Skip slot before creating inherent data providers during major sync (p…

…aritytech#5344)

# Description

Moves `create_inherent_data_provider` after checking if major sync is in
progress.

## Integration

Change is internal to sc-consensus-slots. It should be no-op unless
someone is using fork of this SDK.

## Review Notes

Motivation for this change is to avoid calling
`create_inherent_data_providers` if it's result is going to be discarded
anyway during major sync. This has potential to speed up node operations
during major sync by not calling possibly expensive
`create_inherent_data_provider`.

TODO: labels T0-node D0-simple
TODO: there is no tests for `Slots`, should I add one for this case?

# Checklist

* [x] My PR includes a detailed description as outlined in the
"Description" and its two subsections above.
* [x] My PR follows the [labeling requirements](CONTRIBUTING.md#Process)
of this project (at minimum one label for `T`
  required)
* External contributors: ask maintainers to put the right label on your
PR.
* [ ] I have made corresponding changes to the documentation (if
applicable)
* [ ] I have added tests that prove my fix is effective or that my
feature works (if applicable)

prdoc/pr_5344.prdoc

@@ -0,0 +1,10 @@
+title: Fix storage weight reclaim bug.
+
+doc:
+  - audience: Node Dev
+    description: |
+      Improvement in slot worker loop that will not call create inherent data providers if the major sync is in progress. Before it was called every slot and the results were discarded during major sync.
+
+crates:
+  - name: sc-consensus-slots
+    bump: minor

substrate/client/consensus/slots/src/lib.rs

@@ -517,16 +517,15 @@ pub async fn start_slot_worker<B, C, W, SO, CIDP, Proof>(
 	CIDP: CreateInherentDataProviders<B, ()> + Send + 'static,
 	CIDP::InherentDataProviders: InherentDataProviderExt + Send,
 {
-	let mut slots = Slots::new(slot_duration.as_duration(), create_inherent_data_providers, client);
+	let mut slots = Slots::new(
+		slot_duration.as_duration(),
+		create_inherent_data_providers,
+		client,
+		sync_oracle,
+	);
 
 	loop {
 		let slot_info = slots.next_slot().await;
-
-		if sync_oracle.is_major_syncing() {
-			debug!(target: LOG_TARGET, "Skipping proposal slot due to sync.");
-			continue
-		}
-
 		let _ = worker.on_slot(slot_info).await;
 	}
 }

substrate/client/consensus/slots/src/slots.rs

@@ -21,7 +21,7 @@
 //! This is used instead of `futures_timer::Interval` because it was unreliable.
 
 use super::{InherentDataProviderExt, Slot, LOG_TARGET};
-use sp_consensus::SelectChain;
+use sp_consensus::{SelectChain, SyncOracle};
 use sp_inherents::{CreateInherentDataProviders, InherentDataProvider};
 use sp_runtime::traits::{Block as BlockT, Header as HeaderT};
 
@@ -87,39 +87,43 @@ impl<B: BlockT> SlotInfo<B> {
 }
 
 /// A stream that returns every time there is a new slot.
-pub(crate) struct Slots<Block, SC, IDP> {
+pub(crate) struct Slots<Block, SC, IDP, SO> {
 	last_slot: Slot,
 	slot_duration: Duration,
 	until_next_slot: Option<Delay>,
 	create_inherent_data_providers: IDP,
 	select_chain: SC,
+	sync_oracle: SO,
 	_phantom: std::marker::PhantomData<Block>,
 }
 
-impl<Block, SC, IDP> Slots<Block, SC, IDP> {
+impl<Block, SC, IDP, SO> Slots<Block, SC, IDP, SO> {
 	/// Create a new `Slots` stream.
 	pub fn new(
 		slot_duration: Duration,
 		create_inherent_data_providers: IDP,
 		select_chain: SC,
+		sync_oracle: SO,
 	) -> Self {
 		Slots {
 			last_slot: 0.into(),
 			slot_duration,
 			until_next_slot: None,
 			create_inherent_data_providers,
 			select_chain,
+			sync_oracle,
 			_phantom: Default::default(),
 		}
 	}
 }
 
-impl<Block, SC, IDP> Slots<Block, SC, IDP>
+impl<Block, SC, IDP, SO> Slots<Block, SC, IDP, SO>
 where
 	Block: BlockT,
 	SC: SelectChain<Block>,
 	IDP: CreateInherentDataProviders<Block, ()> + 'static,
 	IDP::InherentDataProviders: crate::InherentDataProviderExt,
+	SO: SyncOracle,
 {
 	/// Returns a future that fires when the next slot starts.
 	pub async fn next_slot(&mut self) -> SlotInfo<Block> {
@@ -138,6 +142,11 @@ where
 			let wait_dur = time_until_next_slot(self.slot_duration);
 			self.until_next_slot = Some(Delay::new(wait_dur));
 
+			if self.sync_oracle.is_major_syncing() {
+				log::debug!(target: LOG_TARGET, "Skipping slot: major sync is in progress.");
+				continue;
+			}
+
 			let chain_head = match self.select_chain.best_chain().await {
 				Ok(x) => x,
 				Err(e) => {