n]
getEventFamily(family).add(el)
return el
}
func (el *eventLog) Finish() {
getEventFamily(el.Family).remove(el)
el.unref() // matches ref in New
}
var (
famMu sync.RWMutex
families = make(map[string]*eventFamily) // family name => family
)
func getEventFamily(fam string) *eventFamily {
famMu.Lock()
defer famMu.Unlock()
f := families[fam]
if f == nil {
f = &eventFamily{}
families[fam] = f
}
return f
}
type eventFamily struct {
mu sync.RWMutex
eventLogs eventLogs
}
func (f *eventFamily) add(el *eventLog) {
f.mu.Lock()
f.eventLogs = append(f.eventLogs, el)
f.mu.Unlock()
}
func (f *eventFamily) remove(el *eventLog) {
f.mu.Lock()
defer f.mu.Unlock()
for i, el0 := range f.eventLogs {
if el == el0 {
copy(f.eventLogs[i:], f.eventLogs[i+1:])
f.eventLogs = f.eventLogs[:len(f.eventLogs)-1]
return
}
}
}
func (f *eventFamily) Count(now time.Time, maxErrAge time.Duration) (n int) {
f.mu.RLock()
defer f.mu.RUnlock()
for _, el := range f.eventLogs {
if el.hasRecentError(now, maxErrAge) {
n++
}
}
return
}
func (f *eventFamily) Copy(now time.Time, maxErrAge time.Duration) (els eventLogs) {
f.mu.RLock()
defer f.mu.RUnlock()
els = make(eventLogs, 0, len(f.eventLogs))
for _, el := range f.eventLogs {
if el.hasRecentError(now, maxErrAge) {
el.ref()
els = append(els, el)
}
}
return
}
type eventLogs []*eventLog
// Free calls unref on each element of the list.
func (els eventLogs) Free() {
for _, el := range els {
el.unref()
}
}
// eventLogs may be sorted in reverse chronological order.
func (els eventLogs) Len() int { return len(els) }
func (els eventLogs) Less(i, j int) bool { return els[i].Start.After(els[j].Start) }
func (els eventLogs) Swap(i, j int) { els[i], els[j] = els[j], els[i] }
// A logEntry is a timestamped log entry in an event log.
type logEntry struct {
When time.Time
Elapsed time.Duration // since previous event in log
NewDay bool // whether this event is on a different day to the previous event
What string
IsErr bool
}
// WhenString returns a string representation of the elapsed time of the event.
// It will include the date if midnight was crossed.
func (e logEntry) WhenString() string {
if e.NewDay {
return e.When.Format("2006/01/02 15:04:05.000000")
}
return e.When.Format("15:04:05.000000")
}
// An eventLog represents an active event log.
type eventLog struct {
// Family is the top-level grouping of event logs to which this belongs.
Family string
// Title is the title of this event log.
Title string
// Timing information.
Start time.Time
// Call stack where this event log was created.
stack []uintptr
// Append-only sequence of events.
//
// TODO(sameer): change this to a ring buffer to avoid the array copy
// when we hit maxEventsPerLog.
mu sync.RWMutex
events []logEntry
LastErrorTime time.Time
discarded int
refs int32 // how many buckets this is in
}
func (el *eventLog) reset() {
// Clear all but the mutex. Mutexes may not be copied, even when unlocked.
el.Family = ""
el.Title = ""
el.Start = time.Time{}
el.stack = nil
el.events = nil
el.LastErrorTime = time.Time{}
el.discarded = 0
el.refs = 0
}
func (el *eventLog) hasRecentError(now time.Time, maxErrAge time.Duration) bool {
if maxErrAge == 0 {
return true
}
el.mu.RLock()
defer el.mu.RUnlock()
return now.Sub(el.LastErrorTime) < maxErrAge
}
// delta returns the elapsed time since the last event or the log start,
// and whether it spans midnight.
// L >= el.mu
func (el *eventLog) delta(t time.Time) (time.Duration, bool) {
if len(el.events) == 0 {
return t.Sub(el.Start), false
}
prev := el.events[len(el.events)-1].When
return t.Sub(prev), prev.Day() != t.Day()
}
func (el *eventLog) Printf(format string, a ...interface{}) {
el.printf(false, format, a...)
}
func (el *eventLog) Errorf(format string, a ...interface{}) {
el.printf(true, format, a...)
}
func (el *eventLog) printf(isErr bool, format string, a ...interface{}) {
e := logEntry{When: time.Now(), IsErr: isErr, What: fmt.Sprintf(format, a...)}
el.mu.Lock()
e.Elapsed, e.NewDay = el.delta(e.When)
if len(el.events) < maxEventsPerLog {
el.events = append(el.events, e)
} else {
// Discard the oldest event.
if el.discarded == 0 {
// el.discarded starts at two to count for the event it
// is replacing, plus the next one that we are about to
// drop.
el.discarded = 2
} else {
el.discarded++
}
// TODO(sameer): if this causes allocations on a critical path,
// change eventLog.What to be a fmt.Stringer, as in trace.go.
el.events[0].What = fmt.Sprintf("(%d events discarded)", el.discarded)
// The timestamp of the discarded meta-event should be
// the time of the last event it is representing.
