Pathfinder Load Shedder

=== This is a currently in an experimental stage. Buyer-beware! Right now it relies on Axum, should be generalized to just use Tower. ===

Overview

Pathfinder Load Shedder is a middleware service built using the tower library in Rust. It is designed to manage and limit the number of concurrent requests globally, particularly targeting your heaviest paths to shed excess load by returning a 503 Service Unavailable status with a customizable body.

Features

• Global Request Limiting: Define paths to be globally monitored and limit concurrent requests across these paths.
• Customizable 503 Responses: Configure custom response bodies for 503 status.
• Timeouts: A timeout can be set specifically for the requests affected by this middleware.

Example

A basic example of how to integrate Pathfinder Load Shedder into an Axum application.

use axum::{Router, routing::get, response::IntoResponse};
use tower::ServiceBuilder;
use std::sync::Arc;

#[tokio::main]
async fn main() {
    // Define paths to globally limit.
    // Any requests to paths not in this list are simply passed through, unaffected.
    let paths = vec![
        PathfinderPath { path: "/api/v1/resource" },
        PathfinderPath { path: "/api/v1/other" },
    ];

    // Create PathfinderLoadShedderLayer with a global max of 2 concurrent requests with a 10 second timeout.
    let load_shedder_layer = PathfinderLoadShedderLayer::new(paths, 2, 10000)
        .set_pathfinder_503_body("Service Temporarily Unavailable");

    // Build our application with some routes
    let app = Router::new()
        .route("/api/v1/resource", get(handler))
        .route("/api/v1/other", get(handler))
        .layer(ServiceBuilder::new().layer(load_shedder_layer));

    // Run our application
    axum::Server::bind(&"0.0.0.0:3000".parse().unwrap())
        .serve(app.into_make_service())
        .await
        .unwrap();
}

async fn handler() -> impl IntoResponse {
    "Hello, world!"
}