feat: bootstrap from Fabric monorepo

src/common/metrics.service.ts

@@ -0,0 +1,35 @@
+import { Injectable } from '@nestjs/common';
+
+type Bucket = {
+  requests: number;
+  errors: number;
+  totalDurationMs: number;
+};
+
+@Injectable()
+export class MetricsService {
+  private readonly bucket: Bucket = { requests: 0, errors: 0, totalDurationMs: 0 };
+  private startedAt = Date.now();
+
+  record(statusCode: number, durationMs: number): void {
+    this.bucket.requests += 1;
+    if (statusCode >= 400) this.bucket.errors += 1;
+    this.bucket.totalDurationMs += durationMs;
+  }
+
+  snapshot() {
+    const uptimeSec = Math.max(1, Math.floor((Date.now() - this.startedAt) / 1000));
+    const qps = this.bucket.requests / uptimeSec;
+    const avgLatencyMs = this.bucket.requests > 0 ? this.bucket.totalDurationMs / this.bucket.requests : 0;
+    const errorRate = this.bucket.requests > 0 ? this.bucket.errors / this.bucket.requests : 0;
+
+    return {
+      requests: this.bucket.requests,
+      errors: this.bucket.errors,
+      qps,
+      avgLatencyMs,
+      errorRate,
+      uptimeSec,
+    };
+  }
+}