feat: add live server-time card with host

README.md

@@ -16,8 +16,10 @@ miniature:
   routes keep precedence
 - **Live updates over SSE** — new/removed signatures stream to every open tab,
   with a real-time **connected-clients** ("N online") indicator
-- **Version badge** — the serving build's version is shown in the UI and
-  `/api/info`; ideal for watching a **canary rollout** decide which build answers
+- **Version badge + live server-time card** — the serving build's version is
+  shown in the UI and `/api/info`, and a **live clock** (streamed over SSE with
+  the server's `version` + `host`) makes a **canary rollout** obvious: the card
+  is new in v2, and its time/host reveal exactly which build/replica served you
 - **[GORM](https://gorm.io) with PostgreSQL _or_ SQLite** — `uint` PKs and soft
   deletes, the same conventions Miabi uses. Attach a Miabi managed Postgres, or
   fall back to a zero-config SQLite file (pure-Go driver, no CGO).
@@ -44,20 +46,23 @@ and keeps the container tiny.
 | Method   | Path                 | Description                        |
 |----------|----------------------|------------------------------------|
 | `GET`    | `/healthz`           | Liveness/readiness (checks the DB), reports `version` |
-| `GET`    | `/api/info`          | App name, serving `version`, connected-client count |
+| `GET`    | `/api/info`          | App name, serving `version`, `host`, connected-client count |
+| `GET`    | `/api/time`          | Current server time + `version` + `host` (v2 — canary probe) |
 | `GET`    | `/api/entries`       | List entries + total; paginated via `?limit=&offset=` |
 | `POST`   | `/api/entries`       | Create `{ "name", "message" }` (broadcast live) |
 | `DELETE` | `/api/entries/{id}`  | Delete an entry (broadcast live)   |
-| `GET`    | `/api/stream`        | **SSE** stream: `welcome`, `created`, `deleted`, `presence` events |
+| `GET`    | `/api/stream`        | **SSE** stream: `welcome`, `created`, `deleted`, `presence`, `tick` events |
 | `GET`    | `/` · `/all`         | The web UI (home · all-signatures page) |
 
 ### Live updates (SSE)
 
 `/api/stream` is a Server-Sent Events endpoint. On connect the client gets a
-`welcome` event (serving version + online count); thereafter the server pushes
-`created` / `deleted` events as the wall changes and `presence` events whenever
-the number of connected clients changes. The UI uses these to update the wall in
-real time and show a live **“N online”** indicator — no polling.
+`welcome` event (serving version + host + online count); thereafter the server
+pushes `created` / `deleted` events as the wall changes, `presence` events when
+the connected-client count changes, and a `tick` event once a second carrying
+the live server time (with `version` + `host`). The UI uses these to update the
+wall in real time, show a live **“N online”** indicator, and drive the
+**server-time card** — all without polling.
 
 ## Configuration
 
@@ -130,10 +135,19 @@ docker build --build-arg VERSION=2.0.0 -t miabi/guestbook:2.0.0 .
 1. Deploy `1.0.0` as the app; attach a **shared** managed Postgres.
 2. Roll out `2.0.0` as a **canary** with a small weight (e.g. 10%).
 3. Refresh the page a few times: ~1 in 10 loads shows the `v2.0.0` badge (a
-   different colour), the rest `v1.0.0`. Because both versions share the same
-   database, signatures created on either build appear on both — and stream
-   live to every open tab via SSE.
-4. Shift the weight up and promote `2.0.0` when you're happy.
+   different colour) **and the new live server-time card**, the rest `v1.0.0`
+   without it. Because both versions share the same database, signatures created
+   on either build appear on both — and stream live to every open tab via SSE.
+4. Watch routing from the shell — each request may hit a different build/replica:
+   ```bash
+   watch -n1 'curl -s https://your-domain/api/time'
+   # {"time":"…","version":"2.0.0","host":"…"}  ← version/host flips under canary
+   ```
+5. Shift the weight up and promote `2.0.0` when you're happy.
+
+> The server-time card is the **v2 change**: v1 (built before this feature) has
+> no clock, so its presence — and the version/host it shows — is an at-a-glance
+> signal of which build a viewer landed on.
 
