Quick start
This guide gets you started with gRPC in Go with a simple working example.
Quick start
Prerequisites
Go, any one of the two latest major releases of Go.
For installation instructions, see Go’s Getting Started guide.
Protocol buffer compiler,
protoc
, version 3.For installation instructions, see Protocol Buffer Compiler Installation.
Go plugins for the protocol compiler:
Install the protocol compiler plugins for Go using the following commands:
go install google.golang.org/protobuf/cmd/protoc-gen-go@latest go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@latest
Update your
PATH
so that theprotoc
compiler can find the plugins:export PATH="$PATH:$(go env GOPATH)/bin"
Get the example code
The example code is part of the grpc-go repo.
Download the repo as a zip file and unzip it, or clone the repo:
git clone -b v1.68.0 --depth 1 https://github.com/grpc/grpc-go
Change to the quick start example directory:
cd grpc-go/examples/helloworld
Run the example
From the examples/helloworld
directory:
Compile and execute the server code:
go run greeter_server/main.go
From a different terminal, compile and execute the client code to see the client output:
go run greeter_client/main.go Greeting: Hello world
Congratulations! You’ve just run a client-server application with gRPC.
Update the gRPC service
In this section you’ll update the application with an extra server method. The
gRPC service is defined using protocol buffers. To learn more about how to
define a service in a .proto
file see Basics tutorial.
For now, all you need to know is that both the
server and the client stub have a SayHello()
RPC method that takes a
HelloRequest
parameter from the client and returns a HelloReply
from the
server, and that the method is defined like this:
// The greeting service definition.
service Greeter {
// Sends a greeting
rpc SayHello (HelloRequest) returns (HelloReply) {}
}
// The request message containing the user's name.
message HelloRequest {
string name = 1;
}
// The response message containing the greetings
message HelloReply {
string message = 1;
}
Open helloworld/helloworld.proto
and add a new SayHelloAgain()
method, with
the same request and response types:
// The greeting service definition.
service Greeter {
// Sends a greeting
rpc SayHello (HelloRequest) returns (HelloReply) {}
// Sends another greeting
rpc SayHelloAgain (HelloRequest) returns (HelloReply) {}
}
// The request message containing the user's name.
message HelloRequest {
string name = 1;
}
// The response message containing the greetings
message HelloReply {
string message = 1;
}
Remember to save the file!
Regenerate gRPC code
Before you can use the new service method, you need to recompile the updated
.proto
file.
While still in the examples/helloworld
directory, run the following command:
protoc --go_out=. --go_opt=paths=source_relative \
--go-grpc_out=. --go-grpc_opt=paths=source_relative \
helloworld/helloworld.proto
This will regenerate the helloworld/helloworld.pb.go
and helloworld/helloworld_grpc.pb.go
files, which contain:
- Code for populating, serializing, and retrieving
HelloRequest
andHelloReply
message types. - Generated client and server code.
Update and run the application
You have regenerated server and client code, but you still need to implement and call the new method in the human-written parts of the example application.
Update the server
Open greeter_server/main.go
and add the following function to it:
func (s *server) SayHelloAgain(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
return &pb.HelloReply{Message: "Hello again " + in.GetName()}, nil
}
Update the client
Open greeter_client/main.go
to add the following code to the end of the
main()
function body:
r, err = c.SayHelloAgain(ctx, &pb.HelloRequest{Name: *name})
if err != nil {
log.Fatalf("could not greet: %v", err)
}
log.Printf("Greeting: %s", r.GetMessage())
Remember to save your changes.
Run!
Run the client and server like you did before. Execute the following commands
from the examples/helloworld
directory:
Run the server:
go run greeter_server/main.go
From another terminal, run the client. This time, add a name as a command-line argument:
go run greeter_client/main.go --name=Alice
You’ll see the following output:
Greeting: Hello Alice Greeting: Hello again Alice
What’s next
- Learn how gRPC works in Introduction to gRPC and Core concepts.
- Work through the Basics tutorial.
- Explore the API reference.