Add service config protobuf definition

gRPC doesn't expose service config definition. The service config dial
option also receives raw-JSON string. We could either build a raw JSON
string, or create our own proto mimicking the one in grpc-go library.
The later is better, because it provides a stronger type guarantee
while generating the configs.

3 files changed, 818 insertions, 0 deletions

diff --git a/proto/go/gitalypb/protolist.go b/proto/go/gitalypb/protolist.go
index ed2f064f9..29137d0db 100644
--- a/proto/go/gitalypb/protolist.go
+++ b/proto/go/gitalypb/protolist.go
@@ -22,6 +22,7 @@ var GitalyProtos = []string{
 	"remote.proto",
 	"repository.proto",
 	"server.proto",
+	"service_config.proto",
 	"shared.proto",
 	"smarthttp.proto",
 	"ssh.proto",
diff --git a/proto/go/gitalypb/service_config.pb.go b/proto/go/gitalypb/service_config.pb.go
new file mode 100644
index 000000000..553feec08
--- /dev/null
+++ b/proto/go/gitalypb/service_config.pb.go
@@ -0,0 +1,735 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// versions:
+// 	protoc-gen-go v1.28.1
+// 	protoc        v3.21.7
+// source: service_config.proto
+
+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"
+	wrapperspb "google.golang.org/protobuf/types/known/wrapperspb"
+	reflect "reflect"
+	sync "sync"
+)
+
+const (
+	// Verify that this generated code is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
+	// Verify that runtime/protoimpl is sufficiently up-to-date.
+	_ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
+)
+
+// ServiceConfig defines the configuration that allows service owners to publish parameters to be
+// automatically used by all clients of their service. gRPC doesn't export this protobuf. So, we
+// built a minimized version to for Gitaly use. The completed version is defined at
+// https://github.com/grpc/grpc-proto/blob/master/grpc/service_config/service_config.proto
+type ServiceConfig struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// protolint:disable:next REPEATED_FIELD_NAMES_PLURALIZED
+	LoadBalancingConfig []*LoadBalancingConfig `protobuf:"bytes,1,rep,name=load_balancing_config,json=loadBalancingConfig,proto3" json:"load_balancing_config,omitempty"`
+	// protolint:disable:next REPEATED_FIELD_NAMES_PLURALIZED
+	MethodConfig []*MethodConfig `protobuf:"bytes,2,rep,name=method_config,json=methodConfig,proto3" json:"method_config,omitempty"`
+}
+
+func (x *ServiceConfig) Reset() {
+	*x = ServiceConfig{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_service_config_proto_msgTypes[0]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *ServiceConfig) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*ServiceConfig) ProtoMessage() {}
+
+func (x *ServiceConfig) ProtoReflect() protoreflect.Message {
+	mi := &file_service_config_proto_msgTypes[0]
+	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 ServiceConfig.ProtoReflect.Descriptor instead.
+func (*ServiceConfig) Descriptor() ([]byte, []int) {
+	return file_service_config_proto_rawDescGZIP(), []int{0}
+}
+
+func (x *ServiceConfig) GetLoadBalancingConfig() []*LoadBalancingConfig {
+	if x != nil {
+		return x.LoadBalancingConfig
+	}
+	return nil
+}
+
+func (x *ServiceConfig) GetMethodConfig() []*MethodConfig {
+	if x != nil {
+		return x.MethodConfig
+	}
+	return nil
+}
+
+// LoadBalancingConfig wraps around the round-robin strategies. Only one strategy can be selected.
+type LoadBalancingConfig struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// Types that are assignable to Policy:
+	//
+	//	*LoadBalancingConfig_PickFirst
+	//	*LoadBalancingConfig_RoundRobin
+	Policy isLoadBalancingConfig_Policy `protobuf_oneof:"policy"`
+}
+
+func (x *LoadBalancingConfig) Reset() {
+	*x = LoadBalancingConfig{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_service_config_proto_msgTypes[1]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *LoadBalancingConfig) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*LoadBalancingConfig) ProtoMessage() {}
+
+func (x *LoadBalancingConfig) ProtoReflect() protoreflect.Message {
+	mi := &file_service_config_proto_msgTypes[1]
+	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 LoadBalancingConfig.ProtoReflect.Descriptor instead.
