79 lines
3.7 KiB
Markdown
79 lines
3.7 KiB
Markdown
## State
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### Signing Info
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Every block includes a set of precommits by the validators for the previous block,
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known as the LastCommit. A LastCommit is valid so long as it contains precommits from +2/3 of voting power.
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Proposers are incentivized to include precommits from all
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validators in the LastCommit by receiving additional fees
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proportional to the difference between the voting power included in the
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LastCommit and +2/3 (see [TODO](https://github.com/cosmos/cosmos-sdk/issues/967)).
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Validators are penalized for failing to be included in the LastCommit for some
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number of blocks by being automatically unbonded.
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Information about validator activity is tracked in a `ValidatorSigningInfo`.
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It is indexed in the store as follows:
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- SigningInfo: ` 0x01 | ValTendermintAddr -> amino(valSigningInfo)`
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- SigningBitArray: ` 0x02 | ValTendermintAddr | LittleEndianUint64(signArrayIndex) -> VarInt(didSign)`
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The first map allows us to easily lookup the recent signing info for a
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validator, according to the Tendermint validator address. The second map acts as
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a bit-array of size `SIGNED_BLOCKS_WINDOW` that tells us if the validator signed for a given index in the bit-array.
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The index in the bit-array is given as little endian uint64.
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The result is a `varint` that takes on `0` or `1`, where `0` indicates the
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validator did not sign the corresponding block, and `1` indicates they did.
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Note that the SigningBitArray is not explicitly initialized up-front. Keys are
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added as we progress through the first `SIGNED_BLOCKS_WINDOW` blocks for a newly
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bonded validator.
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The information stored for tracking validator liveness is as follows:
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```go
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type ValidatorSigningInfo struct {
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StartHeight int64 // Height at which the validator became able to sign blocks
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IndexOffset int64 // Offset into the signed block bit array
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JailedUntil int64 // Block height until which the validator is jailed,
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// or sentinel value of 0 for not jailed
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SignedBlocksCounter int64 // Running counter of signed blocks
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}
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```
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Where:
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* `StartHeight` is set to the height that the candidate became an active validator (with non-zero voting power).
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* `IndexOffset` is incremented each time the candidate was a bonded validator in a block (and may have signed a precommit or not).
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* `JailedUntil` is set whenever the candidate is revoked due to downtime
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* `SignedBlocksCounter` is a counter kept to avoid unnecessary array reads. `SignedBlocksBitArray.Sum() == SignedBlocksCounter` always.
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### Slashing Period
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A slashing period is a start and end time associated with a particular validator,
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within which only the "worst infraction counts": the total amount of slashing for
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infractions committed within the period (and discovered whenever) is capped at the
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penalty for the worst offense.
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This period starts when a validator is first bonded and ends when a validator is slashed & jailed
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for double-signing (but does not end if they are slashed & jailed for just missing blocks).
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When the validator voluntarily unjails themselves (and possibly changes signing keys), they reset the period.
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Slashing periods are indexed in the store as follows:
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- SlashingPeriod: ` 0x03 | ValTendermintAddr -> amino(slashingPeriod) `
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This allows us to look up slashing period by validator address, the only lookup necessary.
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```go
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type SlashingPeriod struct {
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ValidatorAddr sdk.ValAddress // Tendermint address of the validator
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StartHeight int64 // Block height at which slashing period begin
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EndHeight int64 // Block height at which slashing period ended
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SlashedSoFar sdk.Rat // Fraction slashed so far, cumulative
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}
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```
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