feat(statesync): implement statesync spec for the new approach (#663)

* feat: add ordered_map.go

* feat: introduce a new approach of a state sync

* refactor: modify kvstore to be compatible with a new statesync approach

abci/example/kvstore/kvstore.go

@@ -493,7 +493,7 @@ func (app *Application) LoadSnapshotChunk(_ context.Context, req *abci.RequestLo
 	app.mu.Lock()
 	defer app.mu.Unlock()
 
-	chunk, err := app.snapshots.LoadChunk(req.Height, req.Format, req.Chunk)
+	chunk, err := app.snapshots.LoadChunk(req.Height, req.Version, req.ChunkId)
 	if err != nil {
 		return &abci.ResponseLoadSnapshotChunk{}, err
 	}
@@ -523,7 +523,11 @@ func (app *Application) ApplySnapshotChunk(_ context.Context, req *abci.RequestA
 	if app.offerSnapshot == nil {
 		return &abci.ResponseApplySnapshotChunk{}, fmt.Errorf("no restore in progress")
 	}
-	app.offerSnapshot.addChunk(int(req.Index), req.Chunk)
+
+	resp := &abci.ResponseApplySnapshotChunk{
+		Result:     abci.ResponseApplySnapshotChunk_ACCEPT,
+		NextChunks: app.offerSnapshot.addChunk(req.ChunkId, req.Chunk),
+	}
 
 	if app.offerSnapshot.isFull() {
 		chunks := app.offerSnapshot.bytes()
@@ -538,11 +542,10 @@ func (app *Application) ApplySnapshotChunk(_ context.Context, req *abci.RequestA
 			"snapshot_height", app.offerSnapshot.snapshot.Height,
 			"snapshot_apphash", app.offerSnapshot.appHash,
 		)
+		resp.Result = abci.ResponseApplySnapshotChunk_COMPLETE_SNAPSHOT
 		app.offerSnapshot = nil
 	}
 
-	resp := &abci.ResponseApplySnapshotChunk{Result: abci.ResponseApplySnapshotChunk_ACCEPT}
-
 	app.logger.Debug("ApplySnapshotChunk", "resp", resp)
 	return resp, nil
 }
@@ -556,7 +559,9 @@ func (app *Application) createSnapshot() error {
 	if err != nil {
 		return fmt.Errorf("create snapshot: %w", err)
 	}
-	app.logger.Info("created state sync snapshot", "height", height, "apphash", app.LastCommittedState.GetAppHash())
+	app.logger.Info("created state sync snapshot",
+		"height", height,
+		"apphash", app.LastCommittedState.GetAppHash())
 	err = app.snapshots.Prune(maxSnapshotCount)
 	if err != nil {
 		return fmt.Errorf("prune snapshots: %w", err)

abci/example/kvstore/kvstore_test.go

@@ -493,24 +493,20 @@ func TestSnapshots(t *testing.T) {
 	})
 	require.NoError(t, err)
 	assert.Equal(t, types.ResponseOfferSnapshot_ACCEPT, respOffer.Result)
+	loaded, err := app.LoadSnapshotChunk(ctx, &types.RequestLoadSnapshotChunk{
+		Height:  recentSnapshot.Height,
+		ChunkId: recentSnapshot.Hash,
+		Version: recentSnapshot.Version,
+	})
+	require.NoError(t, err)
 
-	for chunk := uint32(0); chunk < recentSnapshot.Chunks; chunk++ {
-		loaded, err := app.LoadSnapshotChunk(ctx, &types.RequestLoadSnapshotChunk{
-			Height: recentSnapshot.Height,
-			Chunk:  chunk,
-			Format: recentSnapshot.Format,
-		})
-		require.NoError(t, err)
-
-		applied, err := dstApp.ApplySnapshotChunk(ctx, &types.RequestApplySnapshotChunk{
-			Index:  chunk,
-			Chunk:  loaded.Chunk,
-			Sender: "app",
-		})
-		require.NoError(t, err)
-		assert.Equal(t, types.ResponseApplySnapshotChunk_ACCEPT, applied.Result)
-	}
-
+	applied, err := dstApp.ApplySnapshotChunk(ctx, &types.RequestApplySnapshotChunk{
+		ChunkId: recentSnapshot.Hash,
+		Chunk:   loaded.Chunk,
+		Sender:  "app",
+	})
+	require.NoError(t, err)
+	assert.Equal(t, types.ResponseApplySnapshotChunk_COMPLETE_SNAPSHOT, applied.Result)
 	infoResp, err := dstApp.Info(ctx, &types.RequestInfo{})
 	require.NoError(t, err)
 	assertRespInfo(t, int64(recentSnapshot.Height), appHashes[snapshotHeight], *infoResp)

abci/example/kvstore/snapshots.go

@@ -3,10 +3,10 @@ package kvstore
 
 import (
 	"bytes"
+	"encoding/hex"
 	"encoding/json"
 	"errors"
 	"fmt"
-	"math"
 	"os"
 	"path/filepath"
 
