I'm looking to add what's essentially a "status" boolean field to my gRPC Server. The idea is that the state of the server could be set when certain conditions are met, so when any new gRPC requests come in, the response would be tailored accordingly.
I have a server struct that I'm using, and for this example, I've added a HappyHour bool field.
I have a goroutine that runs when the server is started, and every minute it checks the time of day. If the time of day is between 5-7pm, HappyHour gets set to true. Otherwise, it gets set to false.
type server struct {
HappyHour bool
mu sync.RWMutex
}
func (s *server) OrderDrink(ctx context.Context, req *bar.DrinkRequest) (*flatbuffers.Builder, error) {
drink := string(req.drink())
qty := req.qty()
// Code here to look up the price of the drink in the database
total := price*qty
// Use a mutex to check HappyHour status
s.mu.RLock()
defer mu.RLock()
if s.HappyHour == true {
total=total/2
}
b := flatbuffers.NewBuilder(0)
// Serialize the response and send it to the client
}
func main() {
lis, err := net.Listen("tcp", "0.0.0.0:50051")
if err != nil {
log.Fatal(err)
}
s := grpc.NewServer(grpc.CustomCodec(flatbuffers.FlatbuffersCodec{}))
var srv server
bar.RegisterBARServer(s, &srv)
// Monitor happy hour
go happyHour(&srv)
}
Things seem to be working from my initial testing, but I'm quite new to gRPC, and am a bit worried about using a mutex on the server struct.
Will there be negative performance impacts if there are many clients connecting to the server? If I'm reading or updating HappyHour, and the lock has been acquired, would this impact new users connecting or sending requests? Or would this only impact the actual HappyHour field?
