Building a Better Debugging Experience: A Deep Dive into Capturing and Replaying gRPC Traffic

Debugging microservices is hard because it's difficult to see the data flowing between them. We built a "Request Capture Engine" that acts like a flight recorder for our gRPC traffic. It uses gRPC interceptors to automatically record request/response payloads, which are stored in object storage and correlated with OpenTelemetry trace IDs. This allows us to perfectly replay production traffic for debugging, find specific payloads with a simple command-line tool (`rcap`), and even power interactive UIs for A/B testing and analysis. This post explains how you can build a similar system.