transit¶

Shared HTTP & gRPC transport middleware for Go services — structured request logging, OpenTelemetry instrumentation, circuit breaking, rate limiting and client retry, from one framework-free module.

go get gitlab.com/phpboyscout/go/transit

gitlab.com/phpboyscout/go/transit gives a service's HTTP and gRPC edges a single, shared implementation of the cross-cutting transport concerns — the same logging, tracing, circuit-breaking and rate-limiting behaviour whether the traffic arrives over REST or gRPC, and whether the code is a server accepting calls or a client making them. It is the middleware layer extracted from go-tool-base.

Why¶

• Framework-free. It carries the gRPC SDK and the OpenTelemetry gRPC/HTTP contrib instrumentation — that is the middleware's job — but nothing else. A depfootprint_test.go guard forbids go-tool-base, Viper/Cobra, Charm and the cloud SDKs; the remaining dependencies are golang.org/x/time/rate, go/redact and cockroachdb/errors.
• *slog.Logger at the seam. Every middleware that logs takes a plain *slog.Logger, so nothing here pulls in a logging framework.
• Server and client, both transports. http and grpc each provide server handlers/interceptors and client round-trippers/interceptors, so a service and the clients it calls share one implementation of each concern. See the middleware model.
• Resilience is one package. The circuit breaker and the keyed token-bucket rate-limiter store live in resilience; the HTTP and gRPC layers wrap them into transport-shaped middleware.

Where next¶

What transit does not do¶

Worth knowing before you build on it:

• No distributed state. Every circuit breaker and rate limiter is per-process and in-memory. A limit of 50 rps across ten replicas admits 500.
• No configuration loading. Constructors take Go structs; decoding a config file onto them is your service's job.
• No *http.Client constructor. transit ships transports, not connection policy — TLS, redirects and timeouts belong to the layer above.
• No gRPC retry. The gRPC SDK already has it, via a service config policy.
• No metrics. Retries, rejections and breaker trips are not counted; callbacks are provided so you can count them.

The full list, with the reasoning for each, is in What transit does not do.

Part of the phpboyscout Go toolkit — small, framework-free Go modules extracted from go-tool-base.

Further reading¶

The blog carries a curated route through this subject: Building a web service in Go collects everything written about it, ordered so you can start at the beginning rather than newest-first.