Summary - gRPC
- Go course
- Advanced
- Lesson 42/68
- 4 min
Combine server and client to write a gRPC service.
gRPC summary
The flow: write the contract in a .proto → generate Go code with protoc → on the server implement the interface, Register and Serve → on the client make calls with timeouts using NewClient + the generated client. Errors travel with status and codes.
Never change field numbers; mark removed ones reserved.
Interceptors
The gRPC counterpart of middleware is the interceptor. It is added to the server with the grpc.UnaryInterceptor(...) option and runs before/after every unary call:
func logla(ctx context.Context, req any, info *grpc.UnaryServerInfo, h grpc.UnaryHandler) (any, error) {
bas := time.Now()
resp, err := h(ctx, req)
log.Println(info.FullMethod, time.Since(bas))
return resp, err
}Practice Interceptor simulation
Define type Handler func(string) string. Write intercept(h Handler) Handler: print ">" before the call and "<" after, then return the result. Print the result of intercept(func(s string) string { return s + "!" })("go").
Starter code
package main
import "fmt"
func main() {
// buraya yaz
}Sample solution
package main
import "fmt"
type Handler func(string) string
func intercept(h Handler) Handler {
return func(s string) string {
fmt.Println(">")
r := h(s)
fmt.Println("<")
return r
}
}
func main() {
fmt.Println(intercept(func(s string) string { return s + "!" })("go"))
}Expected output
> < go!
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 How does a client recognize a "resource not found" case?
- When the response is empty
- status.Code(err) == codes.NotFound Correct answer
- err == nil
- From an HTTP 404 header
Explanation: gRPC error codes are read through the status package; NotFound is the code the server returns with status.Error(codes.NotFound, ...).
2 Error code
return nil, status.Error(codes.____, "ürün yok")return nil, status.Error(codes.NotFound, "ürün yok")Explanation: codes.NotFound is the gRPC status code reporting that the requested record doesn't exist.
3 Group summary
| Term | Meaning |
|---|---|
.proto |
Contract |
protoc |
Code generation |
Interceptor |
gRPC middleware |
codes.DeadlineExceeded |
Time ran out |