1 unstable release

0.2.0 Feb 16, 2021

#11 in #vercel

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75 downloads per month
Used in 2 crates

MIT license

489 lines


Community based builder for using rust on the Vercel platform

Looking for maintainers

I don't use this project any longer, and the time I can dedicate to maintaining this project is very low. If you'd like to help maintain the project, please contact me via an issue or email.

This is a vercel builder which allows you to run your rust code as lambdas on the vercel platform!

This was originally provided officially by Vercel's now archived now-builders monorepo, but has since been moved to a community-maintained project.


If you're unfamiliar with vercel runtimes, please read the runtime docs first. This runtime can be used like any other Community Runtime.

	"functions": {
		"api/**/*.rs": {
			"runtime": "vercel-rust@3.0.0"

That's the simplest way to use this runtime!


The entrypoint, in this case every file that matches api/**/*.rs, is used to create a Serverless Function for you. Note that the Cargo.toml file must exist on the same level as the .rs files.


This Builder supports installing dependencies defined in the Cargo.toml file.

Furthermore, more system dependencies can be installed at build time with the presence of a shell build.sh file in the same directory as the entrypoint file.

Unlisted Utility Functions

Utility functions could be created as described in Prevent Endpoint Listing. To make use of them make sure to include them in the Cargo.toml under [lib].


This could be our api/user.rs file:

use util::print_foo;
use http::{StatusCode};
use vercel_lambda::{lambda, error::VercelError, IntoResponse, Request, Response};
use std::error::Error;

fn handler(_: Request) -> Result<impl IntoResponse, VercelError> {
	let response = Response::builder()
		.header("Content-Type", "text/plain")
		.body("user endpoint")
		.expect("Internal Server Error");


// Start the runtime with the handler
fn main() -> Result<(), Box<dyn Error>> {

Our helper utilities api/_util.rs file:

pub fn print_foo() {

Our api/Cargo.toml could look like this:

name = "index"
version = "2.0.0"
authors = ["Mike Engel <mike@mike-engel.com>"]
edition = "2018"

http = "0.1"
vercel_lambda = "*"

name = "util"
path = "_util.rs"

Finally we need a vercel.json file to specify the runtime for api/user.rs:

	"functions": {
		"api/**/*.rs": {
			"runtime": "vercel-rust@3.0.0"


Are cargo workspaces supported?

Not quite. Cargo's workspaces feature is a great tool when working on multiple binaries and libraries in a single project. If a cargo workspace is found in the entrypoint, however, vercel-rust will fail to build.

To get around this limitation, create build entries in your vercel.json file for each Cargo.toml that represents a lambda function within your workspace. In your .vercelignore, you'll want to add any binary or library project folders that aren't needed for your lambdas to speed up the build process like your Cargo.toml workspace.

It's also recommended to have a Cargo.lock alongside your lambda Cargo.toml files to speed up the build process. You can do this by running cargo check or a similar command within each project folder that contains a lambda.

If you have a compelling case for workspaces to be supported by vercel-rust which are too cumbersome with this workaround, please submit an issue! We're always looking for feedback.

How do I use this during local development?

The vercel dev command allows you to develop lambdas locally on your machine. With vercel dev and vercel-rust you can develop your rust-based lamdas on your own machine.

During local development with vercel dev, the assumption is that rust and cargo are already installed and available in your PATH since they will not be installed automatically. The recommended way to install rust and cargo on your machine is with rustup.

Can I use musl/static linking?

Unfortunately, the AWS lambda runtime for rust relies (tangentially) on proc_macro, which won't compile on musl targets. Without musl, all linking must be dynamic. If you have a crate that relies on system libraries like postgres or mysql, you can include those library files with the includeFiles config option and set the proper environment variables, config, etc. that you need to get the library to compile.

For more info, please see issue #2.

Why does this project use tabs over spaces?

Please refer to this tweet.


Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms.

Issues and pull requests are welcome!


Since this project contains both rust and node code, you need to install the relevant dependencies. If you're only working on the javascript side, you only need to install those dependencies. The oppoosite is true for the rust side.

# install node dependencies
npm install

# install cargo dependencies
cargo fetch

At this point, you're all set up and can start making edits!

Note: During the migration period, tests will be broken until we get CI set up!



Contributors ✨

Thanks goes to these wonderful people (emoji key):

Mike Engel
Mike Engel

💬 💻 📖 💡 ⚠️ 👀 🚧 🎨 🚇 🤔 🖋
Antonio Nuno Monteiro
Antonio Nuno Monteiro

💬 💻 📖 💡 ⚠️ 👀 🚧 🎨 🚇 🤔 🖋
Jacob Mischka
Jacob Mischka



This project follows the all-contributors specification. Contributions of any kind welcome!


~254K SLoC