Add Tower TraceLayer examples (#500)

This example shows how to print a log for every incoming request and outgoing response automatically.

Signed-off-by: David Calavera <[email protected]>

Author: calavera

examples/http-tower-trace/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "http-tower-trace"
+version = "0.1.0"
+edition = "2021"
+
+
+# Use cargo-edit(https://github.com/killercup/cargo-edit#installation)
+# to manage dependencies.
+# Running `cargo add DEPENDENCY_NAME` will
+# add the latest version of a dependency to the list,
+# and it will keep the alphabetic ordering for you.
+
+[dependencies]
+lambda_http = { path = "../../lambda-http" }
+lambda_runtime = "0.5.1"
+tokio = { version = "1", features = ["macros"] }
+tower-http = { version = "0.3.4", features = ["trace"] }
+tracing = { version = "0.1", features = ["log"] }
+tracing-subscriber = { version = "0.3", default-features = false, features = ["fmt"] }

examples/http-tower-trace/src/main.rs

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+use lambda_http::{run, tower::ServiceBuilder, Error};
+use lambda_http::{Request, Response};
+use tower_http::trace::{DefaultOnRequest, DefaultOnResponse, TraceLayer};
+use tracing::Level;
+
+async fn handler(_req: Request) -> Result<Response<String>, Error> {
+    Ok(Response::new("Success".into()))
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Error> {
+    tracing_subscriber::fmt().without_time().init();
+
+    let layer = TraceLayer::new_for_http()
+        .on_request(DefaultOnRequest::new().level(Level::INFO))
+        .on_response(DefaultOnResponse::new().level(Level::INFO));
+
+    let service = ServiceBuilder::new().layer(layer).service_fn(handler);
+
+    run(service).await?;
+    Ok(())
+}