CNS-368: fixation store fix refcount and deletions

common/fixation_entry.go

@@ -26,7 +26,9 @@ import (
 //    - GetEntry(index, *entry): get a copy (and reference) of the latest version of an entry
 //    - PutEntry(index, block): drop a reference of a version of an entry
 //    - [TBD] RemoveEntry(index): mark an entry as unavailable for new GetEntry() calls
-//    - GetAllEntryIndex(): get all the entries indices (without versions)
+//    - GetAllEntryIndices(): get all the entries indices (without versions)
+//    - GetAllEntryVersions(index): get all the versions of an entry (for testing)
+//    - AdvanceBlock(): notify of block progress (e.g. BeginBlock) for garbage collection
 //
 // Entry names (index) must contain only visible ascii characters (ascii values 32-125).
 // The ascii 'DEL' invisible character is used internally to terminate the index values
@@ -69,6 +71,7 @@ type FixationStore struct {
 	storeKey sdk.StoreKey
 	cdc      codec.BinaryCodec
 	prefix   string
+	tstore   TimerStore
 }
 
 const (
@@ -136,7 +139,7 @@ func (fs *FixationStore) AppendEntry(
 		fs.setEntryIndex(ctx, safeIndex)
 	} else {
 		// make sure the new entry's block is not smaller than the latest entry's block
-		if block < latestEntry.GetBlock() {
+		if block < latestEntry.Block {
 			details := map[string]string{
 				"latestBlock": strconv.FormatUint(latestEntry.GetBlock(), 10),
 				"block":       strconv.FormatUint(block, 10),
@@ -147,17 +150,11 @@ func (fs *FixationStore) AppendEntry(
 		}
 
 		// if the new entry's block is equal to the latest entry, overwrite the latest entry
-		if block == latestEntry.GetBlock() {
+		if block == latestEntry.Block {
 			return fs.ModifyEntry(ctx, index, block, entryData)
 		}
 
-		// if the old latest entry has refcount of 0, then update its "stale_at" time
-		// TODO: remove this when the latest entry gets its own refcount.
-		if latestEntry.Refcount == 0 {
-			// never overflows because because ctx.BlockHeight is int64
-			latestEntry.StaleAt = uint64(ctx.BlockHeight()) + uint64(types.STALE_ENTRY_TIME)
-			fs.setEntry(ctx, latestEntry)
-		}
+		fs.putEntry(ctx, latestEntry)
 	}
 
 	// marshal the new entry's data
@@ -169,42 +166,72 @@ func (fs *FixationStore) AppendEntry(
 		Block:    block,
 		StaleAt:  math.MaxUint64,
 		Data:     marshaledEntryData,
-		Refcount: 0,
+		Refcount: 1,
 	}
 
 	fs.setEntry(ctx, entry)
-
-	fs.deleteStaleEntries(ctx, safeIndex)
-
 	return nil
 }
 
 func (fs *FixationStore) deleteStaleEntries(ctx sdk.Context, safeIndex string) {
 	fs.assertSanitizedIndex(safeIndex)
 	store := fs.getStore(ctx, safeIndex)
+
 	iterator := sdk.KVStorePrefixIterator(store, []byte{})
 	defer iterator.Close()
 
-	for iterator.Valid() {
-		// umarshal the old entry version
-		var oldEntry types.Entry
-		fs.cdc.MustUnmarshal(iterator.Value(), &oldEntry)
+	// "stale" entry versions are ones that reached refcount zero at least
+	// STALE_TIME blocks ago; they are not visible in lookups, hence may be
+	// discarded. specifically, a stale entry version becomes "elgibile for
+	// removal" , if either it is:
+	//   one that follows a stale entry version, -OR-
+	//   the oldest entry version
+	// rationale: entries are generally valid from their block time until
+	// the block time of the following newer entry. this newer entry marks
+	// the end of the previous entry, and hence may not be removed until
+	// that previous entry gets discarded. keeping the stale entry versions
+	// ensures (future FindEntry) that blocks from that entry onward are
+	// stale (otherwise, a lookup might resolve successfully with an older
+	// non-stale entry version). For this, one - the oldest - marker is
+	// enough, and additional younger markers can be discarded.
+	// for example, consider this situation with versions A through E:
+	//   A(stale), B, C(stale), D(stale), E
+	// in this case, A can be discarded because it is the oldest. C cannot
+	// be discarded because it marks that new blocks are stale (while older
+	// blocks between B and C map to B). D is unneeded as marker because C
+	// is already there, and can be discarded too.
+
+	var removals []uint64
+	safeToDeleteEntry := true // if oldest, or if previous entry was stale
+	safeToDeleteIndex := true // if non of the entry versions was skipped
 
-		iterator.Next()
+	for ; iterator.Valid(); iterator.Next() {
+		// umarshal the old entry version
+		var entry types.Entry
+		fs.cdc.MustUnmarshal(iterator.Value(), &entry)
 
-		// skipping removal of latest version
-		if !iterator.Valid() {
-			break
+		if !entry.IsStale(ctx) {
+			safeToDeleteEntry = false
+			safeToDeleteIndex = false
+			continue
 		}
 
-		// delete stale entries (if they are at the end of the list)
-		if oldEntry.IsStale(ctx) {
-			fs.removeEntry(ctx, oldEntry.GetIndex(), oldEntry.GetBlock())
-		} else {
-			// avoid removal of entries in the middle of the list, because it would
-			// break future lookup that may involve that (stale) entry.
-			break
+		if !safeToDeleteEntry {
+			safeToDeleteEntry = true
+			safeToDeleteIndex = false
+			continue
 		}
+
+		removals = append(removals, entry.Block)
+	}
+
+	for _, block := range removals {
+		fs.removeEntry(ctx, safeIndex, block)
+	}
+
+	if safeToDeleteIndex {
+		// non was skipped - so all were removed: delete the entry index
+		fs.removeEntryIndex(ctx, safeIndex)
 	}
 }
 
