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approval-voting: Make importing of duplicate assignment idempotent #6971

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Merged
alexggh merged 7 commits into from
Jan 15, 2025
Merged

approval-voting: Make importing of duplicate assignment idempotent #6971

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24f8fdd
Fix importing of duplicate assingmnents
alexggh Dec 20, 2024
443309f
Fix import duplicate on restart
alexggh Dec 20, 2024
4e2788b
Minor fixes
alexggh Jan 7, 2025
a49f7e0
Update polkadot/node/core/approval-voting/src/persisted_entries.rs
alexggh Jan 7, 2025
fd9c784
Merge branch 'master' into alexggh/fix_reimport_of_duplicate
alexggh Jan 8, 2025
1a18e57
Remove redundant checks
alexggh Jan 13, 2025
8d610ce
Add prdoc
alexggh Jan 13, 2025
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78 changes: 50 additions & 28 deletions polkadot/node/core/approval-voting/src/approval_checking.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -712,13 +712,13 @@ mod tests {
}
.into();

approval_entry.import_assignment(0, ValidatorIndex(0), block_tick);
approval_entry.import_assignment(0, ValidatorIndex(1), block_tick);
approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, false);
approval_entry.import_assignment(0, ValidatorIndex(1), block_tick, false);

approval_entry.import_assignment(1, ValidatorIndex(2), block_tick + 1);
approval_entry.import_assignment(1, ValidatorIndex(3), block_tick + 1);
approval_entry.import_assignment(1, ValidatorIndex(2), block_tick + 1, false);
approval_entry.import_assignment(1, ValidatorIndex(3), block_tick + 1, false);

approval_entry.import_assignment(2, ValidatorIndex(4), block_tick + 2);
approval_entry.import_assignment(2, ValidatorIndex(4), block_tick + 2, false);

let approvals = bitvec![u8, BitOrderLsb0; 1; 5];

Expand Down Expand Up @@ -757,8 +757,10 @@ mod tests {
}
.into();

approval_entry.import_assignment(0, ValidatorIndex(0), block_tick);
approval_entry.import_assignment(1, ValidatorIndex(2), block_tick);
approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, false);
approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, true);
approval_entry.import_assignment(1, ValidatorIndex(2), block_tick, false);
approval_entry.import_assignment(1, ValidatorIndex(2), block_tick, true);

let approvals = bitvec![u8, BitOrderLsb0; 0; 10];

Expand Down Expand Up @@ -798,10 +800,10 @@ mod tests {
}
.into();

approval_entry.import_assignment(0, ValidatorIndex(0), block_tick);
approval_entry.import_assignment(0, ValidatorIndex(1), block_tick);
approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, false);
approval_entry.import_assignment(0, ValidatorIndex(1), block_tick, false);

approval_entry.import_assignment(1, ValidatorIndex(2), block_tick);
approval_entry.import_assignment(1, ValidatorIndex(2), block_tick, false);

let mut approvals = bitvec![u8, BitOrderLsb0; 0; 10];
approvals.set(0, true);
Expand Down Expand Up @@ -844,11 +846,11 @@ mod tests {
}
.into();

approval_entry.import_assignment(0, ValidatorIndex(0), block_tick);
approval_entry.import_assignment(0, ValidatorIndex(1), block_tick);
approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, false);
approval_entry.import_assignment(0, ValidatorIndex(1), block_tick, false);

approval_entry.import_assignment(1, ValidatorIndex(2), block_tick);
approval_entry.import_assignment(1, ValidatorIndex(3), block_tick);
approval_entry.import_assignment(1, ValidatorIndex(2), block_tick, false);
approval_entry.import_assignment(1, ValidatorIndex(3), block_tick, false);

let mut approvals = bitvec![u8, BitOrderLsb0; 0; n_validators];
approvals.set(0, true);
Expand Down Expand Up @@ -913,14 +915,24 @@ mod tests {
}
.into();

approval_entry.import_assignment(0, ValidatorIndex(0), block_tick);
approval_entry.import_assignment(0, ValidatorIndex(1), block_tick);
approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, false);
approval_entry.import_assignment(0, ValidatorIndex(1), block_tick, false);

approval_entry.import_assignment(1, ValidatorIndex(2), block_tick + 1);
approval_entry.import_assignment(1, ValidatorIndex(3), block_tick + 1);
approval_entry.import_assignment(1, ValidatorIndex(2), block_tick + 1, false);
approval_entry.import_assignment(1, ValidatorIndex(3), block_tick + 1, false);

approval_entry.import_assignment(2, ValidatorIndex(4), block_tick + no_show_duration + 2);
approval_entry.import_assignment(2, ValidatorIndex(5), block_tick + no_show_duration + 2);
approval_entry.import_assignment(
2,
ValidatorIndex(4),
block_tick + no_show_duration + 2,
false,
);
approval_entry.import_assignment(
2,
ValidatorIndex(5),
block_tick + no_show_duration + 2,
false,
);