 > No build args? Set `APP_VERSION=1.0.0` / `APP_VERSION=2.0.0` in each app's
 > environment instead — same effect.

broker.go

@@ -8,11 +8,15 @@ import "sync"
 //   - "created"  → Entry is set (a new signature)
 //   - "deleted"  → ID is set (a removed signature)
 //   - "presence" → Online is set (connected-client count changed)
+//   - "tick"     → Time/Version/Host are set (live server clock; new in v2)
 type Event struct {
-	Type   string `json:"type"`
-	Entry  *Entry `json:"entry,omitempty"`
-	ID     uint   `json:"id,omitempty"`
-	Online int    `json:"online,omitempty"`
+	Type    string `json:"type"`
+	Entry   *Entry `json:"entry,omitempty"`
+	ID      uint   `json:"id,omitempty"`
+	Online  int    `json:"online,omitempty"`
+	Time    string `json:"time,omitempty"`
+	Version string `json:"version,omitempty"`
+	Host    string `json:"host,omitempty"`
 }
 
 // Broker is a tiny in-process pub/sub hub. Each connected SSE client holds one

handlers.go

@@ -16,6 +16,18 @@ type Handler struct {
 	broker  *Broker
 	appName string
 	version string
+	host    string
+}
+
+// serverTime is the shape of the live clock payload (v2 feature). It carries
+// the version and host so a canary viewer can see exactly which build/replica
+// answered.
+func (h *Handler) serverTime() okapi.M {
+	return okapi.M{
+		"time":    time.Now().Format(time.RFC3339),
+		"version": h.version,
+		"host":    h.host,
+	}
 }
 
 // createEntryRequest is the POST /api/entries body.
@@ -50,9 +62,16 @@ func (h *Handler) Info(c *okapi.Context) error {
 		"app":     h.appName,
 		"version": h.version,
 		"online":  h.broker.Online(),
+		"host":    h.host,
 	})
 }
 
+// Time returns the current server time (plus version + host). Handy for probing
+// a canary rollout from the shell: `watch curl -s .../api/time`.
+func (h *Handler) Time(c *okapi.Context) error {
+	return c.OK(h.serverTime())
+}
+
 // ListEntries returns guestbook entries, newest first, with simple pagination.
 // Query params: limit (default 100, max 200) and offset (default 0). The home
 // page requests a small limit; the "All signatures" page pages through them.
@@ -162,6 +181,7 @@ func (h *Handler) Stream(c *okapi.Context) error {
 		welcome := okapi.Message{Event: "welcome", Data: okapi.M{
 			"version": h.version,
 			"online":  h.broker.Online(),
+			"host":    h.host,
 		}}
 		select {
 		case msgs <- welcome:

main.go

@@ -16,6 +16,7 @@ package main
 import (
 	"context"
 	"embed"
+	"os"
 	"time"
 
 	"github.com/jkaninda/logger"
@@ -51,8 +52,14 @@ func main() {
 		}
 	}
 
+	host, _ := os.Hostname()
 	broker := NewBroker()
-	h := &Handler{store: store, broker: broker, appName: cfg.AppName, version: cfg.Version}
+	h := &Handler{store: store, broker: broker, appName: cfg.AppName, version: cfg.Version, host: host}
+
+	// Broadcast a live server-time "tick" to all SSE clients once a second
+	// (the v2 clock card). Stopped on shutdown.
+	tickCtx, stopTicks := context.WithCancel(ctx)
+	go publishTicks(tickCtx, broker, cfg.Version, host)
 
 	app := okapi.New(okapi.WithPort(cfg.Port))
 	app.WithDebug()
@@ -61,6 +68,7 @@ func main() {
 	app.Get("/healthz", h.Health)
 	api := app.Group("/api")
 	api.Get("/info", h.Info)
+	api.Get("/time", h.Time) // current server time (v2 clock card)
 	api.Get("/entries", h.ListEntries)
 	api.Post("/entries", h.CreateEntry)
 	api.Delete("/entries/{id:int}", h.DeleteEntry)
@@ -81,6 +89,7 @@ func main() {
 			},
 			OnShutdown: func() {
 				logger.Info("shutting down")
+				stopTicks()
 				_ = store.Close()
 			},
 		})
@@ -92,6 +101,27 @@ func main() {
 	}
 }
 
