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package evidence
import (
"fmt"
wire "github.com/tendermint/go-wire"
"github.com/tendermint/tendermint/types"
dbm "github.com/tendermint/tmlibs/db"
)
/*
Requirements:
- Valid new evidence must be persisted immediately and never forgotten
- Uncommitted evidence must be continuously broadcast
- Uncommitted evidence has a partial order, the evidence's priority
Impl:
- First commit atomically in outqueue, pending, lookup.
- Once broadcast, remove from outqueue. No need to sync
- Once committed, atomically remove from pending and update lookup.
- TODO: If we crash after committed but before removing/updating,
we'll be stuck broadcasting evidence we never know we committed.
so either share the state db and atomically MarkCommitted
with ApplyBlock, or check all outqueue/pending on Start to see if its committed
Schema for indexing evidence (note you need both height and hash to find a piece of evidence):
"evidence-lookup"/<evidence-height>/<evidence-hash> -> EvidenceInfo
"evidence-outqueue"/<priority>/<evidence-height>/<evidence-hash> -> EvidenceInfo
"evidence-pending"/<evidence-height>/<evidence-hash> -> EvidenceInfo
*/
type EvidenceInfo struct {
Committed bool
Priority int64
Evidence types.Evidence
}
const (
baseKeyLookup = "evidence-lookup" // all evidence
baseKeyOutqueue = "evidence-outqueue" // not-yet broadcast
baseKeyPending = "evidence-pending" // broadcast but not committed
)
func keyLookup(evidence types.Evidence) []byte {
return keyLookupFromHeightAndHash(evidence.Height(), evidence.Hash())
}
// big endian padded hex
func bE(h int64) string {
return fmt.Sprintf("%0.16X", h)
}
func keyLookupFromHeightAndHash(height int64, hash []byte) []byte {
return _key("%s/%s/%X", baseKeyLookup, bE(height), hash)
}
func keyOutqueue(evidence types.Evidence, priority int64) []byte {
return _key("%s/%s/%s/%X", baseKeyOutqueue, bE(priority), bE(evidence.Height()), evidence.Hash())
}
func keyPending(evidence types.Evidence) []byte {
return _key("%s/%s/%X", baseKeyPending, bE(evidence.Height()), evidence.Hash())
}
func _key(fmt_ string, o ...interface{}) []byte {
return []byte(fmt.Sprintf(fmt_, o...))
}
// EvidenceStore is a store of all the evidence we've seen, including
// evidence that has been committed, evidence that has been verified but not broadcast,
// and evidence that has been broadcast but not yet committed.
type EvidenceStore struct {
db dbm.DB
}
func NewEvidenceStore(db dbm.DB) *EvidenceStore {
return &EvidenceStore{
db: db,
}
}
// PriorityEvidence returns the evidence from the outqueue, sorted by highest priority.
func (store *EvidenceStore) PriorityEvidence() (evidence []types.Evidence) {
// reverse the order so highest priority is first
l := store.ListEvidence(baseKeyOutqueue)
l2 := make([]types.Evidence, len(l))
for i := range l {
l2[i] = l[len(l)-1-i]
}
return l2
}
// PendingEvidence returns all known uncommitted evidence.
func (store *EvidenceStore) PendingEvidence() (evidence []types.Evidence) {
return store.ListEvidence(baseKeyPending)
}
// ListEvidence lists the evidence for the given prefix key.
// It is wrapped by PriorityEvidence and PendingEvidence for convenience.
func (store *EvidenceStore) ListEvidence(prefixKey string) (evidence []types.Evidence) {
iter := dbm.IteratePrefix(store.db, []byte(prefixKey))
for ; iter.Valid(); iter.Next() {
val := iter.Value()
var ei EvidenceInfo
wire.ReadBinaryBytes(val, &ei)
evidence = append(evidence, ei.Evidence)
}
return evidence
}
// GetEvidence fetches the evidence with the given height and hash.
func (store *EvidenceStore) GetEvidence(height int64, hash []byte) *EvidenceInfo {
key := keyLookupFromHeightAndHash(height, hash)
val := store.db.Get(key)
if len(val) == 0 {
return nil
}
var ei EvidenceInfo
wire.ReadBinaryBytes(val, &ei)
return &ei
}
// AddNewEvidence adds the given evidence to the database.
// It returns false if the evidence is already stored.
func (store *EvidenceStore) AddNewEvidence(evidence types.Evidence, priority int64) bool {
// check if we already have seen it
ei_ := store.GetEvidence(evidence.Height(), evidence.Hash())
if ei_ != nil && ei_.Evidence != nil {
return false
}
ei := EvidenceInfo{
Committed: false,
Priority: priority,
Evidence: evidence,
}
eiBytes := wire.BinaryBytes(ei)
// add it to the store
key := keyOutqueue(evidence, priority)
store.db.Set(key, eiBytes)
key = keyPending(evidence)
store.db.Set(key, eiBytes)
key = keyLookup(evidence)
store.db.SetSync(key, eiBytes)
return true
}
// MarkEvidenceAsBroadcasted removes evidence from Outqueue.
func (store *EvidenceStore) MarkEvidenceAsBroadcasted(evidence types.Evidence) {
ei := store.getEvidenceInfo(evidence)
key := keyOutqueue(evidence, ei.Priority)
store.db.Delete(key)
}
// MarkEvidenceAsPending removes evidence from pending and outqueue and sets the state to committed.
func (store *EvidenceStore) MarkEvidenceAsCommitted(evidence types.Evidence) {
// if its committed, its been broadcast
store.MarkEvidenceAsBroadcasted(evidence)
pendingKey := keyPending(evidence)
store.db.Delete(pendingKey)
ei := store.getEvidenceInfo(evidence)
ei.Committed = true
lookupKey := keyLookup(evidence)
store.db.SetSync(lookupKey, wire.BinaryBytes(ei))
}
//---------------------------------------------------
// utils
func (store *EvidenceStore) getEvidenceInfo(evidence types.Evidence) EvidenceInfo {
key := keyLookup(evidence)
var ei EvidenceInfo
b := store.db.Get(key)
wire.ReadBinaryBytes(b, &ei)
return ei
}