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use deep object walking for more robust handling of transactional references

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This commit is contained in:
vyzo 2021-07-04 18:37:53 +03:00
parent 1f02428225
commit 680af8eb09
1 changed files with 193 additions and 116 deletions
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181
blockstore/splitstore/splitstore.go
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@ -143,6 +143,7 @@ type SplitStore struct {
// protection for concurrent read/writes during compaction
txnLk sync.RWMutex
txnActive bool
txnBoundaryEpoch abi.ChainEpoch
txnEnv MarkSetEnv
txnProtect MarkSet
txnMarkSet MarkSet
@ -600,11 +601,16 @@ func (s *SplitStore) trackTxnRef(c cid.Cid, recursive bool) error {
// we have finished marking, protect the reference
if !recursive {
// shallow protect
return s.txnProtect.Mark(c)
}
// it's a recursive reference in vm context, protect links if they are not in the markset already
return s.walkObject(c, cid.NewSet(), func(c cid.Cid) error {
// we do a deep walk to visit the children first, short-circuiting if the parent has been marked.
// the deep walk is necessary as internal references may be missing, e.g. because a defunct object
// got recreated by the VM.
return s.walkObjectDeep(c, cid.NewSet(),
func(c cid.Cid) error {
mark, err := s.txnMarkSet.Has(c)
if err != nil {
return xerrors.Errorf("error checking mark set for %s: %w", c, err)
@ -615,15 +621,19 @@ func (s *SplitStore) trackTxnRef(c cid.Cid, recursive bool) error {
return errStopWalk
}
live, err := s.txnProtect.Has(c)
// old block reference -- see comment in doCompact about the necessity of this
isOldBlock, err := s.isOldBlockHeader(c, s.txnBoundaryEpoch)
if err != nil {
return xerrors.Errorf("error checking portected set for %s: %w", c, err)
return xerrors.Errorf("error checking object type for %s: %w", c, err)
}
if live {
if isOldBlock {
return errStopWalk
}
return nil
},
func(c cid.Cid) error {
// this occurs check is necessary because cold objects are purged in arbitrary order
has, err := s.hot.Has(c)
if err != nil {
@ -636,7 +646,12 @@ func (s *SplitStore) trackTxnRef(c cid.Cid, recursive bool) error {
return errMissingObject
}
// mark it
// mark it in *both* sets, so that we can short-circuit a concurrent walk.
err = s.txnMarkSet.Mark(c)
if err != nil {
return xerrors.Errorf("error marking %s: %w", c, err)
}
return s.txnProtect.Mark(c)
})
}
@ -657,7 +672,7 @@ func (s *SplitStore) trackTxnRefMany(cids []cid.Cid) error {
return nil
}
// we have finished marking, protect the refs
// we have finished marking, shallow protect the refs
for _, c := range cids {
err := s.txnProtect.Mark(c)
if err != nil {
@ -794,6 +809,7 @@ func (s *SplitStore) doCompact(curTs *types.TipSet) error {
s.txnLk.Lock()
s.txnRefs = make(map[cid.Cid]struct{})
s.txnActive = true
s.txnBoundaryEpoch = boundaryEpoch
s.txnLk.Unlock()
// 1. mark reachable objects by walking the chain from the current epoch to the boundary epoch
@ -839,11 +855,13 @@ func (s *SplitStore) doCompact(curTs *types.TipSet) error {
}()
// 1.1 Update markset for references created during marking
log.Info("updating mark set for live references")
var missing []cid.Cid
if len(txnRefs) > 0 {
log.Info("updating mark set for live references", "refs", len(txnRefs))
startMark = time.Now()
walked := cid.NewSet()
count = 0
var missing []cid.Cid
for c := range txnRefs {
mark, err := markSet.Has(c)
if err != nil {
@ -854,7 +872,10 @@ func (s *SplitStore) doCompact(curTs *types.TipSet) error {
continue
}
err = s.walkObject(c, walked, func(c cid.Cid) error {
// we have to do a deep walk here, as an early mark would stick even if there are
// missing references that haven't been written yet!
err = s.walkObjectDeep(c, walked,
func(c cid.Cid) error {
mark, err := markSet.Has(c)
if err != nil {
return xerrors.Errorf("error checking markset for %s: %w", c, err)
@ -864,6 +885,26 @@ func (s *SplitStore) doCompact(curTs *types.TipSet) error {
return errStopWalk
}
// we also short-circuit on old blocks, as these can come from a network request
// and cause us to fail because we have purged its consistituents (or missing from
// the beginning in case of snapshot sync, e.g. parent message receipts or old messages)
// if these blocks are on our chain, they would have been marked but they might be
// from a fork.
//
// Ideally, we would have API options to preclude us from trcking references to such
// objects, but we don't so we have to do this check
isOldBlock, err := s.isOldBlockHeader(c, boundaryEpoch)
if err != nil {
return xerrors.Errorf("error checking object type for %s: %w", c, err)
}
if isOldBlock {
return errStopWalk
}
return nil
},
func(c cid.Cid) error {
count++
return markSet.Mark(c)
})
@ -877,23 +918,26 @@ func (s *SplitStore) doCompact(curTs *types.TipSet) error {
}
}
}
log.Infow("update marking set done", "took", time.Since(startMark), "marked", count, "missing", len(missing))
// 1.2 rescan for missing objects (after waiting a minute), as they might have not been copied yet
// by the vm
log.Infow("update marking set done", "took", time.Since(startMark), "marked", count, "missing", len(missing))
}
// 1.2 rescan for missing objects (after waiting a bit), as they might have not been copied yet
// by the vm at the time of the update walk.
