Documentation
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Overview ¶
Package evidence handles all evidence storage and gossiping from detection to block proposal. For the different types of evidence refer to the `evidence.go` file in the types package or https://github.com/mydexchain/spec/blob/master/spec/consensus/light-client/accountability.md.
Gossiping ¶
The core functionality begins with the evidence reactor (see reactor. go) which operates both the sending and receiving of evidence.
The `Receive` function takes a list of evidence and does the following:
1. Breaks it down into individual evidence if it is `Composite Evidence` (see types/evidence.go#ConflictingHeadersEvidence)
2. Checks that it does not already have the evidence stored
3. Verifies the evidence against the node's state (see state/validation.go#VerifyEvidence)
4. Stores the evidence to a db and a concurrent list
The gossiping of evidence is initiated when a peer is added which starts a go routine to broadcast currently uncommitted evidence at intervals of 60 seconds (set by the by broadcastEvidenceIntervalS). It uses a concurrent list to store the evidence and before sending verifies that each evidence is still valid in the sense that it has not exceeded the max evidence age and height (see types/params.go#EvidenceParams).
Three are four buckets that evidence can be stored in: Pending, Committed, Awaiting and POLC's.
1. Pending is awaiting to be committed (evidence is usually broadcasted then)
2. Committed is for those already on the block and is to ensure that evidence isn't submitted twice
3. AwaitingTrial primarily refers to PotentialAmnesiaEvidence which must wait for a trial period before being ready to be submitted (see docs/architecture/adr-056)
4. POLC's store all the ProofOfLockChanges that the node has done as part of consensus. To change lock is to vote for a different block in a later round. The consensus module calls `AddPOLC()` to add to this bucket.
All evidence is proto encoded to disk.
Proposing ¶
When a new block is being proposed (in state/execution.go#CreateProposalBlock), `PendingEvidence(maxNum)` is called to send up to the maxNum number of uncommitted evidence, from the evidence store, prioritized in order of age. All evidence is checked for expiration.
When a node receives evidence in a block it will use the evidence module as a cache first to see if it has already verified the evidence before trying to verify it again.
Once the proposed evidence is submitted, the evidence is marked as committed and is moved from the broadcasted set to the committed set. As a result it is also removed from the concurrent list so that it is no longer gossiped.
Minor Functionality ¶
As all evidence (including POLC's) are bounded by an expiration date, those that exceed this are no longer needed and hence pruned. Currently, only committed evidence in which a marker to the height that the evidence was committed and hence very small is saved. All updates are made from the `Update(block, state)` function which should be called when a new block is committed.
Index ¶
- Constants
- type BlockStore
- type PeerState
- type Pool
- func (evpool *Pool) AddEvidence(evidence types.Evidence) error
- func (evpool *Pool) AddPOLC(polc *types.ProofOfLockChange) error
- func (evpool *Pool) AllPendingEvidence() []types.Evidence
- func (evpool *Pool) EvidenceFront() *clist.CElement
- func (evpool *Pool) EvidenceWaitChan() <-chan struct{}
- func (evpool *Pool) Has(evidence types.Evidence) bool
- func (evpool *Pool) Header(height int64) *types.Header
- func (evpool *Pool) IsCommitted(evidence types.Evidence) bool
- func (evpool *Pool) IsEvidenceExpired(evidence types.Evidence) bool
- func (evpool *Pool) IsExpired(height int64, time time.Time) bool
- func (evpool *Pool) IsOnTrial(evidence types.Evidence) bool
- func (evpool *Pool) IsPending(evidence types.Evidence) bool
- func (evpool *Pool) MarkEvidenceAsCommitted(height int64, evidence []types.Evidence)
- func (evpool *Pool) PendingEvidence(maxNum uint32) []types.Evidence
- func (evpool *Pool) RetrievePOLC(height int64, round int32) (*types.ProofOfLockChange, error)
- func (evpool *Pool) SetLogger(l log.Logger)
- func (evpool *Pool) State() sm.State
- func (evpool *Pool) Update(block *types.Block, state sm.State)
- type Reactor
Constants ¶
const (
EvidenceChannel = byte(0x38)
)
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type BlockStore ¶
type PeerState ¶
type PeerState interface {
GetHeight() int64
}
PeerState describes the state of a peer.
type Pool ¶
type Pool struct {
// contains filtered or unexported fields
}
Pool maintains a pool of valid evidence to be broadcasted and committed
func NewPool ¶
func NewPool(stateDB, evidenceDB dbm.DB, blockStore BlockStore) (*Pool, error)
Creates a new pool. If using an existing evidence store, it will add all pending evidence to the concurrent list.
func (*Pool) AddEvidence ¶
AddEvidence checks the evidence is valid and adds it to the pool. If evidence is composite (ConflictingHeadersEvidence), it will be broken up into smaller pieces.
func (*Pool) AddPOLC ¶
func (evpool *Pool) AddPOLC(polc *types.ProofOfLockChange) error
AddPOLC adds a proof of lock change to the evidence database that may be needed in the future to verify votes
func (*Pool) AllPendingEvidence ¶
AllPendingEvidence returns all evidence ready to be proposed and committed.
func (*Pool) EvidenceFront ¶
EvidenceFront goes to the first evidence in the clist
func (*Pool) EvidenceWaitChan ¶
func (evpool *Pool) EvidenceWaitChan() <-chan struct{}
EvidenceWaitChan is a channel that closes once the first evidence in the list is there. i.e Front is not nil
func (*Pool) Header ¶
Header gets the header from the block store at a specified height. Is used for validation of LunaticValidatorEvidence
func (*Pool) IsCommitted ¶
IsCommitted returns true if we have already seen this exact evidence and it is already marked as committed.
func (*Pool) IsEvidenceExpired ¶
IsEvidenceExpired checks whether evidence is past the maximum age where it can be used
func (*Pool) IsExpired ¶
IsExpired checks whether evidence or a polc is expired by checking whether a height and time is older than set by the evidence consensus parameters
func (*Pool) IsOnTrial ¶
IsOnTrial checks whether a piece of evidence is in the awaiting bucket. Only Potential Amnesia Evidence is stored here.
func (*Pool) IsPending ¶
IsPending checks whether the evidence is already pending. DB errors are passed to the logger.
func (*Pool) MarkEvidenceAsCommitted ¶
MarkEvidenceAsCommitted marks all the evidence as committed and removes it from the queue.
func (*Pool) PendingEvidence ¶
PendingEvidence is used primarily as part of block proposal and returns up to maxNum of uncommitted evidence. If maxNum is -1, all evidence is returned. Pending evidence is prioritized based on time.
func (*Pool) RetrievePOLC ¶
RetrievePOLC attempts to find a polc at the given height and round, if not there than exist returns false, all database errors are automatically logged
type Reactor ¶
type Reactor struct {
p2p.BaseReactor
// contains filtered or unexported fields
}
Reactor handles evpool evidence broadcasting amongst peers.
func NewReactor ¶
NewReactor returns a new Reactor with the given config and evpool.
func (*Reactor) GetChannels ¶
func (evR *Reactor) GetChannels() []*p2p.ChannelDescriptor
GetChannels implements Reactor. It returns the list of channels for this reactor.
func (*Reactor) SetEventBus ¶
SetEventBus implements events.Eventable.
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