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