Show route churn as a whole count per minute (closes #160)

The status page showed route churn per second as a one-minute moving
average, so a quiet feed gave a fraction such as 0.1. The average was
correct.

The metrics tracker now also counts prefix announcements and
withdrawals, from all peers, in each clock minute. /api/v1/stats
reports the count for the last full minute as route_churn_per_min in
stream, in place of route_churn_per_sec. The status page shows it as
"Route Churn/min".

The status and home pages round messages and updates per second to
whole numbers.

Model: opus-5-5

internal/metrics/metrics.go

@@ -34,7 +34,7 @@ type Tracker struct {
 	// Announcement/withdrawal metrics
 	announcementCounter metrics.Counter
 	withdrawalCounter   metrics.Counter
-	churnRate           metrics.Meter // combined announcements + withdrawals per second
+	churnPerMinute      minuteCounter // prefix announcements and withdrawals
 
 	// BGP peer tracking
 	bgpPeerCount atomic.Int32
@@ -56,7 +56,7 @@ func New() *Tracker {
 		ipv6UpdateRate:      metrics.NewMeter(),
 		announcementCounter: metrics.NewCounter(),
 		withdrawalCounter:   metrics.NewCounter(),
-		churnRate:           metrics.NewMeter(),
+		churnPerMinute:      minuteCounter{now: time.Now},
 	}
 }
 
@@ -156,13 +156,13 @@ func (t *Tracker) RecordIPv6Update() {
 // RecordAnnouncement records a route announcement
 func (t *Tracker) RecordAnnouncement() {
 	t.announcementCounter.Inc(1)
-	t.churnRate.Mark(1)
+	t.churnPerMinute.add()
 }
 
 // RecordWithdrawal records a route withdrawal
 func (t *Tracker) RecordWithdrawal() {
 	t.withdrawalCounter.Inc(1)
-	t.churnRate.Mark(1)
+	t.churnPerMinute.add()
 }
 
 // SetBGPPeerCount updates the current BGP peer count
@@ -198,9 +198,10 @@ func (t *Tracker) GetWithdrawalCount() uint64 {
 	return uint64(count)
 }
 
-// GetChurnRate returns the route churn rate per second
-func (t *Tracker) GetChurnRate() float64 {
-	return t.churnRate.Rate1()
+// GetChurnPerMinute returns the number of prefix announcements and
+// withdrawals, from all peers, in the last full clock minute.
+func (t *Tracker) GetChurnPerMinute() int {
+	return t.churnPerMinute.lastFullMinute()
 }
 
 // GetRouteMetrics returns current route update metrics

internal/metrics/minutecounter.go

@@ -0,0 +1,59 @@
+package metrics
+
+import (
+	"sync"
+	"time"
+)
+
+// minuteCounter counts events in each clock minute and reports the count of
+// the last full minute. It is safe for concurrent use.
+type minuteCounter struct {
+	mu  sync.Mutex
+	now func() time.Time
+
+	// minute is the start of the minute that count belongs to.
+	minute time.Time
+	count  int
+	// lastMinuteCount is the count of the minute just before minute.
+	lastMinuteCount int
+}
+
+// add counts one event in the current minute.
+func (c *minuteCounter) add() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	c.moveToCurrentMinute()
+	c.count++
+}
+
+// lastFullMinute returns the number of events in the minute that ended most
+// recently.
+func (c *minuteCounter) lastFullMinute() int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	c.moveToCurrentMinute()
+
+	return c.lastMinuteCount
+}
+
+// moveToCurrentMinute starts a new count when the clock has moved into
+// another minute. The count it ends becomes the last full minute's count when
+// its minute is the one just before the current minute. Otherwise the last
+// full minute had no events. The caller holds mu.
+func (c *minuteCounter) moveToCurrentMinute() {
+	minute := c.now().Truncate(time.Minute)
+	if minute.Equal(c.minute) {
+		return
+	}
+
+	if minute.Sub(c.minute) == time.Minute {
+		c.lastMinuteCount = c.count
+	} else {
+		c.lastMinuteCount = 0
+	}
+
+	c.minute = minute
+	c.count = 0
+}

