Faster synchronization with asynchronous deletion of old checkpoints

db/kvdb/kvdb.go

@@ -49,6 +49,8 @@ type KVDB struct {
 	CurrentIdx   common.Idx
 	CurrentBatch common.BatchNum
 	m            sync.Mutex
+	mutexDelOld  sync.Mutex
+	wg           sync.WaitGroup
 	last         *Last
 }
 
@@ -444,10 +446,15 @@ func (k *KVDB) MakeCheckpoint() error {
 			return tracerr.Wrap(err)
 		}
 	}
-	// delete old checkpoints
-	if err := k.deleteOldCheckpoints(); err != nil {
-		return tracerr.Wrap(err)
-	}
+
+	k.wg.Add(1)
+	go func() {
+		delErr := k.DeleteOldCheckpoints()
+		if delErr != nil {
+			log.Errorw("delete old checkpoints failed", "err", delErr)
+		}
+		k.wg.Done()
+	}()
 
 	return nil
 }
@@ -509,9 +516,12 @@ func (k *KVDB) ListCheckpoints() ([]int, error) {
 	return checkpoints, nil
 }
 
-// deleteOldCheckpoints deletes old checkpoints when there are more than
+// DeleteOldCheckpoints deletes old checkpoints when there are more than
 // `s.keep` checkpoints
-func (k *KVDB) deleteOldCheckpoints() error {
+func (k *KVDB) DeleteOldCheckpoints() error {
+	k.mutexDelOld.Lock()
+	defer k.mutexDelOld.Unlock()
+
 	list, err := k.ListCheckpoints()
 	if err != nil {
 		return tracerr.Wrap(err)
@@ -584,4 +594,6 @@ func (k *KVDB) Close() {
 	if k.last != nil {
 		k.last.close()
 	}
+	// wait for deletion of old checkpoints
+	k.wg.Wait()
 }

db/kvdb/kvdb_test.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
+	"sync"
 	"testing"
 
 	"github.com/hermeznetwork/hermez-node/common"
@@ -190,12 +191,67 @@ func TestDeleteOldCheckpoints(t *testing.T) {
 	for i := 0; i < numCheckpoints; i++ {
 		err = db.MakeCheckpoint()
 		require.NoError(t, err)
+		err = db.DeleteOldCheckpoints()
+		require.NoError(t, err)
 		checkpoints, err := db.ListCheckpoints()
 		require.NoError(t, err)
 		assert.LessOrEqual(t, len(checkpoints), keep)
 	}
 }
 
+func TestConcurrentDeleteOldCheckpoints(t *testing.T) {
+	dir, err := ioutil.TempDir("", "tmpdb")
+	require.NoError(t, err)
+	defer require.NoError(t, os.RemoveAll(dir))
+
+	keep := 16
+	db, err := NewKVDB(Config{Path: dir, Keep: keep})
+	require.NoError(t, err)
+
+	numCheckpoints := 32
+
+	var wg sync.WaitGroup
+	wg.Add(numCheckpoints)
+
+	// do checkpoints and check that we never have more than `keep`
+	// checkpoints.
+	// 1 async DeleteOldCheckpoint after 1 MakeCheckpoint
+	for i := 0; i < numCheckpoints; i++ {
+		err = db.MakeCheckpoint()
+		require.NoError(t, err)
+		go func() {
+			err = db.DeleteOldCheckpoints()
+			require.NoError(t, err)
+			wg.Done()
+		}()
+	}
+	wg.Wait()
+	checkpoints, err := db.ListCheckpoints()
+	require.NoError(t, err)
+	assert.LessOrEqual(t, len(checkpoints), keep)
+
+	wg.Add(numCheckpoints)
+
+	// do checkpoints and check that we never have more than `keep`
+	// checkpoints
+	// 32 concurrent DeleteOldCheckpoint after 32 MakeCheckpoint
+	for i := 0; i < numCheckpoints; i++ {
+		err = db.MakeCheckpoint()
+		require.NoError(t, err)
+	}
+	for i := 0; i < numCheckpoints; i++ {
+		go func() {
+			err = db.DeleteOldCheckpoints()
+			require.NoError(t, err)
+			wg.Done()
+		}()
+	}
+	wg.Wait()
+	checkpoints, err = db.ListCheckpoints()
+	require.NoError(t, err)
+	assert.LessOrEqual(t, len(checkpoints), keep)
+}
+
 func TestGetCurrentIdx(t *testing.T) {
 	dir, err := ioutil.TempDir("", "tmpdb")
 	require.NoError(t, err)

db/statedb/statedb.go

@@ -227,6 +227,12 @@ func (s *StateDB) MakeCheckpoint() error {
 	return s.db.MakeCheckpoint()
 }
 
+// DeleteOldCheckpoints deletes old checkpoints when there are more than
+// `cfg.keep` checkpoints
+func (s *StateDB) DeleteOldCheckpoints() error {
+	return s.db.DeleteOldCheckpoints()
+}
+
 // CurrentBatch returns the current in-memory CurrentBatch of the StateDB.db
 func (s *StateDB) CurrentBatch() common.BatchNum {
 	return s.db.CurrentBatch

db/statedb/statedb_test.go

@@ -7,6 +7,7 @@ import (
 	"math/big"
 	"os"
 	"strings"
+	"sync"
 	"testing"
 
 	ethCommon "github.com/ethereum/go-ethereum/common"
@@ -588,6 +589,48 @@ func TestDeleteOldCheckpoints(t *testing.T) {
 	for i := 0; i < numCheckpoints; i++ {
 		err = sdb.MakeCheckpoint()
 		require.NoError(t, err)
+		err := sdb.DeleteOldCheckpoints()
+		require.NoError(t, err)
+		checkpoints, err := sdb.db.ListCheckpoints()
+		require.NoError(t, err)
+		assert.LessOrEqual(t, len(checkpoints), keep)
+	}
+}
+
+// TestConcurrentDeleteOldCheckpoints performs almost the same test than
+// kvdb/kvdb_test.go TestConcurrentDeleteOldCheckpoints, but over the StateDB
+func TestConcurrentDeleteOldCheckpoints(t *testing.T) {
+	dir, err := ioutil.TempDir("", "tmpdb")
+	require.NoError(t, err)
+	defer require.NoError(t, os.RemoveAll(dir))
+
+	keep := 16
+	sdb, err := NewStateDB(Config{Path: dir, Keep: keep, Type: TypeSynchronizer, NLevels: 32})
+	require.NoError(t, err)
+
+	numCheckpoints := 32
+	// do checkpoints and check that we never have more than `keep`
+	// checkpoints
+	for i := 0; i < numCheckpoints; i++ {
+		err = sdb.MakeCheckpoint()
+		require.NoError(t, err)
+		wg := sync.WaitGroup{}
+		n := 10
+		wg.Add(n)
+		for j := 0; j < n; j++ {
+			go func() {
+				err := sdb.DeleteOldCheckpoints()
+				require.NoError(t, err)
+				checkpoints, err := sdb.db.ListCheckpoints()
+				require.NoError(t, err)
+				assert.LessOrEqual(t, len(checkpoints), keep)
+				wg.Done()
+			}()
+			_, err := sdb.db.ListCheckpoints()
+			// only checking here for absence of errors, not the count of checkpoints
+			require.NoError(t, err)
+		}
+		wg.Wait()
 		checkpoints, err := sdb.db.ListCheckpoints()
 		require.NoError(t, err)
 		assert.LessOrEqual(t, len(checkpoints), keep)