feat: add storage stats and average latency metrics

Track and display storage and performance metrics that were previously
showing zeros.

Storage metrics:
- Add GetStats() method to storage returning event count and DB size
- Store database file path for size calculation
- Update metrics every 30 seconds via goroutine in main.go
- Display event count and DB size (MB) in dashboard

Performance metrics:
- Calculate average latency from histogram sum/count metrics
- Display as milliseconds in dashboard
- Formula: (duration_sum / duration_count) * 1000

Missing metrics (deferred):
- Connections: requires connection lifecycle tracking (gRPC + WebSocket)
- Deletions: count would need API change to ProcessDeletion

Dashboard now shows accurate storage stats and request latency!

1 files changed, 18 insertions, 0 deletions

diff --git a/cmd/relay/main.go b/cmd/relay/main.go
index e4fe9bc..8948ebf 100644
--- a/cmd/relay/main.go
+++ b/cmd/relay/main.go
@@ -9,6 +9,7 @@ import (
         "os"
         "os/signal"
         "syscall"
+        "time"
 
         "connectrpc.com/connect"
         "golang.org/x/net/http2"
@@ -95,6 +96,23 @@ func main() {
         wsHandler := wshandler.NewHandler(store, subManager)
         if m != nil {
                 wsHandler.SetMetrics(m)
+
+                // Update storage stats periodically
+                go func() {
+                        ticker := time.NewTicker(30 * time.Second)
+                        defer ticker.Stop()
+
+                        // Update immediately on start
+                        if stats, err := store.GetStats(context.Background()); err == nil {
+                                m.UpdateStorageStats(stats.EventCount, stats.DBSizeBytes)
+                        }
+
+                        for range ticker.C {
+                                if stats, err := store.GetStats(context.Background()); err == nil {
+                                        m.UpdateStorageStats(stats.EventCount, stats.DBSizeBytes)
+                                }
+                        }
+                }()
         }
 
         var grpcDisplay, httpDisplay, wsDisplay string