feat:splitstore:retain tipset references in hot store (#9960)

* Retain tipset reference

Co-authored-by: zenground0 <ZenGround0@users.noreply.github.com>

blockstore/splitstore/splitstore_compact.go

@@ -905,6 +905,10 @@ func (s *SplitStore) walkChain(ts *types.TipSet, inclState, inclMsgs abi.ChainEp
 	walkCnt := new(int64)
 	scanCnt := new(int64)
 
+	tsRef := func(blkCids []cid.Cid) (cid.Cid, error) {
+		return types.NewTipSetKey(blkCids...).Cid()
+	}
+
 	stopWalk := func(_ cid.Cid) error { return errStopWalk }
 
 	walkBlock := func(c cid.Cid) error {
@@ -926,11 +930,19 @@ func (s *SplitStore) walkChain(ts *types.TipSet, inclState, inclMsgs abi.ChainEp
 		err = s.view(c, func(data []byte) error {
 			return hdr.UnmarshalCBOR(bytes.NewBuffer(data))
 		})
-
 		if err != nil {
 			return xerrors.Errorf("error unmarshaling block header (cid: %s): %w", c, err)
 		}
 
+		// tipset CID references are retained
+		pRef, err := tsRef(hdr.Parents)
+		if err != nil {
+			return xerrors.Errorf("error computing cid reference to parent tipset")
+		}
+		if err := s.walkObjectIncomplete(pRef, visitor, fHot, stopWalk); err != nil {
+			return xerrors.Errorf("error walking parent tipset cid reference")
+		}
+
 		// message are retained if within the inclMsgs boundary
 		if hdr.Height >= inclMsgs && hdr.Height > 0 {
 			if inclMsgs < inclState {
@@ -981,6 +993,15 @@ func (s *SplitStore) walkChain(ts *types.TipSet, inclState, inclMsgs abi.ChainEp
 		return nil
 	}
 
+	// retain ref to chain head
+	hRef, err := tsRef(ts.Cids())
+	if err != nil {
+		return xerrors.Errorf("error computing cid reference to parent tipset")
+	}
+	if err := s.walkObjectIncomplete(hRef, visitor, fHot, stopWalk); err != nil {
+		return xerrors.Errorf("error walking parent tipset cid reference")
+	}
+
 	for len(toWalk) > 0 {
 		// walking can take a while, so check this with every opportunity
 		if err := s.checkClosing(); err != nil {

itests/splitstore_test.go

@@ -249,6 +249,49 @@ func TestMessagesMode(t *testing.T) {
 	assert.True(g.t, g.Exists(ctx, garbageM), "Garbage message not found in splitstore")
 }
 
+func TestCompactRetainsTipSetRef(t *testing.T) {
+	ctx := context.Background()
+	// disable sync checking because efficient itests require that the node is out of sync : /
+	splitstore.CheckSyncGap = false
+	opts := []interface{}{kit.MockProofs(), kit.SplitstoreDiscard()}
+	full, genesisMiner, ens := kit.EnsembleMinimal(t, opts...)
+	bm := ens.InterconnectAll().BeginMining(4 * time.Millisecond)[0]
+	_ = genesisMiner
+	_ = bm
+
+	check, err := full.ChainHead(ctx)
+	require.NoError(t, err)
+	e := check.Height()
+	checkRef, err := check.Key().Cid()
+	require.NoError(t, err)
+	assert.True(t, ipldExists(ctx, t, checkRef, full)) // reference to tipset key should be persisted before compaction
+
+	// Determine index of compaction that covers tipset "check" and wait for compaction
+	for {
+		bm.Pause()
+		if splitStoreCompacting(ctx, t, full) {
+			bm.Restart()
+			time.Sleep(1 * time.Second)
+		} else {
+			break
+		}
+	}
+	lastCompactionEpoch := splitStoreBaseEpoch(ctx, t, full)
+	garbageCompactionIndex := splitStoreCompactionIndex(ctx, t, full) + 1
+	boundary := lastCompactionEpoch + splitstore.CompactionThreshold - splitstore.CompactionBoundary
+
+	for e > boundary {
+		boundary += splitstore.CompactionThreshold - splitstore.CompactionBoundary
+		garbageCompactionIndex++
+	}
+	bm.Restart()
+
+	// wait for compaction to occur
+	waitForCompaction(ctx, t, garbageCompactionIndex, full)
+	assert.True(t, ipldExists(ctx, t, checkRef, full)) // reference to tipset key should be persisted after compaction
+	bm.Stop()
+}
+
 func waitForCompaction(ctx context.Context, t *testing.T, cIdx int64, n *kit.TestFullNode) {
 	for {
 		if splitStoreCompactionIndex(ctx, t, n) >= cIdx {
@@ -307,6 +350,16 @@ func splitStorePruneIndex(ctx context.Context, t *testing.T, n *kit.TestFullNode
 	return pruneIndex
 }
 
+func ipldExists(ctx context.Context, t *testing.T, c cid.Cid, n *kit.TestFullNode) bool {
+	_, err := n.ChainReadObj(ctx, c)
+	if ipld.IsNotFound(err) {
+		return false
+	} else if err != nil {
+		t.Fatalf("ChainReadObj failure on existence check: %s", err)
+	}
+	return true
+}
+
 // Create on chain unreachable garbage for a network to exercise splitstore
 // one garbage cid created at a time
 //