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package evidence
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import (
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"fmt"
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wire "github.com/tendermint/go-wire"
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"github.com/tendermint/tendermint/types"
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dbm "github.com/tendermint/tmlibs/db"
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)
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/*
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Requirements:
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- Valid new evidence must be persisted immediately and never forgotten
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- Uncommitted evidence must be continuously broadcast
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- Uncommitted evidence has a partial order, the evidence's priority
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Impl:
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- First commit atomically in outqueue, pending, lookup.
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- Once broadcast, remove from outqueue. No need to sync
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- Once committed, atomically remove from pending and update lookup.
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- TODO: If we crash after committed but before removing/updating,
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we'll be stuck broadcasting evidence we never know we committed.
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so either share the state db and atomically MarkCommitted
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with ApplyBlock, or check all outqueue/pending on Start to see if its committed
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Schema for indexing evidence (note you need both height and hash to find a piece of evidence):
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"evidence-lookup"/<evidence-height>/<evidence-hash> -> EvidenceInfo
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"evidence-outqueue"/<priority>/<evidence-height>/<evidence-hash> -> EvidenceInfo
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"evidence-pending"/<evidence-height>/<evidence-hash> -> EvidenceInfo
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*/
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type EvidenceInfo struct {
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Committed bool
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Priority int
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Evidence types.Evidence
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}
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const (
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baseKeyLookup = "evidence-lookup" // all evidence
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baseKeyOutqueue = "evidence-outqueue" // not-yet broadcast
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baseKeyPending = "evidence-pending" // broadcast but not committed
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)
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func keyLookup(evidence types.Evidence) []byte {
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return keyLookupFromHeightAndHash(evidence.Height(), evidence.Hash())
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}
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// big endian padded hex
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func be(h int) string {
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return fmt.Sprintf("%0.16X", h)
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}
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func keyLookupFromHeightAndHash(height int, hash []byte) []byte {
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return _key("%s/%s/%X", baseKeyLookup, be(height), hash)
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}
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func keyOutqueue(evidence types.Evidence, priority int) []byte {
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return _key("%s/%s/%s/%X", baseKeyOutqueue, be(priority), be(evidence.Height()), evidence.Hash())
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}
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func keyPending(evidence types.Evidence) []byte {
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return _key("%s/%s/%X", baseKeyPending, be(evidence.Height()), evidence.Hash())
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}
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func _key(fmt_ string, o ...interface{}) []byte {
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return []byte(fmt.Sprintf(fmt_, o...))
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}
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// EvidenceStore is a store of all the evidence we've seen, including
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// evidence that has been committed, evidence that has been verified but not broadcast,
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// and evidence that has been broadcast but not yet committed.
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type EvidenceStore struct {
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db dbm.DB
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}
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func NewEvidenceStore(db dbm.DB) *EvidenceStore {
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return &EvidenceStore{
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db: db,
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}
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}
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// PriorityEvidence returns the evidence from the outqueue, sorted by highest priority.
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func (store *EvidenceStore) PriorityEvidence() (evidence []types.Evidence) {
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// reverse the order so highest priority is first
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l := store.ListEvidence(baseKeyOutqueue)
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l2 := make([]types.Evidence, len(l))
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for i, _ := range l {
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l2[i] = l[len(l)-1-i]
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}
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return l2
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}
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// PendingEvidence returns all known uncommitted evidence.
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func (store *EvidenceStore) PendingEvidence() (evidence []types.Evidence) {
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return store.ListEvidence(baseKeyPending)
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}
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// ListEvidence lists the evidence for the given prefix key.
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// It is wrapped by PriorityEvidence and PendingEvidence for convenience.
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func (store *EvidenceStore) ListEvidence(prefixKey string) (evidence []types.Evidence) {
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iter := store.db.IteratorPrefix([]byte(prefixKey))
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for iter.Next() {
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val := iter.Value()
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var ei EvidenceInfo
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wire.ReadBinaryBytes(val, &ei)
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evidence = append(evidence, ei.Evidence)
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}
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return evidence
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}
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// GetEvidence fetches the evidence with the given height and hash.
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func (store *EvidenceStore) GetEvidence(height int, hash []byte) *EvidenceInfo {
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key := keyLookupFromHeightAndHash(height, hash)
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val := store.db.Get(key)
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if len(val) == 0 {
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return nil
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}
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ei := new(EvidenceInfo)
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wire.ReadBinaryBytes(val, ei)
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return ei
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}
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// AddNewEvidence adds the given evidence to the database.
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func (store *EvidenceStore) AddNewEvidence(evidence types.Evidence, priority int) bool {
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// check if we already have seen it
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ei_ := store.GetEvidence(evidence.Height(), evidence.Hash())
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if ei_ != nil && ei_.Evidence != nil {
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return false
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}
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ei := EvidenceInfo{
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Committed: false,
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Priority: priority,
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Evidence: evidence,
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}
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eiBytes := wire.BinaryBytes(ei)
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// add it to the store
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key := keyOutqueue(evidence, priority)
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store.db.Set(key, eiBytes)
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key = keyPending(evidence)
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store.db.Set(key, eiBytes)
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key = keyLookup(evidence)
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store.db.SetSync(key, eiBytes)
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return true
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}
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// MarkEvidenceAsBroadcasted removes evidence from Outqueue.
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func (store *EvidenceStore) MarkEvidenceAsBroadcasted(evidence types.Evidence) {
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ei := store.getEvidenceInfo(evidence)
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key := keyOutqueue(evidence, ei.Priority)
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store.db.Delete(key)
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}
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// MarkEvidenceAsPending removes evidence from pending and outqueue and sets the state to committed.
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func (store *EvidenceStore) MarkEvidenceAsCommitted(evidence types.Evidence) {
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// if its committed, its been broadcast
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store.MarkEvidenceAsBroadcasted(evidence)
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pendingKey := keyPending(evidence)
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store.db.Delete(pendingKey)
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ei := store.getEvidenceInfo(evidence)
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ei.Committed = true
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// TODO: we should use the state db and db.Sync in state.Save instead.
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// Else, if we call this before state.Save, we may never mark committed evidence as committed.
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// Else, if we call this after state.Save, we may get stuck broadcasting evidence we never know we committed.
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lookupKey := keyLookup(evidence)
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store.db.SetSync(lookupKey, wire.BinaryBytes(ei))
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}
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//---------------------------------------------------
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// utils
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func (store *EvidenceStore) getEvidenceInfo(evidence types.Evidence) EvidenceInfo {
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key := keyLookup(evidence)
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var ei EvidenceInfo
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b := store.db.Get(key)
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wire.ReadBinaryBytes(b, &ei)
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return ei
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}
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