e2pg/web: refactor. query and encdoe updates json once for all clients

cmd/e2pg/main.go

@@ -119,6 +119,10 @@ func main() {
 		check(pprof.StartCPUProfile(&pbuf))
 	}
 
+	go func() {
+		check(wh.PushUpdates())
+	}()
+
 	go func() {
 		for {
 			check(e2pg.PruneIntg(ctx, pg))

e2pg/web/web.go

@@ -1,6 +1,7 @@
 package web
 
 import (
+	"context"
 	_ "embed"
 	"encoding/json"
 	"fmt"
@@ -40,28 +41,38 @@ type Handler struct {
 	conf  *e2pg.Config
 
 	clientsMutex sync.Mutex
-	clients      map[string]chan uint64
+	clients      map[string]chan []byte
 
 	templates map[string]*template.Template
 }
 
 func New(mgr *e2pg.Manager, conf *e2pg.Config, pgp *pgxpool.Pool) *Handler {
-	h := &Handler{
+	return &Handler{
 		pgp:       pgp,
 		mgr:       mgr,
 		conf:      conf,
-		clients:   make(map[string]chan uint64),
+		clients:   make(map[string]chan []byte),
 		templates: make(map[string]*template.Template),
 	}
-	go func() {
-		for {
-			tid := mgr.Updates()
+}
+
+func (h *Handler) PushUpdates() error {
+	ctx := context.Background()
+	for ; ; h.mgr.Updates() {
+		tus, err := e2pg.TaskUpdates(ctx, h.pgp)
+		if err != nil {
+			return fmt.Errorf("querying task updates: %w", err)
+		}
+		for _, update := range tus {
+			j, err := json.Marshal(update)
+			if err != nil {
+				return fmt.Errorf("marshaling task update: %w", err)
+			}
 			for _, c := range h.clients {
-				c <- tid
+				c <- j
 			}
 		}
-	}()
-	return h
+	}
 }
 
 func (h *Handler) template(name string) (*template.Template, error) {
@@ -219,7 +230,7 @@ func (h *Handler) Updates(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Connection", "keep-alive")
 
 	slog.InfoContext(r.Context(), "start sse", "c", r.RemoteAddr, "n", len(h.clients))
-	c := make(chan uint64)
+	c := make(chan []byte)
 	h.clientsMutex.Lock()
 	h.clients[r.RemoteAddr] = c
 	h.clientsMutex.Unlock()
@@ -233,28 +244,16 @@ func (h *Handler) Updates(w http.ResponseWriter, r *http.Request) {
 
 	for {
 		select {
-		case <-c:
-		case <-r.Context().Done(): // disconnect
-			return
-		}
-		tus, err := e2pg.TaskUpdates(r.Context(), h.pgp)
-		if err != nil {
-			slog.ErrorContext(r.Context(), "json error", "e", err)
-			return
-		}
-		for i := range tus {
-			sjson, err := json.Marshal(tus[i])
-			if err != nil {
-				slog.ErrorContext(r.Context(), "json error", "e", err)
-				return
-			}
-			fmt.Fprintf(w, "data: %s\n\n", sjson)
+		case j := <-c:
+			fmt.Fprintf(w, "data: %s\n\n", j)
 			flusher, ok := w.(http.Flusher)
 			if !ok {
 				http.Error(w, "Streaming unsupported", http.StatusInternalServerError)
 				return
 			}
 			flusher.Flush()
+		case <-r.Context().Done(): // disconnect
+			return
 		}
 	}
 }