mirror of
https://github.com/fluencelabs/tendermint
synced 2025-04-25 14:52:17 +00:00
4905640e9b
* VoteSignBytes builds CanonicalVote * CommitVotes implements VoteSetReader - new CommitVotes struct holds both the Commit and the ValidatorSet and implements VoteSetReader - ToVote takes a ValidatorSet * fix TestCommit * use CommitSig.BlockID Commits may include votes for a different BlockID, could be nil, or different altogether. This means we can't use `commit.BlockID` for reconstructing the sign bytes, since up to -1/3 of the commits might be for independent BlockIDs. This means CommitSig will need to include an indicator for what BlockID it signed - if it's not the committed one or nil, it will need to include it fully in order to be verified. This is unfortunate but unavoidable so long as we include votes for non-committed BlockIDs (which we do to track validator liveness) * fixes from review * remove CommitVotes. CommitSig contains address * remove commit.canonicalVote method * toVote -> getVote, takes valIdx * update adr-025 * commit.ToVoteSet -> CommitToVoteSet * add test * fix from review
96 lines
3.2 KiB
Markdown
96 lines
3.2 KiB
Markdown
# ADR 025 Commit
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## Context
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Currently the `Commit` structure contains a lot of potentially redundant or unnecessary data.
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It contains a list of precommits from every validator, where the precommit
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includes the whole `Vote` structure. Thus each of the commit height, round,
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type, and blockID are repeated for every validator, and could be deduplicated.
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```
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type Commit struct {
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BlockID BlockID `json:"block_id"`
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Precommits []*Vote `json:"precommits"`
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}
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type Vote struct {
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ValidatorAddress Address `json:"validator_address"`
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ValidatorIndex int `json:"validator_index"`
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Height int64 `json:"height"`
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Round int `json:"round"`
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Timestamp time.Time `json:"timestamp"`
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Type byte `json:"type"`
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BlockID BlockID `json:"block_id"`
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Signature []byte `json:"signature"`
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}
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```
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References:
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[#1648](https://github.com/tendermint/tendermint/issues/1648)
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[#2179](https://github.com/tendermint/tendermint/issues/2179)
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[#2226](https://github.com/tendermint/tendermint/issues/2226)
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## Proposed Solution
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We can improve efficiency by replacing the usage of the `Vote` struct with a subset of each vote, and by storing the constant values (`Height`, `Round`, `BlockID`) in the Commit itself.
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```
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type Commit struct {
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Height int64
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Round int
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BlockID BlockID `json:"block_id"`
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Precommits []*CommitSig `json:"precommits"`
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}
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type CommitSig struct {
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BlockID BlockIDFlag
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ValidatorAddress Address
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Timestamp time.Time
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Signature []byte
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}
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// indicate which BlockID the signature is for
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type BlockIDFlag int
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const (
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BlockIDFlagAbsent BlockIDFlag = iota // vote is not included in the Commit.Precommits
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BlockIDFlagCommit // voted for the Commit.BlockID
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BlockIDFlagNil // voted for nil
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)
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```
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Note the need for an extra byte to indicate whether the signature is for the BlockID or for nil.
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This byte can also be used to indicate an absent vote, rather than using a nil object like we currently do,
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which has been [problematic for compatibility between Amino and proto3](https://github.com/tendermint/go-amino/issues/260).
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Note we also continue to store the `ValidatorAddress` in the `CommitSig`.
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While this still takes 20-bytes per signature, it ensures that the Commit has all
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information necessary to reconstruct Vote, which simplifies mapping between Commit and Vote objects
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and with debugging. It also may be necessary for the light-client to know which address a signature corresponds to if
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it is trying to verify a current commit with an older validtor set.
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## Status
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Proposed
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## Consequences
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### Positive
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Removing the Type/Height/Round/Index and the BlockID saves roughly 80 bytes per precommit.
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It varies because some integers are varint. The BlockID contains two 32-byte hashes an integer,
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and the Height is 8-bytes.
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For a chain with 100 validators, that's up to 8kB in savings per block!
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### Negative
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- Large breaking change to the block and commit structure
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- Requires differentiating in code between the Vote and CommitSig objects, which may add some complexity (votes need to be reconstructed to be verified and gossiped)
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### Neutral
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- Commit.Precommits no longer contains nil values
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