k8s.io/apiserver@v0.31.1/pkg/server/routes/flags.go (about) 1 /* 2 Copyright 2018 The Kubernetes Authors. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 */ 16 17 package routes 18 19 import ( 20 "fmt" 21 "html/template" 22 "io/ioutil" 23 "net/http" 24 "path" 25 "sync" 26 27 "k8s.io/klog/v2" 28 29 "k8s.io/apiserver/pkg/server/mux" 30 ) 31 32 var ( 33 lock = &sync.RWMutex{} 34 registeredFlags = map[string]debugFlag{} 35 ) 36 37 // DebugFlags adds handlers for flags under /debug/flags. 38 type DebugFlags struct { 39 } 40 41 // Install registers the APIServer's flags handler. 42 func (f DebugFlags) Install(c *mux.PathRecorderMux, flag string, handler func(http.ResponseWriter, *http.Request)) { 43 c.UnlistedHandle("/debug/flags", http.HandlerFunc(f.Index)) 44 c.UnlistedHandlePrefix("/debug/flags/", http.HandlerFunc(f.Index)) 45 46 url := path.Join("/debug/flags", flag) 47 c.UnlistedHandleFunc(url, handler) 48 49 f.addFlag(flag) 50 } 51 52 // Index responds with the `/debug/flags` request. 53 // For example, "/debug/flags/v" serves the "--v" flag. 54 // Index responds to a request for "/debug/flags/" with an HTML page 55 // listing the available flags. 56 func (f DebugFlags) Index(w http.ResponseWriter, r *http.Request) { 57 lock.RLock() 58 defer lock.RUnlock() 59 if err := indexTmpl.Execute(w, registeredFlags); err != nil { 60 klog.Error(err) 61 } 62 } 63 64 var indexTmpl = template.Must(template.New("index").Parse(`<html> 65 <head> 66 <title>/debug/flags/</title> 67 </head> 68 <body> 69 /debug/flags/<br> 70 <br> 71 flags:<br> 72 <table> 73 {{range .}} 74 <tr>{{.Flag}}<br> 75 {{end}} 76 </table> 77 <br> 78 full flags configurable<br> 79 </body> 80 </html> 81 `)) 82 83 type debugFlag struct { 84 Flag string 85 } 86 87 func (f DebugFlags) addFlag(flag string) { 88 lock.Lock() 89 defer lock.Unlock() 90 registeredFlags[flag] = debugFlag{flag} 91 } 92 93 // StringFlagSetterFunc is a func used for setting string type flag. 94 type StringFlagSetterFunc func(string) (string, error) 95 96 // StringFlagPutHandler wraps an http Handler to set string type flag. 97 func StringFlagPutHandler(setter StringFlagSetterFunc) http.HandlerFunc { 98 return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) { 99 switch { 100 case req.Method == "PUT": 101 body, err := ioutil.ReadAll(req.Body) 102 if err != nil { 103 writePlainText(http.StatusBadRequest, "error reading request body: "+err.Error(), w) 104 return 105 } 106 defer req.Body.Close() 107 response, err := setter(string(body)) 108 if err != nil { 109 writePlainText(http.StatusBadRequest, err.Error(), w) 110 return 111 } 112 writePlainText(http.StatusOK, response, w) 113 return 114 default: 115 writePlainText(http.StatusNotAcceptable, "unsupported http method", w) 116 return 117 } 118 }) 119 } 120 121 // writePlainText renders a simple string response. 122 func writePlainText(statusCode int, text string, w http.ResponseWriter) { 123 w.Header().Set("Content-Type", "text/plain") 124 w.Header().Set("X-Content-Type-Options", "nosniff") 125 w.WriteHeader(statusCode) 126 fmt.Fprintln(w, text) 127 }