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package statesync
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import (
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"bytes"
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"context"
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"errors"
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"fmt"
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"sync"
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"time"
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abci "github.com/tendermint/tendermint/abci/types"
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"github.com/tendermint/tendermint/libs/log"
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"github.com/tendermint/tendermint/p2p"
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ssproto "github.com/tendermint/tendermint/proto/tendermint/statesync"
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"github.com/tendermint/tendermint/proxy"
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sm "github.com/tendermint/tendermint/state"
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"github.com/tendermint/tendermint/types"
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)
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const (
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// defaultDiscoveryTime is the time to spend discovering snapshots.
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defaultDiscoveryTime = 20 * time.Second
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// chunkFetchers is the number of concurrent chunk fetchers to run.
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chunkFetchers = 4
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// chunkTimeout is the timeout while waiting for the next chunk from the chunk queue.
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chunkTimeout = 2 * time.Minute
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// requestTimeout is the timeout before rerequesting a chunk, possibly from a different peer.
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chunkRequestTimeout = 10 * time.Second
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)
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var (
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// errAbort is returned by Sync() when snapshot restoration is aborted.
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errAbort = errors.New("state sync aborted")
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// errRetrySnapshot is returned by Sync() when the snapshot should be retried.
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errRetrySnapshot = errors.New("retry snapshot")
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// errRejectSnapshot is returned by Sync() when the snapshot is rejected.
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errRejectSnapshot = errors.New("snapshot was rejected")
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// errRejectFormat is returned by Sync() when the snapshot format is rejected.
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errRejectFormat = errors.New("snapshot format was rejected")
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// errRejectSender is returned by Sync() when the snapshot sender is rejected.
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errRejectSender = errors.New("snapshot sender was rejected")
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// errVerifyFailed is returned by Sync() when app hash or last height verification fails.
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errVerifyFailed = errors.New("verification failed")
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// errTimeout is returned by Sync() when we've waited too long to receive a chunk.
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errTimeout = errors.New("timed out waiting for chunk")
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// errNoSnapshots is returned by SyncAny() if no snapshots are found and discovery is disabled.
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errNoSnapshots = errors.New("no suitable snapshots found")
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)
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// syncer runs a state sync against an ABCI app. Use either SyncAny() to automatically attempt to
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// sync all snapshots in the pool (pausing to discover new ones), or Sync() to sync a specific
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// snapshot. Snapshots and chunks are fed via AddSnapshot() and AddChunk() as appropriate.
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type syncer struct {
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logger log.Logger
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stateProvider StateProvider
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conn proxy.AppConnSnapshot
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connQuery proxy.AppConnQuery
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snapshots *snapshotPool
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tempDir string
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mtx sync.RWMutex
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chunks *chunkQueue
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}
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// newSyncer creates a new syncer.
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func newSyncer(logger log.Logger, conn proxy.AppConnSnapshot, connQuery proxy.AppConnQuery,
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stateProvider StateProvider, tempDir string) *syncer {
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return &syncer{
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logger: logger,
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stateProvider: stateProvider,
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conn: conn,
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connQuery: connQuery,
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snapshots: newSnapshotPool(stateProvider),
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tempDir: tempDir,
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}
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}
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// AddChunk adds a chunk to the chunk queue, if any. It returns false if the chunk has already
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// been added to the queue, or an error if there's no sync in progress.
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func (s *syncer) AddChunk(chunk *chunk) (bool, error) {
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s.mtx.RLock()
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defer s.mtx.RUnlock()
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if s.chunks == nil {
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return false, errors.New("no state sync in progress")
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}
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added, err := s.chunks.Add(chunk)
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if err != nil {
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return false, err
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}
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if added {
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s.logger.Debug("Added chunk to queue", "height", chunk.Height, "format", chunk.Format,
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"chunk", chunk.Index)
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} else {
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s.logger.Debug("Ignoring duplicate chunk in queue", "height", chunk.Height, "format", chunk.Format,
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"chunk", chunk.Index)
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}
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return added, nil
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}
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// AddSnapshot adds a snapshot to the snapshot pool. It returns true if a new, previously unseen
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// snapshot was accepted and added.
