Support load-balanced runner groups for multitenant compute isolation (#814)

* Initial stab at the protocol

* initial protocol sketch for node pool manager

* Added http header frame as a message

* Force the use of WithAgent variants when creating a server

* adds grpc models for node pool manager plus go deps

* Naming things is really hard

* Merge (and optionally purge) details received by the NPM

* WIP: starting to add the runner-side functionality of the new data plane

* WIP: Basic startup of grpc server for pure runner. Needs proper certs.

* Go fmt

* Initial agent for LB nodes.

* Agent implementation for LB nodes.

* Pass keys and certs to LB node agent.

* Remove accidentally left reference to env var.

* Add env variables for certificate files

* stub out the capacity and group membership server channels

* implement server-side runner manager service

* removes unused variable

* fixes build error

* splits up GetCall and GetLBGroupId

* Change LB node agent to use TLS connection.

* Encode call model as JSON to send to runner node.

* Use hybrid client in LB node agent.

This should provide access to get app and route information for the call
from an API node.

* More error handling on the pure runner side

* Tentative fix for GetCall problem: set deadlines correctly when reserving slot

* Connect loop for LB agent to runner nodes.

* Extract runner connection function in LB agent.

* drops committed capacity counts

* Bugfix - end state tracker only in submit

* Do logs properly

* adds first pass of tracking capacity metrics in agent

* maked memory capacity metric uint64

* maked memory capacity metric uint64

* removes use of old capacity field

* adds remove capacity call

* merges overwritten reconnect logic

* First pass of a NPM

Provide a service that talks to a (simulated) CP.

- Receive incoming capacity assertions from LBs for LBGs
- expire LB requests after a short period
- ask the CP to add runners to a LBG
- note runner set changes and readvertise
- scale down by marking runners as "draining"
- shut off draining runners after some cool-down period

* add capacity update on schedule

* Send periodic capcacity metrics

Sending capcacity metrics to node pool manager

* splits grpc and api interfaces for capacity manager

* failure to advertise capacity shouldn't panic

* Add some instructions for starting DP/CP parts.

* Create the poolmanager server with TLS

* Use logrus

* Get npm compiling with cert fixups.

* Fix: pure runner should not start async processing

* brings runner, nulb and npm together

* Add field to acknowledgment to record slot allocation latency; fix a bug too

* iterating on pool manager locking issue

* raises timeout of placement retry loop

* Fix up NPM

Improve logging

Ensure that channels etc. are actually initialised in the structure
creation!

* Update the docs - runners GRPC port is 9120

* Bugfix: return runner pool accurately.

* Double locking

* Note purges as LBs stop talking to us

* Get the purging of old LBs working.

* Tweak: on restart, load runner set before making scaling decisions.

* more agent synchronization improvements

* Deal with teh CP pulling out active hosts from under us.

* lock at lbgroup level

* Send request and receive response from runner.

* Add capacity check right before slot reservation

* Pass the full Call into the receive loop.

* Wait for the data from the runner before finishing

* force runner list refresh every time

* Don't init db and mq for pure runners

* adds shutdown of npm

* fixes broken log line

* Extract an interface for the Predictor used by the NPM

* purge drained connections from npm

* Refactor of the LB agent into the agent package

* removes capacitytest wip

* Fix undefined err issue

* updating README for poolmanager set up

* ues retrying dial for lb to npm connections

* Rename lb_calls to lb_agent now that all functionality is there

* Use the right deadline and errors in LBAgent

* Make stream error flag per-call rather than global otherwise the whole runner is damaged by one call dropping

* abstracting gRPCNodePool

* Make stream error flag per-call rather than global otherwise the whole runner is damaged by one call dropping

* Add some init checks for LB and pure runner nodes

* adding some useful debug

* Fix default db and mq for lb node

* removes unreachable code, fixes typo

* Use datastore as logstore in API nodes.

This fixes a bug caused by trying to insert logs into a nil logstore. It
was nil because it wasn't being set for API nodes.

* creates placement abstraction and moves capacity APIs to NodePool

* removed TODO, added logging

* Dial reconnections for LB <-> runners

LB grpc connections to runners are established using a backoff stategy
in event of reconnections, this allows to let the LB up even in case one
of the runners go away and reconnect to it as soon as it is back.

* Add a status call to the Runner protocol

Stub at the moment. To be used for things like draindown, health checks.

* Remove comment.

* makes assign/release capacity lockless

* Fix hanging issue in lb agent when connections drop

* Add the CH hash from fnlb

Select this with FN_PLACER=ch when launching the LB.

* small improvement for locking on reloadLBGmembership

* Stabilise the list of Runenrs returned by NodePool

The NodePoolManager makes some attempt to keep the list of runner nodes advertised as
stable as possible. Let's preserve this effort in the client side. The main point of this
is to attempt to keep the same runner at the same inxed in the []Runner returned by
NodePool.Runners(lbgid); the ch algorithm likes it when this is the case.

* Factor out a generator function for the Runners so that mocks can be injected

* temporarily allow lbgroup to be specified in HTTP header, while we sort out changes to the model

* fixes bug with nil runners

* Initial work for mocking things in tests

* fix for anonymouse go routine error

* fixing lb_test to compile

* Refactor: internal objects for gRPCNodePool are now injectable, with defaults for the real world case

* Make GRPC port configurable, fix weird handling of web port too

* unit test reload Members

* check on runner creation failure

* adding nullRunner in case of failure during runner creation

* Refactored capacity advertisements/aggregations. Made grpc advertisement post asynchronous and non-blocking.

* make capacityEntry private

* Change the runner gRPC bind address.

This uses the existing `whoAmI` function, so that the gRPC server works
when the runner is running on a different host.

* Add support for multiple fixed runners to pool mgr

* Added harness for dataplane system tests, minor refactors

* Add Dockerfiles for components, along with docs.

* Doc fix: second runner needs a different name.

