Grafbase Gateway Hooks

This crate provides the necessary types and macros to implement hooks for the Grafbase Gateway. A hook is a function that is called by the gateway at specific points in the request processing.

Build your own hooks by implementing the [Hooks] trait, add the [grafbase_hooks] attribute on top of the hooks implementation and register the hooks type to the gateway using the [register_hooks] macro.

The hooks component is a WASM module that is loaded by the gateway at startup. Your hooks library must be compiled with the cargo-component toolchain, which compiles the hooks as a wasm32-wasip1 module, and inserts the needed shims so the module can act as a wasm32-wasip2 component.

Usage

Create a new rust library project with cargo:

cargo new --lib my-hooks
cd my-hooks

Add the grafbase-hooks as a dependency:

cargo add grafbase-hooks --features derive

Edit the src/lib.rs file and add the following code:

use grafbase_hooks::{grafbase_hooks, register_hooks, Context, ErrorResponse, Headers};

struct MyHooks;

#[grafbase_hooks]
impl Hooks for MyHooks {
fn new() -> Self
where
Self: Sized,
{
MyHooks
}

fn on_gateway_request(
&mut self,
context: Context,
headers: Headers
) -> Result<(), ErrorResponse> {
if let Some(ref auth_header) = headers.get("authorization") {
context.set("auth", auth_header);
}

Ok(())
}
}

register_hooks!(MyHooks);

The example above implements the [Hooks#on_gateway_request] hook, which will be available in the gateway and will be called for every request.

The [grafbase_hooks] attribute is used to generate the necessary code for the hooks implementation and the [register_hooks] macro registers the hooks type to the gateway. The macro must be called in the library crate root.

The hooks are compiled with the cargo-component subcommand:

cargo component build --release

The compiled hooks wasm module is located in the target/wasm32-wasip1/release directory. You can configure the gateway to load the hooks in the grafbase.toml configuration file:

[hooks]
location = "path/to/my_hooks.wasm"