Expose relay version metric (#1750)

* expose relay version metric

* spelling

* and clippy

* clippy

* typo

* use version directly and determine git commit

* typos and leftovers

bridges/relays/utils/src/metrics.rs

@@ -99,6 +99,39 @@ impl Default for MetricsAddress {
 }
 
 impl MetricsParams {
+	/// Creates metrics params from metrics address.
+	pub fn new(
+		address: Option<MetricsAddress>,
+		relay_version: String,
+		relay_commit: String,
+	) -> Result<Self, PrometheusError> {
+		const BUILD_INFO_METRIC: &str = "substrate_relay_build_info";
+
+		let registry = Registry::new();
+		register(
+			Gauge::<U64>::with_opts(
+				Opts::new(
+					BUILD_INFO_METRIC,
+					"A metric with a constant '1' value labeled by version",
+				)
+				.const_label("version", &relay_version)
+				.const_label("commit", &relay_commit),
+			)?,
+			&registry,
+		)?
+		.set(1);
+
+		log::info!(
+			target: "bridge",
+			"Exposed {} metric: version={} commit={}",
+			BUILD_INFO_METRIC,
+			relay_version,
+			relay_commit,
+		);
+
+		Ok(MetricsParams { address, registry })
+	}
+
 	/// Creates metrics params so that metrics are not exposed.
 	pub fn disabled() -> Self {
 		MetricsParams { address: None, registry: Registry::new() }
@@ -112,12 +145,6 @@ impl MetricsParams {
 	}
 }
 
-impl From<Option<MetricsAddress>> for MetricsParams {
-	fn from(address: Option<MetricsAddress>) -> Self {
-		MetricsParams { address, registry: Registry::new() }
-	}
-}
-
 /// Returns metric name optionally prefixed with given prefix.
 pub fn metric_name(prefix: Option<&str>, name: &str) -> String {
 	if let Some(prefix) = prefix {