Grafana integration (#3913)

* Very WIP

* record_metrics macro works

* Integrate into service

* Licenses and documentation

* Remove unused Debugs, make respond function clearer

* Conform to line widths, fix service test

* Switch to storing the timestamps as millis instead

* Update core/grafana-data-source/src/lib.rs

Co-Authored-By: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Transform timestamps to i64 in serialization

* Fix license date

* Binary sort to find selection range for metrics

* Obey maxDataPoints

* Run a cleaning future

* Newlines at EOF

* Update core/service/Cargo.toml

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

* Update core/grafana-data-source/src/lib.rs

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

* Fix indentation

* Improve select_points

* Made test more accurate

* Inprogress

* Use the same futures version as hyper for now

* Error handling

* Remove dependence on hyper's tokio feature

* Added target_os flag

* Update Cargo.toml

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

* Simplify example

* Remove compat wildcard

* Updated lock file

* Fix indentation 😉

substrate/client/grafana-data-source/src/lib.rs

@@ -0,0 +1,58 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! [Grafana] data source server
+//!
+//! To display node statistics with [Grafana], this module exposes a `run_server` function that
+//! starts up a HTTP server that conforms to the [`grafana-json-data-source`] API. The
+//! `record_metrics` macro can be used to pass metrics to this server.
+//!
+//! [Grafana]: https://grafana.com/
+//! [`grafana-json-data-source`]: https://github.com/simPod/grafana-json-datasource
+
+use lazy_static::lazy_static;
+use std::collections::HashMap;
+use parking_lot::RwLock;
+
+mod types;
+mod server;
+mod util;
+#[cfg(not(target_os = "unknown"))]
+mod networking;
+
+pub use server::run_server;
+pub use util::now_millis;
+
+type Metrics = HashMap<&'static str, Vec<(f32, i64)>>;
+
+lazy_static! {
+	/// The `RwLock` wrapping the metrics. Not intended to be used directly.
+	#[doc(hidden)]
+	pub static ref METRICS: RwLock<Metrics> = RwLock::new(Metrics::new());
+}
+
+/// Write metrics to `METRICS`.
+#[macro_export]
+macro_rules! record_metrics(
+	($($key:expr => $value:expr),*) => {
+		use $crate::{METRICS, now_millis};
+		let mut metrics = METRICS.write();
+		let now = now_millis();
+		$(
+			metrics.entry($key).or_insert_with(Vec::new).push(($value as f32, now));
+		)*
+	}
+);