@@ -15,6 +15,7 @@ import (
 	abci "github.com/tendermint/tendermint/abci/types"
 	"github.com/tendermint/tendermint/crypto"
 	tmbytes "github.com/tendermint/tendermint/libs/bytes"
+	"github.com/tendermint/tendermint/libs/ds"
 )
 
 const (
@@ -27,11 +28,17 @@ const (
 // SnapshotStore stores state sync snapshots. Snapshots are stored simply as
 // JSON files, and chunks are generated on-the-fly by splitting the JSON data
 // into fixed-size chunks.
-type SnapshotStore struct {
-	sync.RWMutex
-	dir      string
-	metadata []abci.Snapshot
-}
+type (
+	SnapshotStore struct {
+		sync.RWMutex
+		dir      string
+		metadata []abci.Snapshot
+	}
+	chunkItem struct {
+		Data         []byte   `json:"data"`
+		NextChunkIDs [][]byte `json:"nextChunkIDs"`
+	}
+)
 
 // NewSnapshotStore creates a new snapshot store.
 func NewSnapshotStore(dir string) (*SnapshotStore, error) {
@@ -49,7 +56,7 @@ func NewSnapshotStore(dir string) (*SnapshotStore, error) {
 // called internally on construction.
 func (s *SnapshotStore) loadMetadata() error {
 	file := filepath.Join(s.dir, "metadata.json")
-	metadata := []abci.Snapshot{}
+	var metadata []abci.Snapshot
 
 	bz, err := os.ReadFile(file)
 	switch {
@@ -96,10 +103,9 @@ func (s *SnapshotStore) Create(state State) (abci.Snapshot, error) {
 	}
 	height := state.GetHeight()
 	snapshot := abci.Snapshot{
-		Height: uint64(height),
-		Format: 1,
-		Hash:   crypto.Checksum(bz),
-		Chunks: byteChunks(bz),
+		Height:  uint64(height),
+		Version: 1,
+		Hash:    crypto.Checksum(bz),
 	}
 	err = os.WriteFile(filepath.Join(s.dir, fmt.Sprintf("%v.json", height)), bz, 0644)
 	if err != nil {
@@ -152,16 +158,18 @@ func (s *SnapshotStore) List() ([]*abci.Snapshot, error) {
 }
 
 // LoadChunk loads a snapshot chunk.
-func (s *SnapshotStore) LoadChunk(height uint64, format uint32, chunk uint32) ([]byte, error) {
+func (s *SnapshotStore) LoadChunk(height uint64, version uint32, chunkID []byte) ([]byte, error) {
 	s.RLock()
 	defer s.RUnlock()
 	for _, snapshot := range s.metadata {
-		if snapshot.Height == height && snapshot.Format == format {
-			bz, err := os.ReadFile(filepath.Join(s.dir, fmt.Sprintf("%v.json", height)))
+		if snapshot.Height == height && snapshot.Version == version {
+			bz, err := os.ReadFile(filepath.Join(s.dir, fmt.Sprintf("%d.json", height)))
 			if err != nil {
 				return nil, err
 			}
-			return byteChunk(bz, chunk), nil
+			chunks := makeChunks(bz, snapshotChunkSize)
+			item := makeChunkItem(chunks, chunkID)
+			return json.Marshal(item)
 		}
 	}
 	return nil, nil
@@ -170,54 +178,79 @@ func (s *SnapshotStore) LoadChunk(height uint64, format uint32, chunk uint32) ([
 type offerSnapshot struct {
 	snapshot *abci.Snapshot
 	appHash  tmbytes.HexBytes
-	chunks   [][]byte
-	chunkCnt int
+	chunks   *ds.OrderedMap[string, []byte]
 }
 
 func newOfferSnapshot(snapshot *abci.Snapshot, appHash tmbytes.HexBytes) *offerSnapshot {
 	return &offerSnapshot{
 		snapshot: snapshot,
 		appHash:  appHash,
-		chunks:   make([][]byte, snapshot.Chunks),
-		chunkCnt: 0,
+		chunks:   ds.NewOrderedMap[string, []byte](),
 	}
 }
 
