proto: Add LimitError as a structured errorjc-limit-error-proto

When Gitaly enforces a limit, either due rate limiting or concurrency
limiting, it needs to be able to return an error to its clients to
provide context into why it failed so that clients can then inform its
callers of why the call failed.

Changelog: added

3 files changed, 114 insertions, 13 deletions

diff --git a/proto/errors.proto b/proto/errors.proto
index 8e0b2298b..101c58bf7 100644
--- a/proto/errors.proto
+++ b/proto/errors.proto
@@ -4,6 +4,8 @@ package gitaly;
 
 option go_package = "gitlab.com/gitlab-org/gitaly/v14/proto/go/gitalypb";
 
+import "google/protobuf/duration.proto";
+
 // AccessCheckError is an error returned by GitLab's `/internal/allowed`
 // endpoint.
 message AccessCheckError {
@@ -43,3 +45,12 @@ message ResolveRevisionError {
   // Revision is the name of the revision that was tried to be resolved.
   bytes revision = 1;
 }
+
+// LimitError is an error returned when Gitaly enforces request limits.
+message LimitError {
+	// ErrorMessage provides context into why a limit was enforced.
+	string error_message = 1;
+	// RetryAfter provides the duration after which a retry is safe.
+	// 0 indicates non-retryable.
+	google.protobuf.Duration retry_after = 2;
+}
diff --git a/proto/go/gitalypb/errors.pb.go b/proto/go/gitalypb/errors.pb.go
index a228353dc..6443c2825 100644
--- a/proto/go/gitalypb/errors.pb.go
+++ b/proto/go/gitalypb/errors.pb.go
@@ -9,6 +9,7 @@ package gitalypb
 import (
 	protoreflect "google.golang.org/protobuf/reflect/protoreflect"
 	protoimpl "google.golang.org/protobuf/runtime/protoimpl"
+	durationpb "google.golang.org/protobuf/types/known/durationpb"
 	reflect "reflect"
 	sync "sync"
 )
@@ -267,11 +268,72 @@ func (x *ResolveRevisionError) GetRevision() []byte {
 	return nil
 }
 
+// LimitError is an error returned when Gitaly enforces request limits.
+type LimitError struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// ErrorMessage provides context into why a limit was enforced.
+	ErrorMessage string `protobuf:"bytes,1,opt,name=error_message,json=errorMessage,proto3" json:"error_message,omitempty"`
+	// RetryAfter provides the duration after which a retry is safe.
+	// 0 indicates non-retryable.
+	RetryAfter *durationpb.Duration `protobuf:"bytes,2,opt,name=retry_after,json=retryAfter,proto3" json:"retry_after,omitempty"`
+}
+
+func (x *LimitError) Reset() {
+	*x = LimitError{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_errors_proto_msgTypes[4]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *LimitError) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*LimitError) ProtoMessage() {}
+
+func (x *LimitError) ProtoReflect() protoreflect.Message {
+	mi := &file_errors_proto_msgTypes[4]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use LimitError.ProtoReflect.Descriptor instead.
+func (*LimitError) Descriptor() ([]byte, []int) {
+	return file_errors_proto_rawDescGZIP(), []int{4}
+}
+
+func (x *LimitError) GetErrorMessage() string {
+	if x != nil {
+		return x.ErrorMessage
+	}
+	return ""
+}
+
+func (x *LimitError) GetRetryAfter() *durationpb.Duration {
+	if x != nil {
+		return x.RetryAfter
+	}
+	return nil
+}
+
 var File_errors_proto protoreflect.FileDescriptor
 
