Заместитель на Rust
Заместитель — это объект, который выступает прослойкой между клиентом и реальным сервисным объектом. Заместитель получает вызовы от клиента, выполняет свою функцию (контроль доступа, кеширование, изменение запроса и прочее), а затем передаёт вызов сервисному объекту.
Заместитель имеет тот же интерфейс, что и реальный объект, поэтому для клиента нет разницы — работать через заместителя или напрямую.
Conceptual Example: Nginx Proxy
A web server such as Nginx can act as a proxy for your application server:
- It provides controlled access to your application server.
- It can do rate limiting.
- It can do request caching.
server.rs
mod application;
mod nginx;
pub use nginx::NginxServer;
pub trait Server {
fn handle_request(&mut self, url: &str, method: &str) -> (u16, String);
}
server/application.rs
use super::Server;
pub struct Application;
impl Server for Application {
fn handle_request(&mut self, url: &str, method: &str) -> (u16, String) {
if url == "/app/status" && method == "GET" {
return (200, "Ok".into());
}
if url == "/create/user" && method == "POST" {
return (201, "User Created".into());
}
(404, "Not Ok".into())
}
}
server/nginx.rs
use std::collections::HashMap;
use super::{application::Application, Server};
/// NGINX server is a proxy to an application server.
pub struct NginxServer {
application: Application,
max_allowed_requests: u32,
rate_limiter: HashMap<String, u32>,
}
impl NginxServer {
pub fn new() -> Self {
Self {
application: Application,
max_allowed_requests: 2,
rate_limiter: HashMap::default(),
}
}
pub fn check_rate_limiting(&mut self, url: &str) -> bool {
let rate = self.rate_limiter.entry(url.to_string()).or_insert(1);
if *rate > self.max_allowed_requests {
return false;
}
*rate += 1;
true
}
}
impl Server for NginxServer {
fn handle_request(&mut self, url: &str, method: &str) -> (u16, String) {
if !self.check_rate_limiting(url) {
return (403, "Not Allowed".into());
}
self.application.handle_request(url, method)
}
}
main.rs
mod server;
use crate::server::{NginxServer, Server};
fn main() {
let app_status = &"/app/status".to_string();
let create_user = &"/create/user".to_string();
let mut nginx = NginxServer::new();
let (code, body) = nginx.handle_request(app_status, "GET");
println!("Url: {}\nHttpCode: {}\nBody: {}\n", app_status, code, body);
let (code, body) = nginx.handle_request(app_status, "GET");
println!("Url: {}\nHttpCode: {}\nBody: {}\n", app_status, code, body);
let (code, body) = nginx.handle_request(app_status, "GET");
println!("Url: {}\nHttpCode: {}\nBody: {}\n", app_status, code, body);
let (code, body) = nginx.handle_request(create_user, "POST");
println!("Url: {}\nHttpCode: {}\nBody: {}\n", create_user, code, body);
let (code, body) = nginx.handle_request(create_user, "GET");
println!("Url: {}\nHttpCode: {}\nBody: {}\n", create_user, code, body);
}
Output
Url: /app/status HttpCode: 200 Body: Ok Url: /app/status HttpCode: 200 Body: Ok Url: /app/status HttpCode: 403 Body: Not Allowed Url: /create/user HttpCode: 201 Body: User Created Url: /create/user HttpCode: 404 Body: Not Ok