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func (s *syncer) AddSnapshot(peer p2p.Peer, snapshot *snapshot) (bool, error) {
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added, err := s.snapshots.Add(peer, snapshot)
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if err != nil {
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return false, err
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}
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if added {
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s.logger.Info("Discovered new snapshot", "height", snapshot.Height, "format", snapshot.Format,
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"hash", fmt.Sprintf("%X", snapshot.Hash))
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}
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return added, nil
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}
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// AddPeer adds a peer to the pool. For now we just keep it simple and send a single request
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// to discover snapshots, later we may want to do retries and stuff.
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func (s *syncer) AddPeer(peer p2p.Peer) {
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s.logger.Debug("Requesting snapshots from peer", "peer", peer.ID())
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peer.Send(SnapshotChannel, mustEncodeMsg(&ssproto.SnapshotsRequest{}))
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}
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// RemovePeer removes a peer from the pool.
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func (s *syncer) RemovePeer(peer p2p.Peer) {
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s.logger.Debug("Removing peer from sync", "peer", peer.ID())
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s.snapshots.RemovePeer(peer.ID())
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}
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// SyncAny tries to sync any of the snapshots in the snapshot pool, waiting to discover further
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// snapshots if none were found and discoveryTime > 0. It returns the latest state and block commit
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// which the caller must use to bootstrap the node.
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func (s *syncer) SyncAny(discoveryTime time.Duration) (sm.State, *types.Commit, error) {
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if discoveryTime > 0 {
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s.logger.Info(fmt.Sprintf("Discovering snapshots for %v", discoveryTime))
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time.Sleep(discoveryTime)
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}
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// The app may ask us to retry a snapshot restoration, in which case we need to reuse
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// the snapshot and chunk queue from the previous loop iteration.
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var (
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snapshot *snapshot
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chunks *chunkQueue
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err error
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)
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for {
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// If not nil, we're going to retry restoration of the same snapshot.
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if snapshot == nil {
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snapshot = s.snapshots.Best()
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chunks = nil
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}
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if snapshot == nil {
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if discoveryTime == 0 {
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return sm.State{}, nil, errNoSnapshots
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}
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s.logger.Info(fmt.Sprintf("Discovering snapshots for %v", discoveryTime))
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time.Sleep(discoveryTime)
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continue
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}
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if chunks == nil {
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chunks, err = newChunkQueue(snapshot, s.tempDir)
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if err != nil {
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return sm.State{}, nil, fmt.Errorf("failed to create chunk queue: %w", err)
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}
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defer chunks.Close() // in case we forget to close it elsewhere
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}
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newState, commit, err := s.Sync(snapshot, chunks)
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switch {
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case err == nil:
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return newState, commit, nil
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case errors.Is(err, errAbort):
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return sm.State{}, nil, err
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case errors.Is(err, errRetrySnapshot):
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chunks.RetryAll()
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s.logger.Info("Retrying snapshot", "height", snapshot.Height, "format", snapshot.Format,
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"hash", fmt.Sprintf("%X", snapshot.Hash))
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continue
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case errors.Is(err, errTimeout):
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s.snapshots.Reject(snapshot)
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s.logger.Error("Timed out waiting for snapshot chunks, rejected snapshot",
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"height", snapshot.Height, "format", snapshot.Format, "hash", fmt.Sprintf("%X", snapshot.Hash))
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case errors.Is(err, errRejectSnapshot):
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s.snapshots.Reject(snapshot)
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s.logger.Info("Snapshot rejected", "height", snapshot.Height, "format", snapshot.Format,
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"hash", fmt.Sprintf("%X", snapshot.Hash))
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case errors.Is(err, errRejectFormat):
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s.snapshots.RejectFormat(snapshot.Format)
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s.logger.Info("Snapshot format rejected", "format", snapshot.Format)
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case errors.Is(err, errRejectSender):
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s.logger.Info("Snapshot senders rejected", "height", snapshot.Height, "format", snapshot.Format,
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"hash", fmt.Sprintf("%X", snapshot.Hash))
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for _, peer := range s.snapshots.GetPeers(snapshot) {
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s.snapshots.RejectPeer(peer.ID())
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s.logger.Info("Snapshot sender rejected", "peer", peer.ID())
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}
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default:
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return sm.State{}, nil, fmt.Errorf("snapshot restoration failed: %w", err)
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}
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// Discard snapshot and chunks for next iteration
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err = chunks.Close()
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if err != nil {
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s.logger.Error("Failed to clean up chunk queue", "err", err)
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}
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snapshot = nil
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chunks = nil
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}
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}
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// Sync executes a sync for a specific snapshot, returning the latest state and block commit which
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// the caller must use to bootstrap the node.