* Let us have three runners in system tests, why not

* The first system test running a function in API/LB/PureRunner mode

* Add unit test for Advertiser logic

* Fix issue with Pure Runner not sending the last data frame

* use config in models.Call as a temporary mechanism to override lb group ID

* make gofmt happy

* Updates documentation for how to configure lb groups for an app/route

* small refactor unit test

* Factor NodePool into its own package

* Lots of fixes to Pure Runner - concurrency woes with errors and cancellations

* New dataplane with static runnerpool (#813)

Added static node pool as default implementation

* moved nullRunner to grpc package

* remove duplication in README

* fix go vet issues

* Fix server initialisation in api tests

* Tiny logging changes in pool manager.

Using `WithError` instead of `Errorf` when appropriate.

* Change some log levels in the pure runner

* fixing readme

* moves multitenant compute documentation

* adds introduction to multitenant readme

* Proper triggering of system tests in makefile

* Fix insructions about starting up the components

* Change db file for system tests to avoid contention in parallel tests

* fixes revisions from merge

* Fix merge issue with handling of reserved slot

* renaming nulb to lb in the doc and images folder

* better TryExec sleep logic clean shutdown

In this change we implement a better way to deal with the sleep inside
the for loop during the attempt for placing a call.
Plus we added a clean way to shutdown the connections with external
component when we shut down the server.

* System_test mysql port

set mysql port for system test to a different value to the one set for
the api tests to avoid conflicts as they can run in parallel.

* change the container name for system-test

* removes flaky test TestRouteRunnerExecution pending resolution by issue #796

* amend remove_containers to remove new added containers

* Rework capacity reservation logic at a higher level for now

* LB agent implements Submit rather than delegating.