@@ -256,7 +283,7 @@ func (fs *FixationStore) getUnmarshaledEntryForBlock(ctx sdk.Context, safeIndex
 		var entry types.Entry
 		fs.cdc.MustUnmarshal(iterator.Value(), &entry)
 
-		if entry.GetBlock() <= block {
+		if entry.Block <= block {
 			if entry.IsStale(ctx) {
 				break
 			}
@@ -308,6 +335,23 @@ func (fs *FixationStore) GetEntry(ctx sdk.Context, index string, entryData codec
 	return true
 }
 
+// putEntry decrements the refcount of an entry and marks for staleness if needed
+func (fs *FixationStore) putEntry(ctx sdk.Context, entry types.Entry) {
+	if entry.Refcount == 0 {
+		panic("Fixation: prefix " + fs.prefix + ": negative refcount safeIndex: " + entry.Index)
+	}
+
+	entry.Refcount -= 1
+
+	if entry.Refcount == 0 {
+		// never overflows because ctx.BlockHeight is int64
+		entry.StaleAt = uint64(ctx.BlockHeight()) + uint64(types.STALE_ENTRY_TIME)
+		fs.tstore.AddTimerByBlockHeight(ctx, entry.StaleAt, entry.Index)
+	}
+
+	fs.setEntry(ctx, entry)
+}
+
 // PutEntry finds the entry by index and block and decrements the refcount
 func (fs *FixationStore) PutEntry(ctx sdk.Context, index string, block uint64) {
 	safeIndex, err := sanitizeIndex(index)
@@ -320,18 +364,12 @@ func (fs *FixationStore) PutEntry(ctx sdk.Context, index string, block uint64) {
 		panic("PutEntry with unknown index: " + index)
 	}
 
-	if entry.Refcount == 0 {
-		panic("PutEntry with refcount zero index: " + index)
+	if entry.Block != block {
+		panic("PutEntry with block mismatch index: " + index +
+			" got " + strconv.Itoa(int(entry.Block)) + " expected " + strconv.Itoa(int(block)))
 	}
 
-	entry.Refcount -= 1
-
-	if entry.Refcount == 0 {
-		// never overflows because because ctx.BlockHeight is int64
-		entry.StaleAt = uint64(ctx.BlockHeight()) + uint64(types.STALE_ENTRY_TIME) - 1
-	}
-
-	fs.setEntry(ctx, entry)
+	fs.putEntry(ctx, entry)
 }
 
 // removeEntry removes an entry from the store
@@ -344,8 +382,15 @@ func (fs *FixationStore) createStoreKey(index string) string {
 	return types.EntryKey + fs.prefix + index
 }
 
+func (fs *FixationStore) AdvanceBlock(ctx sdk.Context) {
+	fs.tstore.Tick(ctx)
+}
+
 // NewFixationStore returns a new FixationStore object
 func NewFixationStore(storeKey sdk.StoreKey, cdc codec.BinaryCodec, prefix string) *FixationStore {
 	fs := FixationStore{storeKey: storeKey, cdc: cdc, prefix: prefix}
+	callback := func(ctx sdk.Context, data string) { fs.deleteStaleEntries(ctx, data) }
+	tstore := NewTimerStore(storeKey, cdc, prefix).WithCallbackByBlockHeight(callback)
+	fs.tstore = *tstore
 	return &fs
 }

common/fixation_entry_index.go

@@ -4,6 +4,7 @@ import (
 	"github.com/cosmos/cosmos-sdk/store/prefix"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/lavanet/lava/common/types"
+	"github.com/lavanet/lava/utils"
 )
 
 // FixationStore manages lists of entries with versions in the store.
@@ -58,11 +59,38 @@ func (fs FixationStore) GetAllEntryIndicesWithPrefix(ctx sdk.Context, prefix str
 	return indexList
 }
 
-// GetAllEntryIndex returns all Entry indices
+// GetAllEntryIndices returns all Entry indices
 func (fs FixationStore) GetAllEntryIndices(ctx sdk.Context) []string {
 	return fs.GetAllEntryIndicesWithPrefix(ctx, "")
 }
 
+// GetAllEntryVersions returns a list of all versions (blocks) of an entry.
+// If stale == true, then the output will include stale versions (for testing).
+func (fs *FixationStore) GetAllEntryVersions(ctx sdk.Context, index string, stale bool) (blocks []uint64) {
+	safeIndex, err := sanitizeIndex(index)
+	if err != nil {
+		details := map[string]string{"index": index}
+		utils.LavaError(ctx, ctx.Logger(), "GetAllEntryVersions", details, "invalid non-ascii entry")
+		return nil
+	}
+
+	store := fs.getStore(ctx, safeIndex)
+
+	iterator := sdk.KVStorePrefixIterator(store, []byte{})
+	defer iterator.Close()
+
+	for ; iterator.Valid(); iterator.Next() {
+		var entry types.Entry
+		fs.cdc.MustUnmarshal(iterator.Value(), &entry)
+		if !stale && entry.IsStale(ctx) {
+			continue
+		}
+		blocks = append(blocks, entry.Block)
+	}
+
+	return blocks
+}
+
 func (fs FixationStore) createEntryIndexStoreKey() string {
 	return types.EntryIndexKey + fs.prefix
 }