Server-side streaming RPC
- client측 java code: https://github.com/grpc/grpc-java/blob/master/examples/src/main/java/io/grpc/examples/routeguide/RouteGuideUtil.java
- server 측 golang code: https://github.com/grpc/grpc-go/blob/master/examples/route_guide/server/server.go
먼저 protocol buffer의 spec을 보도록 하자.
service RouteGuide {
// A simple RPC.
//
// Obtains the feature at a given position.
//
// A feature with an empty name is returned if there's no feature at the given
// position.
rpc GetFeature(Point) returns (Feature) {}
// A server-to-client streaming RPC.
//
// Obtains the Features available within the given Rectangle. Results are
// streamed rather than returned at once (e.g. in a response message with a
// repeated field), as the rectangle may cover a large area and contain a
// huge number of features.
rpc ListFeatures(Rectangle) returns (stream Feature) {}
...
}우리가 사용했던 simple grpc인 GetFeature과 달리 ListFeatures의 return type 부분을 보면 stream이라는 지시어를 볼 수 있다.
이는 Feature 데이터를 다량의 stream으로 전달하겠다는 것이다. 즉, 서버 측에서 단일 요청인 Rectangle을 받고 다량의 Feature stream 데이터를 전달한다는 것이다.
Server-side streaming RPC golang 서버 구현
routeGuideServer에 ListFeatures만 구현 추가해주면 된다.
- go-routeguide/server/routeguide_server.go
func (s *routeGuideServer) ListFeatures(rect *pb.Rectangle, stream grpc.ServerStreamingServer[pb.Feature]) error {
for _, feature := range s.savedFeatures {
if inRange(feature.Location, rect) {
if err := stream.Send(feature); err != nil {
return err
}
}
}
return nil
}
func inRange(point *pb.Point, rect *pb.Rectangle) bool {
left := math.Min(float64(rect.Lo.Longitude), float64(rect.Hi.Longitude))
right := math.Max(float64(rect.Lo.Longitude), float64(rect.Hi.Longitude))
top := math.Max(float64(rect.Lo.Latitude), float64(rect.Hi.Latitude))
bottom := math.Min(float64(rect.Lo.Latitude), float64(rect.Hi.Latitude))
if float64(point.Longitude) >= left &&
float64(point.Longitude) <= right &&
float64(point.Latitude) >= bottom &&
float64(point.Latitude) <= top {
return true
}
return false
}ListFeatures 메서드의 스펙은 RouteGuideServer을 보고 똑같이 쓰면 된다. 단, 지금의 경우 pb.Feature 타입에 대한 generic을 사용하고 있지만 generic 사용이 불가능한 버전에서는 호환성을 위해서 다음의 메서드도 있을 것이다.
- go-routeguide/gorouteguide/route_guide_grpc.pb.go
// This type alias is provided for backwards compatibility with existing code that references the prior non-generic stream type by name.
type RouteGuide_ListFeaturesServer = grpc.ServerStreamingServer[Feature]이 타입을 사용해도 똑같이 동작한다.
func (s *routeGuideServer) ListFeatures(rect *pb.Rectangle, stream RouteGuide_ListFeaturesServer) error {
for _, feature := range s.savedFeatures {
if inRange(feature.Location, rect) {
if err := stream.Send(feature); err != nil {
return err
}
}
}
return nil
}함수 구현을 보면 client로 부터 rect 데이터를 받고 rect안에 있다면 stream.Send로 다량의 stream을 보내주는 방식이다.
stream 변수인 grpc.ServerStreamServer을 보면 다음과 같다.
type ServerStreamingServer[Res any] interface {
// Send sends a response message to the client. The server handler may
// call Send multiple times to send multiple messages to the client. An
// error is returned if the stream was terminated unexpectedly, and the
// handler method should return, as the stream is no longer usable.
Send(*Res) error
// ServerStream is embedded to provide Context, SetHeader, SendHeader, and
// SetTrailer functionality. No other methods in the ServerStream should
// be called directly.
ServerStream
}Send가 있고 ServerStream 구조체를 임베딩하고 있는 데, 주석에 볼 수 있듯이 서버 측에서는 Context, SetHeader, SendHeader, SetTrailer 기능 이외에는 사용하지 말도록 하자. 내부를 보면 Recv도 있는데 이런 건 호출하면 안된다는 것이다.
클라이언트 측으로 가기 전에 서버측의 데이터를 좀 더 추가해주도록 하자.
