examples: update to tracing 0.1.16, use #[instrument] (#354)

* examples: update to `tracing` 0.1.14, use `#[instrument]`

Now that `tracing-attributes`'s `#[instrument]` macro plays nicely with
`async-trait`, we can update the tracing example to use `instrument`.
This lets us simplify the events emitted in the example.

Signed-off-by: Eliza Weisman <[email protected]>

* feat(transport): Dynamic load balancing (#341)

* Fix typo (#356)

Co-authored-by: Dawid Nowak <[email protected]>
Co-authored-by: Paulo Duarte <[email protected]>

examples/src/tracing/server.rs

@@ -9,22 +9,23 @@ use hello_world::{
     HelloReply, HelloRequest,
 };
 
-#[derive(Default)]
+#[derive(Debug, Default)]
 pub struct MyGreeter {}
 
 #[tonic::async_trait]
 impl Greeter for MyGreeter {
+    #[tracing::instrument]
     async fn say_hello(
         &self,
         request: Request<HelloRequest>,
     ) -> Result<Response<HelloReply>, Status> {
-        tracing::info!(message = "Inbound request.", metadata = ?request.metadata());
+        tracing::info!("received request");
 
         let reply = hello_world::HelloReply {
             message: format!("Hello {}!", request.into_inner().name),
         };
 
-        tracing::debug!(message = "Sending reply.", response = %reply.message);
+        tracing::debug!("sending response");
 
         Ok(Response::new(reply))
     }
@@ -32,7 +33,7 @@ impl Greeter for MyGreeter {
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    tracing_subscriber::FmtSubscriber::builder()
+    tracing_subscriber::fmt()
         .with_max_level(tracing::Level::DEBUG)
         .init();