* Fix go vet linting errors

* Changed a couple of error levels

* Fix formatting

* removes commmented out test

* adds snappy to vendor directory

* updates Gopkg and vendor directories, removing snappy and addhing siphash

* wait for db containers to come up before starting the tests

* make system tests start API node on 8085 to avoid port conflict with api_tests

* avoid port conflicts with api_test.sh which are run in parallel

* fixes postgres port conflict and issue with removal of old containers

* Remove spurious println

vendor/google.golang.org/grpc/grpclb/grpc_lb_v1/messages/messages.pb.go

@@ -0,0 +1,615 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// source: grpc_lb_v1/messages/messages.proto
+
+/*
+Package messages is a generated protocol buffer package.
+
+It is generated from these files:
+	grpc_lb_v1/messages/messages.proto
+
+It has these top-level messages:
+	Duration
+	Timestamp
+	LoadBalanceRequest
+	InitialLoadBalanceRequest
+	ClientStats
+	LoadBalanceResponse
+	InitialLoadBalanceResponse
+	ServerList
+	Server
+*/
+package messages
+
+import proto "github.com/golang/protobuf/proto"
+import fmt "fmt"
+import math "math"
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+// A compilation error at this line likely means your copy of the
+// proto package needs to be updated.
+const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package
+
+type Duration struct {
+	// Signed seconds of the span of time. Must be from -315,576,000,000
+	// to +315,576,000,000 inclusive.
+	Seconds int64 `protobuf:"varint,1,opt,name=seconds" json:"seconds,omitempty"`
+	// Signed fractions of a second at nanosecond resolution of the span
+	// of time. Durations less than one second are represented with a 0
+	// `seconds` field and a positive or negative `nanos` field. For durations
+	// of one second or more, a non-zero value for the `nanos` field must be
+	// of the same sign as the `seconds` field. Must be from -999,999,999
+	// to +999,999,999 inclusive.
+	Nanos int32 `protobuf:"varint,2,opt,name=nanos" json:"nanos,omitempty"`
+}
+
+func (m *Duration) Reset()                    { *m = Duration{} }
+func (m *Duration) String() string            { return proto.CompactTextString(m) }
+func (*Duration) ProtoMessage()               {}
+func (*Duration) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{0} }
+
+func (m *Duration) GetSeconds() int64 {
+	if m != nil {
+		return m.Seconds
+	}
+	return 0
+}
+
+func (m *Duration) GetNanos() int32 {
+	if m != nil {
+		return m.Nanos
+	}
+	return 0
+}
+
+type Timestamp struct {
+	// Represents seconds of UTC time since Unix epoch
+	// 1970-01-01T00:00:00Z. Must be from 0001-01-01T00:00:00Z to
+	// 9999-12-31T23:59:59Z inclusive.
+	Seconds int64 `protobuf:"varint,1,opt,name=seconds" json:"seconds,omitempty"`
+	// Non-negative fractions of a second at nanosecond resolution. Negative
+	// second values with fractions must still have non-negative nanos values
+	// that count forward in time. Must be from 0 to 999,999,999
+	// inclusive.
+	Nanos int32 `protobuf:"varint,2,opt,name=nanos" json:"nanos,omitempty"`
+}
+
+func (m *Timestamp) Reset()                    { *m = Timestamp{} }
+func (m *Timestamp) String() string            { return proto.CompactTextString(m) }
+func (*Timestamp) ProtoMessage()               {}
+func (*Timestamp) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{1} }
+
+func (m *Timestamp) GetSeconds() int64 {
+	if m != nil {
+		return m.Seconds
+	}
+	return 0
+}
+
+func (m *Timestamp) GetNanos() int32 {
+	if m != nil {
+		return m.Nanos
+	}
+	return 0
+}
+
+type LoadBalanceRequest struct {
+	// Types that are valid to be assigned to LoadBalanceRequestType:
+	//	*LoadBalanceRequest_InitialRequest
+	//	*LoadBalanceRequest_ClientStats
+	LoadBalanceRequestType isLoadBalanceRequest_LoadBalanceRequestType `protobuf_oneof:"load_balance_request_type"`
+}
+
+func (m *LoadBalanceRequest) Reset()                    { *m = LoadBalanceRequest{} }
+func (m *LoadBalanceRequest) String() string            { return proto.CompactTextString(m) }
+func (*LoadBalanceRequest) ProtoMessage()               {}
+func (*LoadBalanceRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{2} }
+
+type isLoadBalanceRequest_LoadBalanceRequestType interface {
+	isLoadBalanceRequest_LoadBalanceRequestType()
+}
+
+type LoadBalanceRequest_InitialRequest struct {
+	InitialRequest *InitialLoadBalanceRequest `protobuf:"bytes,1,opt,name=initial_request,json=initialRequest,oneof"`
+}
+type LoadBalanceRequest_ClientStats struct {
+	ClientStats *ClientStats `protobuf:"bytes,2,opt,name=client_stats,json=clientStats,oneof"`
+}
+
+func (*LoadBalanceRequest_InitialRequest) isLoadBalanceRequest_LoadBalanceRequestType() {}
+func (*LoadBalanceRequest_ClientStats) isLoadBalanceRequest_LoadBalanceRequestType()    {}
+
+func (m *LoadBalanceRequest) GetLoadBalanceRequestType() isLoadBalanceRequest_LoadBalanceRequestType {
+	if m != nil {
+		return m.LoadBalanceRequestType
+	}
+	return nil
+}
+
+func (m *LoadBalanceRequest) GetInitialRequest() *InitialLoadBalanceRequest {
+	if x, ok := m.GetLoadBalanceRequestType().(*LoadBalanceRequest_InitialRequest); ok {
+		return x.InitialRequest
+	}
+	return nil
+}
+
+func (m *LoadBalanceRequest) GetClientStats() *ClientStats {
+	if x, ok := m.GetLoadBalanceRequestType().(*LoadBalanceRequest_ClientStats); ok {
+		return x.ClientStats
+	}
+	return nil
+}
+
+// XXX_OneofFuncs is for the internal use of the proto package.
+func (*LoadBalanceRequest) XXX_OneofFuncs() (func(msg proto.Message, b *proto.Buffer) error, func(msg proto.Message, tag, wire int, b *proto.Buffer) (bool, error), func(msg proto.Message) (n int), []interface{}) {
+	return _LoadBalanceRequest_OneofMarshaler, _LoadBalanceRequest_OneofUnmarshaler, _LoadBalanceRequest_OneofSizer, []interface{}{
