always do full walks, not only when there is a sync gap

blockstore/splitstore/splitstore.go

@@ -69,11 +69,6 @@ var (
 	// all active blocks into the hotstore.
 	warmupEpochKey = dstore.NewKey("/splitstore/warmupEpoch")
 
-	// syncGapEpochKey stores the last epoch where a sync gap was detected.
-	// If there is a sync gap after the boundary epoch, compaction will perform
-	// a slower full walk from the current epoch to the boundary epoch
-	syncGapEpochKey = dstore.NewKey("/splitstore/syncGapEpoch")
-
 	// markSetSizeKey stores the current estimate for the mark set size.
 	// this is first computed at warmup and updated in every compaction
 	markSetSizeKey = dstore.NewKey("/splitstore/markSetSize")
@@ -121,7 +116,6 @@ type SplitStore struct {
 	cfg *Config
 
 	baseEpoch   abi.ChainEpoch
-	syncGapEpoch abi.ChainEpoch
 	warmupEpoch abi.ChainEpoch
 	writeEpoch  abi.ChainEpoch
 
@@ -382,17 +376,6 @@ func (s *SplitStore) Start(chain ChainAccessor) error {
 		return xerrors.Errorf("error loading warmup epoch: %w", err)
 	}
 
-	// load sync gap epoch from metadata ds
-	bs, err = s.ds.Get(syncGapEpochKey)
-	switch err {
-	case nil:
-		s.syncGapEpoch = bytesToEpoch(bs)
-
-	case dstore.ErrNotFound:
-	default:
-		return xerrors.Errorf("error loading sync gap epoch: %w", err)
-	}
-
 	// load markSetSize from metadata ds
 	// if none, the splitstore will compute it during warmup and update in every compaction
 	bs, err = s.ds.Get(markSetSizeKey)
@@ -447,11 +430,6 @@ func (s *SplitStore) HeadChange(_, apply []*types.TipSet) error {
 
 	timestamp := time.Unix(int64(curTs.MinTimestamp()), 0)
 	if time.Since(timestamp) > SyncGapTime {
-		err := s.setSyncGapEpoch(epoch)
-		if err != nil {
-			log.Warnf("error saving sync gap epoch: %s", err)
-		}
-
 		// don't attempt compaction before we have caught up syncing
 		return nil
 	}
@@ -469,7 +447,7 @@ func (s *SplitStore) HeadChange(_, apply []*types.TipSet) error {
 			log.Info("compacting splitstore")
 			start := time.Now()
 
-			s.compact(curTs, s.syncGapEpoch)
+			s.compact(curTs)
 
 			log.Infow("compaction done", "took", time.Since(start))
 		}()
@@ -697,7 +675,7 @@ func (s *SplitStore) doWarmup(curTs *types.TipSet) error {
 }
 
 // Compaction/GC Algorithm
-func (s *SplitStore) compact(curTs *types.TipSet, syncGapEpoch abi.ChainEpoch) {
+func (s *SplitStore) compact(curTs *types.TipSet) {
 	var err error
 	if s.markSetSize == 0 {
 		start := time.Now()
@@ -713,7 +691,7 @@ func (s *SplitStore) compact(curTs *types.TipSet, syncGapEpoch abi.ChainEpoch) {
 	}
 
 	start := time.Now()
-	err = s.doCompact(curTs, syncGapEpoch)
+	err = s.doCompact(curTs)
 	took := time.Since(start).Milliseconds()
 	stats.Record(context.Background(), metrics.SplitstoreCompactionTimeSeconds.M(float64(took)/1e3))
 
@@ -740,7 +718,7 @@ func (s *SplitStore) estimateMarkSetSize(curTs *types.TipSet) error {
 	return nil
 }
 
-func (s *SplitStore) doCompact(curTs *types.TipSet, syncGapEpoch abi.ChainEpoch) error {
+func (s *SplitStore) doCompact(curTs *types.TipSet) error {
 	currentEpoch := curTs.Height()
 	boundaryEpoch := currentEpoch - CompactionBoundary
 	coldEpoch := boundaryEpoch - CompactionSlack
@@ -757,30 +735,8 @@ func (s *SplitStore) doCompact(curTs *types.TipSet, syncGapEpoch abi.ChainEpoch)
 	log.Infow("marking reachable blocks", "currentEpoch", currentEpoch, "boundaryEpoch", boundaryEpoch)
 	startMark := time.Now()
 
-	var inclMsgs bool
-	var markTs *types.TipSet
-	if syncGapEpoch > boundaryEpoch {
-		// There is a sync gap that may have caused writes that are logically after the boundary
-		// epoch to be written before the respective head change notification and hence be tracked
-		// at the wrong epoch.
-		// This can happen if the node is offline or falls out of sync for an extended period of time.
-		// In this case we perform a full walk to avoid pathologies with pushing actually hot
-		// objects into the coldstore.
-		markTs = curTs
-		inclMsgs = true
-		log.Infof("sync gap detected at epoch %d; marking from current epoch to boundary epoch", syncGapEpoch)
-	} else {
-		// There is no pathological sync gap, so we can use the much faster single tipset walk at
-		// the boundary epoch.
-		boundaryTs, err := s.chain.GetTipsetByHeight(context.Background(), boundaryEpoch, curTs, true)
-		if err != nil {
-			return xerrors.Errorf("error getting tipset at boundary epoch: %w", err)
-		}
-		markTs = boundaryTs
-	}
-
 	var count int64
-	err = s.walk(markTs, boundaryEpoch, inclMsgs,
+	err = s.walk(curTs, boundaryEpoch, true,
 		func(cid cid.Cid) error {
 			count++
 			return markSet.Mark(cid)
@@ -1100,11 +1056,6 @@ func (s *SplitStore) setBaseEpoch(epoch abi.ChainEpoch) error {
 	return s.ds.Put(baseEpochKey, epochToBytes(epoch))
 }
 
-func (s *SplitStore) setSyncGapEpoch(epoch abi.ChainEpoch) error {
-	s.syncGapEpoch = epoch
-	return s.ds.Put(syncGapEpochKey, epochToBytes(epoch))
-}
-
 func epochToBytes(epoch abi.ChainEpoch) []byte {
 	return uint64ToBytes(uint64(epoch))
 }