diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/cache/cache.go b/vendor/github.com/syndtr/goleveldb/leveldb/cache/cache.go
index a287d0e5e..f28e1bdea 100644
--- a/vendor/github.com/syndtr/goleveldb/leveldb/cache/cache.go
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/cache/cache.go
@@ -511,18 +511,12 @@ func (r *Cache) EvictAll() {
 	}
 }
 
-// Close closes the 'cache map' and releases all 'cache node'.
+// Close closes the 'cache map' and forcefully releases all 'cache node'.
 func (r *Cache) Close() error {
 	r.mu.Lock()
 	if !r.closed {
 		r.closed = true
 
-		if r.cacher != nil {
-			if err := r.cacher.Close(); err != nil {
-				return err
-			}
-		}
-
 		h := (*mNode)(r.mHead)
 		h.initBuckets()
 
@@ -541,10 +535,37 @@ func (r *Cache) Close() error {
 				for _, f := range n.onDel {
 					f()
 				}
+				n.onDel = nil
 			}
 		}
 	}
 	r.mu.Unlock()
+
+	// Avoid deadlock.
+	if r.cacher != nil {
+		if err := r.cacher.Close(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// CloseWeak closes the 'cache map' and evict all 'cache node' from cacher, but
+// unlike Close it doesn't forcefully releases 'cache node'.
+func (r *Cache) CloseWeak() error {
+	r.mu.Lock()
+	if !r.closed {
+		r.closed = true
+	}
+	r.mu.Unlock()
+
+	// Avoid deadlock.
+	if r.cacher != nil {
+		r.cacher.EvictAll()
+		if err := r.cacher.Close(); err != nil {
+			return err
+		}
+	}
 	return nil
 }
 
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/db.go b/vendor/github.com/syndtr/goleveldb/leveldb/db.go
index eb6abd0fb..1aed20943 100644
--- a/vendor/github.com/syndtr/goleveldb/leveldb/db.go
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/db.go
@@ -1062,6 +1062,8 @@ func (db *DB) Close() error {
 	if db.journal != nil {
 		db.journal.Close()
 		db.journalWriter.Close()
+		db.journal = nil
+		db.journalWriter = nil
 	}
 
 	if db.writeDelayN > 0 {
@@ -1077,15 +1079,11 @@ func (db *DB) Close() error {
 		if err1 := db.closer.Close(); err == nil {
 			err = err1
 		}
+		db.closer = nil
 	}
 
-	// NIL'ing pointers.
-	db.s = nil
-	db.mem = nil
-	db.frozenMem = nil
-	db.journal = nil
-	db.journalWriter = nil
-	db.closer = nil
+	// Clear memdbs.
+	db.clearMems()
 
 	return err
 }
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/db_state.go b/vendor/github.com/syndtr/goleveldb/leveldb/db_state.go
index 40f454da1..b7de09e15 100644
--- a/vendor/github.com/syndtr/goleveldb/leveldb/db_state.go
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/db_state.go
@@ -67,12 +67,11 @@ func (db *DB) sampleSeek(ikey internalKey) {
 }
 
 func (db *DB) mpoolPut(mem *memdb.DB) {
-	defer func() {
-		recover()
-	}()
-	select {
-	case db.memPool <- mem:
-	default:
+	if !db.isClosed() {
+		select {
+		case db.memPool <- mem:
+		default:
+		}
 	}
 }
 
@@ -101,6 +100,12 @@ func (db *DB) mpoolDrain() {
 			default:
 			}
 		case _, _ = <-db.closeC:
+			ticker.Stop()
+			// Make sure the pool is drained.
+			select {
+			case <-db.memPool:
+			case <-time.After(time.Second):
+			}
 			close(db.memPool)
 			return
 		}
@@ -148,10 +153,11 @@ func (db *DB) newMem(n int) (mem *memDB, err error) {
 func (db *DB) getMems() (e, f *memDB) {
 	db.memMu.RLock()
 	defer db.memMu.RUnlock()
-	if db.mem == nil {
+	if db.mem != nil {
+		db.mem.incref()
+	} else if !db.isClosed() {
 		panic("nil effective mem")
 	}
-	db.mem.incref()
 	if db.frozenMem != nil {
 		db.frozenMem.incref()
 	}
@@ -162,10 +168,11 @@ func (db *DB) getMems() (e, f *memDB) {
 func (db *DB) getEffectiveMem() *memDB {
 	db.memMu.RLock()
 	defer db.memMu.RUnlock()
-	if db.mem == nil {
+	if db.mem != nil {
+		db.mem.incref()
+	} else if !db.isClosed() {
 		panic("nil effective mem")
 	}
-	db.mem.incref()
 	return db.mem
 }
 