+		(*LoadBalanceRequest_InitialRequest)(nil),
+		(*LoadBalanceRequest_ClientStats)(nil),
+	}
+}
+
+func _LoadBalanceRequest_OneofMarshaler(msg proto.Message, b *proto.Buffer) error {
+	m := msg.(*LoadBalanceRequest)
+	// load_balance_request_type
+	switch x := m.LoadBalanceRequestType.(type) {
+	case *LoadBalanceRequest_InitialRequest:
+		b.EncodeVarint(1<<3 | proto.WireBytes)
+		if err := b.EncodeMessage(x.InitialRequest); err != nil {
+			return err
+		}
+	case *LoadBalanceRequest_ClientStats:
+		b.EncodeVarint(2<<3 | proto.WireBytes)
+		if err := b.EncodeMessage(x.ClientStats); err != nil {
+			return err
+		}
+	case nil:
+	default:
+		return fmt.Errorf("LoadBalanceRequest.LoadBalanceRequestType has unexpected type %T", x)
+	}
+	return nil
+}
+
+func _LoadBalanceRequest_OneofUnmarshaler(msg proto.Message, tag, wire int, b *proto.Buffer) (bool, error) {
+	m := msg.(*LoadBalanceRequest)
+	switch tag {
+	case 1: // load_balance_request_type.initial_request
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		msg := new(InitialLoadBalanceRequest)
+		err := b.DecodeMessage(msg)
+		m.LoadBalanceRequestType = &LoadBalanceRequest_InitialRequest{msg}
+		return true, err
+	case 2: // load_balance_request_type.client_stats
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		msg := new(ClientStats)
+		err := b.DecodeMessage(msg)
+		m.LoadBalanceRequestType = &LoadBalanceRequest_ClientStats{msg}
+		return true, err
+	default:
+		return false, nil
+	}
+}
+
+func _LoadBalanceRequest_OneofSizer(msg proto.Message) (n int) {
+	m := msg.(*LoadBalanceRequest)
+	// load_balance_request_type
+	switch x := m.LoadBalanceRequestType.(type) {
+	case *LoadBalanceRequest_InitialRequest:
+		s := proto.Size(x.InitialRequest)
+		n += proto.SizeVarint(1<<3 | proto.WireBytes)
+		n += proto.SizeVarint(uint64(s))
+		n += s
+	case *LoadBalanceRequest_ClientStats:
+		s := proto.Size(x.ClientStats)
+		n += proto.SizeVarint(2<<3 | proto.WireBytes)
+		n += proto.SizeVarint(uint64(s))
+		n += s
+	case nil:
+	default:
+		panic(fmt.Sprintf("proto: unexpected type %T in oneof", x))
+	}
+	return n
+}
+
+type InitialLoadBalanceRequest struct {
+	// Name of load balanced service (IE, balancer.service.com)
+	// length should be less than 256 bytes.
+	Name string `protobuf:"bytes,1,opt,name=name" json:"name,omitempty"`
+}
+
+func (m *InitialLoadBalanceRequest) Reset()                    { *m = InitialLoadBalanceRequest{} }
+func (m *InitialLoadBalanceRequest) String() string            { return proto.CompactTextString(m) }
+func (*InitialLoadBalanceRequest) ProtoMessage()               {}
+func (*InitialLoadBalanceRequest) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{3} }
+
+func (m *InitialLoadBalanceRequest) GetName() string {
+	if m != nil {
+		return m.Name
+	}
+	return ""
+}
+
+// Contains client level statistics that are useful to load balancing. Each
+// count except the timestamp should be reset to zero after reporting the stats.
+type ClientStats struct {
+	// The timestamp of generating the report.
+	Timestamp *Timestamp `protobuf:"bytes,1,opt,name=timestamp" json:"timestamp,omitempty"`
+	// The total number of RPCs that started.
+	NumCallsStarted int64 `protobuf:"varint,2,opt,name=num_calls_started,json=numCallsStarted" json:"num_calls_started,omitempty"`
+	// The total number of RPCs that finished.
+	NumCallsFinished int64 `protobuf:"varint,3,opt,name=num_calls_finished,json=numCallsFinished" json:"num_calls_finished,omitempty"`
+	// The total number of RPCs that were dropped by the client because of rate
+	// limiting.
+	NumCallsFinishedWithDropForRateLimiting int64 `protobuf:"varint,4,opt,name=num_calls_finished_with_drop_for_rate_limiting,json=numCallsFinishedWithDropForRateLimiting" json:"num_calls_finished_with_drop_for_rate_limiting,omitempty"`
+	// The total number of RPCs that were dropped by the client because of load
+	// balancing.
+	NumCallsFinishedWithDropForLoadBalancing int64 `protobuf:"varint,5,opt,name=num_calls_finished_with_drop_for_load_balancing,json=numCallsFinishedWithDropForLoadBalancing" json:"num_calls_finished_with_drop_for_load_balancing,omitempty"`
+	// The total number of RPCs that failed to reach a server except dropped RPCs.
+	NumCallsFinishedWithClientFailedToSend int64 `protobuf:"varint,6,opt,name=num_calls_finished_with_client_failed_to_send,json=numCallsFinishedWithClientFailedToSend" json:"num_calls_finished_with_client_failed_to_send,omitempty"`
+	// The total number of RPCs that finished and are known to have been received
+	// by a server.
+	NumCallsFinishedKnownReceived int64 `protobuf:"varint,7,opt,name=num_calls_finished_known_received,json=numCallsFinishedKnownReceived" json:"num_calls_finished_known_received,omitempty"`
+}
+
+func (m *ClientStats) Reset()                    { *m = ClientStats{} }
+func (m *ClientStats) String() string            { return proto.CompactTextString(m) }
+func (*ClientStats) ProtoMessage()               {}
+func (*ClientStats) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{4} }
+
+func (m *ClientStats) GetTimestamp() *Timestamp {
+	if m != nil {
+		return m.Timestamp
+	}
+	return nil
+}
+
+func (m *ClientStats) GetNumCallsStarted() int64 {
+	if m != nil {
+		return m.NumCallsStarted
+	}
+	return 0
+}
+
+func (m *ClientStats) GetNumCallsFinished() int64 {
+	if m != nil {
+		return m.NumCallsFinished
+	}
+	return 0
+}
+
+func (m *ClientStats) GetNumCallsFinishedWithDropForRateLimiting() int64 {
+	if m != nil {
+		return m.NumCallsFinishedWithDropForRateLimiting
+	}
+	return 0
+}
+
+func (m *ClientStats) GetNumCallsFinishedWithDropForLoadBalancing() int64 {
+	if m != nil {
+		return m.NumCallsFinishedWithDropForLoadBalancing
+	}
+	return 0
+}
+
+func (m *ClientStats) GetNumCallsFinishedWithClientFailedToSend() int64 {
+	if m != nil {
