108 lines
2.0 KiB
Go
108 lines
2.0 KiB
Go
package eventstream
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import (
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"encoding/json"
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"fmt"
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"io"
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"net/http"
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"strconv"
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"strings"
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"time"
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)
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type Event struct {
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ID int64
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Kind string
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Data any
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}
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func ParseSinceID(r *http.Request) int64 {
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sinceStr := strings.TrimSpace(r.URL.Query().Get("since"))
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if sinceStr == "" {
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sinceStr = strings.TrimSpace(r.Header.Get("Last-Event-ID"))
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}
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if sinceStr == "" {
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return 0
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}
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if v, err := strconv.ParseInt(sinceStr, 10, 64); err == nil && v >= 0 {
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return v
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}
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return 0
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}
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func Serve(w http.ResponseWriter, r *http.Request, pollEvery, heartbeat time.Duration, loadSince func(int64) []Event) {
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if r.Method != http.MethodGet {
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http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
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return
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}
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flusher, ok := w.(http.Flusher)
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if !ok {
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http.Error(w, "streaming unsupported", http.StatusBadRequest)
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return
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}
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w.Header().Set("Content-Type", "text/event-stream")
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w.Header().Set("Cache-Control", "no-cache")
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w.Header().Set("Connection", "keep-alive")
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if pollEvery <= 0 {
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pollEvery = 500 * time.Millisecond
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}
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if heartbeat <= 0 {
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heartbeat = 15 * time.Second
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}
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ctx := r.Context()
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since := ParseSinceID(r)
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send := func(ev Event) error {
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payload, err := json.Marshal(ev.Data)
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if err != nil {
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return err
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}
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if _, err := fmt.Fprintf(w, "id: %d\nevent: %s\ndata: %s\n\n", ev.ID, ev.Kind, string(payload)); err != nil {
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return err
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}
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flusher.Flush()
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return nil
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}
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if loadSince != nil {
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for _, ev := range loadSince(since) {
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if err := send(ev); err != nil {
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return
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}
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since = ev.ID
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}
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}
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pollTicker := time.NewTicker(pollEvery)
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pingTicker := time.NewTicker(heartbeat)
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defer pollTicker.Stop()
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defer pingTicker.Stop()
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for {
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select {
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case <-ctx.Done():
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return
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case <-pingTicker.C:
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_, _ = io.WriteString(w, ": ping\n\n")
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flusher.Flush()
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case <-pollTicker.C:
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if loadSince == nil {
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continue
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}
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evs := loadSince(since)
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if len(evs) == 0 {
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continue
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}
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for _, ev := range evs {
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if err := send(ev); err != nil {
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return
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}
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since = ev.ID
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}
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}
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}
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}
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