Run a Rust Tokio app

This example uses Tokio, a popular Rust asynchronous runtime. To run this example, follow these steps:

1. Install the kraft CLI tool and a container runtime engine, e.g. Docker.

2. Clone the examples repository and cd into the examples/http-rust1.75-tokio/ directory:

git clone https://github.com/kraftcloud/examples
cd examples/http-rust1.75-tokio/

Make sure to log into Unikraft Cloud by setting your token and a metro close to you. We use fra0 (Frankfurt, 🇩🇪) in this guide:

# Set Unikraft Cloud access token
export UKC_TOKEN=token
# Set metro to Frankfurt, DE
export UKC_METRO=fra0

When done, invoke the following command to deploy this application on Unikraft Cloud:

kraft cloud deploy -p 443:8080 .

The output shows the instance URL and other details:

[●] Deployed successfully!
 │
 ├────────── name: http-rust175-tokio-6gxsp
 ├────────── uuid: d5719f64-0653-42d7-b2de-aa6dee0ce467
 ├───────── state: running
 ├─────────── url: https://empty-dawn-3coedrce.fra0.kraft.host
 ├───────── image: http-rust175-tokio@sha256:0ce75912711aa2329232a2ca6c3ccb7a244b6d546fafc081f815c2fde8224856
 ├───── boot time: 21.41 ms
 ├──────── memory: 128 Mi
 ├─────── service: empty-dawn-3coedrce
 ├── private fqdn: http-rust175-tokio-6gxsp.internal
 ├──── private ip: 172.16.6.3
 └────────── args: /server

In this case, the instance name is http-rust175-tokio-6gxsp and the URL is `https://empty-dawn-3coedrce.fra0.kraft.host. They are different for each run.

Use curl to query the Unikraft Cloud instance of the Tokio-based HTTP web server:

curl https://empty-dawn-3coedrce.fra0.kraft.host

Hello, World!

At any point in time, you can list information about the instance:

kraft cloud instance list

NAME                           FQDN                         STATE    CREATED AT      IMAGE                                                                         MEMORY   ARGS     BOOT TIME
http-rust175-tokio-6gxsp       empty-dawn-3coedrce.fra0...  running  1 minute ago    http-rust175-tokio@sha256:0ce75912711aa2329232a2ca6c3ccb7a244b6d546fafc08...  128 MiB  /server  21412us

When done, you can remove the instance:

kraft cloud instance remove http-rust175-tokio-6gxsp

Customize your Application

To customize the application, update the files in the repository, listed below:

• src/main.rs: the actual server
• Cargo.toml: the Cargo package manager configuration file
• Kraftfile: the Unikraft Cloud specification
• Dockerfile: the Docker-specified application filesystem

Kraftfile

spec: v0.6

runtime: base:latest

rootfs: ./Dockerfile

cmd: ["/server"]

src/main.rs

use std::net::SocketAddr;
use tokio::net::TcpListener;
use tokio::io::{AsyncReadExt, AsyncWriteExt};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
let addr = SocketAddr::from(([0, 0, 0, 0], 8080));
let listener = TcpListener::bind(&addr).await?;

println!("Listening on: http://{}", addr);

loop {
    let (mut stream, _) = listener.accept().await?;

    tokio::spawn(async move {
        loop {
            let mut buffer = [0; 1024];
            let _ = stream.read(&mut buffer).await;

            let contents = "Hello, World!\r\n";
            let content_length = contents.len();
            let response = format!("HTTP/1.1 200 OK\r\nContent-Length: {content_length}\r\n\r\n{contents}");
            let _ = stream.write_all(response.as_bytes()).await;
        }
    });
}
}

Cargo.toml

[package]
name = "http-tokio"
version = "0.1.0"
edition = "2021"


[dependencies]
tokio = {version = "1",  features = ["rt-multi-thread", "net", "time", "macros", "io-util"] }

Dockerfile

FROM rust:1.75.0-bookworm AS build

WORKDIR /src

COPY ./src /src/src
COPY ./Cargo.toml /src/Cargo.toml

RUN cargo build

FROM scratch

COPY --from=build src/target/debug/http-tokio /server
COPY --from=build /lib/x86_64-linux-gnu/libc.so.6 /lib/x86_64-linux-gnu/libc.so.6
COPY --from=build /lib/x86_64-linux-gnu/libm.so.6 /lib/x86_64-linux-gnu/libm.so.6
COPY --from=build /lib/x86_64-linux-gnu/libgcc_s.so.1 /lib/x86_64-linux-gnu/libgcc_s.so.1
COPY --from=build /lib64/ld-linux-x86-64.so.2 /lib64/ld-linux-x86-64.so.2

The following options are available for customizing the application:

• If only updating the implementation in the src/main.rs source file, no other change is required.

• If new files are added, these have to be copied in the application filesystem, using the COPY command in the Dockerfile. If new Rust source code files are added, be sure to configure required dependencies in the Cargo.toml file.

• If a new executable is built, update the cmd line in the Kraftfile and replace /server with the path to the new executable.

• More extensive changes may require expanding the Dockerfile with additional Dockerfile commands.

Learn More

Use the --help option for detailed information on using Unikraft Cloud:

kraft cloud --help

Or visit the CLI Reference.