examples: Add ProxyRequestLayer example for URI redirection

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

examples/examples/http_proxy_middleware.rs

@@ -0,0 +1,101 @@
+// Copyright 2019-2022 Parity Technologies (UK) Ltd.
+//
+// Permission is hereby granted, free of charge, to any
+// person obtaining a copy of this software and associated
+// documentation files (the "Software"), to deal in the
+// Software without restriction, including without
+// limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of
+// the Software, and to permit persons to whom the Software
+// is furnished to do so, subject to the following
+// conditions:
+//
+// The above copyright notice and this permission notice
+// shall be included in all copies or substantial portions
+// of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+// ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+// PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+// SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+// IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+//! This example utilizes the `ProxyRequest` layer for redirecting
+//! `GET /path` requests to internal RPC methods.
+//!
+//! The RPC server registers a method named `system_health` which
+//! returns `serde_json::Value`. Redirect any `GET /health`
+//! requests to the internal method, and return only the method's
+//! response in the body (ie, without any jsonRPC 2.0 overhead).
+//!
+//! # Note
+//!
+//! This functionality is useful for services which would
+//! like to query a certain `URI` path for statistics.
+
+use hyper::{Body, Client, Request};
+use std::net::SocketAddr;
+use std::time::Duration;
+
+use jsonrpsee::core::client::ClientT;
+use jsonrpsee::http_client::HttpClientBuilder;
+use jsonrpsee::http_server::middlewares::proxy_request::ProxyRequestLayer;
+use jsonrpsee::http_server::{HttpServerBuilder, HttpServerHandle, RpcModule};
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+	tracing_subscriber::FmtSubscriber::builder()
+		.with_env_filter(tracing_subscriber::EnvFilter::from_default_env())
+		.try_init()
+		.expect("setting default subscriber failed");
+
+	let (addr, _handler) = run_server().await?;
+	let url = format!("http://{}", addr);
+
+	// Use RPC client to get the response of `say_hello` method.
+	let client = HttpClientBuilder::default().build(&url)?;
+	let response: String = client.request("say_hello", None).await?;
+	println!("[main]: response: {:?}", response);
+
+	// Use hyper client to manually submit a `GET /health` request.
+	let http_client = Client::new();
+	let uri = format!("http://{}/health", addr);
+
+	let req = Request::builder().method("GET").uri(&uri).body(Body::empty())?;
+	println!("[main]: Submit proxy request: {:?}", req);
+	let res = http_client.request(req).await?;
+	println!("[main]: Received proxy response: {:?}", res);
+
+	// Interpret the response as String.
+	let bytes = hyper::body::to_bytes(res.into_body()).await.unwrap();
+	let out = String::from_utf8(bytes.to_vec()).unwrap();
+	println!("[main]: Interpret proxy response: {:?}", out);
+	assert_eq!(out.as_str(), "{\"health\":true}");
+
+	Ok(())
+}
+
+async fn run_server() -> anyhow::Result<(SocketAddr, HttpServerHandle)> {
+	// Custom tower service to handle the RPC requests
+	let service_builder = tower::ServiceBuilder::new()
+		// Proxy `GET /health` requests to internal `system_health` method.
+		.layer(ProxyRequestLayer::new("/health", "system_health"))
+		.timeout(Duration::from_secs(2));
+
+	let server =
+		HttpServerBuilder::new().set_middleware(service_builder).build("127.0.0.1:0".parse::<SocketAddr>()?).await?;
+
+	let addr = server.local_addr()?;
+
+	let mut module = RpcModule::new(());
+	module.register_method("say_hello", |_, _| Ok("lo")).unwrap();
+	module.register_method("system_health", |_, _| Ok(serde_json::json!({ "health": true }))).unwrap();
+
+	let handler = server.start(module)?;
+
+	Ok((addr, handler))
+}