+// publishTicks broadcasts a live server-time "tick" event to all connected SSE
+// clients once a second. Each replica sends its own time/host, so under a
+// canary rollout the clock card reveals exactly which build served you.
+func publishTicks(ctx context.Context, b *Broker, version, host string) {
+	t := time.NewTicker(time.Second)
+	defer t.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case now := <-t.C:
+			b.Publish(Event{
+				Type:    "tick",
+				Time:    now.Format(time.RFC3339),
+				Version: version,
+				Host:    host,
+			})
+		}
+	}
+}
+
 func migrateWithRetry(store *Store, attempts int, wait time.Duration) error {
 	var err error
 	for i := 0; i < attempts; i++ {

web/index.html

@@ -84,6 +84,18 @@
       background: var(--card); border: 1px solid var(--card-border);
       border-radius: var(--radius); backdrop-filter: blur(12px);
     }
+    .clock {
+      display: flex; align-items: center; justify-content: space-between; gap: 14px;
+      padding: 16px 20px; margin-bottom: 18px;
+    }
+    .clock-left { display: flex; flex-direction: column; gap: 2px; }
+    .clock-label { font-size: 11px; text-transform: uppercase; letter-spacing: 0.08em; color: var(--muted); }
+    .clock-time { font-size: 26px; font-weight: 800; font-variant-numeric: tabular-nums;
+      letter-spacing: 0.02em; color: var(--text); }
+    .clock-meta { font-size: 12px; color: var(--muted); text-align: right; line-height: 1.6; }
+    .clock-meta b { color: var(--text); font-weight: 600; }
+    .clock.stale { opacity: .5; }
+
     form.compose { padding: 20px; box-shadow: var(--shadow); margin-bottom: 14px; }
     .row { display: flex; gap: 12px; flex-wrap: wrap; }
     input, textarea {
@@ -190,6 +202,15 @@ <h1>The <span class="grad">Guestbook</span></h1>
       </nav>
     </header>
 
+    <!-- Live server clock (new in v2) -->
+    <div class="card clock" id="clock">
+      <div class="clock-left">
+        <div class="clock-label">Server time</div>
+        <div class="clock-time" id="clockTime">—</div>
+      </div>
+      <div class="clock-meta" id="clockMeta">waiting for server…</div>
+    </div>
+
     <!-- Home view -->
     <section id="view-home">
       <form class="compose card" id="form">
@@ -249,6 +270,7 @@ <h2>All signatures</h2>
 
     const api = {
       info:   ()               => fetch('/api/info').then(r => r.json()),
+      time:   ()               => fetch('/api/time').then(r => r.json()),
       list:   (limit, offset)  => fetch(`/api/entries?limit=${limit}&offset=${offset}`).then(r => r.json()),
       create: (body)           => fetch('/api/entries', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify(body) }),
       remove: (id)             => fetch('/api/entries/' + id, { method: 'DELETE' }),
@@ -378,12 +400,28 @@ <h2>All signatures</h2>
       if (currentView() === 'all') loadAll();
     }
 
+    // ---- live server clock (v2) --------------------------------------------
+    let clockStaleTimer;
+    function showTime({ time, version, host }) {
+      const d = new Date(time);
+      $('clockTime').textContent = isNaN(d) ? time : d.toLocaleTimeString();
+      const bits = [];
+      if (version) bits.push(`<b>v${esc(version)}</b>`);
+      if (host) bits.push(`host <b>${esc(host)}</b>`);
+      $('clockMeta').innerHTML = bits.join(' · ') || 'live';
+      $('clock').classList.remove('stale');
+      // If ticks stop (server gone / tab backgrounded), dim the card.
+      clearTimeout(clockStaleTimer);
+      clockStaleTimer = setTimeout(() => $('clock').classList.add('stale'), 4000);
+    }
+
     function connectSSE() {
       const es = new EventSource('/api/stream');
       es.addEventListener('welcome',  (e) => { const d = JSON.parse(e.data); setVersion(d.version); setOnline(d.online); });
       es.addEventListener('presence', (e) => { const d = JSON.parse(e.data); setOnline(d.online); });
       es.addEventListener('created',  (e) => { const d = JSON.parse(e.data); if (d.entry) onCreated(d.entry); });
       es.addEventListener('deleted',  (e) => { const d = JSON.parse(e.data); onDeleted(d.id); });
+      es.addEventListener('tick',     (e) => { const d = JSON.parse(e.data); showTime(d); setVersion(d.version); });
       // EventSource auto-reconnects on error; nothing to do here.
     }
 
@@ -420,6 +458,7 @@ <h2>All signatures</h2>
 
     // ---- boot ---------------------------------------------------------------
     api.info().then((d) => { setVersion(d.version); setOnline(d.online); }).catch(() => {});
+    api.time().then(showTime).catch(() => {}); // immediate clock; SSE ticks keep it live
     route();
     connectSSE();
   </script>