internal/metrics/minutecounter_internal_test.go

@@ -0,0 +1,86 @@
+package metrics
+
+import (
+	"sync"
+	"testing"
+	"time"
+)
+
+// TestChurnPerMinuteCountsLastFullMinute announces and withdraws prefixes on
+// an injected clock and expects each minute's whole count once that minute
+// has ended, and 0 for a minute with none.
+func TestChurnPerMinuteCountsLastFullMinute(t *testing.T) {
+	t.Parallel()
+
+	now := time.Date(2026, 10, 26, 12, 0, 30, 0, time.UTC)
+	tracker := New()
+	tracker.churnPerMinute.now = func() time.Time { return now }
+
+	expectChurn := func(want int, why string) {
+		t.Helper()
+
+		got := tracker.GetChurnPerMinute()
+		if got != want {
+			t.Fatalf("at %s churn = %d, want %d: %s",
+				now.Format(time.TimeOnly), got, want, why)
+		}
+	}
+
+	const firstMinuteChurn = 2
+
+	tracker.RecordAnnouncement()
+	tracker.RecordWithdrawal()
+	expectChurn(0, "12:00 has not ended")
+
+	now = time.Date(2026, 10, 26, 12, 1, 59, 0, time.UTC)
+
+	tracker.RecordAnnouncement()
+	expectChurn(firstMinuteChurn, "12:00 had one announcement and one withdrawal")
+
+	now = time.Date(2026, 10, 26, 12, 2, 0, 0, time.UTC)
+
+	expectChurn(1, "12:01 had one announcement")
+
+	now = time.Date(2026, 10, 26, 12, 4, 0, 0, time.UTC)
+
+	expectChurn(0, "12:03 had none")
+
+	tracker.RecordWithdrawal()
+
+	now = time.Date(2026, 10, 26, 12, 6, 0, 0, time.UTC)
+
+	expectChurn(0, "12:05 had none, though 12:04 had one withdrawal")
+}
+
+// TestChurnPerMinuteCountsConcurrentRecords announces prefixes from several
+// goroutines at once and expects every one counted.
+func TestChurnPerMinuteCountsConcurrentRecords(t *testing.T) {
+	t.Parallel()
+
+	const (
+		goroutines          = 8
+		recordsPerGoroutine = 1000
+	)
+
+	now := time.Date(2026, 10, 26, 12, 0, 0, 0, time.UTC)
+	tracker := New()
+	tracker.churnPerMinute.now = func() time.Time { return now }
+
+	var wg sync.WaitGroup
+	for range goroutines {
+		wg.Go(func() {
+			for range recordsPerGoroutine {
+				tracker.RecordAnnouncement()
+			}
+		})
+	}
+
+	wg.Wait()
+
+	now = now.Add(time.Minute)
+
+	want := goroutines * recordsPerGoroutine
+	if got := tracker.GetChurnPerMinute(); got != want {
+		t.Fatalf("churn = %d, want %d", got, want)
+	}
+}

internal/server/handlers.go

@@ -441,10 +441,10 @@ type GCStats struct {
 //
 //nolint:tagliatelle // field names are the existing JSON API
 type StreamStats struct {
-	Announcements    uint64  `json:"announcements"`
-	Withdrawals      uint64  `json:"withdrawals"`
-	RouteChurnPerSec float64 `json:"route_churn_per_sec"`
-	BGPPeerCount     int     `json:"bgp_peer_count"`
+	Announcements    uint64 `json:"announcements"`
+	Withdrawals      uint64 `json:"withdrawals"`
+	RouteChurnPerMin int    `json:"route_churn_per_min"`
+	BGPPeerCount     int    `json:"bgp_peer_count"`
 }
 
 // StatsResponse represents the API statistics response
@@ -545,7 +545,7 @@ func (s *Server) streamStats() StreamStats {
 	return StreamStats{
 		Announcements:    metricsTracker.GetAnnouncementCount(),
 		Withdrawals:      metricsTracker.GetWithdrawalCount(),
-		RouteChurnPerSec: metricsTracker.GetChurnRate(),
+		RouteChurnPerMin: metricsTracker.GetChurnPerMinute(),
 		BGPPeerCount:     metricsTracker.GetBGPPeerCount(),
 	}
 }

internal/server/handlers_internal_test.go

@@ -195,6 +195,51 @@ func TestStatsHandlersAnswerFromMemory(t *testing.T) {
 	}
 }
 
+// TestStatsAnswerCarriesChurnPerMinute checks that the stream object of the
+// /api/v1/stats answer holds route_churn_per_min as a whole number, and no
+// longer route_churn_per_sec, the moving average it replaces
+// (https://git.eeqj.de/sneak/routewatch/issues/160).
+func TestStatsAnswerCarriesChurnPerMinute(t *testing.T) {
+	t.Parallel()
+
+	s := newServerWithTestRoutes(t)
+
+	rec := httptest.NewRecorder()
+	s.handleStats()(rec,
+		httptest.NewRequestWithContext(t.Context(), http.MethodGet, statsPath, nil))
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status %d, want %d; body %s", rec.Code, http.StatusOK, rec.Body)
+	}
+
+	var body struct {
+		Data struct {
+			Stream map[string]json.RawMessage `json:"stream"`
+		} `json:"data"`
+	}
+
+	err := json.Unmarshal(rec.Body.Bytes(), &body)
+	if err != nil {
+		t.Fatalf("decoding the answer: %v", err)
+	}
+
+	churn, ok := body.Data.Stream["route_churn_per_min"]
+	if !ok {
+		t.Fatalf("stream has no route_churn_per_min: %s", rec.Body)
+	}
+
+	var count int
+
+	err = json.Unmarshal(churn, &count)
+	if err != nil {
+		t.Errorf("route_churn_per_min = %s, want a whole number: %v", churn, err)
+	}
+
+	if _, ok := body.Data.Stream["route_churn_per_sec"]; ok {
+		t.Errorf("stream still has route_churn_per_sec: %s", rec.Body)
+	}
+}
+
 // newServerWithTestRoutes returns a server on a new database that holds a
 // route for testPrefixV4 and one for testPrefixV6.
 func newServerWithTestRoutes(t *testing.T) *Server {