@@ -200,6 +207,14 @@ func (db *DB) dropFrozenMem() {
 	db.memMu.Unlock()
 }
 
+// Clear mems ptr; used by DB.Close().
+func (db *DB) clearMems() {
+	db.memMu.Lock()
+	db.mem = nil
+	db.frozenMem = nil
+	db.memMu.Unlock()
+}
+
 // Set closed flag; return true if not already closed.
 func (db *DB) setClosed() bool {
 	return atomic.CompareAndSwapUint32(&db.closed, 0, 1)
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/db_test.go b/vendor/github.com/syndtr/goleveldb/leveldb/db_test.go
index 37d08eb86..6eaf0d558 100644
--- a/vendor/github.com/syndtr/goleveldb/leveldb/db_test.go
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/db_test.go
@@ -116,7 +116,6 @@ func (h *dbHarness) closeDB() {
 		if err := h.closeDB0(); err != nil {
 			h.t.Error("Close: got error: ", err)
 		}
-		h.db = nil
 	}
 	h.stor.CloseCheck()
 	runtime.GC()
@@ -2827,3 +2826,82 @@ func TestDB_BulkInsertDelete(t *testing.T) {
 		t.Fatalf("too many uncompacted tables: %d (%s)", tot, h.getTablesPerLevel())
 	}
 }
+
+func TestDB_GracefulClose(t *testing.T) {
+	runtime.GOMAXPROCS(4)
+	h := newDbHarnessWopt(t, &opt.Options{
+		DisableLargeBatchTransaction: true,
+		Compression:                  opt.NoCompression,
+		CompactionTableSize:          1 * opt.MiB,
+		WriteBuffer:                  1 * opt.MiB,
+	})
+	defer h.close()
+
+	var closeWait sync.WaitGroup
+
+	// During write.
+	n := 0
+	closing := false
+	for i := 0; i < 1000000; i++ {
+		if !closing && h.totalTables() > 3 {
+			t.Logf("close db during write, index=%d", i)
+			closeWait.Add(1)
+			go func() {
+				h.closeDB()
+				closeWait.Done()
+			}()
+			closing = true
+		}
+		if err := h.db.Put([]byte(fmt.Sprintf("%09d", i)), []byte(fmt.Sprintf("VAL-%09d", i)), h.wo); err != nil {
+			t.Logf("Put error: %s (expected)", err)
+			n = i
+			break
+		}
+	}
+	closeWait.Wait()
+
+	// During read.
+	h.openDB()
+	closing = false
+	for i := 0; i < n; i++ {
+		if !closing && i > n/2 {
+			t.Logf("close db during read, index=%d", i)
+			closeWait.Add(1)
+			go func() {
+				h.closeDB()
+				closeWait.Done()
+			}()
+			closing = true
+		}
+		if _, err := h.db.Get([]byte(fmt.Sprintf("%09d", i)), h.ro); err != nil {
+			t.Logf("Get error: %s (expected)", err)
+			break
+		}
+	}
+	closeWait.Wait()
+
+	// During iterate.
+	h.openDB()
+	closing = false
+	iter := h.db.NewIterator(nil, h.ro)
+	for i := 0; iter.Next(); i++ {
+		if len(iter.Key()) == 0 || len(iter.Value()) == 0 {
+			t.Error("Key or value has zero length")
+		}
+		if !closing {
+			t.Logf("close db during iter, index=%d", i)
+			closeWait.Add(1)
+			go func() {
+				h.closeDB()
+				closeWait.Done()
+			}()
+			closing = true
+		}
+		time.Sleep(time.Millisecond)
+	}
+	if err := iter.Error(); err != nil {
+		t.Logf("Iter error: %s (expected)", err)
+	}
+	iter.Release()
+	closeWait.Wait()
+}
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/db_write.go b/vendor/github.com/syndtr/goleveldb/leveldb/db_write.go
index 5576761fe..37acb3f3a 100644
--- a/vendor/github.com/syndtr/goleveldb/leveldb/db_write.go
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/db_write.go
@@ -73,6 +73,10 @@ func (db *DB) flush(n int) (mdb *memDB, mdbFree int, err error) {
 		v := db.s.version()
 		defer v.release()
 		mdb = db.getEffectiveMem()
+		if mdb == nil {
+			err = ErrClosed
+			return false
+		}
 		defer func() {
 			if retry {
 				mdb.decref()
@@ -310,6 +314,9 @@ func (db *DB) CompactRange(r util.Range) error {
 
