swarm/storage: release chunk storage after stop swarm (#3651)

closes #3650

swarm/storage/dbstore.go

@@ -408,7 +408,7 @@ func (s *DbStore) getEntryCnt() uint64 {
 	return s.entryCnt
 }
 
-func (s *DbStore) close() {
+func (s *DbStore) Close() {
 	s.db.Close()
 }
 

swarm/storage/dbstore_test.go

@@ -38,7 +38,7 @@ func initDbStore(t *testing.T) *DbStore {
 
 func testDbStore(l int64, branches int64, t *testing.T) {
 	m := initDbStore(t)
-	defer m.close()
+	defer m.Close()
 	testStore(m, l, branches, t)
 }
 
@@ -64,7 +64,7 @@ func TestDbStore2_100_(t *testing.T) {
 
 func TestDbStoreNotFound(t *testing.T) {
 	m := initDbStore(t)
-	defer m.close()
+	defer m.Close()
 	_, err := m.Get(ZeroKey)
 	if err != notFound {
 		t.Errorf("Expected notFound, got %v", err)
@@ -73,7 +73,7 @@ func TestDbStoreNotFound(t *testing.T) {
 
 func TestDbStoreSyncIterator(t *testing.T) {
 	m := initDbStore(t)
-	defer m.close()
+	defer m.Close()
 	keys := []Key{
 		Key(common.Hex2Bytes("0000000000000000000000000000000000000000000000000000000000000000")),
 		Key(common.Hex2Bytes("4000000000000000000000000000000000000000000000000000000000000000")),

swarm/storage/dpa.go

@@ -237,3 +237,8 @@ func (self *dpaChunkStore) Put(entry *Chunk) {
 	self.n++
 	self.netStore.Put(chunk)
 }
+
+// Close chunk store
+func (self *dpaChunkStore) Close() {
+	return
+}

swarm/storage/localstore.go

@@ -72,3 +72,8 @@ func (self *LocalStore) Get(key Key) (chunk *Chunk, err error) {
 	self.memStore.Put(chunk)
 	return
 }
+
+// Close local store
+func (self *LocalStore) Close() {
+	return
+}

swarm/storage/memstore.go

@@ -314,3 +314,8 @@ func (s *MemStore) removeOldest() {
 		}
 	}
 }
+
+// Close memstore
+func (s *MemStore) Close() {
+	return
+}

swarm/storage/netstore.go

@@ -132,3 +132,8 @@ func (self *NetStore) Get(key Key) (*Chunk, error) {
 	go self.cloud.Retrieve(chunk)
 	return chunk, nil
 }
+
+// Close netstore
+func (self *NetStore) Close() {
+	return
+}

swarm/storage/types.go

@@ -167,6 +167,7 @@ The ChunkStore interface is implemented by :
 type ChunkStore interface {
 	Put(*Chunk) // effectively there is no error even if there is an error
 	Get(Key) (*Chunk, error)
+	Close()
 }
 
 /*