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main.go
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main.go
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package main
import (
"context"
"flag"
"fmt"
"log"
"log/slog"
"net"
"os"
"os/signal"
"github.com/cappuccinotm/gcache"
"github.com/cappuccinotm/gcache/_example/client-caching/order"
"google.golang.org/grpc"
"google.golang.org/grpc/credentials/insecure"
"google.golang.org/grpc/metadata"
)
var modeFlag = flag.String("mode", "server", "run mode")
func main() {
flag.Parse()
ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
defer stop()
switch *modeFlag {
case "server":
if err := runServer(ctx); err != nil {
log.Fatalf("failed to run server: %v", err)
}
case "client":
if err := runClient(ctx); err != nil {
log.Fatalf("failed to run client: %v", err)
}
default:
log.Fatalf("unknown mode: %s", *modeFlag)
}
}
func runServer(ctx context.Context) error {
srv := grpc.NewServer()
order.RegisterOrderServiceServer(srv, &server{})
log.Printf("starting server")
l, err := net.Listen("tcp", ":8080")
if err != nil {
return fmt.Errorf("listen: %w", err)
}
go func() {
<-ctx.Done()
log.Printf("shutting down server")
srv.GracefulStop()
}()
if err = srv.Serve(l); err != nil {
return fmt.Errorf("serve: %w", err)
}
return nil
}
type server struct {
order.UnimplementedOrderServiceServer
}
const timeStamp = "2021-01-01T00:00:00Z"
func (s *server) GetOrder(ctx context.Context, req *order.GetOrderRequest) (*order.Order, error) {
etag := gcache.ETag(ctx)
log.Printf("requested order, etag: %s", etag)
if etag == timeStamp {
log.Printf("skipping, not modified")
return nil, gcache.NotChanged(ctx, timeStamp)
}
log.Printf("delivering actual order")
if err := grpc.SendHeader(ctx, metadata.Pairs("ETag", timeStamp)); err != nil {
return nil, fmt.Errorf("send header: %w", err)
}
return &order.Order{
Id: "order-1",
CustomerId: "customer-1",
Items: []*order.Order_OrderItem{{
Id: "item-1",
Name: "Pizza",
Quantity: 1,
}},
}, nil
}
func runClient(ctx context.Context) error {
icptr := gcache.NewInterceptor(gcache.WithLogger(slog.Default()))
conn, err := grpc.NewClient("localhost:8080",
grpc.WithTransportCredentials(insecure.NewCredentials()),
grpc.WithUnaryInterceptor(icptr.UnaryClientInterceptor()),
)
if err != nil {
return fmt.Errorf("dial localhost:8080: %w", err)
}
client := order.NewOrderServiceClient(conn)
resp, err := client.GetOrder(ctx, &order.GetOrderRequest{})
if err != nil {
return fmt.Errorf("get order: %w", err)
}
log.Printf("order: %v", resp)
if resp, err = client.GetOrder(ctx, &order.GetOrderRequest{}); err != nil {
return fmt.Errorf("get order: %w", err)
}
log.Printf("order: %v", resp)
return nil
}