I’ve recently been working on a Rust course for the Qvault app. In order to write a more engaging course, I want students to be able to write and execute code right in the browser. As I’ve learned from my previous posts on this topic, the easiest way to sandbox code execution on a server is to not execute code on a server. Enter Web Assembly, stage left.
For those of you who don’t care about how it works, and just want to give it a try, checkout the demo: Rust WASM Playground.
The architecture is fairly simple:
Writing code and shipping it to the server hopefully needs no explanation, it’s a simple text editor coupled with the fetch API. The first interesting thing we do is compile the code on the server.
Qvault’s server is written in Go. I have a simple HTTP handler with the following signature:
func (cfg config) compileRustHandler(w http.ResponseWriter, r *http.Request)
At the start of the function we unmarshal the code which was provided in a JSON body:
type parameters struct {
Code string
}
decoder := json.NewDecoder(r.Body)
params := parameters{}
err := decoder.Decode(¶ms)
if err != nil {
respondWithError(w, 500, "Couldn't decode parameters")
return
}
Next, we create a temporary folder on disk that we’ll use as a “scratch pad” to create a Rust project.
usr, err := user.Current()
if err != nil {
respondWithError(w, 500, "Couldn't get system user")
return
}
workingDir := filepath.Join(usr.HomeDir, ".wasm", uuid.New().String())
err = os.MkdirAll(workingDir, os.ModePerm)
if err != nil {
respondWithError(w, 500, "Couldn't create directory for compilation")
return
}
defer func() {
err = os.RemoveAll(workingDir)
if err != nil {
respondWithError(w, 500, "Couldn't clean up code from compilation")
return
}
}()
As you can see, we create the project under the .wasm/uuid
path in the home directory. We also defer
an os.RemoveAll
function that will delete this folder when we are doing handling this request.
#golang #languages #rust #wasm #rust #rustlang #wasm #web assembly