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289 lines
7.6 KiB
289 lines
7.6 KiB
package statesync
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import (
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"crypto/sha256"
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"fmt"
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"math/rand"
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"sort"
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"strings"
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"sync"
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"github.com/tendermint/tendermint/types"
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)
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// snapshotKey is a snapshot key used for lookups.
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type snapshotKey [sha256.Size]byte
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// snapshot contains data about a snapshot.
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type snapshot struct {
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Height uint64
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Format uint32
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Chunks uint32
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Hash []byte
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Metadata []byte
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trustedAppHash []byte // populated by light client
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}
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// Key generates a snapshot key, used for lookups. It takes into account not only the height and
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// format, but also the chunks, hash, and metadata in case peers have generated snapshots in a
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// non-deterministic manner. All fields must be equal for the snapshot to be considered the same.
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func (s *snapshot) Key() snapshotKey {
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// Hash.Write() never returns an error.
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hasher := sha256.New()
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hasher.Write([]byte(fmt.Sprintf("%v:%v:%v", s.Height, s.Format, s.Chunks)))
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hasher.Write(s.Hash)
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hasher.Write(s.Metadata)
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var key snapshotKey
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copy(key[:], hasher.Sum(nil))
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return key
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}
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// snapshotPool discovers and aggregates snapshots across peers.
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type snapshotPool struct {
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sync.Mutex
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snapshots map[snapshotKey]*snapshot
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snapshotPeers map[snapshotKey]map[types.NodeID]types.NodeID
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// indexes for fast searches
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formatIndex map[uint32]map[snapshotKey]bool
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heightIndex map[uint64]map[snapshotKey]bool
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peerIndex map[types.NodeID]map[snapshotKey]bool
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// blacklists for rejected items
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formatBlacklist map[uint32]bool
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peerBlacklist map[types.NodeID]bool
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snapshotBlacklist map[snapshotKey]bool
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}
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// newSnapshotPool creates a new empty snapshot pool.
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func newSnapshotPool() *snapshotPool {
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return &snapshotPool{
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snapshots: make(map[snapshotKey]*snapshot),
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snapshotPeers: make(map[snapshotKey]map[types.NodeID]types.NodeID),
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formatIndex: make(map[uint32]map[snapshotKey]bool),
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heightIndex: make(map[uint64]map[snapshotKey]bool),
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peerIndex: make(map[types.NodeID]map[snapshotKey]bool),
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formatBlacklist: make(map[uint32]bool),
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peerBlacklist: make(map[types.NodeID]bool),
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snapshotBlacklist: make(map[snapshotKey]bool),
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}
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}
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// Add adds a snapshot to the pool, unless the peer has already sent recentSnapshots
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// snapshots. It returns true if this was a new, non-blacklisted snapshot. The
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// snapshot height is verified using the light client, and the expected app hash
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// is set for the snapshot.
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func (p *snapshotPool) Add(peerID types.NodeID, snapshot *snapshot) (bool, error) {
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key := snapshot.Key()
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p.Lock()
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defer p.Unlock()
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switch {
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case p.formatBlacklist[snapshot.Format]:
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return false, nil
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case p.peerBlacklist[peerID]:
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return false, nil
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case p.snapshotBlacklist[key]:
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return false, nil
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case len(p.peerIndex[peerID]) >= recentSnapshots:
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return false, nil
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}
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if p.snapshotPeers[key] == nil {
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p.snapshotPeers[key] = make(map[types.NodeID]types.NodeID)
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}
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p.snapshotPeers[key][peerID] = peerID
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if p.peerIndex[peerID] == nil {
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p.peerIndex[peerID] = make(map[snapshotKey]bool)
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}
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p.peerIndex[peerID][key] = true
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if p.snapshots[key] != nil {
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return false, nil
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}
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p.snapshots[key] = snapshot
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if p.formatIndex[snapshot.Format] == nil {
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p.formatIndex[snapshot.Format] = make(map[snapshotKey]bool)
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}
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p.formatIndex[snapshot.Format][key] = true
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if p.heightIndex[snapshot.Height] == nil {
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p.heightIndex[snapshot.Height] = make(map[snapshotKey]bool)
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}
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p.heightIndex[snapshot.Height][key] = true
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return true, nil
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}
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// Best returns the "best" currently known snapshot, if any.
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func (p *snapshotPool) Best() *snapshot {
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ranked := p.Ranked()
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if len(ranked) == 0 {
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return nil
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}
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return ranked[0]
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}
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// GetPeer returns a random peer for a snapshot, if any.
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func (p *snapshotPool) GetPeer(snapshot *snapshot) types.NodeID {
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peers := p.GetPeers(snapshot)
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if len(peers) == 0 {
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return ""
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}
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return peers[rand.Intn(len(peers))] // nolint:gosec // G404: Use of weak random number generator
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}
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// GetPeers returns the peers for a snapshot.
