| eventsource | |
| go-eventsource | |
| client/client |
A demo of server-sent events (i.e., EventSource).
Hat tip to athoune/broadcast-event-source for an example of SSE in Go.
Example with cURL:
curl -X POST -H "Content-Type: application/json" http://localhost:8888/update -d '{"text":"Hello from cURL"}'
Example with Go client:
go run client/client.go
| $(function() { | |
| var source = new EventSource('/events'); | |
| source.onopen = function (event) { | |
| console.log("eventsource connection open"); | |
| }; | |
| source.onerror = function() { | |
| if (event.target.readyState === 0) { | |
| console.log("reconnecting to eventsource"); | |
| } else { | |
| console.log("eventsource error"); | |
| } | |
| }; | |
| source.onmessage = function(event) { | |
| $('<div>', { | |
| text: event.data, | |
| css: { | |
| display: "none" | |
| } | |
| }) | |
| .prependTo("#messages") | |
| .show("fast") | |
| ; | |
| }; | |
| }); |
| package main | |
| import ( | |
| "bytes" | |
| "encoding/json" | |
| "fmt" | |
| "io/ioutil" | |
| "log" | |
| "net/http" | |
| "time" | |
| ) | |
| func main() { | |
| b, err := json.Marshal(map[string]interface{}{ | |
| "text": fmt.Sprintf("Hello from go client at %s", time.Now().Format(time.Kitchen)), | |
| }) | |
| if err != nil { | |
| log.Fatal(err) | |
| } | |
| buf := bytes.NewBuffer(b) | |
| resp, err := http.Post("http://localhost:8888/update", "application/json", buf) | |
| if err != nil { | |
| log.Fatal(err) | |
| } | |
| defer resp.Body.Close() | |
| body, err := ioutil.ReadAll(resp.Body) | |
| if err != nil { | |
| log.Fatal(err) | |
| } | |
| fmt.Println(string(body)) | |
| } |
| package main | |
| import ( | |
| "encoding/json" | |
| "fmt" | |
| "net/http" | |
| ) | |
| const ( | |
| msgBuf = 10 | |
| ) | |
| type Message struct { | |
| Text string | |
| } | |
| type Response map[string]interface{} | |
| func (r Response) String() (s string) { | |
| b, err := json.Marshal(r) | |
| if err != nil { | |
| s = "" | |
| return | |
| } | |
| s = string(b) | |
| return | |
| } | |
| type Broker struct { | |
| subscribers map[chan []byte]bool | |
| } | |
| func (b *Broker) Subscribe() chan []byte { | |
| ch := make(chan []byte, msgBuf) | |
| b.subscribers[ch] = true | |
| return ch | |
| } | |
| func (b *Broker) Unsubscribe(ch chan []byte) { | |
| delete(b.subscribers, ch) | |
| } | |
| func (b *Broker) Publish(msg []byte) { | |
| for ch := range b.subscribers { | |
| ch <- msg | |
| } | |
| } | |
| func NewBroker() *Broker { | |
| return &Broker{make(map[chan []byte]bool)} | |
| } | |
| var msgBroker *Broker | |
| func messageHandler(w http.ResponseWriter, r *http.Request) { | |
| if r.Method != "POST" { | |
| http.Error(w, "Method not allowed", http.StatusMethodNotAllowed) | |
| return | |
| } | |
| if r.Header.Get("Content-Type")[:16] != "application/json" { | |
| http.Error(w, "Content-Type must be application/json", http.StatusNotAcceptable) | |
| return | |
| } | |
| var m Message | |
| dec := json.NewDecoder(r.Body) | |
| if err := dec.Decode(&m); err != nil { | |
| http.Error(w, err.Error(), http.StatusInternalServerError) | |
| return | |
| } | |
| msgBroker.Publish([]byte(m.Text)) | |
| if r.Header.Get("Accept") == "application/json" { | |
| w.Header().Set("Content-Type", "application/json") | |
| fmt.Fprint(w, Response{"success": true, "message": "OK"}) | |
| return | |
| } | |
| fmt.Fprintln(w, "OK") | |
| } | |
| func timerEventSource(w http.ResponseWriter, r *http.Request) { | |
| f, ok := w.(http.Flusher) | |
| if !ok { | |
| http.Error(w, "streaming unsupported", http.StatusInternalServerError) | |
| return | |
| } | |
| w.Header().Set("Content-Type", "text/event-stream") | |
| w.Header().Set("Cache-Control", "no-cache") | |
| w.Header().Set("Connection", "keep-alive") | |
| ch := msgBroker.Subscribe() | |
| defer msgBroker.Unsubscribe(ch) | |
| for { | |
| msg := <-ch | |
| fmt.Fprintf(w, "data: Message: %s\n\n", msg) | |
| f.Flush() | |
| } | |
| } | |
| func main() { | |
| msgBroker = NewBroker() | |
| http.HandleFunc("/update", messageHandler) | |
| http.HandleFunc("/events", timerEventSource) | |
| http.Handle("/", http.FileServer(http.Dir("static"))) | |
| err := http.ListenAndServe("localhost:8888", nil) | |
| if err != nil { | |
| panic(err) | |
| } | |
| } |
| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <meta charset="utf-8"> | |
| <title>EventSource Demo</title> | |
| <link rel="stylesheet" href="style.css" type="text/css"> | |
| <script src="http://code.jquery.com/jquery-1.8.2.min.js"></script> | |
| </head> | |
| <body> | |
| <div class="container"> | |
| <h1>Messages</h1> | |
| <div id="messages"></div> | |
| </div> | |
| <script src="app.js"></script> | |
| </body> | |
| </html> |
| * { | |
| box-sizing: border-box; | |
| } | |
| body { | |
| background-color: #eee; | |
| font: 100%/1.5 "Source Sans Pro", "Helvetica Neue", Helvetica, sans-serif; | |
| padding-top: 2em; | |
| } | |
| .container { | |
| max-width: 720px; | |
| margin: 0 auto; | |
| padding: 20px; | |
| background-color: #fff; | |
| color: #333; | |
| border: 1px solid #ddd; | |
| } | |
| h1 { | |
| margin-top: 0; | |
| } | |
| #messages { | |
| max-height: 480px; | |
| overflow-y: auto; | |
| } |