+func (*LoadBalancingConfig) Descriptor() ([]byte, []int) {
+	return file_service_config_proto_rawDescGZIP(), []int{1}
+}
+
+func (m *LoadBalancingConfig) GetPolicy() isLoadBalancingConfig_Policy {
+	if m != nil {
+		return m.Policy
+	}
+	return nil
+}
+
+func (x *LoadBalancingConfig) GetPickFirst() *PickFirstConfig {
+	if x, ok := x.GetPolicy().(*LoadBalancingConfig_PickFirst); ok {
+		return x.PickFirst
+	}
+	return nil
+}
+
+func (x *LoadBalancingConfig) GetRoundRobin() *RoundRobinConfig {
+	if x, ok := x.GetPolicy().(*LoadBalancingConfig_RoundRobin); ok {
+		return x.RoundRobin
+	}
+	return nil
+}
+
+type isLoadBalancingConfig_Policy interface {
+	isLoadBalancingConfig_Policy()
+}
+
+type LoadBalancingConfig_PickFirst struct {
+	// PickFirst strategy
+	PickFirst *PickFirstConfig `protobuf:"bytes,1,opt,name=pick_first,proto3,oneof"`
+}
+
+type LoadBalancingConfig_RoundRobin struct {
+	// RoundRobin strategy
+	RoundRobin *RoundRobinConfig `protobuf:"bytes,2,opt,name=round_robin,proto3,oneof"`
+}
+
+func (*LoadBalancingConfig_PickFirst) isLoadBalancingConfig_Policy() {}
+
+func (*LoadBalancingConfig_RoundRobin) isLoadBalancingConfig_Policy() {}
+
+// PickFirstConfig signals the pick_first load-balancing strategy. This strategy is the default
+// strategy of grpc client libraries so that the connection has only one subchannel, which is the
+// first address after resolution
+type PickFirstConfig struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+}
+
+func (x *PickFirstConfig) Reset() {
+	*x = PickFirstConfig{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_service_config_proto_msgTypes[2]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *PickFirstConfig) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*PickFirstConfig) ProtoMessage() {}
+
+func (x *PickFirstConfig) ProtoReflect() protoreflect.Message {
+	mi := &file_service_config_proto_msgTypes[2]
+	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 PickFirstConfig.ProtoReflect.Descriptor instead.
+func (*PickFirstConfig) Descriptor() ([]byte, []int) {
+	return file_service_config_proto_rawDescGZIP(), []int{2}
+}
+
+// RoundRobinConfig indicates the round_robin strategy. This strategy distributes the incoming
+// requests to active subchannels in a round-robin fashion.
+type RoundRobinConfig struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+}
+
+func (x *RoundRobinConfig) Reset() {
+	*x = RoundRobinConfig{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_service_config_proto_msgTypes[3]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *RoundRobinConfig) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*RoundRobinConfig) ProtoMessage() {}
+
+func (x *RoundRobinConfig) ProtoReflect() protoreflect.Message {
+	mi := &file_service_config_proto_msgTypes[3]
+	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 RoundRobinConfig.ProtoReflect.Descriptor instead.
+func (*RoundRobinConfig) Descriptor() ([]byte, []int) {
+	return file_service_config_proto_rawDescGZIP(), []int{3}
+}
+
+// Configuration for a method.
