Module rpc_metrics 

RPC metrics middleware for Prometheus metrics collection.

This middleware collects metrics for JSON-RPC requests, including:

• Request count by method and status
• Request duration by method
• Active request count
• Error count by method and error code

These metrics complement the OpenTelemetry tracing in rpc_tracing.rs, providing aggregated data suitable for dashboards and alerting.

Structs

RpcMetricsMiddleware

Middleware that collects Prometheus metrics for each RPC request.