Initial open source release

internal/rpc/metrics.go

@@ -0,0 +1,25 @@
+package rpc
+
+import "time"
+
+// Metrics 接收 RPC 业务层指标。默认 NopMetrics，后续可对接 Prometheus。
+type Metrics interface {
+	MessageSend(d time.Duration, duplicate bool, err error)
+	MessageRateLimited(retryAfterSeconds int)
+	OutboxClaimed(count int)
+	OutboxDelivered(d time.Duration)
+	OutboxFailed(err error)
+}
+
+// NopMetrics 是 Metrics 的空实现。
+type NopMetrics struct{}
+
+func (NopMetrics) MessageSend(time.Duration, bool, error) {}
+
+func (NopMetrics) MessageRateLimited(int) {}
+
+func (NopMetrics) OutboxClaimed(int) {}
+
+func (NopMetrics) OutboxDelivered(time.Duration) {}
+
+func (NopMetrics) OutboxFailed(error) {}