 var file_errors_proto_rawDesc = []byte{
 	0x0a, 0x0c, 0x65, 0x72, 0x72, 0x6f, 0x72, 0x73, 0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x12, 0x06,
-	0x67, 0x69, 0x74, 0x61, 0x6c, 0x79, 0x22, 0x86, 0x01, 0x0a, 0x10, 0x41, 0x63, 0x63, 0x65, 0x73,
+	0x67, 0x69, 0x74, 0x61, 0x6c, 0x79, 0x1a, 0x1e, 0x67, 0x6f, 0x6f, 0x67, 0x6c, 0x65, 0x2f, 0x70,
+	0x72, 0x6f, 0x74, 0x6f, 0x62, 0x75, 0x66, 0x2f, 0x64, 0x75, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e,
+	0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x22, 0x86, 0x01, 0x0a, 0x10, 0x41, 0x63, 0x63, 0x65, 0x73,
 	0x73, 0x43, 0x68, 0x65, 0x63, 0x6b, 0x45, 0x72, 0x72, 0x6f, 0x72, 0x12, 0x23, 0x0a, 0x0d, 0x65,
 	0x72, 0x72, 0x6f, 0x72, 0x5f, 0x6d, 0x65, 0x73, 0x73, 0x61, 0x67, 0x65, 0x18, 0x01, 0x20, 0x01,
 	0x28, 0x09, 0x52, 0x0c, 0x65, 0x72, 0x72, 0x6f, 0x72, 0x4d, 0x65, 0x73, 0x73, 0x61, 0x67, 0x65,
@@ -294,11 +356,18 @@ var file_errors_proto_rawDesc = []byte{
 	0x4f, 0x69, 0x64, 0x22, 0x32, 0x0a, 0x14, 0x52, 0x65, 0x73, 0x6f, 0x6c, 0x76, 0x65, 0x52, 0x65,
 	0x76, 0x69, 0x73, 0x69, 0x6f, 0x6e, 0x45, 0x72, 0x72, 0x6f, 0x72, 0x12, 0x1a, 0x0a, 0x08, 0x72,
 	0x65, 0x76, 0x69, 0x73, 0x69, 0x6f, 0x6e, 0x18, 0x01, 0x20, 0x01, 0x28, 0x0c, 0x52, 0x08, 0x72,
-	0x65, 0x76, 0x69, 0x73, 0x69, 0x6f, 0x6e, 0x42, 0x34, 0x5a, 0x32, 0x67, 0x69, 0x74, 0x6c, 0x61,
-	0x62, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x67, 0x69, 0x74, 0x6c, 0x61, 0x62, 0x2d, 0x6f, 0x72, 0x67,
-	0x2f, 0x67, 0x69, 0x74, 0x61, 0x6c, 0x79, 0x2f, 0x76, 0x31, 0x34, 0x2f, 0x70, 0x72, 0x6f, 0x74,
-	0x6f, 0x2f, 0x67, 0x6f, 0x2f, 0x67, 0x69, 0x74, 0x61, 0x6c, 0x79, 0x70, 0x62, 0x62, 0x06, 0x70,
-	0x72, 0x6f, 0x74, 0x6f, 0x33,
+	0x65, 0x76, 0x69, 0x73, 0x69, 0x6f, 0x6e, 0x22, 0x6d, 0x0a, 0x0a, 0x4c, 0x69, 0x6d, 0x69, 0x74,
+	0x45, 0x72, 0x72, 0x6f, 0x72, 0x12, 0x23, 0x0a, 0x0d, 0x65, 0x72, 0x72, 0x6f, 0x72, 0x5f, 0x6d,
+	0x65, 0x73, 0x73, 0x61, 0x67, 0x65, 0x18, 0x01, 0x20, 0x01, 0x28, 0x09, 0x52, 0x0c, 0x65, 0x72,
+	0x72, 0x6f, 0x72, 0x4d, 0x65, 0x73, 0x73, 0x61, 0x67, 0x65, 0x12, 0x3a, 0x0a, 0x0b, 0x72, 0x65,
+	0x74, 0x72, 0x79, 0x5f, 0x61, 0x66, 0x74, 0x65, 0x72, 0x18, 0x02, 0x20, 0x01, 0x28, 0x0b, 0x32,
+	0x19, 0x2e, 0x67, 0x6f, 0x6f, 0x67, 0x6c, 0x65, 0x2e, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x62, 0x75,
+	0x66, 0x2e, 0x44, 0x75, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x52, 0x0a, 0x72, 0x65, 0x74, 0x72,
+	0x79, 0x41, 0x66, 0x74, 0x65, 0x72, 0x42, 0x34, 0x5a, 0x32, 0x67, 0x69, 0x74, 0x6c, 0x61, 0x62,
+	0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x67, 0x69, 0x74, 0x6c, 0x61, 0x62, 0x2d, 0x6f, 0x72, 0x67, 0x2f,
+	0x67, 0x69, 0x74, 0x61, 0x6c, 0x79, 0x2f, 0x76, 0x31, 0x34, 0x2f, 0x70, 0x72, 0x6f, 0x74, 0x6f,
+	0x2f, 0x67, 0x6f, 0x2f, 0x67, 0x69, 0x74, 0x61, 0x6c, 0x79, 0x70, 0x62, 0x62, 0x06, 0x70, 0x72,
+	0x6f, 0x74, 0x6f, 0x33,
 }
 
