Add sync-speed metric (#898)

beacon_node/client/src/lib.rs

@@ -1,6 +1,7 @@
 extern crate slog;
 
 pub mod config;
+mod metrics;
 mod notifier;
 
 pub mod builder;

beacon_node/client/src/metrics.rs

@@ -0,0 +1,9 @@
+use lazy_static::lazy_static;
+pub use lighthouse_metrics::*;
+
+lazy_static! {
+    pub static ref SYNC_SLOTS_PER_SECOND: Result<IntGauge> = try_create_int_gauge(
+        "sync_slots_per_second",
+        "The number of blocks being imported per second"
+    );
+}

beacon_node/client/src/notifier.rs

@@ -1,3 +1,4 @@
+use crate::metrics;
 use beacon_chain::{BeaconChain, BeaconChainTypes};
 use environment::RuntimeContext;
 use exit_future::Signal;
@@ -83,6 +84,8 @@ pub fn spawn_notifier<T: BeaconChainTypes>(
             let mut speedo = speedo.lock();
             speedo.observe(head_slot, Instant::now());
 
+            metrics::set_gauge(&metrics::SYNC_SLOTS_PER_SECOND, speedo.slots_per_second().unwrap_or_else(|| 0_f64) as i64);
+
             // The next two lines take advantage of saturating subtraction on `Slot`.
             let head_distance = current_slot - head_slot;