+		return m.NumCallsFinishedWithClientFailedToSend
+	}
+	return 0
+}
+
+func (m *ClientStats) GetNumCallsFinishedKnownReceived() int64 {
+	if m != nil {
+		return m.NumCallsFinishedKnownReceived
+	}
+	return 0
+}
+
+type LoadBalanceResponse struct {
+	// Types that are valid to be assigned to LoadBalanceResponseType:
+	//	*LoadBalanceResponse_InitialResponse
+	//	*LoadBalanceResponse_ServerList
+	LoadBalanceResponseType isLoadBalanceResponse_LoadBalanceResponseType `protobuf_oneof:"load_balance_response_type"`
+}
+
+func (m *LoadBalanceResponse) Reset()                    { *m = LoadBalanceResponse{} }
+func (m *LoadBalanceResponse) String() string            { return proto.CompactTextString(m) }
+func (*LoadBalanceResponse) ProtoMessage()               {}
+func (*LoadBalanceResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{5} }
+
+type isLoadBalanceResponse_LoadBalanceResponseType interface {
+	isLoadBalanceResponse_LoadBalanceResponseType()
+}
+
+type LoadBalanceResponse_InitialResponse struct {
+	InitialResponse *InitialLoadBalanceResponse `protobuf:"bytes,1,opt,name=initial_response,json=initialResponse,oneof"`
+}
+type LoadBalanceResponse_ServerList struct {
+	ServerList *ServerList `protobuf:"bytes,2,opt,name=server_list,json=serverList,oneof"`
+}
+
+func (*LoadBalanceResponse_InitialResponse) isLoadBalanceResponse_LoadBalanceResponseType() {}
+func (*LoadBalanceResponse_ServerList) isLoadBalanceResponse_LoadBalanceResponseType()      {}
+
+func (m *LoadBalanceResponse) GetLoadBalanceResponseType() isLoadBalanceResponse_LoadBalanceResponseType {
+	if m != nil {
+		return m.LoadBalanceResponseType
+	}
+	return nil
+}
+
+func (m *LoadBalanceResponse) GetInitialResponse() *InitialLoadBalanceResponse {
+	if x, ok := m.GetLoadBalanceResponseType().(*LoadBalanceResponse_InitialResponse); ok {
+		return x.InitialResponse
+	}
+	return nil
+}
+
+func (m *LoadBalanceResponse) GetServerList() *ServerList {
+	if x, ok := m.GetLoadBalanceResponseType().(*LoadBalanceResponse_ServerList); ok {
+		return x.ServerList
+	}
+	return nil
+}
+
+// XXX_OneofFuncs is for the internal use of the proto package.
+func (*LoadBalanceResponse) XXX_OneofFuncs() (func(msg proto.Message, b *proto.Buffer) error, func(msg proto.Message, tag, wire int, b *proto.Buffer) (bool, error), func(msg proto.Message) (n int), []interface{}) {
+	return _LoadBalanceResponse_OneofMarshaler, _LoadBalanceResponse_OneofUnmarshaler, _LoadBalanceResponse_OneofSizer, []interface{}{
+		(*LoadBalanceResponse_InitialResponse)(nil),
+		(*LoadBalanceResponse_ServerList)(nil),
+	}
+}
+
+func _LoadBalanceResponse_OneofMarshaler(msg proto.Message, b *proto.Buffer) error {
+	m := msg.(*LoadBalanceResponse)
+	// load_balance_response_type
+	switch x := m.LoadBalanceResponseType.(type) {
+	case *LoadBalanceResponse_InitialResponse:
+		b.EncodeVarint(1<<3 | proto.WireBytes)
+		if err := b.EncodeMessage(x.InitialResponse); err != nil {
+			return err
+		}
+	case *LoadBalanceResponse_ServerList:
+		b.EncodeVarint(2<<3 | proto.WireBytes)
+		if err := b.EncodeMessage(x.ServerList); err != nil {
+			return err
+		}
+	case nil:
+	default:
+		return fmt.Errorf("LoadBalanceResponse.LoadBalanceResponseType has unexpected type %T", x)
+	}
+	return nil
+}
+
+func _LoadBalanceResponse_OneofUnmarshaler(msg proto.Message, tag, wire int, b *proto.Buffer) (bool, error) {
+	m := msg.(*LoadBalanceResponse)
+	switch tag {
+	case 1: // load_balance_response_type.initial_response
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		msg := new(InitialLoadBalanceResponse)
+		err := b.DecodeMessage(msg)
+		m.LoadBalanceResponseType = &LoadBalanceResponse_InitialResponse{msg}
+		return true, err
+	case 2: // load_balance_response_type.server_list
+		if wire != proto.WireBytes {
+			return true, proto.ErrInternalBadWireType
+		}
+		msg := new(ServerList)
+		err := b.DecodeMessage(msg)
+		m.LoadBalanceResponseType = &LoadBalanceResponse_ServerList{msg}
+		return true, err
+	default:
+		return false, nil
+	}
+}
+
+func _LoadBalanceResponse_OneofSizer(msg proto.Message) (n int) {
+	m := msg.(*LoadBalanceResponse)
+	// load_balance_response_type
+	switch x := m.LoadBalanceResponseType.(type) {
+	case *LoadBalanceResponse_InitialResponse:
+		s := proto.Size(x.InitialResponse)
+		n += proto.SizeVarint(1<<3 | proto.WireBytes)
+		n += proto.SizeVarint(uint64(s))
+		n += s
+	case *LoadBalanceResponse_ServerList:
+		s := proto.Size(x.ServerList)
+		n += proto.SizeVarint(2<<3 | proto.WireBytes)
+		n += proto.SizeVarint(uint64(s))
+		n += s
+	case nil:
+	default:
+		panic(fmt.Sprintf("proto: unexpected type %T in oneof", x))
+	}
+	return n
+}
+
+type InitialLoadBalanceResponse struct {
+	// This is an application layer redirect that indicates the client should use
+	// the specified server for load balancing. When this field is non-empty in
+	// the response, the client should open a separate connection to the
+	// load_balancer_delegate and call the BalanceLoad method. Its length should
+	// be less than 64 bytes.
+	LoadBalancerDelegate string `protobuf:"bytes,1,opt,name=load_balancer_delegate,json=loadBalancerDelegate" json:"load_balancer_delegate,omitempty"`
+	// This interval defines how often the client should send the client stats
+	// to the load balancer. Stats should only be reported when the duration is
+	// positive.
+	ClientStatsReportInterval *Duration `protobuf:"bytes,2,opt,name=client_stats_report_interval,json=clientStatsReportInterval" json:"client_stats_report_interval,omitempty"`
+}
+
+func (m *InitialLoadBalanceResponse) Reset()                    { *m = InitialLoadBalanceResponse{} }
+func (m *InitialLoadBalanceResponse) String() string            { return proto.CompactTextString(m) }
+func (*InitialLoadBalanceResponse) ProtoMessage()               {}
