99 lines
3.9 KiB
Markdown
99 lines
3.9 KiB
Markdown
<!--
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order: 4
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-->
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# BeginBlock
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## Liveness Tracking
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At the beginning of each block, we update the `ValidatorSigningInfo` for each
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validator and check if they've crossed below the liveness threshold over a
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sliding window. This sliding window is defined by `SignedBlocksWindow` and the
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index in this window is determined by `IndexOffset` found in the validator's
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`ValidatorSigningInfo`. For each block processed, the `IndexOffset` is incremented
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regardless if the validator signed or not. Once the index is determined, the
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`MissedBlocksBitArray` and `MissedBlocksCounter` are updated accordingly.
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Finally, in order to determine if a validator crosses below the liveness threshold,
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we fetch the maximum number of blocks missed, `maxMissed`, which is
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`SignedBlocksWindow - (MinSignedPerWindow * SignedBlocksWindow)` and the minimum
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height at which we can determine liveness, `minHeight`. If the current block is
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greater than `minHeight` and the validator's `MissedBlocksCounter` is greater than
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`maxMissed`, they will be slashed by `SlashFractionDowntime`, will be jailed
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for `DowntimeJailDuration`, and have the following values reset:
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`MissedBlocksBitArray`, `MissedBlocksCounter`, and `IndexOffset`.
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__Note__: Liveness slashes do **NOT** lead to a tombstombing.
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```go
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height := block.Height
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for vote in block.LastCommitInfo.Votes {
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signInfo := GetValidatorSigningInfo(vote.Validator.Address)
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// This is a relative index, so we counts blocks the validator SHOULD have
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// signed. We use the 0-value default signing info if not present, except for
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// start height.
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index := signInfo.IndexOffset % SignedBlocksWindow()
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signInfo.IndexOffset++
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// Update MissedBlocksBitArray and MissedBlocksCounter. The MissedBlocksCounter
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// just tracks the sum of MissedBlocksBitArray. That way we avoid needing to
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// read/write the whole array each time.
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missedPrevious := GetValidatorMissedBlockBitArray(vote.Validator.Address, index)
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missed := !signed
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switch {
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case !missedPrevious && missed:
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// array index has changed from not missed to missed, increment counter
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SetValidatorMissedBlockBitArray(vote.Validator.Address, index, true)
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signInfo.MissedBlocksCounter++
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case missedPrevious && !missed:
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// array index has changed from missed to not missed, decrement counter
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SetValidatorMissedBlockBitArray(vote.Validator.Address, index, false)
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signInfo.MissedBlocksCounter--
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default:
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// array index at this index has not changed; no need to update counter
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}
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if missed {
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// emit events...
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}
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minHeight := signInfo.StartHeight + SignedBlocksWindow()
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maxMissed := SignedBlocksWindow() - MinSignedPerWindow()
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// If we are past the minimum height and the validator has missed too many
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// jail and slash them.
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if height > minHeight && signInfo.MissedBlocksCounter > maxMissed {
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validator := ValidatorByConsAddr(vote.Validator.Address)
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// emit events...
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// We need to retrieve the stake distribution which signed the block, so we
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// subtract ValidatorUpdateDelay from the block height, and subtract an
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// additional 1 since this is the LastCommit.
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//
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// Note, that this CAN result in a negative "distributionHeight" up to
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// -ValidatorUpdateDelay-1, i.e. at the end of the pre-genesis block (none) = at the beginning of the genesis block.
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// That's fine since this is just used to filter unbonding delegations & redelegations.
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distributionHeight := height - sdk.ValidatorUpdateDelay - 1
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Slash(vote.Validator.Address, distributionHeight, vote.Validator.Power, SlashFractionDowntime())
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Jail(vote.Validator.Address)
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signInfo.JailedUntil = block.Time.Add(DowntimeJailDuration())
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// We need to reset the counter & array so that the validator won't be
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// immediately slashed for downtime upon rebonding.
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signInfo.MissedBlocksCounter = 0
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signInfo.IndexOffset = 0
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ClearValidatorMissedBlockBitArray(vote.Validator.Address)
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}
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SetValidatorSigningInfo(vote.Validator.Address, signInfo)
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}
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```
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