Remove RpcMetrics weirdness (paritytech#7608)

* Remove `RpcMetrics` weirdness

The metrics was returning an error when prometheus was not given. This
was a really weird setup, especially when compared to all other metrics
that just do nothing if there is no registry.

* Fix browser build

Author: bkchr

client/rpc-servers/src/middleware.rs

@@ -32,36 +32,41 @@ use futures::{future::Either, Future};
 /// Metrics for RPC middleware
 #[derive(Debug, Clone)]
 pub struct RpcMetrics {
-	rpc_calls: CounterVec<U64>,
+	rpc_calls: Option<CounterVec<U64>>,
 }
 
 impl RpcMetrics {
 	/// Create an instance of metrics
 	pub fn new(metrics_registry: Option<&Registry>) -> Result<Self, PrometheusError> {
-		metrics_registry.and_then(|r| {
-			Some(RpcMetrics {
-				rpc_calls: register(CounterVec::new(
-					Opts::new(
-						"rpc_calls_total",
-						"Number of rpc calls received",
-					),
-					&["protocol"]
-				).ok()?, r).ok()?,
-			})
-		}).ok_or(PrometheusError::Msg("Cannot register metric".to_string()))
+		Ok(Self {
+			rpc_calls: metrics_registry.map(|r|
+				register(
+					CounterVec::new(
+						Opts::new(
+							"rpc_calls_total",
+							"Number of rpc calls received",
+						),
+						&["protocol"]
+					)?,
+					r,
+				)
+			).transpose()?,
+		})
 	}
 }
 
 /// Middleware for RPC calls
 pub struct RpcMiddleware {
-	metrics: Option<RpcMetrics>,
+	metrics: RpcMetrics,
 	transport_label: String,
 }
 
 impl RpcMiddleware {
-	/// Create an instance of middleware with provided metrics
-	/// transport_label is used as a label for Prometheus collector
-	pub fn new(metrics: Option<RpcMetrics>, transport_label: &str) -> Self {
+	/// Create an instance of middleware.
+	///
+	/// - `metrics`: Will be used to report statistics.
+	/// - `transport_label`: The label that is used when reporting the statistics.
+	pub fn new(metrics: RpcMetrics, transport_label: &str) -> Self {
 		RpcMiddleware {
 			metrics,
 			transport_label: String::from(transport_label),
@@ -78,8 +83,8 @@ impl<M: Metadata> RequestMiddleware<M> for RpcMiddleware {
 		F: Fn(Request, M) -> X + Send + Sync,
 		X: Future<Item = Option<Response>, Error = ()> + Send + 'static,
 	{
-		if let Some(ref metrics) = self.metrics {
-			metrics.rpc_calls.with_label_values(&[self.transport_label.as_str()]).inc();
+		if let Some(ref rpc_calls) = self.metrics.rpc_calls {
+			rpc_calls.with_label_values(&[self.transport_label.as_str()]).inc();
 		}
 
 		Either::B(next(request, meta))

client/service/src/builder.rs

@@ -603,12 +603,12 @@ pub fn spawn_tasks<TBl, TBackend, TExPool, TRpc, TCl>(
 		on_demand.clone(), remote_blockchain.clone(), &*rpc_extensions_builder,
 		backend.offchain_storage(), system_rpc_tx.clone()
 	);
-	let rpc_metrics = sc_rpc_server::RpcMetrics::new(config.prometheus_registry()).ok();
-	let rpc = start_rpc_servers(&config, gen_handler, rpc_metrics.as_ref())?;
+	let rpc_metrics = sc_rpc_server::RpcMetrics::new(config.prometheus_registry())?;
+	let rpc = start_rpc_servers(&config, gen_handler, rpc_metrics.clone())?;
 	// This is used internally, so don't restrict access to unsafe RPC
 	let rpc_handlers = RpcHandlers(Arc::new(gen_handler(
 		sc_rpc::DenyUnsafe::No,
-		sc_rpc_server::RpcMiddleware::new(rpc_metrics.as_ref().cloned(), "inbrowser")
+		sc_rpc_server::RpcMiddleware::new(rpc_metrics, "inbrowser")
 	).into()));
 
 	// Telemetry

client/service/src/lib.rs

@@ -401,7 +401,7 @@ fn start_rpc_servers<
 >(
 	config: &Configuration,
 	mut gen_handler: H,
-	rpc_metrics: Option<&sc_rpc_server::RpcMetrics>
+	rpc_metrics: sc_rpc_server::RpcMetrics,
 ) -> Result<Box<dyn std::any::Any + Send + Sync>, error::Error> {
 	fn maybe_start_server<T, F>(address: Option<SocketAddr>, mut start: F) -> Result<Option<T>, io::Error>
 		where F: FnMut(&SocketAddr) -> Result<T, io::Error>,
@@ -434,7 +434,7 @@ fn start_rpc_servers<
 		config.rpc_ipc.as_ref().map(|path| sc_rpc_server::start_ipc(
 			&*path, gen_handler(
 				sc_rpc::DenyUnsafe::No,
-				sc_rpc_server::RpcMiddleware::new(rpc_metrics.cloned(), "ipc")
+				sc_rpc_server::RpcMiddleware::new(rpc_metrics.clone(), "ipc")
 			)
 		)),
 		maybe_start_server(
@@ -444,7 +444,7 @@ fn start_rpc_servers<
 				config.rpc_cors.as_ref(),
 				gen_handler(
 					deny_unsafe(&address, &config.rpc_methods),
-					sc_rpc_server::RpcMiddleware::new(rpc_metrics.cloned(), "http")
+					sc_rpc_server::RpcMiddleware::new(rpc_metrics.clone(), "http")
 				),
 			),
 		)?.map(|s| waiting::HttpServer(Some(s))),
@@ -456,7 +456,7 @@ fn start_rpc_servers<
 				config.rpc_cors.as_ref(),
 				gen_handler(
 					deny_unsafe(&address, &config.rpc_methods),
-					sc_rpc_server::RpcMiddleware::new(rpc_metrics.cloned(), "ws")
+					sc_rpc_server::RpcMiddleware::new(rpc_metrics.clone(), "ws")
 				),
 			),
 		)?.map(|s| waiting::WsServer(Some(s))),
@@ -471,7 +471,7 @@ fn start_rpc_servers<
 >(
 	_: &Configuration,
 	_: H,
-	_: Option<&sc_rpc_server::RpcMetrics>
+	_: sc_rpc_server::RpcMetrics,
 ) -> Result<Box<dyn std::any::Any + Send + Sync>, error::Error> {
 	Ok(Box::new(()))
 }