 var (
@@ -313,19 +382,22 @@ func file_errors_proto_rawDescGZIP() []byte {
 	return file_errors_proto_rawDescData
 }
 
-var file_errors_proto_msgTypes = make([]protoimpl.MessageInfo, 4)
+var file_errors_proto_msgTypes = make([]protoimpl.MessageInfo, 5)
 var file_errors_proto_goTypes = []interface{}{
 	(*AccessCheckError)(nil),     // 0: gitaly.AccessCheckError
 	(*MergeConflictError)(nil),   // 1: gitaly.MergeConflictError
 	(*ReferenceUpdateError)(nil), // 2: gitaly.ReferenceUpdateError
 	(*ResolveRevisionError)(nil), // 3: gitaly.ResolveRevisionError
+	(*LimitError)(nil),           // 4: gitaly.LimitError
+	(*durationpb.Duration)(nil),  // 5: google.protobuf.Duration
 }
 var file_errors_proto_depIdxs = []int32{
-	0, // [0:0] is the sub-list for method output_type
-	0, // [0:0] is the sub-list for method input_type
-	0, // [0:0] is the sub-list for extension type_name
-	0, // [0:0] is the sub-list for extension extendee
-	0, // [0:0] is the sub-list for field type_name
+	5, // 0: gitaly.LimitError.retry_after:type_name -> google.protobuf.Duration
+	1, // [1:1] is the sub-list for method output_type
+	1, // [1:1] is the sub-list for method input_type
+	1, // [1:1] is the sub-list for extension type_name
+	1, // [1:1] is the sub-list for extension extendee
+	0, // [0:1] is the sub-list for field type_name
 }
 
 func init() { file_errors_proto_init() }
@@ -382,6 +454,18 @@ func file_errors_proto_init() {
 				return nil
 			}
 		}
+		file_errors_proto_msgTypes[4].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*LimitError); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
 	}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
@@ -389,7 +473,7 @@ func file_errors_proto_init() {
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: file_errors_proto_rawDesc,
 			NumEnums:      0,
-			NumMessages:   4,
+			NumMessages:   5,
 			NumExtensions: 0,
 			NumServices:   0,
 		},
diff --git a/ruby/proto/gitaly/errors_pb.rb b/ruby/proto/gitaly/errors_pb.rb
index f344beaaa..b28115768 100644
--- a/ruby/proto/gitaly/errors_pb.rb
+++ b/ruby/proto/gitaly/errors_pb.rb
@@ -1,6 +1,7 @@
 # Generated by the protocol buffer compiler.  DO NOT EDIT!
 # source: errors.proto
 
+require 'google/protobuf/duration_pb'
 require 'google/protobuf'
 
 Google::Protobuf::DescriptorPool.generated_pool.build do
@@ -22,6 +23,10 @@ Google::Protobuf::DescriptorPool.generated_pool.build do
     add_message "gitaly.ResolveRevisionError" do
       optional :revision, :bytes, 1
     end
+    add_message "gitaly.LimitError" do
+      optional :error_message, :string, 1
+      optional :retry_after, :message, 2, "google.protobuf.Duration"
+    end
   end
 end
 
@@ -30,4 +35,5 @@ module Gitaly
   MergeConflictError = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("gitaly.MergeConflictError").msgclass
   ReferenceUpdateError = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("gitaly.ReferenceUpdateError").msgclass
   ResolveRevisionError = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("gitaly.ResolveRevisionError").msgclass
+  LimitError = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("gitaly.LimitError").msgclass
 end