Update etcdserver and client to support DowngradeVersionTest request

Signed-off-by: Benjamin Wang <benjamin.ahrtr@gmail.com>

client/v3/client_test.go

@@ -476,6 +476,10 @@ func (mm mockMaintenance) Downgrade(ctx context.Context, action DowngradeAction,
 	return nil, nil
 }
 
+func (mm mockMaintenance) DowngradeVersionTest(ctx context.Context, version string) (*DowngradeVersionTestResponse, error) {
+	return nil, nil
+}
+
 type mockAuthServer struct {
 	*etcdserverpb.UnimplementedAuthServer
 }

client/v3/maintenance.go

@@ -35,7 +35,8 @@ type (
 	MoveLeaderResponse pb.MoveLeaderResponse
 	DowngradeResponse  pb.DowngradeResponse
 
-	DowngradeAction pb.DowngradeRequest_DowngradeAction
+	DowngradeAction              pb.DowngradeRequest_DowngradeAction
+	DowngradeVersionTestResponse pb.DowngradeVersionTestResponse
 )
 
 const (
@@ -87,6 +88,10 @@ type Maintenance interface {
 	// on the cluster version.
 	// Supported since etcd 3.5.
 	Downgrade(ctx context.Context, action DowngradeAction, version string) (*DowngradeResponse, error)
+
+	// DowngradeVersionTest is for test only! It enables users (test cases)
+	// to send a DowngradeVersionTestRequest to etcdserver.
+	DowngradeVersionTest(ctx context.Context, version string) (*DowngradeVersionTestResponse, error)
 }
 
 // SnapshotResponse is aggregated response from the snapshot stream.
@@ -348,3 +353,8 @@ func (m *maintenance) Downgrade(ctx context.Context, action DowngradeAction, ver
 	resp, err := m.remote.Downgrade(ctx, &pb.DowngradeRequest{Action: actionType, Version: version}, m.callOpts...)
 	return (*DowngradeResponse)(resp), ContextError(ctx, err)
 }
+
+func (m *maintenance) DowngradeVersionTest(ctx context.Context, version string) (*DowngradeVersionTestResponse, error) {
+	resp, err := m.remote.DowngradeVersionTest(ctx, &pb.DowngradeVersionTestRequest{Ver: version})
+	return (*DowngradeVersionTestResponse)(resp), ContextError(ctx, err)
+}

client/v3/retry.go

@@ -233,6 +233,10 @@ type retryAuthClient struct {
 	ac pb.AuthClient
 }
 
+func (rmc *retryMaintenanceClient) DowngradeVersionTest(ctx context.Context, in *pb.DowngradeVersionTestRequest, opts ...grpc.CallOption) (resp *pb.DowngradeVersionTestResponse, err error) {
+	return rmc.mc.DowngradeVersionTest(ctx, in, opts...)
+}
+
 // RetryAuthClient implements a AuthClient.
 func RetryAuthClient(c *Client) pb.AuthClient {
 	return &retryAuthClient{

server/etcdserver/api/v3rpc/maintenance.go

@@ -55,6 +55,7 @@ type Alarmer interface {
 
 type Downgrader interface {
 	Downgrade(ctx context.Context, dr *pb.DowngradeRequest) (*pb.DowngradeResponse, error)
+	DowngradeVersionTest(ctx context.Context, r *pb.DowngradeVersionTestRequest) (*pb.DowngradeVersionTestResponse, error)
 }
 
 type LeaderTransferrer interface {
@@ -296,6 +297,16 @@ func (ms *maintenanceServer) Downgrade(ctx context.Context, r *pb.DowngradeReque
 	return resp, nil
 }
 
+func (ms *maintenanceServer) DowngradeVersionTest(ctx context.Context, r *pb.DowngradeVersionTestRequest) (*pb.DowngradeVersionTestResponse, error) {
+	resp, err := ms.d.DowngradeVersionTest(ctx, r)
+	if err != nil {
+		return nil, togRPCError(err)
+	}
+	resp.Header = &pb.ResponseHeader{}
+	ms.hdr.fill(resp.Header)
+	return resp, nil
+}
+
 type authMaintenanceServer struct {
 	*maintenanceServer
 	*AuthAdmin
@@ -355,3 +366,11 @@ func (ams *authMaintenanceServer) Downgrade(ctx context.Context, r *pb.Downgrade
 
