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CGI apps on Edge

CGI apps on Wasmer Edge

In this tutorial, you will learn how to deploy a CGI app on Wasmer Edge. We will be using the Rust's CGI crate (opens in a new tab) to create a CGI app.

We'll just make a simple Hello, World! CGI app.

What is CGI?

CGI or Common Gateway Interface is a standard for running programs on a web server to generate dynamic content. CGI programs are often written in scripting languages like Perl, Python, or Ruby, but they can also be written in compiled languages like C, C++, or Rust.

CGI with Wasmer

CGI works using the standard input and output streams. Wasmer maps the standard input and output streams to the HTTP request and response. You can read more about WCGI in our article, Announcing WCGI (opens in a new tab).

Prerequisites

The project requires the following tools to be installed on your system:

Creating a CGI app

Install Wasmer

Click here for instructions on how to install Wasmer if you haven't done it already!

Log in into Wasmer

Create a new account in Wasmer (opens in a new tab). Then, log in into the Wasmer CLI and follow the provided steps to provide the CLI access to your Wasmer account.

wasmer login

Install the wasm32-wasi target:

rustup target add wasm32-wasi

This will install the wasm32-wasi target for the Rust compiler.

Initialize the project

We'll initialize an empty rust project using the cargo command-line tool.

cargo init --bin hello-cgi && cd hello-cgi

Add the CGI crate

cargo add cgi

Writing the CGI app

We'll write a simple CGI app that prints Hello, World! to the standard output. This app also accepts a name as a body of the request and prints Hello, {name}!

Note: This cgi app will be wired to WCGI and will be served on the root path.

src/main.rs
use cgi::{http::StatusCode, Request, Response};
 
fn main() {
    cgi::handle(handler);
}
 
fn handler(request: Request) -> Response {
    let who = String::from_utf8_lossy(request.body());
    let who = if who.trim().is_empty() {
        "World"
    } else {
        who.trim()
    };
 
    cgi::text_response(StatusCode::OK, format!("Hello, {who}!"))
}

Building the CGI app

As you see above in the source property, in the module section. We use the release build in wasm32-wasi target.

cargo build --release --target wasm32-wasi

This will create a hello-cgi.wasm file in the target/wasm32-wasi/release directory.

Wiring it up

To run this wcgi app on wasmer, we first need to create a wasmer.toml configuration file. Create a new file wasmer.toml at root level, and copy the following:

wasmer.toml
[package]
name = "<your-namespace>/<your-package-name>" # 👈 Update this
version = "0.1.0"
description = "An application sample for WCGI"
license = "MIT OR Apache-2.0"
 
[[module]]
name = "server"
source = "target/wasm32-wasi/release/hello-cgi.wasm"
abi = "wasi"
 
[[command]]
name = "server"
module = "server"
runner = "https://webc.org/runner/wcgi" # 👈 This is the runner we'll be using
 
[command.annotations.wcgi]
dialect = "rfc-3875" # This is the CGI dialect we'll be using
ℹ️
    1. your-namespace: This is usually your username and also can be your organization name.
    1. your-package-name: This is the name of your package that'll be published to the wasmer-registry.

Your project should now look like this:

      • main.rs
    • Cargo.toml
    • wasmer.toml

    • Running the CGI app

    Now we can test our CGI app locally using the wasmer command-line.

    wasmer run .

    The above command will start a local server on port 8000.

    To test the app, we can use curl to send a request to the server.

    curl http://localhost:8000

    The root path will return Hello, World! as we didn't specify any name in the body.

    Hello, World!
    curl -X POST -d "Wasmer" http://localhost:8000

    The above command will send a POST request with the body Wasmer to the server.

    Hello, Wasmer!

    Deploying the CGI app

    In order to deploy the app, all we need to do is to run:

    wasmer deploy

    This will tigger a wizard which sets up the remaining configuration needed, similar to this:

    It seems you are trying to create a new app!
✔ Who should own this app? · wasmer-user
✔ What should be the name of the app? · hello-cgi
A package manifest was found in path /tmp/tmp.bDul0Ng4o3/hello-cgi/wasmer.toml.
✔ Use it for the app? · yes
✔ Do you want to deploy the app now? · yes
Loading local package (manifest path: /tmp/tmp.bDul0Ng4o3/hello-cgi/.)
✔ Correctly built package locally
✔ Package correctly uploaded
✔ Succesfully pushed release to namespace wasmer-user on the registry
✔ Successfully tagged package wasmer-user/wcgi-hello@0.1.0
Deploying app hello-cgi (wasmer-user) to Wasmer Edge...
 
App hello-cgi (wasmer-user) was successfully deployed 🚀
https://hello-cgi-wasmer-user.wasmer.app
 
→ Unique URL: https://2j6h5i7cpmj6.id.wasmer.app
→ Dashboard:  https://wasmer.io/apps/wasmer-user/hello-cgi
 
Waiting for new deployment to become available...
(You can safely stop waiting now with CTRL-C)
.
𖥔 Deployment complete

    Note how there's been a new file, app.yaml created. This file configures how to deploy your app to Wasmer edge.

    Testing the deployed app

    We can test the deployed app using curl.

    curl https://hello-cgi-wasmer-user.wasmer.app
    ℹ

    The deployment URL follows the format https://<app-name>-<app-owner>.wasmer.app

    Hello, World!

    Works as expected!

    Conclusion

    In this tutorial, we learned how to deploy a CGI app on Wasmer Edge.

    References

    Resources

    We've have also created a template repository for you to get started with CGI apps on Wasmer Edge.

    wasmerio/wcgi-rust-template

    Next steps

    Using Wasmer Edge as a CDNVolumes