A sample knative service demo for a Rust WASI service based on https://github.com/knative/docs/tree/main/code-samples/community/serving/helloworld-rust
A simple web app written in Rust that you can use for testing. It reads in an
env variable TARGET and prints "Hello ${TARGET}!". If
TARGET is not specified, it will use "World" as the TARGET.
- A Kubernetes cluster with Knative installed and DNS configured. Follow the Knative installation instructions if you need to create one.
- A WASMedge with crun enabled in the Kubernetes cluster. Follow the configurations instructions here if you need help installing.
- Docker installed and running on your local machine, and a Docker Hub account configured (we'll use it for a container registry).
While you can clone all of the code from this directory, hello world apps are generally more useful if you build them step-by-step. The following instructions recreate the source files from this folder.
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Create a new file named
Cargo.tomland paste the following code:[package] name = "hellorust" version = "0.0.0" edition = "2018" publish = false [dependencies] hyper = { version = "0.14.7", features = ["full"]} tokio = { version = "1.5.0", features = ["macros", "rt-multi-thread"] } pretty_env_logger = "0.4.0"
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Create a
srcfolder, then create a new file namedmain.rsin that folder and paste the following code. This code creates a basic web server which listens on port 8080:use hyper::{ service::{make_service_fn, service_fn}, Body, Request, Response, Server, }; use std::convert::Infallible; use std::env; use std::net::SocketAddr; #[tokio::main(flavor = "current_thread")] async fn main() { pretty_env_logger::init(); let mut port: u16 = 8080; match env::var("PORT") { Ok(p) => { match p.parse::<u16>() { Ok(n) => { port = n; } Err(_e) => {} }; } Err(_e) => {} }; let addr = SocketAddr::from(([0, 0, 0, 0], port)); let make_svc = make_service_fn(|_| async move { Ok::<_, Infallible>(service_fn(move |_: Request<Body>| async move { let mut hello = "Hello ".to_string(); match env::var("TARGET") { Ok(target) => { hello.push_str(&target); } Err(_e) => hello.push_str("World"), }; Ok::<_, Infallible>(Response::new(Body::from(hello))) })) }); let server = Server::bind(&addr).serve(make_svc); if let Err(e) = server.await { eprintln!("server error: {}", e); } }
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In your project directory, create a file named
Dockerfileand copy the code block below into it.# Use the official Rust image. # https://hub.docker.com/_/rust FROM rust:1.66.0 as builder RUN rustup target add wasm32-wasi # Copy local code to the container image. WORKDIR /usr/src/app COPY . . # Install production dependencies and build a release artifact. RUN cargo build --release FROM scratch COPY --from=builder /usr/src/app/target/wasm32-wasi/release/hellorust.wasm / # Run the web service on container startup. CMD ["./hellorust.wasm"] -
Create a new file,
service.yamland copy the following service definition into the file. Make sure to replace{username}with your Docker Hub username.apiVersion: serving.knative.dev/v1 kind: Service metadata: name: helloworld-rust-wasi namespace: default spec: template: metadata: annotations: module.wasm.image/variant: compat-smart spec: runtimeClassName: crun timeoutSeconds: 1 containers: - name: http-server image: docker.io/{username}/helloworld-rust-wasi ports: - containerPort: 8080 protocol: TCP env: - name: TARGET value: "Rust Sample v1"
Once you have recreated the sample code files (or used the files in the sample folder) you're ready to build and deploy the sample app.
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Use Docker to build the sample code into a container. To build and push with Docker Hub, enter these commands replacing
{username}with your Docker Hub username:# Build the container on your local machine docker build -t {username}/helloworld-rust-wasi . # Push the container to docker registry docker push {username}/helloworld-rust-wasi
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After the build has completed and the container is pushed to Docker Hub, you can deploy the app into your cluster. Ensure that the container image value in
service.yamlmatches the container you built in the previous step. Apply the configuration usingkubectl:kubectl apply --filename service.yaml
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Now that your service is created, Knative will perform the following steps:
- Create a new immutable revision for this version of the app.
- Network programming to create a route, ingress, service, and load balance for your app.
- Automatically scale your pods up and down (including to zero active pods).
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To find the URL for your service, enter:
kubectl get ksvc helloworld-rust --output=custom-columns=NAME:.metadata.name,URL:.status.url NAME URL helloworld-rust http://helloworld-rust.default.1.2.3.4.sslip.io
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Now you can make a request to your app and see the result. Replace the URL below with the URL returned in the previous command.
curl http://helloworld-rust.default.1.2.3.4.sslip.io Hello World!
To remove the sample app from your cluster, delete the service record:
kubectl delete --filename service.yaml