internal/templates/index.html

@@ -400,7 +400,7 @@
                     }
 
                     const totalUpdates = data.ipv4_updates_per_sec + data.ipv6_updates_per_sec;
-                    document.getElementById('stat-updates').textContent = totalUpdates.toFixed(1);
+                    document.getElementById('stat-updates').textContent = Math.round(totalUpdates).toLocaleString();
                 })
                 .catch(() => {
                     document.getElementById('stat-status').textContent = 'Error';

internal/templates/status.html

@@ -231,8 +231,8 @@
                 <span class="metric-value" id="withdrawals">-</span>
             </div>
             <div class="metric">
-                <span class="metric-label">Route Churn/sec</span>
-                <span class="metric-value" id="route_churn_per_sec">-</span>
+                <span class="metric-label">Route Churn/min</span>
+                <span class="metric-value" id="route_churn_per_min">-</span>
             </div>
             <div class="metric">
                 <span class="metric-label">Total Data</span>
@@ -511,7 +511,7 @@
             document.getElementById('messages_per_sec').textContent = '-';
             document.getElementById('announcements').textContent = '-';
             document.getElementById('withdrawals').textContent = '-';
-            document.getElementById('route_churn_per_sec').textContent = '-';
+            document.getElementById('route_churn_per_min').textContent = '-';
             document.getElementById('total_wire_bytes').textContent = '-';
             document.getElementById('wire_mbits_per_sec').textContent = '-';
             document.getElementById('gc_num').textContent = '-';
@@ -578,7 +578,7 @@
                     document.getElementById('connection_duration').textContent = data.connection_duration;
                     document.getElementById('reconnect_count').textContent = formatNumber(data.reconnect_count);
                     document.getElementById('total_messages').textContent = formatNumber(data.total_messages);
-                    document.getElementById('messages_per_sec').textContent = data.messages_per_sec.toFixed(1);
+                    document.getElementById('messages_per_sec').textContent = formatNumber(Math.round(data.messages_per_sec));
                     document.getElementById('total_wire_bytes').textContent = formatBytes(data.total_wire_bytes);
                     document.getElementById('wire_mbits_per_sec').textContent = data.wire_mbits_per_sec.toFixed(2) + ' Mbps';
                     document.getElementById('asns').textContent = formatNumber(data.asns);
@@ -591,8 +591,8 @@
                     document.getElementById('live_routes').textContent = formatNumber(data.live_routes);
                     document.getElementById('ipv4_routes').textContent = formatNumber(data.ipv4_routes);
                     document.getElementById('ipv6_routes').textContent = formatNumber(data.ipv6_routes);
-                    document.getElementById('ipv4_updates_per_sec').textContent = data.ipv4_updates_per_sec.toFixed(1);
-                    document.getElementById('ipv6_updates_per_sec').textContent = data.ipv6_updates_per_sec.toFixed(1);
+                    document.getElementById('ipv4_updates_per_sec').textContent = formatNumber(Math.round(data.ipv4_updates_per_sec));
+                    document.getElementById('ipv6_updates_per_sec').textContent = formatNumber(Math.round(data.ipv6_updates_per_sec));
                     document.getElementById('oldest_route').textContent = formatRelativeTime(data.oldest_route);
                     document.getElementById('newest_route').textContent = formatRelativeTime(data.newest_route);
 
@@ -601,7 +601,7 @@
                         document.getElementById('bgp_peer_count').textContent = formatNumber(data.stream.bgp_peer_count);
                         document.getElementById('announcements').textContent = formatNumber(data.stream.announcements);
                         document.getElementById('withdrawals').textContent = formatNumber(data.stream.withdrawals);
-                        document.getElementById('route_churn_per_sec').textContent = data.stream.route_churn_per_sec.toFixed(1);
+                        document.getElementById('route_churn_per_min').textContent = formatNumber(data.stream.route_churn_per_min);
                     }
 
                     // Update GC stats