+type MethodConfig struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// name defines the list of affected services/methods
+	// The name should be  is the definition of grpc. Nothing we can do about it
+	// protolint:disable:next REPEATED_FIELD_NAMES_PLURALIZED
+	Name []*MethodConfig_Name `protobuf:"bytes,1,rep,name=name,proto3" json:"name,omitempty"`
+	// The following fields are unused by Gitaly at the moment. Please refer to the original
+	// documentation for more information
+	// protolint:disable FIELDS_HAVE_COMMENT
+	WaitForReady            *wrapperspb.BoolValue   `protobuf:"bytes,2,opt,name=wait_for_ready,json=waitForReady,proto3" json:"wait_for_ready,omitempty"`
+	Timeout                 *durationpb.Duration    `protobuf:"bytes,3,opt,name=timeout,proto3" json:"timeout,omitempty"`
+	MaxRequestMessageBytes  *wrapperspb.UInt32Value `protobuf:"bytes,4,opt,name=max_request_message_bytes,json=maxRequestMessageBytes,proto3" json:"max_request_message_bytes,omitempty"`
+	MaxResponseMessageBytes *wrapperspb.UInt32Value `protobuf:"bytes,5,opt,name=max_response_message_bytes,json=maxResponseMessageBytes,proto3" json:"max_response_message_bytes,omitempty"`
+	// protolint:enable FIELDS_HAVE_COMMENT
+	// retry_policy defines the exponential backoff configuration for the affected services/methods
+	RetryPolicy *MethodConfig_RetryPolicy `protobuf:"bytes,6,opt,name=retry_policy,json=retryPolicy,proto3" json:"retry_policy,omitempty"`
+}
+
+func (x *MethodConfig) Reset() {
+	*x = MethodConfig{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_service_config_proto_msgTypes[4]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *MethodConfig) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*MethodConfig) ProtoMessage() {}
+
+func (x *MethodConfig) ProtoReflect() protoreflect.Message {
+	mi := &file_service_config_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 MethodConfig.ProtoReflect.Descriptor instead.
+func (*MethodConfig) Descriptor() ([]byte, []int) {
+	return file_service_config_proto_rawDescGZIP(), []int{4}
+}
+
+func (x *MethodConfig) GetName() []*MethodConfig_Name {
+	if x != nil {
+		return x.Name
+	}
+	return nil
+}
+
+func (x *MethodConfig) GetWaitForReady() *wrapperspb.BoolValue {
+	if x != nil {
+		return x.WaitForReady
+	}
+	return nil
+}
+
+func (x *MethodConfig) GetTimeout() *durationpb.Duration {
+	if x != nil {
+		return x.Timeout
+	}
+	return nil
+}
+
+func (x *MethodConfig) GetMaxRequestMessageBytes() *wrapperspb.UInt32Value {
+	if x != nil {
+		return x.MaxRequestMessageBytes
+	}
+	return nil
+}
+
+func (x *MethodConfig) GetMaxResponseMessageBytes() *wrapperspb.UInt32Value {
+	if x != nil {
+		return x.MaxResponseMessageBytes
+	}
+	return nil
+}
+
+func (x *MethodConfig) GetRetryPolicy() *MethodConfig_RetryPolicy {
+	if x != nil {
+		return x.RetryPolicy
+	}
+	return nil
+}
+
+// Name is an object indicating which services/methods being affected by the config
+type MethodConfig_Name struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// service is name of the service,including its package. For example: gitaly.SmartHTTPService
+	Service string `protobuf:"bytes,1,opt,name=service,proto3" json:"service,omitempty"`
+	// method is the name of the method within the above service. Empty method name implies the
+	// method policy is effective for all methods of the service
+	Method string `protobuf:"bytes,2,opt,name=method,proto3" json:"method,omitempty"`
+}
+
+func (x *MethodConfig_Name) Reset() {
+	*x = MethodConfig_Name{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_service_config_proto_msgTypes[5]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *MethodConfig_Name) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*MethodConfig_Name) ProtoMessage() {}
+
+func (x *MethodConfig_Name) ProtoReflect() protoreflect.Message {
+	mi := &file_service_config_proto_msgTypes[5]
+	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 MethodConfig_Name.ProtoReflect.Descriptor instead.
