gRPC client
- Go course
- Advanced
- Lesson 41/68
- 4 min
Learn to call a remote method with a gRPC client.
A gRPC client
The client opens a connection and makes calls with the generated client type. Every call gets a context with a timeout:
conn, err := grpc.NewClient("localhost:50051",
grpc.WithTransportCredentials(insecure.NewCredentials()))
if err != nil { log.Fatal(err) }
defer conn.Close()
c := pb.NewSelamlayiciClient(conn)
ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
r, err := c.Selam(ctx, &pb.SelamIstek{Ad: "Ada"})Share the connection
A grpc.ClientConn is expensive and safe for concurrent use; instead of opening a new connection per call, one is shared across the application. insecure.NewCredentials() is only for local development; production uses TLS credentials.
Practice Timeout
Create ctx, cancel := context.WithTimeout(context.Background(), 10*time.Millisecond) and write defer cancel(). Wait with select on time.After(50*time.Millisecond) and ctx.Done(); if the context ends first, print ctx.Err().
Starter code
package main
import (
"context"
"fmt"
"time"
)
func main() {
// buraya yaz
}Sample solution
package main
import (
"context"
"fmt"
"time"
)
func main() {
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Millisecond)
defer cancel()
select {
case <-time.After(50 * time.Millisecond):
fmt.Println("yanıt geldi")
case <-ctx.Done():
fmt.Println(ctx.Err())
}
}Expected output
context deadline exceeded
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Why is a context with a timeout passed to a client call?
- To open the connection
- To read the proto file
- So the call doesn't wait forever if the server doesn't respond Correct answer
- To encrypt the message
Explanation: When time runs out the call ends with codes.DeadlineExceeded; the deadline also propagates to the server, which can stop working.
2 Create the client
c := pb.____(conn)c := pb.NewSelamlayiciClient(conn)Explanation: The generated New...Client function builds a client from the connection.
3 Client parts
| Term | Meaning |
|---|---|
grpc.NewClient |
Connection |
New...Client |
Generated client |
context.WithTimeout |
Time limit |
conn.Close |
Closes the connection |