 	return ams.maintenanceServer.Downgrade(ctx, r)
 }
+
+func (ams *authMaintenanceServer) DowngradeVersionTest(ctx context.Context, r *pb.DowngradeVersionTestRequest) (*pb.DowngradeVersionTestResponse, error) {
+	if err := ams.isPermitted(ctx); err != nil {
+		return nil, togRPCError(err)
+	}
+
+	return ams.maintenanceServer.DowngradeVersionTest(ctx, r)
+}

server/etcdserver/server.go

@@ -2006,7 +2006,7 @@ func (s *EtcdServer) applyEntryNormal(e *raftpb.Entry, shouldApplyV3 membership.
 }
 
 func (s *EtcdServer) applyInternalRaftRequest(r *pb.InternalRaftRequest, shouldApplyV3 membership.ShouldApplyV3) *apply.Result {
-	if r.ClusterVersionSet == nil && r.ClusterMemberAttrSet == nil && r.DowngradeInfoSet == nil {
+	if r.ClusterVersionSet == nil && r.ClusterMemberAttrSet == nil && r.DowngradeInfoSet == nil && r.DowngradeVersionTest == nil {
 		if !shouldApplyV3 {
 			return nil
 		}
@@ -2029,6 +2029,10 @@ func (s *EtcdServer) applyInternalRaftRequest(r *pb.InternalRaftRequest, shouldA
 	case r.DowngradeInfoSet != nil:
 		op = "DowngradeInfoSet" // Implemented in 3.5.x
 		membershipApplier.DowngradeInfoSet(r.DowngradeInfoSet, shouldApplyV3)
+	case r.DowngradeVersionTest != nil:
+		op = "DowngradeVersionTest"
+		// do nothing, we are good as long as a WAL record
+		// has already been generated for this request.
 	default:
 		s.lg.Panic("not implemented apply", zap.Stringer("raft-request", r))
 		return nil

server/etcdserver/v3_server.go

@@ -1044,6 +1044,16 @@ func (s *EtcdServer) downgradeEnable(ctx context.Context, r *pb.DowngradeRequest
 	return &resp, nil
 }
 
+// DowngradeVersionTest is for test only! We intentionally send
+// a raft request so that a related WAL record can be generated.
+func (s *EtcdServer) DowngradeVersionTest(ctx context.Context, r *pb.DowngradeVersionTestRequest) (*pb.DowngradeVersionTestResponse, error) {
+	resp, err := s.raftRequest(ctx, pb.InternalRaftRequest{DowngradeVersionTest: r})
+	if err != nil {
+		return nil, err
+	}
+	return resp.(*pb.DowngradeVersionTestResponse), nil
+}
+
 func (s *EtcdServer) downgradeCancel(ctx context.Context) (*pb.DowngradeResponse, error) {
 	err := s.Version().DowngradeCancel(ctx)
 	if err != nil {

server/proxy/grpcproxy/adapter/maintenance_client_adapter.go

@@ -56,6 +56,10 @@ func (s *mts2mtc) Downgrade(ctx context.Context, r *pb.DowngradeRequest, opts ..
 	return s.mts.Downgrade(ctx, r)
 }
 
+func (s *mts2mtc) DowngradeVersionTest(ctx context.Context, r *pb.DowngradeVersionTestRequest, opts ...grpc.CallOption) (*pb.DowngradeVersionTestResponse, error) {
+	return s.mts.DowngradeVersionTest(ctx, r)
+}
+
 func (s *mts2mtc) Snapshot(ctx context.Context, in *pb.SnapshotRequest, opts ...grpc.CallOption) (pb.Maintenance_SnapshotClient, error) {
 	cs := newPipeStream(ctx, func(ss chanServerStream) error {
 		return s.mts.Snapshot(in, &ss2scServerStream{ss})

server/proxy/grpcproxy/maintenance.go

@@ -86,3 +86,7 @@ func (mp *maintenanceProxy) MoveLeader(ctx context.Context, r *pb.MoveLeaderRequ
 func (mp *maintenanceProxy) Downgrade(ctx context.Context, r *pb.DowngradeRequest) (*pb.DowngradeResponse, error) {
 	return mp.maintenanceClient.Downgrade(ctx, r)
 }
+
+func (mp *maintenanceProxy) DowngradeVersionTest(ctx context.Context, r *pb.DowngradeVersionTestRequest) (*pb.DowngradeVersionTestResponse, error) {
+	return mp.maintenanceClient.DowngradeVersionTest(ctx, r)
+}