 	// Check for overlaps in memdb.
 	mdb := db.getEffectiveMem()
+	if mdb == nil {
+		return ErrClosed
+	}
 	defer mdb.decref()
 	if isMemOverlaps(db.s.icmp, mdb.DB, r.Start, r.Limit) {
 		// Memdb compaction.
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/session.go b/vendor/github.com/syndtr/goleveldb/leveldb/session.go
index b0d3fef1d..c9679b6b5 100644
--- a/vendor/github.com/syndtr/goleveldb/leveldb/session.go
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/session.go
@@ -87,7 +87,7 @@ func (s *session) close() {
 	}
 	s.manifest = nil
 	s.manifestWriter = nil
-	s.stVersion = nil
+	s.setVersion(&version{s: s, closing: true})
 }
 
 // Release session lock.
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/table.go b/vendor/github.com/syndtr/goleveldb/leveldb/table.go
index 310ba6c22..81d18a531 100644
--- a/vendor/github.com/syndtr/goleveldb/leveldb/table.go
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/table.go
@@ -434,7 +434,7 @@ func (t *tOps) close() {
 	t.bpool.Close()
 	t.cache.Close()
 	if t.bcache != nil {
-		t.bcache.Close()
+		t.bcache.CloseWeak()
 	}
 }
 
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/table/reader.go b/vendor/github.com/syndtr/goleveldb/leveldb/table/reader.go
index ae61bece9..1edf4e2ba 100644
--- a/vendor/github.com/syndtr/goleveldb/leveldb/table/reader.go
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/table/reader.go
@@ -888,7 +888,7 @@ func (r *Reader) Find(key []byte, filtered bool, ro *opt.ReadOptions) (rkey, val
 	return r.find(key, filtered, ro, false)
 }
 
-// Find finds key that is greater than or equal to the given key.
+// FindKey finds key that is greater than or equal to the given key.
 // It returns ErrNotFound if the table doesn't contain such key.
 // If filtered is true then the nearest 'block' will be checked against
 // 'filter data' (if present) and will immediately return ErrNotFound if
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/version.go b/vendor/github.com/syndtr/goleveldb/leveldb/version.go
index d274eeff2..c60f12c20 100644
--- a/vendor/github.com/syndtr/goleveldb/leveldb/version.go
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/version.go
@@ -34,7 +34,8 @@ type version struct {
 
 	cSeek unsafe.Pointer
 
-	ref int
+	closing bool
+	ref     int
 	// Succeeding version.
 	next *version
 }
@@ -131,6 +132,10 @@ func (v *version) walkOverlapping(aux tFiles, ikey internalKey, f func(level int
 }
 
 func (v *version) get(aux tFiles, ikey internalKey, ro *opt.ReadOptions, noValue bool) (value []byte, tcomp bool, err error) {
+	if v.closing {
+		return nil, false, ErrClosed
+	}
+
 	ukey := ikey.ukey()
 
 	var (
diff --git a/vendor/manifest b/vendor/manifest
index 63ca6c919..a5af4f3a2 100644
--- a/vendor/manifest
+++ b/vendor/manifest
@@ -233,7 +233,7 @@
 		{
 			"importpath": "github.com/syndtr/goleveldb",
 			"repository": "https://github.com/syndtr/goleveldb",
-			"revision": "ab8b5dcf1042e818ab68e770d465112a899b668e",
+			"revision": "6ae1797c0b42b9323fc27ff7dcf568df88f2f33d",
 			"branch": "master"
 		},
 		{