How to inject an immutable object into service code in actix-web? - rust

Question

I'm using actix framework to build a server that should support an opportunity to show both age/balance to a user given a user_id:
fn show_balance(req: &HttpRequest) -> HttpResponse {
let client = create_client();
let user_id = req.match_info().get("user_id").unwrap();
let balance = client.load_grade(user_id); // Returns a balance as a String
HttpResponse::Ok()
.content_type("text/plain")
.body(format!("Hello! Your balance is {}", balance))
}
fn show_age(req: &HttpRequest) -> HttpResponse {
let client = create_client();
let user_id = req.match_info().get("user_id").unwrap();
let age = client.load_grade(user_id); // Returns an age as a String
HttpResponse::Ok()
.content_type("text/plain")
.body(format!("Hello! Your balance is {}", age))
}
fn main() {
env::set_var("RUST_LOG", "actix_web=debug");
env::set_var("RUST_BACKTRACE", "1");
env_logger::init();
let sys = actix::System::new("basic-example");
let addr = server::new(
|| App::new()
// enable logger
.middleware(middleware::Logger::default())
.resource("/balance/{user_id}", |r| r.method(Method::GET).f(show_balance))
.resource("/age/{user_id}", |r| r.method(Method::GET).f(show_age))
.bind("127.0.0.1:8080").expect("Can not bind to 127.0.0.1:8080")
.start();
println!("Starting http server: 127.0.0.1:8080");
let _ = sys.run();
}
fn create_client() -> UserDataClient {
let enviroment = grpcio::EnvBuilder::new().build();
let channel = grpcio::ChannelBuilder::new(enviroment)
.connect(API_URL);
UserDataClient::new(channel)
}
This code works, but my concern is that I have to create a client (and open a channel) for every incoming request which is inefficient and readable, I think it's a good idea to make sort of a singleton instead (since I can reuse it). I looked through the example folder and found that todo example is kinda similar to what I'm doing. So I found the following two options to inject my client object (after I create a single instance of it in main():
Put it in an app state
Inject it as a middleware (1, 2)?
What's the best/correct one to implement?
I thought about just passing a client object to every handler as an argument but I didn't manage to make it work (and doesn't look good anyway).