Code generation is one of the most important features of gRPC. In this lecture we're gonna learn how it's done with protocol buffer.
In order to generate stubs for server and client, we first need to write the
API contract which includes a description of the services and their payload
messages in a protocol buffer file that looks something like this.
In this file, a Hello method is defined, which
takes a HelloRequest as input and returns a HelloResponse. The
HelloRequest contains only a string name and the HelloResponse has a
string greet. Very simple, right? We will learn much more detail about this
later. In the hands-on with protocol buffer lecture from this proto file, the
server and client stub codes are generated by the protocol buffer compiler
(or protoc). Depending on the programming language, we will have to tell the
compiler to use the correct gRPC plugins for it. The generated code for Rust
and Go will look something like this.
OK, so you may wonder why gRPC uses protocol buffer. Well there are many reasons. First, it's super easy to read and understand. Second, it's language interoperable with automatic code generation for many languages. It represents data in binary format which is smaller size, faster to transport and more efficient to serialize than some text-based format like JSON or XML. It provides a strong-type API contact between client and server, which is super safe to work with. And it has a great set of rules for API evolution to ensure backward and forward compatibility. Sounds pretty amazing, right. But, is protocol buffer required to work with gRPC? The answer is no. You can use Google flatbuffers or Microsoft bond instead. But in my opinion, protocol buffer is already a great choice.
Picture 1 - gRPC code generation with Protocol Buffer
It supports a lot of programming languages with 10 officially supported where Go, Java and NodeJs are purely implemented and 7 others are wrappers of the gRPC-core C namely C++, C#, Objective-C, Python, Ruby, DART and PHP. Besides, there are many other unofficial libraries for other languages such as Swift, Rust, Typescript, Haskell and so on. Alright, now we know how gRPC generate codes for us. I hope you find it interesting. In the next lecture, we will explore another secret weapon of gRPC which is HTTP version 2. See you then!
Picture 2 - Languages supported by gRPC