gRPC, RPC, How It Works, HTTP API Comparison
RPC: Remote Procedure Calls #
A protocol that allows a program on one computer to execute a procedure on another computer.
Developers don't need to explicitly code the details of remote interactions -> the framework handles it automatically.
In client code, it appears as if server code functions are being called directly.
Client code language != server code language: can be written in different languages.
gRPC = Communication Framework #
Microservices are built with various programming languages (e.g., Back-End: Go, Front-End: js).
Communication between these servers is necessary.
The number of messages exchanged between microservices is enormous >>> fast communication is preferable.
Developers should focus only on implementing core logic and leave communication to the framework.
gRPC = High-performance Open-source Feature-rich Framework
- originally developed by Google
- Now part of the Cloud Native Computing Foundation (CNCF - like Kubernetes)
- gRPC messages are primarily encoded in Protobuf (binary format) > efficient for transmission/reception but not human-readable
gRPC generates client code and server interface code via Protocol Buffers. The generated language can be changed based on options.
-> A single .proto file can be used to generate server/client code in multiple languages such as Go, Python, Java, etc.
How gRPC Works #
- The client generates a stub (providing the same methods as the server).
- The stub calls the gRPC framework (calling via the internal network).
- Client and server use stubs for interaction -> only requiring access to each other's core service logic.
gRPC vs HTTP API #
| Feature | gRPC | HTTP API |
|---|---|---|
| Contract | Required (.proto) | Optional (OpenAPI) |
| Protocol | HTTP/2 (fast) | HTTP |
| Payload | Protobuf (compact, binary message format) | JSON (larger, human-readable) |
| Norms | Strict specification | Loose. Any HTTP is valid. |
| Streaming | Client, Server, Bidirectional | Client, Server |
| Browser Support | No (gRPC-Web required) | Yes |
| Security | Transport (TLS) | Transport (TLS) |
| Client Code Generation | Yes | OpenAPI + Third-party tools |
.proto file: Defines gRPC service/message contracts.
Limitations #
Cannot directly call gRPC services from a browser.
- Use gRPC-Web (bidirectional streaming not possible, server streaming limited)
- Use gRPC services with annotations in .proto files as HTTP metadata in a RESTful JSON Web API
(Application supports both JSON Web API and gRPC)