#async #http #performance #small

nightly micro_http_async

A small, lightweight and hassle-free crate using async to serve web pages or web apis with high performance and extremely low overhead

11 releases

new 0.1.2 Sep 17, 2021
0.1.1 Sep 16, 2021
0.0.9 Feb 12, 2021

#184 in Web programming

27 downloads per month

MIT license

523 lines


What is it for?

A small, lightweight crate using async to serve web pages or web apis with high performance and low overhead.

How do I use it?

Firstly, install the crate and dependencies:

micro_http_async = "*"
tokio = "1.11.0"

And if you want to support JSON:

serde_json = "1.0"
serde = {version = "1.0", features = ["derive"]}

This crate is designed to abstract away many of the low level code required to run a safe, asynchronous web server Here is a small example which shows how to route, use asynchronous call backs and load webpage templates from HTML files. For the HTML files included, please go to the repository and check the templates folder. Static files also included. To run the included example (which is the example seen below), run cargo run --example hello_world, and visit Please note this is probably not the final API Example

/// Small example to show the functionings of the crate. Read the comments to see how everything
/// functions
// All the imports we need
use micro_http_async::{HttpServer, JSONResponse};
use micro_http_async::Request;
use micro_http_async::HtmlConstructor;
use micro_http_async::Vars;
use micro_http_async::Variable;
use micro_http_async::Response;
use micro_http_async::Route;
// Macros
use micro_http_async::create_route;
/// # main handler
/// main handler is a test to test our route and function callbacks work
/// And it does!
/// The way it works is that we run test_handler when we recieve a connection.
/// Then, this handler manipulates the request (for post info, or other info etc)
/// after, we return the response as a string. It is then served to the user.
async fn main_handler(request: Request) -> Result<String, String>{    
    println!("{:?} -> {:?} {:?}", request.user_addr, request.method.unwrap(), request.uri);
    // Setup vars, which will define how vars are set in the page
    let mut vars = Vars::new();
    let test_string = "This string will be outputted dynamically to the web page!".to_string();
    vars.insert("test_var".to_string(), Variable::String(test_string));
    // This part will check we have a get request parameter with "name"
    // If we do, we will set a dynamic variable to the key value.
    // It will show how to handle get request parameters
    if request.get_request.contains_key("name"){
        let name = format!("Hello, {}!", request.get_request.get("name").unwrap().to_string());
        vars.insert("name".to_string(), Variable::String(name));
        vars.insert("name".to_string(), Variable::String("".to_string()));
    // Construct the page. We need the response code and page to submit, as well as vars to set. It returns the full page including headers.
    let page = HtmlConstructor::construct_page(Response::from(200), "./templates/index.html", vars).await;
    // Return the page as a Result
/// We have to define a custom error handler, which defines what to do when we have a 404
/// Not doing this WILL result in an unrecoverable panic.
async fn error_handler(request: Request) -> Result<String, String>{
    println!("{:?} -> {:?} {:?}", request.user_addr, request.method.unwrap(), request.uri);
    let mut vars = Vars::new();
    let test_string = format!("Could not load webpage at <code>{}</code>", request.uri);
    vars.insert("uri".to_string(), Variable::String(test_string));
    let page = HtmlConstructor::construct_page(Response::ClientErr, "./templates/err.html", vars).await;
// If we choose to use JSON (eg, for APIs), we can use the following.
// We define the JSON as a rust struct, allowing us to represent it through rust. We serialize this
// using serde.
#[derive(serde::Serialize, serde::Deserialize)]
struct TestResponse{
    pub name: String,
// Then, when we handle the response, we convert the Struct using serde_json. We use the JSONResponse class to create
// a response we can send back to the user, using that weird looking return_future method and the box::pins lol.
async fn json_response_handler(request: Request) -> Result<String, String>{
    println!("{:?} -> {:?} {:?}", request.user_addr, request.method.unwrap(), request.uri);
    let json = serde_json::json!(
            name: "Hello, world!".into()
    // This differs from the HTMLConstructor, as we don't take vars as an input
    let page = JSONResponse::construct_response(Response::Ok, json.to_string()).await;
/// # main
/// Does what it says, just sets up the server and routes
/// then listens for incoming connections
pub async fn main() {
    let mut http_server = HttpServer::new("", "8080").await.expect("Error binding to IP/Port");
    // must be placed on heap so it can be allocated at runtime (alternative is static)
    http_server.routes.add_route("/".to_string(), create_route!(main_handler)).await; // Use the macro
    http_server.routes.add_route("err".to_string(), Route::new(Box::new(error_handler))).await; // Do it manually
    http_server.routes.add_route("/json".to_string(), create_route!(json_response_handler)).await;

This crate aims only to simplify web api or lightweight web creation - not intended to run full scale web apps like chatrooms or other high intensity applications. It implements a simple asynchronous routing system (Made using hash maps for speed and efficiency) as well as asynchronous file loading and more. The demo above uses 0% CPU under no load, and less than 10mb of memory under usage. It compiles in 1m 34s on an i5 5500u (release) from scratch and sits at 700kb. Changelog v0.1.2: Added rudementary post requests. There are some explainations of usage in the example hello_world.


~100K SLoC