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122 lines
4.1 KiB
Markdown
122 lines
4.1 KiB
Markdown
# State
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The state contains information whose cryptographic digest is included in block headers, and thus is
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necessary for validating new blocks. For instance, the validators set and the results of
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transactions are never included in blocks, but their Merkle roots are:
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the state keeps track of them.
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The `State` object itself is an implementation detail, since it is never
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included in a block or gossiped over the network, and we never compute
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its hash. The persistence or query interface of the `State` object
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is an implementation detail and not included in the specification.
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However, the types in the `State` object are part of the specification, since
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the Merkle roots of the `State` objects are included in blocks and values are used during
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validation.
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```go
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type State struct {
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ChainID string
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InitialHeight int64
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LastBlockHeight int64
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LastBlockID types.BlockID
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LastBlockTime time.Time
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Version Version
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LastResults []Result
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AppHash []byte
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LastValidators ValidatorSet
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Validators ValidatorSet
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NextValidators ValidatorSet
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ConsensusParams ConsensusParams
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}
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```
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The chain ID and initial height are taken from the genesis file, and not changed again. The
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initial height will be `1` in the typical case, `0` is an invalid value.
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Note there is a hard-coded limit of 10000 validators. This is inherited from the
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limit on the number of votes in a commit.
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Further information on [`Validator`'s](./data_structures.md#validator),
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[`ValidatorSet`'s](./data_structures.md#validatorset) and
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[`ConsensusParams`'s](./data_structures.md#consensusparams) can
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be found in [data structures](./data_structures.md)
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## Execution
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State gets updated at the end of executing a block. Of specific interest is `ResponseEndBlock` and
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`ResponseCommit`
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```go
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type ResponseEndBlock struct {
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ValidatorUpdates []ValidatorUpdate `protobuf:"bytes,1,rep,name=validator_updates,json=validatorUpdates,proto3" json:"validator_updates"`
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ConsensusParamUpdates *types1.ConsensusParams `protobuf:"bytes,2,opt,name=consensus_param_updates,json=consensusParamUpdates,proto3" json:"consensus_param_updates,omitempty"`
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Events []Event `protobuf:"bytes,3,rep,name=events,proto3" json:"events,omitempty"`
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}
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```
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where
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```go
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type ValidatorUpdate struct {
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PubKey crypto.PublicKey `protobuf:"bytes,1,opt,name=pub_key,json=pubKey,proto3" json:"pub_key"`
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Power int64 `protobuf:"varint,2,opt,name=power,proto3" json:"power,omitempty"`
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}
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```
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and
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```go
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type ResponseCommit struct {
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// reserve 1
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Data []byte `protobuf:"bytes,2,opt,name=data,proto3" json:"data,omitempty"`
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RetainHeight int64 `protobuf:"varint,3,opt,name=retain_height,json=retainHeight,proto3" json:"retain_height,omitempty"`
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}
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```
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`ValidatorUpdates` are used to add and remove validators to the current set as well as update
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validator power. Setting validator power to 0 in `ValidatorUpdate` will cause the validator to be
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removed. `ConsensusParams` are safely copied across (i.e. if a field is nil it gets ignored) and the
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`Data` from the `ResponseCommit` is used as the `AppHash`
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## Version
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```go
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type Version struct {
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consensus Consensus
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software string
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}
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```
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[`Consensus`](./data_structures.md#version) contains the protocol version for the blockchain and the
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application.
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## Block
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The total size of a block is limited in bytes by the `ConsensusParams.Block.MaxBytes`.
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Proposed blocks must be less than this size, and will be considered invalid
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otherwise.
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Blocks should additionally be limited by the amount of "gas" consumed by the
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transactions in the block, though this is not yet implemented.
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## Evidence
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For evidence in a block to be valid, it must satisfy:
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```go
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block.Header.Time-evidence.Time < ConsensusParams.Evidence.MaxAgeDuration &&
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block.Header.Height-evidence.Height < ConsensusParams.Evidence.MaxAgeNumBlocks
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```
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A block must not contain more than `ConsensusParams.Evidence.MaxBytes` of evidence. This is
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implemented to mitigate spam attacks.
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## Validator
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Validators from genesis file and `ResponseEndBlock` must have pubkeys of type ∈
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`ConsensusParams.Validator.PubKeyTypes`.
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