Part 4. Add a Middleware
Next, let’s look at how to add middleware to Volo.
For example, if we need a middleware that prints out the received requests, the returned responses and the elapsed time, we could write a Service in lib.rs
:
#[derive(Clone)]
pub struct LogService<S>(S);
#[volo::service]
impl<Cx, Req, S> volo::Service<Cx, Req> for LogService<S>
where
Req: std::fmt::Debug + Send + 'static,
S: Send + 'static + volo::Service<Cx, Req> + Sync,
S::Response: std::fmt::Debug,
S::Error: std::fmt::Debug,
Cx: Send + 'static,
{
async fn call(&self, cx: &mut Cx, req: Req) -> Result<S::Response, S::Error> {
let now = std::time::Instant::now();
tracing::debug!("Received request {:?}", &req);
let resp = self.0.call(cx, req).await;
tracing::debug!("Sent response {:?}", &resp);
tracing::info!("Request took {}ms", now.elapsed().as_millis());
resp
}
}
Then we wrap a Layer around the Service:
pub struct LogLayer;
impl<S> volo::Layer<S> for LogLayer {
type Service = LogService<S>;
fn layer(self, inner: S) -> Self::Service {
LogService(inner)
}
}
Finally, we add this Layer to client and server:
use volo_example::LogLayer;
// client.rs
static ref CLIENT: volo_gen::volo::example::ItemServiceClient = {
let addr: SocketAddr = "127.0.0.1:8080".parse().unwrap();
volo_gen::volo::example::ItemServiceClientBuilder::new("volo-example")
.layer_outer(LogLayer)
.address(addr)
.build()
};
// server.rs
volo_gen::volo::example::ItemServiceServer::new(S)
.layer_front(LogLayer)
.run(addr)
.await
.unwrap();
At this point, at the INFO log level, it prints out how long the request took; At the DEBUG logging level, it also types the details of the request and response.
Last modified
August 2, 2023
: docs: add document http3 (#737) (5cdb2f3)