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status.go
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status.go
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// Copyright 2016 Google, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package status
import (
"bytes"
"fmt"
"html"
"html/template"
"io"
"net/http"
"os"
"path/filepath"
"sync"
"time"
"golang.org/x/net/context"
log "github.com/golang/glog"
)
var (
binaryName = filepath.Base(os.Args[0])
hostname string
serverStart = time.Now()
statusMu sync.RWMutex
statusSections []section
statusTmpl = template.Must(reparse(nil))
statusFuncMap = make(template.FuncMap)
)
type section struct {
Banner string
Fragment string
F func() interface{}
}
// AddStatusFuncs merges the provided functions into the set of
// functions used to render /debug/status. Call this before AddStatusPart
// if your template requires custom functions.
func AddStatusFuncs(fmap template.FuncMap) {
statusMu.Lock()
defer statusMu.Unlock()
for name, fun := range fmap {
if _, ok := statusFuncMap[name]; ok {
panic("duplicate status func registered: " + name)
}
statusFuncMap[name] = fun
}
}
var statusHTML = `<!DOCTYPE html>
<html>
<head>
<title>Status for {{.BinaryName}}</title>
<style>
body {
font-family: sans-serif;
}
h1 {
clear: both;
width: 100%;
text-align: center;
font-size: 120%;
background: #eef;
}
.lefthand {
float: left;
width: 80%;
}
.righthand {
text-align: right;
}
</style>
</head>
<h1>Status for {{.BinaryName}}</h1>
<div>
<div class=lefthand>
Started: {{.StartTime}}<br>
</div>
<div class=righthand>
Running on {{.Hostname}}<br>
View <a href=/debug/vars>variables</a>,
<a href=/debug/pprof>debugging profiles</a>,
<a href=/debug/resources>resources</a>,
</div>
</div>`
func reparse(sections []section) (*template.Template, error) {
var buf bytes.Buffer
io.WriteString(&buf, `{{define "status"}}`)
io.WriteString(&buf, statusHTML)
for i, sec := range sections {
fmt.Fprintf(&buf, "<h1>%s</h1>\n", html.EscapeString(sec.Banner))
fmt.Fprintf(&buf, "{{$sec := index .Sections %d}}\n", i)
fmt.Fprintf(&buf, `{{template "sec-%d" call $sec.F}}`+"\n", i)
}
fmt.Fprintf(&buf, `</html>`)
io.WriteString(&buf, "{{end}}\n")
for i, sec := range sections {
fmt.Fprintf(&buf, `{{define "sec-%d"}}%s{{end}}\n`, i, sec.Fragment)
}
return template.New("").Funcs(statusFuncMap).Parse(buf.String())
}
// AddStatusPart adds a new section to status. frag is used as a
// subtemplate of the template used to render /debug/status, and will
// be executed using the value of invoking f at the time of the
// /debug/status request. frag is parsed and executed with the
// html/template package. Functions registered with AddStatusFuncs
// may be used in the template.
func AddStatusPart(banner, frag string, f func(context.Context) interface{}) {
statusMu.Lock()
defer statusMu.Unlock()
secs := append(statusSections, section{
Banner: banner,
Fragment: frag,
F: func() interface{} { return f(context.Background()) },
})
var err error
statusTmpl, err = reparse(secs)
if err != nil {
secs[len(secs)-1] = section{
Banner: banner,
Fragment: "<code>bad status template: {{.}}</code>",
F: func() interface{} { return err },
}
}
statusTmpl, _ = reparse(secs)
statusSections = secs
}
// AddStatusSection registers a function that generates extra
// information for /debug/status. If banner is not empty, it will be
// used as a header before the information. If more complex output
// than a simple string is required use AddStatusPart instead.
func AddStatusSection(banner string, f func(context.Context) string) {
AddStatusPart(banner, `{{.}}`, func(ctx context.Context) interface{} { return f(ctx) })
}
func statusHandler(w http.ResponseWriter, r *http.Request) {
statusMu.Lock()
defer statusMu.Unlock()
data := struct {
Sections []section
BinaryName string
Hostname string
StartTime string
}{
Sections: statusSections,
BinaryName: binaryName,
Hostname: hostname,
StartTime: serverStart.Format(time.RFC1123),
}
if err := statusTmpl.ExecuteTemplate(w, "status", data); err != nil {
log.Errorf("servenv: couldn't execute template: %v", err)
}
}
// StatusURLPath returns the path to the status page.
func StatusURLPath() string {
return "/debug/status"
}
func init() {
var err error
hostname, err = os.Hostname()
if err != nil {
log.Fatalf("os.Hostname: %v", err)
}
http.HandleFunc("/debug/status", statusHandler)
}