Flow Control

Middleware that provides flow control functionality.

Main Features

RateIssuer provides an abstraction for identifying visitor identity keys. RemoteIpIssuer is an implementation that identifies visitors based on their request IP address. The key does not have to be a string type; any type satisfying the Hash + Eq + Send + Sync + 'static constraints can be used as a key.
RateGuard provides an abstraction for flow control algorithms. It comes with two built-in implementations: fixed window (FixedGuard) and sliding window (SlidingGuard).
RateStore provides an abstraction for data storage and retrieval. MokaStore is a built-in in-memory cache implementation based on moka. You can also define your own custom implementations.
RateLimiter is a struct that implements Handler. It contains a skipper field, which can be used to specify requests that should bypass rate limiting. By default, it uses none_skipper, which does not skip any requests.
QuotaGetter provides an abstraction for retrieving quotas. It can fetch a quota object based on the visitor's Key. This means user quota information can be configured in a database, allowing for dynamic changes and retrieval.

Example Code

Static Quota Example

main.rs

Cargo.toml

rate-limiter-static/src/main.rs

use salvo::prelude::*;
use salvo::rate_limiter::{BasicQuota, FixedGuard, MokaStore, RateLimiter, RemoteIpIssuer};

#[handler]
async fn hello() -> &'static str {
"Hello World"
}

#[tokio::main]
async fn main() {
tracing_subscriber::fmt().init();

let limiter = RateLimiter::new(
    FixedGuard::new(),
    MokaStore::new(),
    RemoteIpIssuer,
    BasicQuota::per_second(1),
);
let router = Router::with_hoop(limiter).get(hello);
let acceptor = TcpListener::new("0.0.0.0:5800").bind().await;
Server::new(acceptor).serve(router).await;
}

Dynamic Quota Example

main.rs

Cargo.toml

rate-limiter-dynamic/src/main.rs

use std::borrow::Borrow;
use std::collections::HashMap;
use std::hash::Hash;
use std::sync::LazyLock;

use salvo::Error;
use salvo::prelude::*;
use salvo::rate_limiter::{
CelledQuota, MokaStore, QuotaGetter, RateIssuer, RateLimiter, SlidingGuard,
};

static USER_QUOTAS: LazyLock<HashMap<String, CelledQuota>> = LazyLock::new(|| {
let mut map = HashMap::new();
map.insert("user1".into(), CelledQuota::per_second(1, 1));
map.insert("user2".into(), CelledQuota::set_seconds(1, 1, 5));
map.insert("user3".into(), CelledQuota::set_seconds(1, 1, 10));
map
});

struct UserIssuer;
impl RateIssuer for UserIssuer {
type Key = String;
async fn issue(&self, req: &mut Request, _depot: &Depot) -> Option<Self::Key> {
    req.query::<Self::Key>("user")
}
}

struct CustomQuotaGetter;
impl QuotaGetter<String> for CustomQuotaGetter {
type Quota = CelledQuota;
type Error = Error;

async fn get<Q>(&self, key: &Q) -> Result<Self::Quota, Self::Error>
where
    String: Borrow<Q>,
    Q: Hash + Eq + Sync,
{
    USER_QUOTAS
        .get(key)
        .cloned()
        .ok_or_else(|| Error::other("user not found"))
}
}

#[handler]
async fn limited() -> &'static str {
"Limited page"
}
#[handler]
async fn home() -> Text<&'static str> {
Text::Html(HOME_HTML)
}

#[tokio::main]
async fn main() {
tracing_subscriber::fmt().init();

let limiter = RateLimiter::new(
    SlidingGuard::new(),
    MokaStore::new(),
    UserIssuer,
    CustomQuotaGetter,
);
let router = Router::new()
    .get(home)
    .push(Router::with_path("limited").hoop(limiter).get(limited));
let acceptor = TcpListener::new("0.0.0.0:5800").bind().await;
Server::new(acceptor).serve(router).await;
}

static HOME_HTML: &str = r#"
<!DOCTYPE html>
<html>
<head>
    <title>Rate Limiter Dynmaic</title>
</head>
<body>
    <h2>Rate Limiter Dynamic</h2>
    <p>
        This example shows how to set limit for different users.
    </p>
    <p>
        <a href="/limited?user=user1" target="_blank">Limited page for user1: 1/second</a>
    </p>
    <p>
        <a href="/limited?user=user2" target="_blank">Limited page for user2: 1/5seconds</a>
    </p>
    <p>
        <a href="/limited?user=user3" target="_blank">Limited page for user3: 1/10seconds</a>
    </p>
</body>
</html>
"#;

On this page

#Flow Control

#Main Features

#Static Quota Example

#Dynamic Quota Example

Flow Control

Main Features

Static Quota Example

Dynamic Quota Example