+func (*InitialLoadBalanceResponse) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{6} }
+
+func (m *InitialLoadBalanceResponse) GetLoadBalancerDelegate() string {
+	if m != nil {
+		return m.LoadBalancerDelegate
+	}
+	return ""
+}
+
+func (m *InitialLoadBalanceResponse) GetClientStatsReportInterval() *Duration {
+	if m != nil {
+		return m.ClientStatsReportInterval
+	}
+	return nil
+}
+
+type ServerList struct {
+	// Contains a list of servers selected by the load balancer. The list will
+	// be updated when server resolutions change or as needed to balance load
+	// across more servers. The client should consume the server list in order
+	// unless instructed otherwise via the client_config.
+	Servers []*Server `protobuf:"bytes,1,rep,name=servers" json:"servers,omitempty"`
+}
+
+func (m *ServerList) Reset()                    { *m = ServerList{} }
+func (m *ServerList) String() string            { return proto.CompactTextString(m) }
+func (*ServerList) ProtoMessage()               {}
+func (*ServerList) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{7} }
+
+func (m *ServerList) GetServers() []*Server {
+	if m != nil {
+		return m.Servers
+	}
+	return nil
+}
+
+// Contains server information. When none of the [drop_for_*] fields are true,
+// use the other fields. When drop_for_rate_limiting is true, ignore all other
+// fields. Use drop_for_load_balancing only when it is true and
+// drop_for_rate_limiting is false.
+type Server struct {
+	// A resolved address for the server, serialized in network-byte-order. It may
+	// either be an IPv4 or IPv6 address.
+	IpAddress []byte `protobuf:"bytes,1,opt,name=ip_address,json=ipAddress,proto3" json:"ip_address,omitempty"`
+	// A resolved port number for the server.
+	Port int32 `protobuf:"varint,2,opt,name=port" json:"port,omitempty"`
+	// An opaque but printable token given to the frontend for each pick. All
+	// frontend requests for that pick must include the token in its initial
+	// metadata. The token is used by the backend to verify the request and to
+	// allow the backend to report load to the gRPC LB system.
+	//
+	// Its length is variable but less than 50 bytes.
+	LoadBalanceToken string `protobuf:"bytes,3,opt,name=load_balance_token,json=loadBalanceToken" json:"load_balance_token,omitempty"`
+	// Indicates whether this particular request should be dropped by the client
+	// for rate limiting.
+	DropForRateLimiting bool `protobuf:"varint,4,opt,name=drop_for_rate_limiting,json=dropForRateLimiting" json:"drop_for_rate_limiting,omitempty"`
+	// Indicates whether this particular request should be dropped by the client
+	// for load balancing.
+	DropForLoadBalancing bool `protobuf:"varint,5,opt,name=drop_for_load_balancing,json=dropForLoadBalancing" json:"drop_for_load_balancing,omitempty"`
+}
+
+func (m *Server) Reset()                    { *m = Server{} }
+func (m *Server) String() string            { return proto.CompactTextString(m) }
+func (*Server) ProtoMessage()               {}
+func (*Server) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{8} }
+
+func (m *Server) GetIpAddress() []byte {
+	if m != nil {
+		return m.IpAddress
+	}
+	return nil
+}
+
+func (m *Server) GetPort() int32 {
+	if m != nil {
+		return m.Port
+	}
+	return 0
+}
+
+func (m *Server) GetLoadBalanceToken() string {
+	if m != nil {
+		return m.LoadBalanceToken
+	}
+	return ""
+}
+
+func (m *Server) GetDropForRateLimiting() bool {
+	if m != nil {
+		return m.DropForRateLimiting
+	}
+	return false
+}
+
+func (m *Server) GetDropForLoadBalancing() bool {
+	if m != nil {
+		return m.DropForLoadBalancing
+	}
+	return false
+}
+
+func init() {
+	proto.RegisterType((*Duration)(nil), "grpc.lb.v1.Duration")
+	proto.RegisterType((*Timestamp)(nil), "grpc.lb.v1.Timestamp")
+	proto.RegisterType((*LoadBalanceRequest)(nil), "grpc.lb.v1.LoadBalanceRequest")
+	proto.RegisterType((*InitialLoadBalanceRequest)(nil), "grpc.lb.v1.InitialLoadBalanceRequest")
+	proto.RegisterType((*ClientStats)(nil), "grpc.lb.v1.ClientStats")
+	proto.RegisterType((*LoadBalanceResponse)(nil), "grpc.lb.v1.LoadBalanceResponse")
+	proto.RegisterType((*InitialLoadBalanceResponse)(nil), "grpc.lb.v1.InitialLoadBalanceResponse")
+	proto.RegisterType((*ServerList)(nil), "grpc.lb.v1.ServerList")
+	proto.RegisterType((*Server)(nil), "grpc.lb.v1.Server")
+}
+
+func init() { proto.RegisterFile("grpc_lb_v1/messages/messages.proto", fileDescriptor0) }
+
+var fileDescriptor0 = []byte{
+	// 709 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x94, 0x55, 0xdd, 0x4e, 0x1b, 0x3b,
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+	0xbf, 0xf9, 0xbe, 0xf1, 0xac, 0xbf, 0x59, 0xf0, 0x06, 0x3a, 0xec, 0xb3, 0xa0, 0xc7, 0xc6, 0xbb,
+	0x3b, 0x43, 0x34, 0x86, 0x0f, 0xd0, 0x4c, 0x16, 0xad, 0x50, 0x2b, 0xab, 0x08, 0x44, 0x98, 0x56,
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+	0xa2, 0xb1, 0x7c, 0x18, 0xfe, 0x75, 0xf2, 0xcf, 0x02, 0x90, 0x13, 0xc5, 0xfd, 0x36, 0x0f, 0xb8,
+	0xec, 0x23, 0xc5, 0xaf, 0x23, 0x34, 0x96, 0x7c, 0x80, 0x45, 0x21, 0x85, 0x15, 0x3c, 0x60, 0x3a,
+	0x0e, 0x39, 0xba, 0xea, 0xde, 0xa3, 0x56, 0x56, 0x75, 0xeb, 0x38, 0x86, 0xdc, 0xcc, 0xef, 0xcc,
+	0xd0, 0x7f, 0x93, 0xfc, 0x94, 0xf1, 0x35, 0x2c, 0xf4, 0x03, 0x81, 0xd2, 0x32, 0x63, 0xb9, 0x8d,
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+	0xdb, 0xb6, 0x1f, 0xc0, 0x6a, 0xa0, 0xb8, 0xcf, 0x7a, 0xb1, 0x4c, 0x5a, 0x14, 0xb3, 0xdf, 0x42,
+	0xf4, 0x76, 0x60, 0xf5, 0xd6, 0x4a, 0x08, 0x81, 0x92, 0xe4, 0x43, 0x74, 0xe5, 0x57, 0xa8, 0x5b,
+	0x7b, 0xdf, 0x4b, 0x50, 0xcd, 0x89, 0x91, 0x7d, 0xa8, 0xd8, 0xb4, 0x83, 0xc9, 0x3d, 0xff, 0xcf,
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+	0x32, 0xf3, 0xdc, 0x3a, 0x32, 0xe3, 0x95, 0x4e, 0x5a, 0x75, 0x81, 0xd2, 0x99, 0xb1, 0x42, 0x6b,
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+	0xa6, 0x4a, 0x06, 0x00, 0x00,
+}