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func (s *syncer) Sync(snapshot *snapshot, chunks *chunkQueue) (sm.State, *types.Commit, error) {
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s.mtx.Lock()
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if s.chunks != nil {
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s.mtx.Unlock()
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return sm.State{}, nil, errors.New("a state sync is already in progress")
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}
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s.chunks = chunks
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s.mtx.Unlock()
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defer func() {
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s.mtx.Lock()
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s.chunks = nil
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s.mtx.Unlock()
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}()
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// Offer snapshot to ABCI app.
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err := s.offerSnapshot(snapshot)
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if err != nil {
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return sm.State{}, nil, err
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}
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// Spawn chunk fetchers. They will terminate when the chunk queue is closed or context cancelled.
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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for i := int32(0); i < chunkFetchers; i++ {
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go s.fetchChunks(ctx, snapshot, chunks)
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}
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// Optimistically build new state, so we don't discover any light client failures at the end.
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state, err := s.stateProvider.State(snapshot.Height)
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if err != nil {
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return sm.State{}, nil, fmt.Errorf("failed to build new state: %w", err)
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}
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commit, err := s.stateProvider.Commit(snapshot.Height)
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if err != nil {
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return sm.State{}, nil, fmt.Errorf("failed to fetch commit: %w", err)
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}
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// Restore snapshot
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err = s.applyChunks(chunks)
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if err != nil {
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return sm.State{}, nil, err
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}
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// Verify app and update app version
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appVersion, err := s.verifyApp(snapshot)
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if err != nil {
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return sm.State{}, nil, err
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}
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state.Version.Consensus.App = appVersion
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// Done! 🎉
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s.logger.Info("Snapshot restored", "height", snapshot.Height, "format", snapshot.Format,
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"hash", fmt.Sprintf("%X", snapshot.Hash))
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return state, commit, nil
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}
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// offerSnapshot offers a snapshot to the app. It returns various errors depending on the app's
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// response, or nil if the snapshot was accepted.
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func (s *syncer) offerSnapshot(snapshot *snapshot) error {
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s.logger.Info("Offering snapshot to ABCI app", "height", snapshot.Height,
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"format", snapshot.Format, "hash", fmt.Sprintf("%X", snapshot.Hash))
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resp, err := s.conn.OfferSnapshotSync(abci.RequestOfferSnapshot{
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Snapshot: &abci.Snapshot{
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Height: snapshot.Height,
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Format: snapshot.Format,
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Chunks: snapshot.Chunks,
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Hash: snapshot.Hash,
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Metadata: snapshot.Metadata,
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},
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AppHash: snapshot.trustedAppHash,
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})
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if err != nil {
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return fmt.Errorf("failed to offer snapshot: %w", err)
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}
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switch resp.Result {
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case abci.ResponseOfferSnapshot_ACCEPT:
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s.logger.Info("Snapshot accepted, restoring", "height", snapshot.Height,
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"format", snapshot.Format, "hash", fmt.Sprintf("%X", snapshot.Hash))
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return nil
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case abci.ResponseOfferSnapshot_ABORT:
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return errAbort
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case abci.ResponseOfferSnapshot_REJECT:
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return errRejectSnapshot
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case abci.ResponseOfferSnapshot_REJECT_FORMAT:
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return errRejectFormat
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case abci.ResponseOfferSnapshot_REJECT_SENDER:
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return errRejectSender
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default:
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return fmt.Errorf("invalid ResponseOfferSnapshot result %v", resp.Result)
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}
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}
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// applyChunks applies chunks to the app. It returns various errors depending on the app's
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// response, or nil once the snapshot is fully restored.
