Embed: In case KVStoreHash verification fails, close the backend.

In case of failed verification, the server used to keep opened backend
(so the file was locked on OS level).

server/embed/etcd.go

@@ -229,6 +229,9 @@ func StartEtcd(inCfg *Config) (e *Etcd, err error) {
 		if err = e.Server.CheckInitialHashKV(); err != nil {
 			// set "EtcdServer" to nil, so that it does not block on "EtcdServer.Close()"
 			// (nothing to close since rafthttp transports have not been started)
+
+			e.cfg.logger.Error("checkInitialHashKV failed", zap.Error(err))
+			e.Server.Cleanup()
 			e.Server = nil
 			return e, err
 		}

server/etcdserver/server.go

@@ -1028,7 +1028,6 @@ func (s *EtcdServer) run() {
 		close(s.stopping)
 		s.wgMu.Unlock()
 		s.cancel()
-
 		sched.Stop()
 
 		// wait for gouroutines before closing raft so wal stays open
@@ -1040,23 +1039,8 @@ func (s *EtcdServer) run() {
 		// by adding a peer after raft stops the transport
 		s.r.stop()
 
-		// kv, lessor and backend can be nil if running without v3 enabled
-		// or running unit tests.
-		if s.lessor != nil {
-			s.lessor.Stop()
-		}
-		if s.kv != nil {
-			s.kv.Close()
-		}
-		if s.authStore != nil {
-			s.authStore.Close()
-		}
-		if s.be != nil {
-			s.be.Close()
-		}
-		if s.compactor != nil {
-			s.compactor.Stop()
-		}
+		s.Cleanup()
+
 		close(s.done)
 	}()
 
@@ -1112,6 +1096,28 @@ func (s *EtcdServer) run() {
 	}
 }
 
+// Cleanup removes allocated objects by EtcdServer.NewServer in
+// situation that EtcdServer::Start was not called (that takes care of cleanup).
+func (s *EtcdServer) Cleanup() {
+	// kv, lessor and backend can be nil if running without v3 enabled
+	// or running unit tests.
+	if s.lessor != nil {
+		s.lessor.Stop()
+	}
+	if s.kv != nil {
+		s.kv.Close()
+	}
+	if s.authStore != nil {
+		s.authStore.Close()
+	}
+	if s.be != nil {
+		s.be.Close()
+	}
+	if s.compactor != nil {
+		s.compactor.Stop()
+	}
+}
+
 func (s *EtcdServer) applyAll(ep *etcdProgress, apply *apply) {
 	s.applySnapshot(ep, apply)
 	s.applyEntries(ep, apply)