HTTPgRPC

HTTPgRPC is a term used to describe a set of approaches for exposing or consuming gRPC services over HTTP-based protocols. It is not a formal protocol standard, but a collection of patterns and implementations intended to bridge the HTTP and gRPC ecosystems. HTTPgRPC typically involves translating or transcoding between HTTP/JSON or HTTP/1.x and gRPC’s HTTP/2 transport and Protobuf payloads, enabling clients that cannot speak native gRPC to access gRPC services.

gRPC is a high-performance remote procedure call framework that uses HTTP/2 for transport and Protocol Buffers for interface definitions and message serialization. It supports unary, client streaming, server streaming, and bidirectional streaming. While gRPC is well-suited for server-to-server communication, browser-based clients require additional mechanisms to interact with gRPC services.

The main implementations of HTTPgRPC include gRPC-Web, which enables web browsers to call gRPC services through a browser-compatible protocol and a proxy (such as Envoy or grpcwebproxy) to translate between gRPC-Web and standard gRPC. Another approach is gRPC transcoding, where RESTful HTTP/JSON requests are mapped to gRPC methods, often used with API gateways or service meshes like Google Endpoints, Istio, or Envoy.

Benefits of HTTPgRPC include broader client compatibility, a unified API surface, and easier integration with existing HTTP tooling. Limitations include potential overhead from transcoding, partial support for some gRPC features (notably certain streaming capabilities in some browser paths), and added architectural complexity.

Common use cases involve API gateways, microservice boundaries that require REST clients, and cloud-native platforms that expose gRPC services to diverse clients. See also: gRPC, HTTP/2, gRPC-Web, REST/JSON transcoding.