server

HTTP server

Please install the prerequisites first!

Quick start with Docker

$ docker run -dp 8080:8080 --rm --runtime=io.containerd.wasmedge.v1 --platform=wasi/wasm secondstate/rust-example-server:latest
... ...

$ curl http://localhost:8080/
Try POSTing data to /echo such as: `curl localhost:8080/echo -XPOST -d 'hello world'`

$ curl http://localhost:8080/echo -X POST -d "Hello WasmEdge"
Hello WasmEdge

Code

The src/main.rs source code shows how to start an async server using the hyper crate.

• The main() function is now an async function and annotated with the tokio macro. That means the tokio controller can spawn multiple instances of the main() app.
• Each instance of the main() app listens at port 8080 without blocking the port for everyone else. It receives a data stream for each incoming HTTP connection it captures.
  • The accept() function runs in a loop. It accepts an incoming connection, processes its data, and then start over.
  • Since the data connection could be slow, the accept() function could take a long time to return. But it is async, meaning that multiple instances of accept() could run concurrently to receive data from multiple connections on the same port.
  • The await blocks each instance of accept() so that the statements after accept() would not run until accept() receives all the data in a connection and returns.
• The tokio::task::spawn API designate the handle_request() function to be called whenever the data stream is available.
• The data in the stream, which is a HTTP request is passed to handle_request(), and the function returns an HTTP response struct.
• Inside handle_request(), it matches both the HTTP request method and path.
  • If the HTTP request is a GET at /, it returns a response with a help message.
  • If the HTTP request is a POST at /echo, it extracts the HTTP body and echoes it back as the HTTP response.
  • If no match is found, it returns an HTTP 404 error code.

Step by step guide

Compile the Rust source code project to a Wasm bytecode file.

$ cargo build --target wasm32-wasi --release

Run the Wasm bytecode file in WasmEdge CLI.

$ wasmedge ../target/wasm32-wasi/release/server.wasm
Listening on http://0.0.0.0:8080

From another terminal window, do the following.

$ curl http://localhost:8080/
Try POSTing data to /echo such as: `curl localhost:8080/echo -XPOST -d 'hello world'`

$ curl http://localhost:8080/echo -X POST -d "Hello WasmEdge"
Hello WasmEdge

Build and publish on Docker

The Dockerfile follows the above steps to build and package a lightweight OCI-compliant container image for the Wasm app. Now, we need to publish the container image to Docker Hub. You just need to specify that the WasmEdge application image is for the wasi/wasm platform.

$ docker buildx build --platform wasi/wasm -t secondstate/rust-example-server .
... ...
$ docker push secondstate/rust-example-server