Rust Runtime for Vercel Functions.
Legacy Runtime
The below documentation is for the vercel_runtime
crate (in beta). If you are looking for the legacy runtime instructions using vercel_lambda
see tree/a9495a0.
Getting Started
Please ensure Vercel CLI and the Rust toolchain is already installed on your system.
We recommended setting up Rust with rustup.
Prefer looking at examples?
Step 1 - Add a vercel.json
file to your project.
{
"functions": {
"api/**/*.rs": {
"runtime": "vercel-rust@4.0.0-beta.4"
}
}
}
This turns every file matching api/**/*.rs
into a Vercel Function.
Note: The npm dependency vercel-rust
defined in functions does not have to be installed manually.
Step 2 - Create a function. As an example, here is api/handler.rs
.
use serde_json::json;
use vercel_runtime::{run, Body, Error, Request, Response, StatusCode};
#[tokio::main]
async fn main() -> Result<(), Error> {
run(handler).await
}
pub async fn handler(_req: Request) -> Result<Response<Body>, Error> {
Ok(Response::builder()
.status(StatusCode::OK)
.header("Content-Type", "application/json")
.body(
json!({
"message": "你好,世界"
})
.to_string()
.into(),
)?)
}
Step 3 - Create a Cargo.toml
in the root directory of your project.
[package]
name = "my-vercel-api"
version = "0.1.0"
edition = "2021"
[dependencies]
tokio = { version = "1", features = ["macros"] }
serde_json = { version = "1", features = ["raw_value"] }
vercel_runtime = { version = "0.2.1" }
[[bin]]
name = "handler"
path = "api/handler.rs"
Step 4 - Create a .vercelignore
in the root directory of your project to ignore build artifacts.
target/
Step 5 - You're all set. Run vercel dev
to develop your project locally. You can connect a Git repository to Vercel, or use vercel
to start deploying your project on Vercel.
Advanced Usage
Toolchain Overrides
An example on how this can be achieved is using a rust-toolchain
file adjacent to your Cargo.toml
. Please refer to Rust Documentation for more details.
Dependencies
By default builder module supports installing dependencies defined in the Cargo.toml
file.
More system dependencies can be installed at build time with the presence of a shell build.sh
file in the root directory of your project.
Prebuilt Deployments
When creating a prebuilt deployment, the build output must be for x86_64 linux
. To do this, create a Cargo build configuration at .cargo/config.toml
with the following contents:
[build]
target = "x86_64-unknown-linux-musl"
You then can build the file and trigger the deployment via Vercel CLI.
vercel build && vercel deploy --prebuilt
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 information, please see this issue.
Experimental Route Merge
This feature allows you to bundle all of your routes into a single deployed Vercel function. Besides optimizing for cold starts, this has the additional benefit of you only needing to annotate a single [[bin]]
in your Cargo.toml
.
Enable this feature by setting the following environment variable in your Vercel project.
VERCEL_RUST_EXPERIMENTAL_ROUTE_MERGE=true
In case you are using workspaces (like examples/route-merge
in this repository), an additional macro prefix has to be provided as an environment variable both locally and in your Vercel project.
# Example for `vercel dev`
VERCEL_RUST_EXPERIMENTAL_MACRO_PREFIX=examples/route-merge/ VERCEL_RUST_EXPERIMENTAL_ROUTE_MERGE=true vc dev
Create a api/vercel/index.rs
.
use serde_json::json;
use vercel_runtime::{include_api, run, Body, Error, Request, Response, StatusCode};
#[tokio::main]
async fn main() -> Result<(), Error> {
run(handler).await
}
#[include_api]
pub async fn handler(req: Request) -> Result<Response<Body>, Error> {
Ok(Response::builder()
.status(StatusCode::NOT_FOUND)
.header("Content-Type", "application/json")
.body(
json!({
"code": "not_found",
"message": "not_found"
})
.to_string()
.into(),
)?)
}
Change your vercel.json
to only specify your api/vercel/index.rs
file.
{
"functions": {
"api/vercel/index.rs": {
"runtime": "vercel-rust@4.0.0-canary.4"
}
}
}
Change your Cargo.toml
to only specify the binary for index.rs
.
[[bin]]
name = "index"
path = "api/vercel/index.rs"
Every route in api/**
must contain a handler
function for the router to work.
use vercel_runtime::{Body, Error, Request, Response, StatusCode};
pub async fn handler(_req: Request) -> Result<Response<Body>, Error> {
Ok(Response::builder()
.status(StatusCode::OK)
.header("Content-Type", "application/json")
.body(Body::Text("Route is /api/foo".into()))?)
}
Contributing
Since this project contains both Rust and Node.js code, you need to install the relevant dependencies. If you're only working on the TypeScript side, you only need to install those dependencies (and vice-versa).
# install node dependencies
pnpm install
# install cargo dependencies
cargo fetch
Builder Module
The npm module vercel-rust
is implementing an interface which is primarily taking care of spawning a development server, caching between consecutive builds, and running the compilation. You can read more about the in-depths of implementing a builder here.
Runtime Crate
The crate vercel_runtime
is what you will consume in your Rust functions. As the name suggests, the runtime crate takes care of everything that happens during run-time. In specific it takes care of creating a Tower service, which expects a specific handler signature. The flow of an invocation can be visualized as the following:
graph TD
A["Function Invocation"] --> |"process_request(event: InvocationEvent<VercelEvent>) → Request"| B[Request]
B --> |"handler_fn(req: Request) → Future<Output = Result<Response<Body>, Error>>"| C["Runtime calls handler_fn"]
C --> |"Ok(r) => process_response(r)"| D["Response"]