-func (s *offerSnapshot) addChunk(index int, chunk []byte) {
-	if s.chunks[index] != nil {
-		return
+func (s *offerSnapshot) addChunk(chunkID tmbytes.HexBytes, data []byte) [][]byte {
+	chunkIDStr := chunkID.String()
+	if s.chunks.Has(chunkIDStr) {
+		return nil
 	}
-	s.chunks[index] = chunk
-	s.chunkCnt++
+	var item chunkItem
+	err := json.Unmarshal(data, &item)
+	if err != nil {
+		panic("failed to decode a chunk data: " + err.Error())
+	}
+	s.chunks.Put(chunkIDStr, item.Data)
+	return item.NextChunkIDs
 }
 
 func (s *offerSnapshot) isFull() bool {
-	return s.chunkCnt == int(s.snapshot.Chunks)
+	return bytes.Equal(crypto.Checksum(s.bytes()), s.snapshot.Hash)
 }
 
 func (s *offerSnapshot) bytes() []byte {
+	chunks := s.chunks.Values()
 	buf := bytes.NewBuffer(nil)
-	for _, chunk := range s.chunks {
+	for _, chunk := range chunks {
 		buf.Write(chunk)
 	}
 	return buf.Bytes()
 }
 
-// byteChunk returns the chunk at a given index from the full byte slice.
-func byteChunk(bz []byte, index uint32) []byte {
-	start := int(index * snapshotChunkSize)
-	end := int((index + 1) * snapshotChunkSize)
-	switch {
-	case start >= len(bz):
-		return nil
-	case end >= len(bz):
-		return bz[start:]
-	default:
-		return bz[start:end]
+// makeChunkItem returns the chunk at a given index from the full byte slice.
+func makeChunkItem(chunks *ds.OrderedMap[string, []byte], chunkID []byte) chunkItem {
+	chunkIDStr := hex.EncodeToString(chunkID)
+	val, ok := chunks.Get(chunkIDStr)
+	if !ok {
+		panic("chunk not found")
 	}
+	chunkIDs := chunks.Keys()
+	ci := chunkItem{Data: val}
+	i := 0
+	for ; i < len(chunkIDs) && chunkIDs[i] != chunkIDStr; i++ {
+	}
+	if i+1 < len(chunkIDs) {
+		data, err := hex.DecodeString(chunkIDs[i+1])
+		if err != nil {
+			panic(err)
+		}
+		ci.NextChunkIDs = [][]byte{data}
+	}
+	return ci
 }
 
-// byteChunks calculates the number of chunks in the byte slice.
-func byteChunks(bz []byte) uint32 {
-	return uint32(math.Ceil(float64(len(bz)) / snapshotChunkSize))
+func makeChunks(bz []byte, chunkSize int) *ds.OrderedMap[string, []byte] {
+	chunks := ds.NewOrderedMap[string, []byte]()
+	totalHash := hex.EncodeToString(crypto.Checksum(bz))
+	key := totalHash
+	for i := 0; i < len(bz); i += chunkSize {
+		j := i + chunkSize
+		if j > len(bz) {
+			j = len(bz)
+		}
+		if i > 1 {
+			key = hex.EncodeToString(crypto.Checksum(bz[i:j]))
+		}
+		chunks.Put(key, append([]byte(nil), bz[i:j]...))
+	}
+	return chunks
 }

abci/example/kvstore/snapshots_test.go

@@ -0,0 +1,37 @@
+package kvstore
+
+import (
+	"encoding/hex"
+	"math/rand"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestChunkItem(t *testing.T) {
+	const size = 64
+	chunks := makeChunks(makeBytes(1032), size)
+	keys := chunks.Keys()
+	values := chunks.Values()
+	for i, key := range keys {
+		chunkID, err := hex.DecodeString(key)
+		require.NoError(t, err)
+		item := makeChunkItem(chunks, chunkID)
+		require.Equal(t, values[i], item.Data)
+		if i+1 < len(keys) {
+			nextChunkID, err := hex.DecodeString(keys[i+1])
+			require.NoError(t, err)
+			require.Equal(t, [][]byte{nextChunkID}, item.NextChunkIDs)
+		} else {
+			require.Nil(t, item.NextChunkIDs)
+		}
+	}
+}
+
+func makeBytes(size int) []byte {
+	bz := make([]byte, size)
+	for i := 0; i < size; i++ {
+		bz[i] = byte(rand.Int63n(256))
+	}
+	return bz
+}