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func (p *snapshotPool) GetPeers(snapshot *snapshot) []types.NodeID {
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key := snapshot.Key()
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p.Lock()
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defer p.Unlock()
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peers := make([]types.NodeID, 0, len(p.snapshotPeers[key]))
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for _, peer := range p.snapshotPeers[key] {
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peers = append(peers, peer)
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}
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// sort results, for testability (otherwise order is random, so tests randomly fail)
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sort.Slice(peers, func(a int, b int) bool {
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return strings.Compare(string(peers[a]), string(peers[b])) < 0
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})
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return peers
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}
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// Ranked returns a list of snapshots ranked by preference. The current heuristic is very naïve,
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// preferring the snapshot with the greatest height, then greatest format, then greatest number of
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// peers. This can be improved quite a lot.
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func (p *snapshotPool) Ranked() []*snapshot {
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p.Lock()
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defer p.Unlock()
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if len(p.snapshots) == 0 {
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return []*snapshot{}
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}
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numPeers := make([]int, 0, len(p.snapshots))
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for key := range p.snapshots {
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numPeers = append(numPeers, len(p.snapshotPeers[key]))
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}
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sort.Ints(numPeers)
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median := len(numPeers) / 2
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if len(numPeers)%2 == 0 {
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median = (numPeers[median-1] + numPeers[median]) / 2
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} else {
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median = numPeers[median]
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}
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commonCandidates := make([]*snapshot, 0, len(p.snapshots)/2)
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uncommonCandidates := make([]*snapshot, 0, len(p.snapshots)/2)
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for key := range p.snapshots {
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if len(p.snapshotPeers[key]) > median {
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commonCandidates = append(commonCandidates, p.snapshots[key])
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continue
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}
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uncommonCandidates = append(uncommonCandidates, p.snapshots[key])
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}
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sort.Slice(commonCandidates, p.sorterFactory(commonCandidates))
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sort.Slice(uncommonCandidates, p.sorterFactory(uncommonCandidates))
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return append(commonCandidates, uncommonCandidates...)
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}
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func (p *snapshotPool) sorterFactory(candidates []*snapshot) func(int, int) bool {
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return func(i, j int) bool {
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a := candidates[i]
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b := candidates[j]
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switch {
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case a.Height > b.Height:
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return true
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case a.Height < b.Height:
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return false
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case len(p.snapshotPeers[a.Key()]) > len(p.snapshotPeers[b.Key()]):
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return true
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case a.Format > b.Format:
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return true
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case a.Format < b.Format:
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return false
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default:
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return false
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}
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}
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}
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// Reject rejects a snapshot. Rejected snapshots will never be used again.
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func (p *snapshotPool) Reject(snapshot *snapshot) {
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key := snapshot.Key()
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p.Lock()
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defer p.Unlock()
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p.snapshotBlacklist[key] = true
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p.removeSnapshot(key)
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}
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// RejectFormat rejects a snapshot format. It will never be used again.
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func (p *snapshotPool) RejectFormat(format uint32) {
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p.Lock()
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defer p.Unlock()
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p.formatBlacklist[format] = true
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for key := range p.formatIndex[format] {
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p.removeSnapshot(key)
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}
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}
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// RejectPeer rejects a peer. It will never be used again.
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func (p *snapshotPool) RejectPeer(peerID types.NodeID) {
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if len(peerID) == 0 {
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return
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}
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p.Lock()
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defer p.Unlock()
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p.removePeer(peerID)
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p.peerBlacklist[peerID] = true
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}
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// RemovePeer removes a peer from the pool, and any snapshots that no longer have peers.
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func (p *snapshotPool) RemovePeer(peerID types.NodeID) {
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p.Lock()
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defer p.Unlock()
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p.removePeer(peerID)
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}
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// removePeer removes a peer. The caller must hold the mutex lock.
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func (p *snapshotPool) removePeer(peerID types.NodeID) {
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for key := range p.peerIndex[peerID] {
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delete(p.snapshotPeers[key], peerID)
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if len(p.snapshotPeers[key]) == 0 {
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p.removeSnapshot(key)
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}
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}
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delete(p.peerIndex, peerID)
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}
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// removeSnapshot removes a snapshot. The caller must hold the mutex lock.
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func (p *snapshotPool) removeSnapshot(key snapshotKey) {
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snapshot := p.snapshots[key]
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if snapshot == nil {
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return
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}
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delete(p.snapshots, key)
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delete(p.formatIndex[snapshot.Format], key)
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delete(p.heightIndex[snapshot.Height], key)
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for peerID := range p.snapshotPeers[key] {
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delete(p.peerIndex[peerID], key)
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}
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delete(p.snapshotPeers, key)
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}
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