let mut approvals = bitvec![u8, BitOrderLsb0; 0; n_validators];
approvals.set(0, true);
Expand Down Expand Up @@ -1007,14 +1019,24 @@ mod tests {
}
.into();

approval_entry.import_assignment(0, ValidatorIndex(0), block_tick);
approval_entry.import_assignment(0, ValidatorIndex(1), block_tick);
approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, false);
approval_entry.import_assignment(0, ValidatorIndex(1), block_tick, false);

approval_entry.import_assignment(1, ValidatorIndex(2), block_tick + 1);
approval_entry.import_assignment(1, ValidatorIndex(3), block_tick + 1);
approval_entry.import_assignment(1, ValidatorIndex(2), block_tick + 1, false);
approval_entry.import_assignment(1, ValidatorIndex(3), block_tick + 1, false);

approval_entry.import_assignment(2, ValidatorIndex(4), block_tick + no_show_duration + 2);
approval_entry.import_assignment(2, ValidatorIndex(5), block_tick + no_show_duration + 2);
approval_entry.import_assignment(
2,
ValidatorIndex(4),
block_tick + no_show_duration + 2,
false,
);
approval_entry.import_assignment(
2,
ValidatorIndex(5),
block_tick + no_show_duration + 2,
false,
);

let mut approvals = bitvec![u8, BitOrderLsb0; 0; n_validators];
approvals.set(0, true);
Expand Down Expand Up @@ -1066,7 +1088,7 @@ mod tests {
},
);

approval_entry.import_assignment(3, ValidatorIndex(6), block_tick);
approval_entry.import_assignment(3, ValidatorIndex(6), block_tick, false);
approvals.set(6, true);

let tranche_now = no_show_duration as DelayTranche + 3;
Expand Down Expand Up @@ -1176,7 +1198,7 @@ mod tests {
// Populate the requested tranches. The assignments aren't inspected in
// this test.
for &t in &test_tranche {
approval_entry.import_assignment(t, ValidatorIndex(0), 0)
approval_entry.import_assignment(t, ValidatorIndex(0), 0, false);
}

let filled_tranches = filled_tranche_iterator(approval_entry.tranches());
Expand Down
2 changes: 1 addition & 1 deletion polkadot/node/core/approval-voting/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2681,7 +2681,7 @@ where
)),
};
is_duplicate &= approval_entry.is_assigned(assignment.validator);
approval_entry.import_assignment(tranche, assignment.validator, tick_now);
approval_entry.import_assignment(tranche, assignment.validator, tick_now, is_duplicate);

// We've imported a new assignment, so we need to schedule a wake-up for when that might
// no-show.
Expand Down
16 changes: 13 additions & 3 deletions polkadot/node/core/approval-voting/src/persisted_entries.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -172,7 +172,7 @@ impl ApprovalEntry {
});

our.map(|a| {
self.import_assignment(a.tranche(), a.validator_index(), tick_now);
self.import_assignment(a.tranche(), a.validator_index(), tick_now, false);

(a.cert().clone(), a.validator_index(), a.tranche())
})
Expand All @@ -197,6 +197,7 @@ impl ApprovalEntry {
tranche: DelayTranche,
validator_index: ValidatorIndex,
tick_now: Tick,
is_duplicate: bool,
) {
// linear search probably faster than binary. not many tranches typically.
let idx = match self.tranches.iter().position(|t| t.tranche >= tranche) {
Expand All @@ -213,8 +214,17 @@ impl ApprovalEntry {
self.tranches.len() - 1
},
};

self.tranches[idx].assignments.push((validator_index, tick_now));
// We already know already if we seen already an assignment from this validator
// and since this function is on the hot path we can avoid going through tranches
// if the assignment is not a duplicate.
if !is_duplicate ||
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@eskimor eskimor Dec 21, 2024

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I am not getting the !is_duplicate part. Can you give me your line of reasoning here, that would help I think. Thanks!

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@alexggh alexggh Jan 6, 2025

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We keep the assignments in two places in assigned_validators: Bitfield, and tranches: Vec<TrancheEntry>, so when we call this function we already know if we saw an assignment for this validator which is really rare case. Given that this is on the hot-path I want to prevent running this iteration if it is not truly needed which is where !is_duplicate helps.

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@ordian ordian Jan 6, 2025

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I think this deserves a comment in the code as it's not obvious how is_duplicate is different from the iter check

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@alexggh alexggh Jan 7, 2025

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Done.

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@alexggh alexggh Jan 13, 2025

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Discussed with @ordian this and we convinced ourselves that iterating on duplicates is actually superfluous, so I removed that part.

!self.tranches[idx]
.assignments
.iter()
.any(|(validator, _)| validator == &validator_index)
{
self.tranches[idx].assignments.push((validator_index, tick_now));
}
self.assigned_validators.set(validator_index.0 as _, true);
}

Expand Down