This crate contains AsyncInterceptor
, an async variant of Tonic's
Interceptor
.
Other than accepting an async interceptor function, it works the same as Interceptor
.
Async interceptor functions are useful for tasks like authentication, where you need to make asynchronous calls to another service or database within the interceptor.
The major/minor version corresponds with that of Tonic; so, if you are using Tonic v0.12.x, then you should likewise use Tonic Async Interceptor v0.12.x.
async fn my_async_interceptor(req: Request<()>) -> Result<Request<()>, Status> {
// do things and stuff
Ok(req)
}
async fn main() {
use tonic::transport::server;
use tonic_async_interceptor::async_interceptor;
let router = server::Server::builder()
.layer(async_interceptor(my_async_interceptor))
.add_service(some_service)
.add_service(another_service);
// ...
}
Here's an example of an async interceptor which authenticates a user and sets a custom extension for the underlying service to use.
// Your custom extension
struct UserContext {
user_id: String,
}
// Async interceptor fn
async fn authenticate(req: Request<()>) -> Result<Request<()>, Status> {
// Inspect the gRPC metadata.
let auth_header_val = match req.metadata().get("x-my-auth-header") {
Some(val) => val,
None => return Err(Status::unauthorized("Request missing creds")),
};
// Call some async function (`verify_auth`).
let maybe_user_id: Result<String> =
verify_auth(auth_header_val).await;
let user_id = match maybe_user_id {
Ok(id) => id,
Err(_) => return Err(Status::unauthorized("Invalid creds")),
};
// Insert an extension, which can be inspected by the service.
req.extensions_mut().insert(UserContext { user_id });
Ok(req)
}
The code in this crate was originally intended to live in the official Tonic crate, alongside the non-async interceptor code. However, the maintainer decided not to merge it due to lack of time and misalignment with his future vision for Tonic.