Continuing this short series of writing a simple echo service web API along with the docker and k8s requirements, we’re now going to turn our attention to a Rust implementation.

Implementation

I’m using JetBrains RustRover for this project, so I created a project named echo_service.

Next, add the following to the dependencies of Cargo.toml

axum = "0.7"
tokio = { version = "1", features = ["full"] }
serde = { version = "1", features = ["derive"] }

and now the main.rs can be replaced with

use axum::{
    routing::get,
    extract::Query,
    http::StatusCode,
    response::IntoResponse,
    Router,
};
use tokio::net::TcpListener;
use axum::serve;
use std::net::SocketAddr;
use serde::Deserialize;

#[derive(Deserialize)]
struct EchoParams {
    text: Option<String>,
}

async fn echo(Query(params): Query<EchoParams>) -> String {
    format!("Rust Echo: {}", params.text.unwrap_or_default())
}

async fn livez() -> impl IntoResponse {
    (StatusCode::OK, "OK")
}

async fn readyz() -> impl IntoResponse {
    (StatusCode::OK, "Ready")
}

#[tokio::main]
async fn main() {
    let app = Router::new()
        .route("/echo", get(echo))
        .route("/livez", get(livez))
        .route("/readyz", get(readyz));

    let addr = SocketAddr::from(([0, 0, 0, 0], 8080));
    println!("Running on http://{}", addr);

    let listener = TcpListener::bind(addr).await.unwrap();
    serve(listener, app).await.unwrap();

}

Dockerfile

Next up we need to create our Dockerfile

FROM rust:1.72-slim AS builder

WORKDIR /app
COPY . .

RUN cargo build --release

FROM debian:bookworm-slim

RUN apt-get update && apt-get install -y ca-certificates && \
    rm -rf /var/lib/apt/lists/*

COPY --from=builder /app/target/release /usr/local/bin/echo_service

RUN chmod +x /usr/local/bin/echo_service

EXPOSE 8080

ENTRYPOINT ["/usr/local/bin/echo_service/echo_service"]

Note: In Linux port 80 might be locked down, hence we use port 8080 by default.

To build this, run

docker build -t putridparrot.echo_service:v1 .

Don’t forget to change the name to your preferred name.

and to test this, run

docker run -p 8080:8080 putridparrot.echo_service:v1

Kubernetes

If all wen well we’ve not tested our application and see it working from a docker image, so now we need to create the deployment etc. for Kubernete’s. Let’s assume you’ve pushed you image to Docker or another container registry such as Azure – I’m call my container registry putridparrotreg.

I’m also not going to use helm at this point as I just want a (relatively) simple yaml file to run from kubectl, so create a deployment.yaml file, we’ll store all the configurations, deployment, service and ingress in this one file jus for simplicity.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: echo
  namespace: dev
  labels:
    app: echo
spec:
  replicas: 1
  selector:
    matchLabels:
      app: echo
  template:
    metadata:
      labels:
        app: echo
    spec:
      containers:
      - name: echo
        image: putridparrotreg/putridparrot.echo_service:v1
        ports:
        - containerPort: 8080
        resources:
          requests:
            memory: "100Mi"
            cpu: "100m"
          limits:
            memory: "200Mi"
            cpu: "200m"
        livenessProbe:
          httpGet:
            path: /livez
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /readyz
            port: 8080
          initialDelaySeconds: 5
          periodSeconds: 5

---
apiVersion: v1
kind: Service
metadata:
  name: echo_service
  namespace: dev
  labels:
    app: echo
spec:
  type: ClusterIP
  selector:
    app: echo 
  ports:
  - name: http
    port: 80
    targetPort: 8080
    protocol: TCP
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: echo-ingress
  namespace: dev
  annotations:
    kubernetes.io/ingress.class: "nginx"
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
  - host: mydomain.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: echo_service
            port:
              number: 80

Don’t forget to change the “host” and image to suit, also this assume you created a namespace “dev” for your app. See Creating a local container registry for information on setting up your own container registry.