vendor/google.golang.org/grpc/grpclb/grpc_lb_v1/messages/messages.proto

@@ -0,0 +1,155 @@
+// Copyright 2016 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package grpc.lb.v1;
+option go_package = "google.golang.org/grpc/grpclb/grpc_lb_v1/messages";
+
+message Duration {
+  // Signed seconds of the span of time. Must be from -315,576,000,000
+  // to +315,576,000,000 inclusive.
+  int64 seconds = 1;
+
+  // Signed fractions of a second at nanosecond resolution of the span
+  // of time. Durations less than one second are represented with a 0
+  // `seconds` field and a positive or negative `nanos` field. For durations
+  // of one second or more, a non-zero value for the `nanos` field must be
+  // of the same sign as the `seconds` field. Must be from -999,999,999
+  // to +999,999,999 inclusive.
+  int32 nanos = 2;
+}
+
+message Timestamp {
+  // Represents seconds of UTC time since Unix epoch
+  // 1970-01-01T00:00:00Z. Must be from 0001-01-01T00:00:00Z to
+  // 9999-12-31T23:59:59Z inclusive.
+  int64 seconds = 1;
+
+  // Non-negative fractions of a second at nanosecond resolution. Negative
+  // second values with fractions must still have non-negative nanos values
+  // that count forward in time. Must be from 0 to 999,999,999
+  // inclusive.
+  int32 nanos = 2;
+}
+
+message LoadBalanceRequest {
+  oneof load_balance_request_type {
+    // This message should be sent on the first request to the load balancer.
+    InitialLoadBalanceRequest initial_request = 1;
+
+    // The client stats should be periodically reported to the load balancer
+    // based on the duration defined in the InitialLoadBalanceResponse.
+    ClientStats client_stats = 2;
+  }
+}
+
+message InitialLoadBalanceRequest {
+  // Name of load balanced service (IE, balancer.service.com)
+  // length should be less than 256 bytes.
+  string name = 1;
+}
+
+// Contains client level statistics that are useful to load balancing. Each
+// count except the timestamp should be reset to zero after reporting the stats.
+message ClientStats {
+  // The timestamp of generating the report.
+  Timestamp timestamp = 1;
+
+  // The total number of RPCs that started.
+  int64 num_calls_started = 2;
+
+  // The total number of RPCs that finished.
+  int64 num_calls_finished = 3;
+
+  // The total number of RPCs that were dropped by the client because of rate
+  // limiting.
+  int64 num_calls_finished_with_drop_for_rate_limiting = 4;
+
+  // The total number of RPCs that were dropped by the client because of load
+  // balancing.
+  int64 num_calls_finished_with_drop_for_load_balancing = 5;
+
+  // The total number of RPCs that failed to reach a server except dropped RPCs.
+  int64 num_calls_finished_with_client_failed_to_send = 6;
+
+  // The total number of RPCs that finished and are known to have been received
+  // by a server.
+  int64 num_calls_finished_known_received = 7;
+}
+
+message LoadBalanceResponse {
+  oneof load_balance_response_type {
+    // This message should be sent on the first response to the client.
+    InitialLoadBalanceResponse initial_response = 1;
+
+    // Contains the list of servers selected by the load balancer. The client
+    // should send requests to these servers in the specified order.
+    ServerList server_list = 2;
+  }
+}
+
+message InitialLoadBalanceResponse {
+  // This is an application layer redirect that indicates the client should use
+  // the specified server for load balancing. When this field is non-empty in
+  // the response, the client should open a separate connection to the
+  // load_balancer_delegate and call the BalanceLoad method. Its length should
+  // be less than 64 bytes.
+  string load_balancer_delegate = 1;
+
+  // This interval defines how often the client should send the client stats
+  // to the load balancer. Stats should only be reported when the duration is
+  // positive.
+  Duration client_stats_report_interval = 2;
+}
+
+message ServerList {
+  // Contains a list of servers selected by the load balancer. The list will
+  // be updated when server resolutions change or as needed to balance load
+  // across more servers. The client should consume the server list in order
+  // unless instructed otherwise via the client_config.
+  repeated Server servers = 1;
+
+  // Was google.protobuf.Duration expiration_interval.
+  reserved 3;
+}
+
+// Contains server information. When none of the [drop_for_*] fields are true,
+// use the other fields. When drop_for_rate_limiting is true, ignore all other
+// fields. Use drop_for_load_balancing only when it is true and
+// drop_for_rate_limiting is false.
+message Server {
+  // A resolved address for the server, serialized in network-byte-order. It may
+  // either be an IPv4 or IPv6 address.
+  bytes ip_address = 1;
+
+  // A resolved port number for the server.
+  int32 port = 2;
+
+  // An opaque but printable token given to the frontend for each pick. All
+  // frontend requests for that pick must include the token in its initial
+  // metadata. The token is used by the backend to verify the request and to
+  // allow the backend to report load to the gRPC LB system.
+  //
+  // Its length is variable but less than 50 bytes.
+  string load_balance_token = 3;
+
+  // Indicates whether this particular request should be dropped by the client
+  // for rate limiting.
+  bool drop_for_rate_limiting = 4;
+
+  // Indicates whether this particular request should be dropped by the client
+  // for load balancing.
+  bool drop_for_load_balancing = 5;
+}

