// Copyright 2023 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. // Outyet is a web server that announces whether or not a particular Go version // has been tagged. package main import ( "expvar" "flag" "fmt" "html/template" "log" "net/http" "sync" "time" ) // Command-line flags. var ( httpAddr = flag.String("http", "localhost:8080", "Listen address") pollPeriod = flag.Duration("poll", 5*time.Second, "Poll period") version = flag.String("version", "1.4", "Go version") ) const baseChangeURL = "https://go.googlesource.com/go/+/" func main() { flag.Parse() changeURL := fmt.Sprintf("%sgo%s", baseChangeURL, *version) http.Handle("/", NewServer(*version, changeURL, *pollPeriod)) log.Printf("serving http://%s", *httpAddr) log.Fatal(http.ListenAndServe(*httpAddr, nil)) } // Exported variables for monitoring the server. // These are exported via HTTP as a JSON object at /debug/vars. var ( hitCount = expvar.NewInt("hitCount") pollCount = expvar.NewInt("pollCount") pollError = expvar.NewString("pollError") pollErrorCount = expvar.NewInt("pollErrorCount") ) // Server implements the outyet server. // It serves the user interface (it's an http.Handler) // and polls the remote repository for changes. type Server struct { version string url string period time.Duration mu sync.RWMutex // protects the yes variable yes bool } // NewServer returns an initialized outyet server. func NewServer(version, url string, period time.Duration) *Server { s := &Server{version: version, url: url, period: period} go s.poll() return s } // poll polls the change URL for the specified period until the tag exists. // Then it sets the Server's yes field true and exits. func (s *Server) poll() { for !isTagged(s.url) { pollSleep(s.period) } s.mu.Lock() s.yes = true s.mu.Unlock() pollDone() } // Hooks that may be overridden for integration tests. var ( pollSleep = time.Sleep pollDone = func() {} ) // isTagged makes an HTTP HEAD request to the given URL and reports whether it // returned a 200 OK response. func isTagged(url string) bool { pollCount.Add(1) r, err := http.Head(url) if err != nil { log.Print(err) pollError.Set(err.Error()) pollErrorCount.Add(1) return false } return r.StatusCode == http.StatusOK } // ServeHTTP implements the HTTP user interface. func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) { hitCount.Add(1) s.mu.RLock() data := struct { URL string Version string Yes bool }{ s.url, s.version, s.yes, } s.mu.RUnlock() err := tmpl.Execute(w, data) if err != nil { log.Print(err) } } // tmpl is the HTML template that drives the user interface. var tmpl = template.Must(template.New("tmpl").Parse(`

Is Go {{.Version}} out yet?

{{if .Yes}} YES! {{else}} No. :-( {{end}}

`))