+func (*MethodConfig_Name) Descriptor() ([]byte, []int) {
+	return file_service_config_proto_rawDescGZIP(), []int{4, 0}
+}
+
+func (x *MethodConfig_Name) GetService() string {
+	if x != nil {
+		return x.Service
+	}
+	return ""
+}
+
+func (x *MethodConfig_Name) GetMethod() string {
+	if x != nil {
+		return x.Method
+	}
+	return ""
+}
+
+// RetryPolicy defines the configuration for exponential backoff when a request fails
+type MethodConfig_RetryPolicy struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	// max_attempts is the total retry attempts client perform before bailing out
+	MaxAttempts uint32 `protobuf:"varint,1,opt,name=max_attempts,json=maxAttempts,proto3" json:"max_attempts,omitempty"`
+	// initial_backoff is the minimum delay for the first retries
+	InitialBackoff *durationpb.Duration `protobuf:"bytes,2,opt,name=initial_backoff,json=initialBackoff,proto3" json:"initial_backoff,omitempty"`
+	// max_backoff is the minimum delay
+	MaxBackoff *durationpb.Duration `protobuf:"bytes,3,opt,name=max_backoff,json=maxBackoff,proto3" json:"max_backoff,omitempty"`
+	// backoff_multiplier is the factor determining "how fast" the delay increases after each retry
+	BackoffMultiplier float32 `protobuf:"fixed32,4,opt,name=backoff_multiplier,json=backoffMultiplier,proto3" json:"backoff_multiplier,omitempty"`
+	// retryable_status_codes defines the list of eligible status codes. The status must be in
+	// capitalized snake_case form. For example, UNAVAILABLE, FAILED_PRECONDITION
+	RetryableStatusCodes []string `protobuf:"bytes,5,rep,name=retryable_status_codes,json=retryableStatusCodes,proto3" json:"retryable_status_codes,omitempty"`
+}
+
+func (x *MethodConfig_RetryPolicy) Reset() {
+	*x = MethodConfig_RetryPolicy{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_service_config_proto_msgTypes[6]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *MethodConfig_RetryPolicy) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*MethodConfig_RetryPolicy) ProtoMessage() {}
+
+func (x *MethodConfig_RetryPolicy) ProtoReflect() protoreflect.Message {
+	mi := &file_service_config_proto_msgTypes[6]
+	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 MethodConfig_RetryPolicy.ProtoReflect.Descriptor instead.
+func (*MethodConfig_RetryPolicy) Descriptor() ([]byte, []int) {
+	return file_service_config_proto_rawDescGZIP(), []int{4, 1}
+}
+
+func (x *MethodConfig_RetryPolicy) GetMaxAttempts() uint32 {
+	if x != nil {
+		return x.MaxAttempts
+	}
+	return 0
+}
+
+func (x *MethodConfig_RetryPolicy) GetInitialBackoff() *durationpb.Duration {
+	if x != nil {
+		return x.InitialBackoff
+	}
+	return nil
+}
+
+func (x *MethodConfig_RetryPolicy) GetMaxBackoff() *durationpb.Duration {
+	if x != nil {
+		return x.MaxBackoff
+	}
+	return nil
+}
+
+func (x *MethodConfig_RetryPolicy) GetBackoffMultiplier() float32 {
+	if x != nil {
+		return x.BackoffMultiplier
+	}
+	return 0
+}
+
+func (x *MethodConfig_RetryPolicy) GetRetryableStatusCodes() []string {
+	if x != nil {
+		return x.RetryableStatusCodes
+	}
+	return nil
+}
+
+var File_service_config_proto protoreflect.FileDescriptor
+
+var file_service_config_proto_rawDesc = []byte{
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+}
+
+var (
+	file_service_config_proto_rawDescOnce sync.Once
+	file_service_config_proto_rawDescData = file_service_config_proto_rawDesc
+)
+
+func file_service_config_proto_rawDescGZIP() []byte {
+	file_service_config_proto_rawDescOnce.Do(func() {
+		file_service_config_proto_rawDescData = protoimpl.X.CompressGZIP(file_service_config_proto_rawDescData)
+	})
+	return file_service_config_proto_rawDescData
+}
+
+var file_service_config_proto_msgTypes = make([]protoimpl.MessageInfo, 7)
+var file_service_config_proto_goTypes = []interface{}{
+	(*ServiceConfig)(nil),            // 0: gitaly.ServiceConfig
+	(*LoadBalancingConfig)(nil),      // 1: gitaly.LoadBalancingConfig
+	(*PickFirstConfig)(nil),          // 2: gitaly.PickFirstConfig
