Scheduler pre block limit note (#13231)

Co-authored-by: parity-processbot <>

substrate/bin/node/runtime/src/lib.rs

@@ -364,7 +364,10 @@ impl pallet_scheduler::Config for Runtime {
 	type RuntimeCall = RuntimeCall;
 	type MaximumWeight = MaximumSchedulerWeight;
 	type ScheduleOrigin = EnsureRoot<AccountId>;
+	#[cfg(feature = "runtime-benchmarks")]
 	type MaxScheduledPerBlock = ConstU32<512>;
+	#[cfg(not(feature = "runtime-benchmarks"))]
+	type MaxScheduledPerBlock = ConstU32<50>;
 	type WeightInfo = pallet_scheduler::weights::SubstrateWeight<Runtime>;
 	type OriginPrivilegeCmp = EqualPrivilegeOnly;
 	type Preimages = Preimage;

substrate/frame/referenda/src/lib.rs

@@ -874,22 +874,21 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		let when = (when.saturating_add(alarm_interval.saturating_sub(One::one())) /
 			alarm_interval)
 			.saturating_mul(alarm_interval);
-		let maybe_result = T::Scheduler::schedule(
+		let result = T::Scheduler::schedule(
 			DispatchTime::At(when),
 			None,
 			128u8,
 			frame_system::RawOrigin::Root.into(),
 			call,
-		)
-		.ok()
-		.map(|x| (when, x));
-		debug_assert!(
-			maybe_result.is_some(),
-			"Unable to schedule a new alarm at #{:?} (now: #{:?})?!",
-			when,
-			frame_system::Pallet::<T>::block_number()
 		);
-		maybe_result
+		debug_assert!(
+			result.is_ok(),
+			"Unable to schedule a new alarm at #{:?} (now: #{:?}), scheduler error: `{:?}`",
+			when,
+			frame_system::Pallet::<T>::block_number(),
+			result.unwrap_err(),
+		);
+		result.ok().map(|x| (when, x))
 	}
 
 	/// Mutate a referendum's `status` into the correct deciding state.

substrate/frame/scheduler/src/lib.rs

@@ -216,6 +216,10 @@ pub mod pallet {
 		type OriginPrivilegeCmp: PrivilegeCmp<Self::PalletsOrigin>;
 
 		/// The maximum number of scheduled calls in the queue for a single block.
+		///
+		/// NOTE:
+		/// + Dependent pallets' benchmarks might require a higher limit for the setting. Set a
+		/// higher limit under `runtime-benchmarks` feature.
 		#[pallet::constant]
 		type MaxScheduledPerBlock: Get<u32>;