vendor/google.golang.org/grpc/grpclb/grpc_lb_v1/service/service.pb.go

@@ -0,0 +1,154 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// source: grpc_lb_v1/service/service.proto
+
+/*
+Package service is a generated protocol buffer package.
+
+It is generated from these files:
+	grpc_lb_v1/service/service.proto
+
+It has these top-level messages:
+*/
+package service
+
+import proto "github.com/golang/protobuf/proto"
+import fmt "fmt"
+import math "math"
+import grpc_lb_v1 "google.golang.org/grpc/grpclb/grpc_lb_v1/messages"
+
+import (
+	context "golang.org/x/net/context"
+	grpc "google.golang.org/grpc"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+// A compilation error at this line likely means your copy of the
+// proto package needs to be updated.
+const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ context.Context
+var _ grpc.ClientConn
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the grpc package it is being compiled against.
+const _ = grpc.SupportPackageIsVersion4
+
+// Client API for LoadBalancer service
+
+type LoadBalancerClient interface {
+	// Bidirectional rpc to get a list of servers.
+	BalanceLoad(ctx context.Context, opts ...grpc.CallOption) (LoadBalancer_BalanceLoadClient, error)
+}
+
+type loadBalancerClient struct {
+	cc *grpc.ClientConn
+}
+
+func NewLoadBalancerClient(cc *grpc.ClientConn) LoadBalancerClient {
+	return &loadBalancerClient{cc}
+}
+
+func (c *loadBalancerClient) BalanceLoad(ctx context.Context, opts ...grpc.CallOption) (LoadBalancer_BalanceLoadClient, error) {
+	stream, err := grpc.NewClientStream(ctx, &_LoadBalancer_serviceDesc.Streams[0], c.cc, "/grpc.lb.v1.LoadBalancer/BalanceLoad", opts...)
+	if err != nil {
+		return nil, err
+	}
+	x := &loadBalancerBalanceLoadClient{stream}
+	return x, nil
+}
+
+type LoadBalancer_BalanceLoadClient interface {
+	Send(*grpc_lb_v1.LoadBalanceRequest) error
+	Recv() (*grpc_lb_v1.LoadBalanceResponse, error)
+	grpc.ClientStream
+}
+
+type loadBalancerBalanceLoadClient struct {
+	grpc.ClientStream
+}
+
+func (x *loadBalancerBalanceLoadClient) Send(m *grpc_lb_v1.LoadBalanceRequest) error {
+	return x.ClientStream.SendMsg(m)
+}
+
+func (x *loadBalancerBalanceLoadClient) Recv() (*grpc_lb_v1.LoadBalanceResponse, error) {
+	m := new(grpc_lb_v1.LoadBalanceResponse)
+	if err := x.ClientStream.RecvMsg(m); err != nil {
+		return nil, err
+	}
+	return m, nil
+}
+
+// Server API for LoadBalancer service
+
+type LoadBalancerServer interface {
+	// Bidirectional rpc to get a list of servers.
+	BalanceLoad(LoadBalancer_BalanceLoadServer) error
+}
+
+func RegisterLoadBalancerServer(s *grpc.Server, srv LoadBalancerServer) {
+	s.RegisterService(&_LoadBalancer_serviceDesc, srv)
+}
+
+func _LoadBalancer_BalanceLoad_Handler(srv interface{}, stream grpc.ServerStream) error {
+	return srv.(LoadBalancerServer).BalanceLoad(&loadBalancerBalanceLoadServer{stream})
+}
+
+type LoadBalancer_BalanceLoadServer interface {
+	Send(*grpc_lb_v1.LoadBalanceResponse) error
+	Recv() (*grpc_lb_v1.LoadBalanceRequest, error)
+	grpc.ServerStream
+}
+
+type loadBalancerBalanceLoadServer struct {
+	grpc.ServerStream
+}
+
+func (x *loadBalancerBalanceLoadServer) Send(m *grpc_lb_v1.LoadBalanceResponse) error {
+	return x.ServerStream.SendMsg(m)
+}
+
+func (x *loadBalancerBalanceLoadServer) Recv() (*grpc_lb_v1.LoadBalanceRequest, error) {
+	m := new(grpc_lb_v1.LoadBalanceRequest)
+	if err := x.ServerStream.RecvMsg(m); err != nil {
+		return nil, err
+	}
+	return m, nil
+}
+
+var _LoadBalancer_serviceDesc = grpc.ServiceDesc{
+	ServiceName: "grpc.lb.v1.LoadBalancer",
+	HandlerType: (*LoadBalancerServer)(nil),
+	Methods:     []grpc.MethodDesc{},
+	Streams: []grpc.StreamDesc{
+		{
+			StreamName:    "BalanceLoad",
+			Handler:       _LoadBalancer_BalanceLoad_Handler,
+			ServerStreams: true,
+			ClientStreams: true,
+		},
+	},
+	Metadata: "grpc_lb_v1/service/service.proto",
+}
+
+func init() { proto.RegisterFile("grpc_lb_v1/service/service.proto", fileDescriptor0) }
+
+var fileDescriptor0 = []byte{
+	// 142 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0x52, 0x48, 0x2f, 0x2a, 0x48,
+	0x8e, 0xcf, 0x49, 0x8a, 0x2f, 0x33, 0xd4, 0x2f, 0x4e, 0x2d, 0x2a, 0xcb, 0x4c, 0x4e, 0x85, 0xd1,
+	0x7a, 0x05, 0x45, 0xf9, 0x25, 0xf9, 0x42, 0x5c, 0x20, 0x15, 0x7a, 0x39, 0x49, 0x7a, 0x65, 0x86,
+	0x52, 0x4a, 0x48, 0xaa, 0x73, 0x53, 0x8b, 0x8b, 0x13, 0xd3, 0x53, 0x8b, 0xe1, 0x0c, 0x88, 0x7a,
+	0xa3, 0x24, 0x2e, 0x1e, 0x9f, 0xfc, 0xc4, 0x14, 0xa7, 0xc4, 0x9c, 0xc4, 0xbc, 0xe4, 0xd4, 0x22,
+	0xa1, 0x20, 0x2e, 0x6e, 0x28, 0x1b, 0x24, 0x2c, 0x24, 0xa7, 0x87, 0x30, 0x4f, 0x0f, 0x49, 0x61,
+	0x50, 0x6a, 0x61, 0x69, 0x6a, 0x71, 0x89, 0x94, 0x3c, 0x4e, 0xf9, 0xe2, 0x82, 0xfc, 0xbc, 0xe2,
+	0x54, 0x0d, 0x46, 0x03, 0x46, 0x27, 0xce, 0x28, 0x76, 0xa8, 0x23, 0x93, 0xd8, 0xc0, 0xb6, 0x1a,
+	0x03, 0x02, 0x00, 0x00, 0xff, 0xff, 0x39, 0x4e, 0xb0, 0xf8, 0xc9, 0x00, 0x00, 0x00,
+}

vendor/google.golang.org/grpc/grpclb/grpc_lb_v1/service/service.proto

@@ -0,0 +1,26 @@
+// Copyright 2016 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package grpc.lb.v1;
+option go_package = "google.golang.org/grpc/grpclb/grpc_lb_v1/service";
+
+import "grpc_lb_v1/messages/messages.proto";
+
+service LoadBalancer {
+  // Bidirectional rpc to get a list of servers.
+  rpc BalanceLoad(stream LoadBalanceRequest)
+      returns (stream LoadBalanceResponse);
+}