+	(*RoundRobinConfig)(nil),         // 3: gitaly.RoundRobinConfig
+	(*MethodConfig)(nil),             // 4: gitaly.MethodConfig
+	(*MethodConfig_Name)(nil),        // 5: gitaly.MethodConfig.Name
+	(*MethodConfig_RetryPolicy)(nil), // 6: gitaly.MethodConfig.RetryPolicy
+	(*wrapperspb.BoolValue)(nil),     // 7: google.protobuf.BoolValue
+	(*durationpb.Duration)(nil),      // 8: google.protobuf.Duration
+	(*wrapperspb.UInt32Value)(nil),   // 9: google.protobuf.UInt32Value
+}
+var file_service_config_proto_depIdxs = []int32{
+	1,  // 0: gitaly.ServiceConfig.load_balancing_config:type_name -> gitaly.LoadBalancingConfig
+	4,  // 1: gitaly.ServiceConfig.method_config:type_name -> gitaly.MethodConfig
+	2,  // 2: gitaly.LoadBalancingConfig.pick_first:type_name -> gitaly.PickFirstConfig
+	3,  // 3: gitaly.LoadBalancingConfig.round_robin:type_name -> gitaly.RoundRobinConfig
+	5,  // 4: gitaly.MethodConfig.name:type_name -> gitaly.MethodConfig.Name
+	7,  // 5: gitaly.MethodConfig.wait_for_ready:type_name -> google.protobuf.BoolValue
+	8,  // 6: gitaly.MethodConfig.timeout:type_name -> google.protobuf.Duration
+	9,  // 7: gitaly.MethodConfig.max_request_message_bytes:type_name -> google.protobuf.UInt32Value
+	9,  // 8: gitaly.MethodConfig.max_response_message_bytes:type_name -> google.protobuf.UInt32Value
+	6,  // 9: gitaly.MethodConfig.retry_policy:type_name -> gitaly.MethodConfig.RetryPolicy
+	8,  // 10: gitaly.MethodConfig.RetryPolicy.initial_backoff:type_name -> google.protobuf.Duration
+	8,  // 11: gitaly.MethodConfig.RetryPolicy.max_backoff:type_name -> google.protobuf.Duration
+	12, // [12:12] is the sub-list for method output_type
+	12, // [12:12] is the sub-list for method input_type
+	12, // [12:12] is the sub-list for extension type_name
+	12, // [12:12] is the sub-list for extension extendee
+	0,  // [0:12] is the sub-list for field type_name
+}
+
+func init() { file_service_config_proto_init() }
+func file_service_config_proto_init() {
+	if File_service_config_proto != nil {
+		return
+	}
+	if !protoimpl.UnsafeEnabled {
+		file_service_config_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*ServiceConfig); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_service_config_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*LoadBalancingConfig); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_service_config_proto_msgTypes[2].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*PickFirstConfig); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_service_config_proto_msgTypes[3].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*RoundRobinConfig); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_service_config_proto_msgTypes[4].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*MethodConfig); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_service_config_proto_msgTypes[5].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*MethodConfig_Name); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+		file_service_config_proto_msgTypes[6].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*MethodConfig_RetryPolicy); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
+	}
+	file_service_config_proto_msgTypes[1].OneofWrappers = []interface{}{
+		(*LoadBalancingConfig_PickFirst)(nil),
+		(*LoadBalancingConfig_RoundRobin)(nil),
+	}
+	type x struct{}
+	out := protoimpl.TypeBuilder{
+		File: protoimpl.DescBuilder{
+			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
+			RawDescriptor: file_service_config_proto_rawDesc,
+			NumEnums:      0,
+			NumMessages:   7,
+			NumExtensions: 0,
+			NumServices:   0,
+		},
+		GoTypes:           file_service_config_proto_goTypes,
+		DependencyIndexes: file_service_config_proto_depIdxs,
+		MessageInfos:      file_service_config_proto_msgTypes,
+	}.Build()
+	File_service_config_proto = out.File
+	file_service_config_proto_rawDesc = nil
+	file_service_config_proto_goTypes = nil
