init

src/realtime/latency_test.go

@@ -0,0 +1,77 @@
+// Copyright (C) 2026 Dcntrlized
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published
+// by the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package realtime
+
+import (
+	"sort"
+	"testing"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/gorilla/websocket"
+)
+
+// TestBroadcastLatency measures the fan-out path on real sockets: from the
+// instant Broadcast is called to the instant BOTH subscribers have decoded the
+// frame. It excludes the HTTP action and the database insert that precede a
+// trigger in production, so it is the floor for the end-to-end number.
+//
+// It logs p50/p95/max and only fails on a gross regression (p95 > 500ms) to
+// stay useful without being flaky on a loaded machine.
+func TestBroadcastLatency(t *testing.T) {
+	alertID := uuid.New()
+	_, wsURL, hub := startTestServer(t, alertID)
+
+	first := dial(t, wsURL)
+	second := dial(t, wsURL)
+	waitClients(t, hub, alertID, 2)
+
+	const iterations = 100
+	samples := make([]time.Duration, 0, iterations)
+	for i := 0; i < iterations; i++ {
+		eventID := uuid.NewString()
+		frame := AlarmFrame{
+			Type:            "alarm",
+			AlertID:         alertID.String(),
+			EventID:         eventID,
+			Action:          "trigger",
+			Message:         "latency probe",
+			ServerTime:      time.Now().UTC().Format(time.RFC3339Nano),
+			AutoStopSeconds: 300,
+		}
+		start := time.Now()
+		if delivered := hub.Broadcast(alertID, frame); delivered != 2 {
+			t.Fatalf("iteration %d: Broadcast delivered to %d clients, want 2", i, delivered)
+		}
+		for _, conn := range []*websocket.Conn{first, second} {
+			got := readAlarm(t, conn)
+			if got.EventID != eventID {
+				t.Fatalf("iteration %d: event id = %q, want %q", i, got.EventID, eventID)
+			}
+		}
+		samples = append(samples, time.Since(start))
+	}
+
+	sort.Slice(samples, func(i, j int) bool { return samples[i] < samples[j] })
+	p50 := samples[len(samples)*50/100]
+	p95 := samples[len(samples)*95/100]
+	max := samples[len(samples)-1]
+	t.Logf("broadcast -> 2 clients decoded: n=%d p50=%v p95=%v max=%v",
+		len(samples), p50, p95, max)
+	if p95 > 500*time.Millisecond {
+		t.Fatalf("p95 latency %v exceeds the 500ms budget", p95)
+	}
+}