if len(missing) > 0 {
try := 0
log.Info("rescanning for missing objects")
startMark = time.Now()
count = 0
for len(missing) > 0 {
if try > maxMissingScanRetries {
return xerrors.Errorf("failed to fully scan transactional refs; %d missing objects", len(missing))
return xerrors.Errorf("failed to fully scan transactional refs; %d missing objects after %d attempts", len(missing), try)
}
// discard previous walk short-cuts
walked = cid.NewSet()
walked := cid.NewSet()
towalk := missing
missing = nil
try++
@ -903,43 +947,33 @@ func (s *SplitStore) doCompact(curTs *types.TipSet) error {
time.Sleep(time.Minute)
for _, c := range towalk {
// we can't reliably check the markset and short-circuit this time, we have to do full walks
// because the object was previously visited top-to-bottom, with root DAGs short circuiting
// their children.
// but we *can* short-circuit on the txn protection filter, as this implies that the object
// will be protected from purge.
err = s.walkObject(c, walked, func(c cid.Cid) error {
mark, err := s.txnProtect.Has(c)
// deep walk here again, as we are concerned about internal references not having been written
err = s.walkObjectDeep(c, walked,
func(c cid.Cid) error {
mark, err := markSet.Has(c)
if err != nil {
return xerrors.Errorf("error checking protected set for %s: %w", c, err)
return xerrors.Errorf("error checking mark set for %s: %w", c, err)
}
if mark {
return errStopWalk
}
// mark it
err = markSet.Mark(c)
// see comment above for this check
isOldBlock, err := s.isOldBlockHeader(c, boundaryEpoch)
if err != nil {
return err
return xerrors.Errorf("error checking object type for %s: %w", c, err)
}
// we also short-circuit in case of a block header, as it may cause us to walk the
// entire chain because of a network request (and fail if we were synced form a snapshot
// because of missing messages or receipts!)
// this is necessary because we don't have interface options to signal network request
// initiated API calls; when we have that, we can stop tracking those references and
// we can remove this check.
isBlock, err := s.isBlockHeader(c)
if err != nil {
return xerrors.Errorf("error checking object type for %s: %W", c, err)
}
if isBlock {
if isOldBlock {
return errStopWalk
}
return nil
},
func(c cid.Cid) error {
count++
return markSet.Mark(c)
})
if err != nil {
@ -953,7 +987,7 @@ func (s *SplitStore) doCompact(curTs *types.TipSet) error {
}
}
log.Infow("rescanning done", "took", time.Since(startMark))
log.Infow("rescanning done", "took", time.Since(startMark), "marked", count)
}
// 2. iterate through the hotstore to collect cold objects
@ -1112,20 +1146,6 @@ func (s *SplitStore) walkChain(ts *types.TipSet, boundary abi.ChainEpoch, inclMs
return nil
}
func (s *SplitStore) isBlockHeader(c cid.Cid) (isBlock bool, err error) {
if c.Prefix().Codec != cid.DagCBOR {
return false, nil
}
err = s.view(c, func(data []byte) error {
var hdr types.BlockHeader
isBlock = hdr.UnmarshalCBOR(bytes.NewBuffer(data)) == nil
return nil
})
return isBlock, err
}
func (s *SplitStore) walkObject(c cid.Cid, walked *cid.Set, f func(cid.Cid) error) error {
if !walked.Visit(c) {
return nil
@ -1164,6 +1184,47 @@ func (s *SplitStore) walkObject(c cid.Cid, walked *cid.Set, f func(cid.Cid) erro
return nil
}
// like walkObject, but it visits leaves first, with pre invoked at the parent node to control
// whether the walk should stop
func (s *SplitStore) walkObjectDeep(c cid.Cid, walked *cid.Set,
pre func(cid.Cid) error, f func(cid.Cid) error) error {
if !walked.Visit(c) {
return nil
}
if err := pre(c); err != nil {
if err == errStopWalk {
return nil
}
return err
}
if c.Prefix().Codec != cid.DagCBOR {
return f(c)
}
var links []cid.Cid
err := s.view(c, func(data []byte) error {
return cbg.ScanForLinks(bytes.NewReader(data), func(c cid.Cid) {
links = append(links, c)
})
})
if err != nil {
return xerrors.Errorf("error scanning linked block (cid: %s): %w", c, err)
}
for _, c := range links {
err := s.walkObjectDeep(c, walked, pre, f)
if err != nil {
return xerrors.Errorf("error walking link (cid: %s): %w", c, err)
}
}
return f(c)
}
// internal version used by walk
func (s *SplitStore) view(cid cid.Cid, cb func([]byte) error) error {
err := s.hot.View(cid, cb)
@ -1176,6 +1237,22 @@ func (s *SplitStore) view(cid cid.Cid, cb func([]byte) error) error {
}
}
func (s *SplitStore) isOldBlockHeader(c cid.Cid, epoch abi.ChainEpoch) (isOldBlock bool, err error) {
if c.Prefix().Codec != cid.DagCBOR {
return false, nil
}
err = s.view(c, func(data []byte) error {
var hdr types.BlockHeader
if hdr.UnmarshalCBOR(bytes.NewBuffer(data)) == nil {
isOldBlock = hdr.Height < epoch
}
return nil
})
return isOldBlock, err
}
func (s *SplitStore) moveColdBlocks(cold []cid.Cid) error {
batch := make([]blocks.Block, 0, batchSize)