go-grpc-helloworld

README

go-grpc-helloworld

go grpc example

Generate gPRC code

protoc --go_out=. --go_opt=paths=source_relative \
    --go-grpc_out=. --go-grpc_opt=paths=source_relative \
    helloworld/protos/*.proto

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 and HelloReply message types.
• Generated client and server code.

from: grpc-go

Compiling error, undefined: grpc.SupportPackageIsVersion

If you are using Go modules:

Ensure your gRPC-Go version is required at the appropriate version in the same module containing the generated .pb.go files. For example, SupportPackageIsVersion6 needs v1.27.0, so in your go.mod file:

module <your module name>

require (
    google.golang.org/grpc v1.27.0
)

If you are not using Go modules:

Update the proto package, gRPC package, and rebuild the .proto files:

go get -u github.com/golang/protobuf/{proto,protoc-gen-go}
go get -u google.golang.org/grpc
protoc --go_out=plugins=grpc:. *.proto

How to turn on logging

The default logger is controlled by environment variables. Turn everything on like this:

$ export GRPC_GO_LOG_VERBOSITY_LEVEL=99
$ export GRPC_GO_LOG_SEVERITY_LEVEL=info

The RPC failed with error "code = Unavailable desc = transport is closing"

This error means the connection the RPC is using was closed, and there are many possible reasons, including:

1. mis-configured transport credentials, connection failed on handshaking
2. bytes disrupted, possibly by a proxy in between
3. server shutdown
4. Keepalive parameters caused connection shutdown, for example if you have configured your server to terminate connections regularly to trigger DNS lookups. If this is the case, you may want to increase your MaxConnectionAgeGrace, to allow longer RPC calls to finish.

It can be tricky to debug this because the error happens on the client side but the root cause of the connection being closed is on the server side. Turn on logging on both client and server, and see if there are any transport errors.