el.events[0].When = el.events[1].When
copy(el.events[1:], el.events[2:])
el.events[maxEventsPerLog-1] = e
}
if e.IsErr {
el.LastErrorTime = e.When
}
el.mu.Unlock()
}
func (el *eventLog) ref() {
atomic.AddInt32(&el.refs, 1)
}
func (el *eventLog) unref() {
if atomic.AddInt32(&el.refs, -1) == 0 {
freeEventLog(el)
}
}
func (el *eventLog) When() string {
return el.Start.Format("2006/01/02 15:04:05.000000")
}
func (el *eventLog) ElapsedTime() string {
elapsed := time.Since(el.Start)
return fmt.Sprintf("%.6f", elapsed.Seconds())
}
func (el *eventLog) Stack() string {
buf := new(bytes.Buffer)
tw := tabwriter.NewWriter(buf, 1, 8, 1, '\t', 0)
printStackRecord(tw, el.stack)
tw.Flush()
return buf.String()
}
// printStackRecord prints the function + source line information
// for a single stack trace.
// Adapted from runtime/pprof/pprof.go.
func printStackRecord(w io.Writer, stk []uintptr) {
for _, pc := range stk {
f := runtime.FuncForPC(pc)
if f == nil {
continue
}
file, line := f.FileLine(pc)
name := f.Name()
// Hide runtime.goexit and any runtime functions at the beginning.
if strings.HasPrefix(name, "runtime.") {
continue
}
fmt.Fprintf(w, "# %s\t%s:%d\n", name, file, line)
}
}
func (el *eventLog) Events() []logEntry {
el.mu.RLock()
defer el.mu.RUnlock()
return el.events
}
// freeEventLogs is a freelist of *eventLog
var freeEventLogs = make(chan *eventLog, 1000)
// newEventLog returns a event log ready to use.
func newEventLog() *eventLog {
select {
case el := <-freeEventLogs:
return el
default:
return new(eventLog)
}
}
// freeEventLog adds el to freeEventLogs if there's room.
// This is non-blocking.
func freeEventLog(el *eventLog) {
el.reset()
select {
case freeEventLogs <- el:
default:
}
}
var eventsTmplCache *template.Template
var eventsTmplOnce sync.Once
func eventsTmpl() *template.Template {
eventsTmplOnce.Do(func() {
eventsTmplCache = template.Must(template.New("events").Funcs(template.FuncMap{
"elapsed": elapsed,
"trimSpace": strings.TrimSpace,
}).Parse(eventsHTML))
})
return eventsTmplCache
}
const eventsHTML = `
<html>
<head>
<title>events</title>
</head>
<style type="text/css">
body {
font-family: sans-serif;
}
table#req-status td.family {
padding-right: 2em;
}
table#req-status td.active {
padding-right: 1em;
}
table#req-status td.empty {
color: #aaa;
}
table#reqs {
margin-top: 1em;
}
table#reqs tr.first {
{{if $.Expanded}}font-weight: bold;{{end}}
}
table#reqs td {
font-family: monospace;
}
table#reqs td.when {
text-align: right;
white-space: nowrap;
}
table#reqs td.elapsed {
padding: 0 0.5em;
text-align: right;
white-space: pre;
width: 10em;
}
address {
font-size: smaller;
margin-top: 5em;
}
</style>
<body>
<h1>/debug/events</h1>
<table id="req-status">
{{range $i, $fam := .Families}}
<tr>
<td class="family">{{$fam}}</td>
{{range $j, $bucket := $.Buckets}}
{{$n := index $.Counts $i $j}}
<td class="{{if not $bucket.MaxErrAge}}active{{end}}{{if not $n}}empty{{end}}">
{{if $n}}<a href="?fam={{$fam}}&b={{$j}}{{if $.Expanded}}&exp=1{{end}}">{{end}}
[{{$n}} {{$bucket.String}}]
{{if $n}}</a>{{end}}
</td>
{{end}}
</tr>{{end}}
</table>
{{if $.EventLogs}}
<hr />
<h3>Family: {{$.Family}}</h3>
{{if $.Expanded}}<a href="?fam={{$.Family}}&b={{$.Bucket}}">{{end}}
[Summary]{{if $.Expanded}}</a>{{end}}
{{if not $.Expanded}}<a href="?fam={{$.Family}}&b={{$.Bucket}}&exp=1">{{end}}
[Expanded]{{if not $.Expanded}}</a>{{end}}
<table id="reqs">
<tr><th>When</th><th>Elapsed</th></tr>
{{range $el := $.EventLogs}}
<tr class="first">
<td class="when">{{$el.When}}</td>
<td class="elapsed">{{$el.ElapsedTime}}</td>
<td>{{$el.Title}}
</tr>
{{if $.Expanded}}
<tr>
<td class="when"></td>
<td class="elapsed"></td>
<td><pre>{{$el.Stack|trimSpace}}</pre></td>
</tr>
{{range $el.Events}}
<tr>
<td class="when">{{.WhenString}}</td>
<td class="elapsed">{{elapsed .Elapsed}}</td>
<td>.{{if .IsErr}}E{{else}}.{{end}}. {{.What}}</td>
</tr>
{{end}}
{{end}}
{{end}}
</table>
{{end}}
</body>
</html>
`
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