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func (s *syncer) applyChunks(chunks *chunkQueue) error {
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for {
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chunk, err := chunks.Next()
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if err == errDone {
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return nil
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} else if err != nil {
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return fmt.Errorf("failed to fetch chunk: %w", err)
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}
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resp, err := s.conn.ApplySnapshotChunkSync(abci.RequestApplySnapshotChunk{
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Index: chunk.Index,
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Chunk: chunk.Chunk,
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Sender: string(chunk.Sender),
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})
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if err != nil {
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return fmt.Errorf("failed to apply chunk %v: %w", chunk.Index, err)
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}
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s.logger.Info("Applied snapshot chunk to ABCI app", "height", chunk.Height,
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"format", chunk.Format, "chunk", chunk.Index, "total", chunks.Size())
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// Discard and refetch any chunks as requested by the app
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for _, index := range resp.RefetchChunks {
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err := chunks.Discard(index)
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if err != nil {
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return fmt.Errorf("failed to discard chunk %v: %w", index, err)
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}
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}
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// Reject any senders as requested by the app
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for _, sender := range resp.RejectSenders {
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if sender != "" {
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s.snapshots.RejectPeer(p2p.ID(sender))
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err := chunks.DiscardSender(p2p.ID(sender))
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if err != nil {
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return fmt.Errorf("failed to reject sender: %w", err)
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}
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}
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}
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switch resp.Result {
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case abci.ResponseApplySnapshotChunk_ACCEPT:
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case abci.ResponseApplySnapshotChunk_ABORT:
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return errAbort
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case abci.ResponseApplySnapshotChunk_RETRY:
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chunks.Retry(chunk.Index)
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case abci.ResponseApplySnapshotChunk_RETRY_SNAPSHOT:
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return errRetrySnapshot
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case abci.ResponseApplySnapshotChunk_REJECT_SNAPSHOT:
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return errRejectSnapshot
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default:
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return fmt.Errorf("unknown ResponseApplySnapshotChunk result %v", resp.Result)
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}
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}
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}
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// fetchChunks requests chunks from peers, receiving allocations from the chunk queue. Chunks
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// will be received from the reactor via syncer.AddChunks() to chunkQueue.Add().
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func (s *syncer) fetchChunks(ctx context.Context, snapshot *snapshot, chunks *chunkQueue) {
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for {
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index, err := chunks.Allocate()
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if err == errDone {
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// Keep checking until the context is cancelled (restore is done), in case any
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// chunks need to be refetched.
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select {
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case <-ctx.Done():
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return
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default:
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}
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time.Sleep(2 * time.Second)
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continue
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}
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if err != nil {
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s.logger.Error("Failed to allocate chunk from queue", "err", err)
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return
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}
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s.logger.Info("Fetching snapshot chunk", "height", snapshot.Height,
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"format", snapshot.Format, "chunk", index, "total", chunks.Size())
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ticker := time.NewTicker(chunkRequestTimeout)
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defer ticker.Stop()
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s.requestChunk(snapshot, index)
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select {
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case <-chunks.WaitFor(index):
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case <-ticker.C:
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s.requestChunk(snapshot, index)
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case <-ctx.Done():
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return
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}
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ticker.Stop()
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}
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}
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// requestChunk requests a chunk from a peer.
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func (s *syncer) requestChunk(snapshot *snapshot, chunk uint32) {
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peer := s.snapshots.GetPeer(snapshot)
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if peer == nil {
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s.logger.Error("No valid peers found for snapshot", "height", snapshot.Height,
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"format", snapshot.Format, "hash", snapshot.Hash)
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return
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}
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s.logger.Debug("Requesting snapshot chunk", "height", snapshot.Height,
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"format", snapshot.Format, "chunk", chunk, "peer", peer.ID())
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peer.Send(ChunkChannel, mustEncodeMsg(&ssproto.ChunkRequest{
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Height: snapshot.Height,
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Format: snapshot.Format,
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Index: chunk,
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}))
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}
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// verifyApp verifies the sync, checking the app hash and last block height. It returns the
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// app version, which should be returned as part of the initial state.
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func (s *syncer) verifyApp(snapshot *snapshot) (uint64, error) {
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resp, err := s.connQuery.InfoSync(proxy.RequestInfo)
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if err != nil {
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return 0, fmt.Errorf("failed to query ABCI app for appHash: %w", err)
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}
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if !bytes.Equal(snapshot.trustedAppHash, resp.LastBlockAppHash) {
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s.logger.Error("appHash verification failed",
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"expected", fmt.Sprintf("%X", snapshot.trustedAppHash),
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"actual", fmt.Sprintf("%X", resp.LastBlockAppHash))
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return 0, errVerifyFailed
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}
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if uint64(resp.LastBlockHeight) != snapshot.Height {
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s.logger.Error("ABCI app reported unexpected last block height",
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"expected", snapshot.Height, "actual", resp.LastBlockHeight)
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return 0, errVerifyFailed
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}
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s.logger.Info("Verified ABCI app", "height", snapshot.Height,
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"appHash", fmt.Sprintf("%X", snapshot.trustedAppHash))
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return resp.AppVersion, nil
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}
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