From 7b8447a95a67af4623530dbabd1132969f61ac96 Mon Sep 17 00:00:00 2001
From: vyzo <vyzo@hackzen.org>
Date: Sun, 30 Jan 2022 19:00:52 +0200
Subject: [PATCH] reinstante waitForMissingRefs

---
 blockstore/splitstore/splitstore_compact.go | 86 +++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/blockstore/splitstore/splitstore_compact.go b/blockstore/splitstore/splitstore_compact.go
index 57a0c7f38..7d84a75a6 100644
--- a/blockstore/splitstore/splitstore_compact.go
+++ b/blockstore/splitstore/splitstore_compact.go
@@ -521,6 +521,15 @@ func (s *SplitStore) doCompact(curTs *types.TipSet) error {
 		return err
 	}
 
+	// now that we have collected cold objects, check for missing references from transactional i/o
+	// and disable further collection of such references (they will not be acted upon as we can't
+	// possibly delete objects we didn't have when we were collecting cold objects)
+	s.waitForMissingRefs(markSet)
+
+	if err := s.checkClosing(); err != nil {
+		return err
+	}
+
 	coldr, err := NewColdSetReader(s.coldSetPath())
 	if err != nil {
 		return xerrors.Errorf("error opening coldset: %w", err)
@@ -1180,3 +1189,80 @@ func (s *SplitStore) completePurge(coldr *ColdSetReader, checkpoint *Checkpoint,
 
 	return nil
 }
+
+// I really don't like having this code, but we seem to have some occasional DAG references with
+// missing constituents. During testing in mainnet *some* of these references *sometimes* appeared
+// after a little bit.
+// We need to figure out where they are coming from and eliminate that vector, but until then we
+// have this gem[TM].
+// My best guess is that they are parent message receipts or yet to be computed state roots; magik
+// thinks the cause may be block validation.
+func (s *SplitStore) waitForMissingRefs(markSet MarkSet) {
+	s.txnLk.Lock()
+	missing := s.txnMissing
+	s.txnMissing = nil
+	s.txnLk.Unlock()
+
+	if len(missing) == 0 {
+		return
+	}
+
+	log.Info("waiting for missing references")
+	start := time.Now()
+	count := 0
+	defer func() {
+		log.Infow("waiting for missing references done", "took", time.Since(start), "marked", count)
+	}()
+
+	for i := 0; i < 3 && len(missing) > 0; i++ {
+		if err := s.checkClosing(); err != nil {
+			return
+		}
+
+		wait := time.Duration(i) * time.Minute
+		log.Infof("retrying for %d missing references in %s (attempt: %d)", len(missing), wait, i+1)
+		if wait > 0 {
+			time.Sleep(wait)
+		}
+
+		towalk := missing
+		visitor := newTmpVisitor()
+		missing = make(map[cid.Cid]struct{})
+
+		for c := range towalk {
+			err := s.walkObjectIncomplete(c, visitor,
+				func(c cid.Cid) error {
+					if isUnitaryObject(c) {
+						return errStopWalk
+					}
+
+					visit, err := markSet.Visit(c)
+					if err != nil {
+						return xerrors.Errorf("error visiting object: %w", err)
+					}
+
+					if !visit {
+						return errStopWalk
+					}
+
+					count++
+					return nil
+				},
+				func(c cid.Cid) error {
+					missing[c] = struct{}{}
+					return errStopWalk
+				})
+
+			if err != nil {
+				log.Warnf("error marking: %s", err)
+			}
+		}
+	}
+
+	if len(missing) > 0 {
+		log.Warnf("still missing %d references", len(missing))
+		for c := range missing {
+			log.Warnf("unresolved missing reference: %s", c)
+		}
+	}
+}