fix(http server): omit jsonrpc details in health API (#785)

* fix(http server): omit jsonrpc details health API

Closing #784
Ordinary GET requests doesn't expect the body the be formatted as
`JSON-RPC` responses which this fixes.

* address grumbles

* Update http-server/src/server.rs

* cargo fmt

http-server/Cargo.toml

@@ -18,7 +18,8 @@ jsonrpsee-core = { path = "../core", version = "0.13.1", features = ["server", "
 globset = "0.4"
 lazy_static = "1.4"
 tracing = "0.1"
-serde_json = "1"
+serde_json = { version = "1.0", features = ["raw_value"] }
+serde = "1"
 tokio = { version = "1.16", features = ["rt-multi-thread", "macros"] }
 unicase = "2.6.0"
 

http-server/src/server.rs

@@ -170,11 +170,20 @@ impl<M> Builder<M> {
 	}
 
 	/// Enable health endpoint.
-	/// Allows you to expose one of the methods under GET /<path> The method will be invoked with no parameters. Error returned from the method will be converted to status 500 response.
-	/// Expects a tuple with (<path>, <rpc-method-name>).
-	pub fn health_api(mut self, path: impl Into<String>, method: impl Into<String>) -> Self {
-		self.health_api = Some(HealthApi { path: path.into(), method: method.into() });
-		self
+	/// Allows you to expose one of the methods under GET /<path> The method will be invoked with no parameters.
+	/// Error returned from the method will be converted to status 500 response.
+	/// Expects a tuple with (</path>, <rpc-method-name>).
+	///
+	/// Fails if the path is missing `/`.
+	pub fn health_api(mut self, path: impl Into<String>, method: impl Into<String>) -> Result<Self, Error> {
+		let path = path.into();
+
+		if !path.starts_with("/") {
+			return Err(Error::Custom(format!("Health endpoint path must start with `/` to work, got: {}", path)));
+		}
+
+		self.health_api = Some(HealthApi { path: path, method: method.into() });
+		Ok(self)
 	}
 
 	/// Finalizes the configuration of the server with customized TCP settings on the socket and on hyper.
@@ -754,7 +763,17 @@ async fn process_health_request(
 	middleware.on_response(request_start);
 
 	match data {
-		Some(resp) if success => Ok(response::ok_response(resp)),
+		Some(data) if success => {
+			#[derive(serde::Deserialize)]
+			struct RpcPayload<'a> {
+				#[serde(borrow)]
+				result: &'a serde_json::value::RawValue,
+			}
+
+			let payload: RpcPayload = serde_json::from_str(&data)
+				.expect("valid JSON-RPC response must have a result field and be valid JSON; qed");
+			Ok(response::ok_response(payload.result.to_string()))
+		}
 		_ => Ok(response::internal_error()),
 	}
 }

tests/tests/helpers.rs

@@ -225,6 +225,7 @@ pub async fn http_server_with_access_control(acl: AccessControl) -> (SocketAddr,
 	let server = HttpServerBuilder::default()
 		.set_access_control(acl)
 		.health_api("/health", "system_health")
+		.unwrap()
 		.build("127.0.0.1:0")
 		.await
 		.unwrap();
@@ -233,7 +234,7 @@ pub async fn http_server_with_access_control(acl: AccessControl) -> (SocketAddr,
 	module.register_method("say_hello", |_, _| Ok("hello")).unwrap();
 	module.register_method("notif", |_, _| Ok("")).unwrap();
 
-	module.register_method("system_health", |_, _| Ok("im ok")).unwrap();
+	module.register_method("system_health", |_, _| Ok(serde_json::json!({ "health": true }))).unwrap();
 
 	let handle = server.start(module).unwrap();
 	(addr, handle)

tests/tests/integration_tests.rs

@@ -767,5 +767,5 @@ async fn http_health_api_works() {
 
 	let bytes = hyper::body::to_bytes(res.into_body()).await.unwrap();
 	let out = String::from_utf8(bytes.to_vec()).unwrap();
-	assert_eq!(out, "{\"jsonrpc\":\"2.0\",\"result\":\"im ok\",\"id\":0}");
+	assert_eq!(out.as_str(), "{\"health\":true}");
 }