Building a Rust Project

Runtime.land is built on Rust and WebAssembly. Rust is first to be supported. You can use Rust to build your functions and deploy them to Runtime.land.

Prerequisites

Before you begin, you'll need to install the wasm32-wasi target for Rust. You can do this using the rustup tool:

rustup target add wasm32-wasi

Create Project

Use land-cli to create project:

land-cli init hello-rust

In Cargo.toml, it shows:

Cargo.toml

[package]
name = "hello-rust"
version = "0.1.0"
edition = "2021"

[dependencies]
anyhow = "1.0.75"
http = "0.2.9"
land-sdk = "0.1.0"
wit-bindgen = "0.11.0"

[lib]
crate-type = ["cdylib"]

HTTP Trigger

In Runtime.land, you can use http_main attribute to mark a function as a HTTP trigger. The function will be called when a HTTP request is received and respond with a HTTP response.

src/lib.rs

use land_sdk::http::{Body, Error, Request, Response};
use land_sdk::http_main;

#[http_main]
pub fn handle_request(req: Request) -> Result<Response, Error> {
    let url = req.uri().clone();
    let method = req.method().to_string().to_uppercase();
    Ok(http::Response::builder()
        .status(200)
        .header("X-Request-Url", url.to_string())
        .header("X-Request-Method", method)
        .body(Body::from("Hello Runtime.land!!"))?)
}

• The key point is the http_main macro. It marks the function as a HTTP trigger. The function must have a Request parameter and return a Response.
• The function handle_request is the entrypoint of the project. It will be executed when a HTTP request is received.
• Request and Response are defined in land_sdk::http. You can use it to access the request and response data. They are type alias of http::Request and http::Response from http crate.
• Body is defined in land_sdk::http. It provides rich API to access the body. You can learn more about it in land-sdk crate.

Fetch Remote Http Resource

It's allowed to fetch remote http resource in Runtime.land. You can use land-sdk::http::fetch method to do this.

src/lib.rs

use land_sdk::http::{fetch, Body, Error, Request, RequestOptions, Response};
use land_sdk::http_main;

#[http_main]
pub fn handle_request(_req: Request) -> Result<Response, Error> {
    let fetch_request = http::Request::builder()
        .method("GET")
        .uri("https://www.rust-lang.org/")
        .body(Body::empty())?;
    let fetch_response = fetch(fetch_request, RequestOptions::default())?;
    Ok(http::Response::builder()
        .status(fetch_response.status())
        .body(fetch_response.into_body())?)
}

tip

The http::Request::builder() method is provided by the Rust http crate. The http crate is already added to template project. If you create a project without using this template, you’ll need to add the http crate yourself via cargo add http.

• The fetch method is defined in land_sdk::http. It takes a http::Request and RequestOptions as parameters. It returns a Result<http::Response, RequestError>. The Result is anyhow::Result and RequestError is defined in land_sdk::http.
• The RequestOptions is defined in land_sdk::http. It provides some options to control the request. You can learn more about it in fetch in land-sdk crate.