+	file_service_config_proto_depIdxs = nil
+}
diff --git a/proto/service_config.proto b/proto/service_config.proto
new file mode 100644
index 000000000..743ede877
--- /dev/null
+++ b/proto/service_config.proto
@@ -0,0 +1,82 @@
+syntax = "proto3";
+
+package gitaly;
+
+import "google/protobuf/duration.proto";
+import "google/protobuf/wrappers.proto";
+
+option go_package = "gitlab.com/gitlab-org/gitaly/v15/proto/go/gitalypb";
+
+// ServiceConfig defines the configuration that allows service owners to publish parameters to be
+// automatically used by all clients of their service. gRPC doesn't export this protobuf. So, we
+// built a minimized version to for Gitaly use. The completed version is defined at
+// https://github.com/grpc/grpc-proto/blob/master/grpc/service_config/service_config.proto
+message ServiceConfig {
+  // protolint:disable:next REPEATED_FIELD_NAMES_PLURALIZED
+  repeated LoadBalancingConfig load_balancing_config = 1;
+  // protolint:disable:next REPEATED_FIELD_NAMES_PLURALIZED
+  repeated MethodConfig method_config = 2;
+}
+
+// LoadBalancingConfig wraps around the round-robin strategies. Only one strategy can be selected.
+message LoadBalancingConfig {
+  oneof policy {
+    // PickFirst strategy
+    PickFirstConfig pick_first = 1 [json_name = "pick_first"];
+    // RoundRobin strategy
+    RoundRobinConfig round_robin = 2 [json_name = "round_robin"];
+  }
+}
+
+// PickFirstConfig signals the pick_first load-balancing strategy. This strategy is the default
+// strategy of grpc client libraries so that the connection has only one subchannel, which is the
+// first address after resolution
+message PickFirstConfig {
+}
+
+// RoundRobinConfig indicates the round_robin strategy. This strategy distributes the incoming
+// requests to active subchannels in a round-robin fashion.
+message RoundRobinConfig {
+}
+
+// Configuration for a method.
+message MethodConfig {
+  // Name is an object indicating which services/methods being affected by the config
+  message Name {
+    // service is name of the service,including its package. For example: gitaly.SmartHTTPService
+    string service = 1;
+    // method is the name of the method within the above service. Empty method name implies the
+    // method policy is effective for all methods of the service
+    string method = 2;
+  }
+
+  // RetryPolicy defines the configuration for exponential backoff when a request fails
+  message RetryPolicy {
+    // max_attempts is the total retry attempts client perform before bailing out
+    uint32 max_attempts = 1;
+    // initial_backoff is the minimum delay for the first retries
+    google.protobuf.Duration initial_backoff = 2;
+    // max_backoff is the minimum delay
+    google.protobuf.Duration max_backoff = 3;
+    // backoff_multiplier is the factor determining "how fast" the delay increases after each retry
+    float backoff_multiplier = 4;
+    // retryable_status_codes defines the list of eligible status codes. The status must be in
+    // capitalized snake_case form. For example, UNAVAILABLE, FAILED_PRECONDITION
+    repeated string retryable_status_codes = 5;
+  }
+
+  // name defines the list of affected services/methods
+  // The name should be  is the definition of grpc. Nothing we can do about it
+  // protolint:disable:next REPEATED_FIELD_NAMES_PLURALIZED
+  repeated Name name = 1;
+  // The following fields are unused by Gitaly at the moment. Please refer to the original
+  // documentation for more information
+  // protolint:disable FIELDS_HAVE_COMMENT
+  google.protobuf.BoolValue wait_for_ready = 2;
+  google.protobuf.Duration timeout = 3;
+  google.protobuf.UInt32Value max_request_message_bytes = 4;
+  google.protobuf.UInt32Value max_response_message_bytes = 5;
+  // protolint:enable FIELDS_HAVE_COMMENT
+  // retry_policy defines the exponential backoff configuration for the affected services/methods
+  RetryPolicy retry_policy = 6;
+}