[#1680] service/object: Fail all operations in maintenance mode

Storage node should not provide NeoFS Object API service when it is
under maintenance.

Declare `Common` service that unifies behavior of all object operations.
The implementation pre-checks if node is under maintenance and returns
`apistatus.NodeUnderMaintenance` if so. Use `Common` service as a first
logical processor in object service pipeline.

Signed-off-by: Leonard Lyubich <ctulhurider@gmail.com>

pkg/services/object/common.go

@@ -0,0 +1,91 @@
+package object
+
+import (
+	"context"
+
+	objectV2 "github.com/nspcc-dev/neofs-api-go/v2/object"
+	apistatus "github.com/nspcc-dev/neofs-sdk-go/client/status"
+)
+
+// NodeState is storage node state processed by Object service.
+type NodeState interface {
+	// IsMaintenance checks if node is under maintenance. Node MUST NOT serve
+	// local object operations. Node MUST respond with apistatus.NodeUnderMaintenance
+	// error if IsMaintenance returns true.
+	IsMaintenance() bool
+}
+
+// Common is an Object API ServiceServer which encapsulates logic spread to all
+// object operations.
+//
+// If underlying NodeState.IsMaintenance returns true, all operations are
+// immediately failed with apistatus.NodeUnderMaintenance.
+type Common struct {
+	state NodeState
+
+	nextHandler ServiceServer
+}
+
+// Init initializes the Common instance.
+func (x *Common) Init(state NodeState, nextHandler ServiceServer) {
+	x.state = state
+	x.nextHandler = nextHandler
+}
+
+var errMaintenance apistatus.NodeUnderMaintenance
+
+func (x *Common) Get(req *objectV2.GetRequest, stream GetObjectStream) error {
+	if x.state.IsMaintenance() {
+		return errMaintenance
+	}
+
+	return x.nextHandler.Get(req, stream)
+}
+
+func (x *Common) Put(ctx context.Context) (PutObjectStream, error) {
+	if x.state.IsMaintenance() {
+		return nil, errMaintenance
+	}
+
+	return x.nextHandler.Put(ctx)
+}
+
+func (x *Common) Head(ctx context.Context, req *objectV2.HeadRequest) (*objectV2.HeadResponse, error) {
+	if x.state.IsMaintenance() {
+		return nil, errMaintenance
+	}
+
+	return x.nextHandler.Head(ctx, req)
+}
+
+func (x *Common) Search(req *objectV2.SearchRequest, stream SearchStream) error {
+	if x.state.IsMaintenance() {
+		return errMaintenance
+	}
+
+	return x.nextHandler.Search(req, stream)
+}
+
+func (x *Common) Delete(ctx context.Context, req *objectV2.DeleteRequest) (*objectV2.DeleteResponse, error) {
+	if x.state.IsMaintenance() {
+		return nil, errMaintenance
+	}
+
+	return x.nextHandler.Delete(ctx, req)
+}
+
+func (x *Common) GetRange(req *objectV2.GetRangeRequest, stream GetObjectRangeStream) error {
+	if x.state.IsMaintenance() {
+		return errMaintenance
+	}
+
+	return x.nextHandler.GetRange(req, stream)
+}
+
+func (x *Common) GetRangeHash(ctx context.Context, req *objectV2.GetRangeHashRequest) (*objectV2.GetRangeHashResponse, error) {
+	if x.state.IsMaintenance() {
+		return nil, errMaintenance
+	}
+
+	return x.nextHandler.GetRangeHash(ctx, req)
+}