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Use the correct lookback for the worker key when creating blocks #4539

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merged 3 commits into from
Oct 23, 2020
Merged

Use the correct lookback for the worker key when creating blocks #4539

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defeba5
Fix lookback for worker key when computing ticket
Stebalien Oct 21, 2020
b056134
Sign blocks with the worker key from the correct lookback epoch
Stebalien Oct 21, 2020
59cfabf
don't resolve the worker key twice
Stebalien Oct 22, 2020
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12 changes: 11 additions & 1 deletion chain/gen/mining.go
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,17 @@ func MinerCreateBlock(ctx context.Context, sm *stmgr.StateManager, w api.WalletA
return nil, xerrors.Errorf("failed to load tipset state: %w", err)
}

worker, err := stmgr.GetMinerWorkerRaw(ctx, sm, st, bt.Miner)
lbts, err := stmgr.GetLookbackTipSetForRound(ctx, sm, pts, bt.Epoch)
if err != nil {
return nil, xerrors.Errorf("getting lookback miner actor state: %w", err)
}

lbst, _, err := sm.TipSetState(ctx, lbts)
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This computes the state, we could just load it (we may also be doing this in GetMiningBase)

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Ah, I see. I should be walking back one fewer blocks and looking at the parent state?

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I'm not sure if I can do this reliably given null blocks. Currently, given:

  1. TS_A
  2. TS_B (parent: state at height 1)
  3. NULL <-- lookback height
  4. NULL
  5. TS_C (parent: state at height 4)

Currently, given a lookback height of 3, we'll use the state computed at height 2 (from TS_B). However, we don't actually record this state CID anywhere on chain. The next recorded state CID is for the state computed at height 4 (after processing two null rounds).

So, I could try to do my best to try to use parent tipset states from the chain, but that's going to be complicated.

Instead, what if we just improved our caching? We already maintain a tipset state cache, we could populate this cache with all tipsets between now and finality. (in a different PR)

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just do GetTipsetByHeight for the lookback height, and ensure prev is false, then take that tipsets epoch, add one, and call GetTipsetByHeight again on that with prev also equal to false.

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Given the null blocks, I'm pretty sure you'd end up with the exact same result.

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Yes but I need the state computed by executing TS_B. If I lookup lookback+1 and take the parent state, I'll get the parent state of TS_B, not the state resulting from the evaluation of TS_B. The fundamental issue here is that the state root produced by executing TS_B isn't recorded anywhere on chain.

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(alternatively, we could have looked at the parent state of the lookback tipset, but that needs a network upgrade)

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What? if a.Parents() == b then TipSetState(b) == a.ParentStateRoot.

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The fundamental issue here is that the state root produced by executing TS_B isn't recorded anywhere on chain.

Yes, its TS_C.ParentStateRoot

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Apparently I need to pay more attention when reading code. @whyrusleeping is correct.

if err != nil {
return nil, err
}

worker, err := stmgr.GetMinerWorkerRaw(ctx, sm, lbst, bt.Miner)
if err != nil {
return nil, xerrors.Errorf("failed to get miner worker: %w", err)
}
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15 changes: 3 additions & 12 deletions miner/miner.go
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Original file line number Diff line number Diff line change
Expand Up @@ -386,7 +386,7 @@ func (m *Miner) mineOne(ctx context.Context, base *MiningBase) (*types.BlockMsg,
rbase = bvals[len(bvals)-1]
}

ticket, err := m.computeTicket(ctx, &rbase, base)
ticket, err := m.computeTicket(ctx, &rbase, base, mbi)
if err != nil {
return nil, xerrors.Errorf("scratching ticket failed: %w", err)
}
Expand Down Expand Up @@ -456,16 +456,7 @@ func (m *Miner) mineOne(ctx context.Context, base *MiningBase) (*types.BlockMsg,
return b, nil
}

func (m *Miner) computeTicket(ctx context.Context, brand *types.BeaconEntry, base *MiningBase) (*types.Ticket, error) {
mi, err := m.api.StateMinerInfo(ctx, m.address, types.EmptyTSK)
if err != nil {
return nil, err
}
worker, err := m.api.StateAccountKey(ctx, mi.Worker, types.EmptyTSK)
if err != nil {
return nil, err
}

func (m *Miner) computeTicket(ctx context.Context, brand *types.BeaconEntry, base *MiningBase, mbi *api.MiningBaseInfo) (*types.Ticket, error) {
buf := new(bytes.Buffer)
if err := m.address.MarshalCBOR(buf); err != nil {
return nil, xerrors.Errorf("failed to marshal address to cbor: %w", err)
Expand All @@ -481,7 +472,7 @@ func (m *Miner) computeTicket(ctx context.Context, brand *types.BeaconEntry, bas
return nil, err
}

vrfOut, err := gen.ComputeVRF(ctx, m.api.WalletSign, worker, input)
vrfOut, err := gen.ComputeVRF(ctx, m.api.WalletSign, mbi.WorkerKey, input)
if err != nil {
return nil, err
}
Expand Down