feat: add metrics for blocked events

Track and display blocked event counts with per-kind breakdown.

- Add events_blocked_total counter with kind label
- Add RecordBlockedEvent method to metrics
- Display blocked count in dashboard Storage section
- Call metric when rejecting non-core protocol kinds

Allows monitoring spam patterns and verifying kind filter effectiveness.
Raw metrics show breakdown by kind (e.g., kind=20001, kind=30311).

2 files changed, 24 insertions, 0 deletions

diff --git a/internal/metrics/dashboard.html b/internal/metrics/dashboard.html
index 9538ac6..1fa1ddf 100644
--- a/internal/metrics/dashboard.html
+++ b/internal/metrics/dashboard.html
@@ -199,6 +199,10 @@
                     <span class="metric-label">Deletions</span>
                     <span class="metric-value" id="event_deletions">0</span>
                 </div>
+                <div class="metric">
+                    <span class="metric-label">Blocked</span>
+                    <span class="metric-value" id="events_blocked">0</span>
+                </div>
             </div>
 
             <div class="card">
@@ -317,6 +321,9 @@
                 document.getElementById('event_deletions').textContent =
                     sumMetric(metrics, `${prefix}_relay_event_deletions_total`);
 
+                document.getElementById('events_blocked').textContent =
+                    sumMetric(metrics, `${prefix}_relay_events_blocked_total`);
+
                 const durationSum = sumMetric(metrics, `${prefix}_relay_request_duration_seconds_sum`);
                 const durationCount = sumMetric(metrics, `${prefix}_relay_request_duration_seconds_count`);
                 const avgLatencyMs = durationCount > 0 ? (durationSum / durationCount * 1000) : 0;
diff --git a/internal/metrics/metrics.go b/internal/metrics/metrics.go
index 74f9ffb..dea0748 100644
--- a/internal/metrics/metrics.go
+++ b/internal/metrics/metrics.go
@@ -2,6 +2,7 @@ package metrics
 
 import (
         _ "embed"
+        "fmt"
         "net/http"
 
         "github.com/prometheus/client_golang/prometheus"
@@ -30,6 +31,7 @@ type Metrics struct {
         eventsTotal         prometheus.Gauge
         dbSizeBytes         prometheus.Gauge
         eventDeletionsTotal prometheus.Counter
+        eventsBlockedTotal  *prometheus.CounterVec
 
         // Config
         config *Config
@@ -195,6 +197,16 @@ func New(config *Config) *Metrics {
                 },
         )
 
+        m.eventsBlockedTotal = promauto.NewCounterVec(
+                prometheus.CounterOpts{
+                        Namespace: config.Namespace,
+                        Subsystem: config.Subsystem,
+                        Name:      "events_blocked_total",
+                        Help:      "Total events blocked by kind filter",
+                },
+                []string{"kind"},
+        )
+
         return m
 }
 
@@ -274,6 +286,11 @@ func (m *Metrics) RecordEventDeletion() {
         m.eventDeletionsTotal.Inc()
 }
 
+// RecordBlockedEvent records an event blocked by kind filter.
+func (m *Metrics) RecordBlockedEvent(kind int32) {
+        m.eventsBlockedTotal.WithLabelValues(fmt.Sprintf("%d", kind)).Inc()
+}
+
 // RequestStatus represents the status of a request for metrics.
 type RequestStatus string