单个Protobuf服务定义中是否可定义多个RPC调用？

Absolutely! You can definitely define multiple RPC methods within a single Protobuf service definition—this isn’t just allowed, it’s a standard practice for grouping related functionality together. Let’s break down your example and clarify the rules:

1. Multiple distinct-named RPCs are fully supported #

Your example includes SayHello and SayHello2—this is totally valid. In real-world use cases, you’ll almost always see services with multiple RPCs: for example, a UserService might have GetUser, CreateUser, UpdateUser, and DeleteUser methods all under the same service to keep related operations organized.

2. Duplicate RPC method names are not allowed #

Where your example hits a problem is the duplicate SayHello method:

rpc SayHello (HelloRequest) returns (HelloResponse);
rpc SayHello (HelloRequest3) returns (HelloResponse3);

Protobuf requires all RPC method names within a single service to be unique, regardless of their request/response types. This is because when Protobuf generates code for your service (in languages like Go, Java, or C#), the method names become identifiers in the target language—duplicate names would cause compilation errors (since you can’t have two methods with the same name in a single class/interface, even if their signatures differ in some languages).

To fix this, you’d just rename the duplicate method to something unique, like:

rpc SayHello (HelloRequest) returns (HelloResponse);
rpc SayHelloWithCustomRequest (HelloRequest3) returns (HelloResponse3);

Why most examples only show one RPC? #

The single-RPC examples you’ve seen are just for simplicity—they’re meant to demonstrate the basic structure of a Protobuf service without adding extra complexity. Real production Protobuf definitions almost always use multiple RPCs per service.

内容的提问来源于stack exchange，提问作者tsar2512