Histogram support in runtime metrics (#6935)

* Histogram support in runtime metrics

Add support for histograms to the runtime metrics. Additionally add
`polkadot_parachain_verify_dispute_signature` histogram which tracks the
time needed from the runtime to verify a single validator signature of a
dispute statement.

* Add noops

* u64 instead of f64

* Update buckets

* Wrap `get_current_time()` in runtime metrics

* Change the dimension of the Histogram from usec to sec

* Fix a compilation error

* Update buckets

* Fix `on_signature_check_complete` calculation

* Update buckets

* Update buckets

* formatting

* Another weights update

* Adjust buckets again

* Final buckets adjustment

* Revert "Fix a compilation error"

This reverts commit 06290b40a39eeb78de2602d8916a39edf7a8b714.

* Update primitives/src/v4/metrics.rs

Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>

* Use `saturating_sub` for time difference calculation

* Pass nanoseconds to client instead of seconds (using f64 in runtime is dangerous)

---------

Co-authored-by: Andrei Sandu <54316454+sandreim@users.noreply.github.com>

polkadot/runtime/parachains/src/disputes.rs

@@ -16,11 +16,14 @@
 
 //! Runtime component for handling disputes of parachain candidates.
 
-use crate::{configuration, initializer::SessionChangeNotification, session_info};
+use crate::{
+	configuration, initializer::SessionChangeNotification, metrics::METRICS, session_info,
+};
 use bitvec::{bitvec, order::Lsb0 as BitOrderLsb0};
 use frame_support::{ensure, weights::Weight};
 use frame_system::pallet_prelude::*;
 use parity_scale_codec::{Decode, Encode};
+use polkadot_runtime_metrics::get_current_time;
 use primitives::{
 	byzantine_threshold, supermajority_threshold, ApprovalVote, CandidateHash,
 	CheckedDisputeStatementSet, CheckedMultiDisputeStatementSet, CompactStatement, ConsensusLog,
@@ -1336,9 +1339,14 @@ fn check_signature(
 			ExplicitDisputeStatement { valid: false, candidate_hash, session }.signing_payload(),
 	};
 
-	if validator_signature.verify(&payload[..], &validator_public) {
-		Ok(())
-	} else {
-		Err(())
-	}
+	let start = get_current_time();
+
+	let res =
+		if validator_signature.verify(&payload[..], &validator_public) { Ok(()) } else { Err(()) };
+
+	let end = get_current_time();
+
+	METRICS.on_signature_check_complete(end.saturating_sub(start)); // ns
+
+	res
 }

polkadot/runtime/parachains/src/metrics.rs

@@ -16,12 +16,12 @@
 
 //! Runtime declaration of the parachain metrics.
 
-use polkadot_runtime_metrics::{Counter, CounterVec};
+use polkadot_runtime_metrics::{Counter, CounterVec, Histogram};
 use primitives::metric_definitions::{
 	PARACHAIN_CREATE_INHERENT_BITFIELDS_SIGNATURE_CHECKS,
 	PARACHAIN_INHERENT_DATA_BITFIELDS_PROCESSED, PARACHAIN_INHERENT_DATA_CANDIDATES_PROCESSED,
 	PARACHAIN_INHERENT_DATA_DISPUTE_SETS_INCLUDED, PARACHAIN_INHERENT_DATA_DISPUTE_SETS_PROCESSED,
-	PARACHAIN_INHERENT_DATA_WEIGHT,
+	PARACHAIN_INHERENT_DATA_WEIGHT, PARACHAIN_VERIFY_DISPUTE_SIGNATURE,
 };
 
 pub struct Metrics {
@@ -37,6 +37,9 @@ pub struct Metrics {
 	disputes_included: Counter,
 	/// Counts bitfield signature checks in `enter_inner`.
 	bitfields_signature_checks: CounterVec,
+
+	/// Histogram with the time spent checking a validator signature of a dispute statement
+	signature_timings: Histogram,
 }
 
 impl Metrics {
@@ -98,11 +101,15 @@ impl Metrics {
 	}
 
 	pub fn on_valid_bitfield_signature(&self) {
-		self.bitfields_signature_checks.with_label_values(&["valid"]).inc();
+		self.bitfields_signature_checks.with_label_values(&["valid"]).inc_by(1);
 	}
 
 	pub fn on_invalid_bitfield_signature(&self) {
-		self.bitfields_signature_checks.with_label_values(&["invalid"]).inc();
+		self.bitfields_signature_checks.with_label_values(&["invalid"]).inc_by(1);
+	}
+
+	pub fn on_signature_check_complete(&self, val: u128) {
+		self.signature_timings.observe(val);
 	}
 }
 
@@ -115,4 +122,5 @@ pub const METRICS: Metrics = Metrics {
 	bitfields_signature_checks: CounterVec::new(
 		PARACHAIN_CREATE_INHERENT_BITFIELDS_SIGNATURE_CHECKS,
 	),
+	signature_timings: Histogram::new(PARACHAIN_VERIFY_DISPUTE_SIGNATURE),
 };