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axum/examples/rest-grpc-multiplex/src/multiplex_service.rs
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2022-05-02 23:52:55 +08:00
use axum::{body::BoxBody, response::IntoResponse};
use futures::{future::BoxFuture, ready};
use hyper::{Body, Request, Response};
use std::{
convert::Infallible,
task::{Context, Poll},
};
use tower::Service;
#[derive(Clone)]
pub struct MultiplexService<A, B> {
rest: A,
rest_ready: bool,
grpc: B,
grpc_ready: bool,
}
impl<A, B> MultiplexService<A, B> {
pub fn new(rest: A, grpc: B) -> Self {
Self {
rest,
rest_ready: false,
grpc,
grpc_ready: false,
}
}
}
impl<A, B> Service<Request<Body>> for MultiplexService<A, B>
where
A: Service<Request<Body>, Error = Infallible>,
A::Response: IntoResponse,
A::Future: Send + 'static,
B: Service<Request<Body>, Error = Infallible>,
B::Response: IntoResponse,
B::Future: Send + 'static,
{
type Response = Response<BoxBody>;
type Error = Infallible;
type Future = BoxFuture<'static, Result<Self::Response, Self::Error>>;
fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
loop {
match (self.rest_ready, self.grpc_ready) {
(true, true) => {
return Ok(()).into();
}
(false, _) => {
ready!(self.rest.poll_ready(cx))?;
self.rest_ready = false;
}
(_, false) => {
ready!(self.grpc.poll_ready(cx))?;
self.grpc_ready = true;
}
}
}
}
fn call(&mut self, req: Request<Body>) -> Self::Future {
if is_grpc_request(&req) {
self.grpc_ready = false;
let future = self.grpc.call(req);
Box::pin(async move {
let res = future.await?;
Ok(res.into_response())
})
} else {
self.rest_ready = false;
let future = self.rest.call(req);
Box::pin(async move {
let res = future.await?;
Ok(res.into_response())
})
}
}
}
fn is_grpc_request<B>(req: &Request<B>) -> bool {
req.headers()
.get("content-type")
.map(|content_type| content_type.as_bytes())
.filter(|content_type| content_type.starts_with(b"application/grpc"))
.is_some()
}