var exampleData = []byte(`[{
"location": {
"latitude": 407838351,
"longitude": -746143763
},
"name": "Patriots Path, Mendham, NJ 07945, USA"
}, {
"location": {
"latitude": 408122808,
"longitude": -743999179
},
"name": "101 New Jersey 10, Whippany, NJ 07981, USA"
}, {
"location": {
"latitude": 413628156,
"longitude": -749015468
},
"name": "U.S. 6, Shohola, PA 18458, USA"
}, {
"location": {
"latitude": 419999544,
"longitude": -740371136
},
"name": "5 Conners Road, Kingston, NY 12401, USA"
}, {
"location": {
"latitude": 414008389,
"longitude": -743951297
},
"name": "Mid Hudson Psychiatric Center, New Hampton, NY 10958, USA"
}, {
"location": {
"latitude": 419611318,
"longitude": -746524769
},
"name": "287 Flugertown Road, Livingston Manor, NY 12758, USA"
}, {
"location": {
"latitude": 406109563,
"longitude": -742186778
},
"name": "4001 Tremley Point Road, Linden, NJ 07036, USA"
}, {
"location": {
"latitude": 416802456,
"longitude": -742370183
},
"name": "352 South Mountain Road, Wallkill, NY 12589, USA"
}, {
"location": {
"latitude": 412950425,
"longitude": -741077389
},
"name": "Bailey Turn Road, Harriman, NY 10926, USA"
}, {
"location": {
"latitude": 412144655,
"longitude": -743949739
},
"name": "193-199 Wawayanda Road, Hewitt, NJ 07421, USA"
}, {
"location": {
"latitude": 415736605,
"longitude": -742847522
},
"name": "406-496 Ward Avenue, Pine Bush, NY 12566, USA"
}, {
"location": {
"latitude": 413843930,
"longitude": -740501726
},
"name": "162 Merrill Road, Highland Mills, NY 10930, USA"
}, {
"location": {
"latitude": 410873075,
"longitude": -744459023
},
"name": "Clinton Road, West Milford, NJ 07480, USA"
}, {
"location": {
"latitude": 412346009,
"longitude": -744026814
},
"name": "16 Old Brook Lane, Warwick, NY 10990, USA"
}, {
"location": {
"latitude": 402948455,
"longitude": -747903913
},
"name": "3 Drake Lane, Pennington, NJ 08534, USA"
}, {
"location": {
"latitude": 406337092,
"longitude": -740122226
},
"name": "6324 8th Avenue, Brooklyn, NY 11220, USA"
}, {
"location": {
"latitude": 406421967,
"longitude": -747727624
},
"name": "1 Merck Access Road, Whitehouse Station, NJ 08889, USA"
}, {
"location": {
"latitude": 416318082,
"longitude": -749677716
},
"name": "78-98 Schalck Road, Narrowsburg, NY 12764, USA"
}, {
"location": {
"latitude": 415301720,
"longitude": -748416257
},
"name": "282 Lakeview Drive Road, Highland Lake, NY 12743, USA"
}, {
"location": {
"latitude": 402647019,
"longitude": -747071791
},
"name": "330 Evelyn Avenue, Hamilton Township, NJ 08619, USA"
}, {
"location": {
"latitude": 412567807,
"longitude": -741058078
},
"name": "New York State Reference Route 987E, Southfields, NY 10975, USA"
}, {
"location": {
"latitude": 416855156,
"longitude": -744420597
},
"name": "103-271 Tempaloni Road, Ellenville, NY 12428, USA"
}, {
"location": {
"latitude": 404663628,
"longitude": -744820157
},
"name": "1300 Airport Road, North Brunswick Township, NJ 08902, USA"
}, {
"location": {
"latitude": 407113723,
"longitude": -749746483
},
"name": ""
}, {
"location": {
"latitude": 402133926,
"longitude": -743613249
},
"name": ""
}, {
"location": {
"latitude": 400273442,
"longitude": -741220915
},
"name": ""
}, {
"location": {
"latitude": 411236786,
"longitude": -744070769
},
"name": ""
}, {
"location": {
"latitude": 411633782,
"longitude": -746784970
},
"name": "211-225 Plains Road, Augusta, NJ 07822, USA"
}, {
"location": {
"latitude": 415830701,
"longitude": -742952812
},
"name": ""
}, {
"location": {
"latitude": 413447164,
"longitude": -748712898
},
"name": "165 Pedersen Ridge Road, Milford, PA 18337, USA"
}, {
"location": {
"latitude": 405047245,
"longitude": -749800722
},
"name": "100-122 Locktown Road, Frenchtown, NJ 08825, USA"
}, {
"location": {
"latitude": 418858923,
"longitude": -746156790
},
"name": ""
}, {
"location": {
"latitude": 417951888,
"longitude": -748484944
},
"name": "650-652 Willi Hill Road, Swan Lake, NY 12783, USA"
}, {
"location": {
"latitude": 407033786,
"longitude": -743977337
},
"name": "26 East 3rd Street, New Providence, NJ 07974, USA"
}, {
"location": {
"latitude": 417548014,
"longitude": -740075041
},
"name": ""
}, {
"location": {
"latitude": 410395868,
"longitude": -744972325
},
"name": ""
}, {
"location": {
"latitude": 404615353,
"longitude": -745129803
},
"name": ""
}, {
"location": {
"latitude": 406589790,
"longitude": -743560121
},
"name": "611 Lawrence Avenue, Westfield, NJ 07090, USA"
}, {
"location": {
"latitude": 414653148,
"longitude": -740477477
},
"name": "18 Lannis Avenue, New Windsor, NY 12553, USA"
}, {
"location": {
"latitude": 405957808,
"longitude": -743255336
},
"name": "82-104 Amherst Avenue, Colonia, NJ 07067, USA"
}, {
"location": {
"latitude": 411733589,
"longitude": -741648093
},
"name": "170 Seven Lakes Drive, Sloatsburg, NY 10974, USA"
}, {
"location": {
"latitude": 412676291,
"longitude": -742606606
},
"name": "1270 Lakes Road, Monroe, NY 10950, USA"
}, {
"location": {
"latitude": 409224445,
"longitude": -748286738
},
"name": "509-535 Alphano Road, Great Meadows, NJ 07838, USA"
}, {
"location": {
"latitude": 406523420,
"longitude": -742135517
},
"name": "652 Garden Street, Elizabeth, NJ 07202, USA"
}, {
"location": {
"latitude": 401827388,
"longitude": -740294537
},
"name": "349 Sea Spray Court, Neptune City, NJ 07753, USA"
}, {
"location": {
"latitude": 410564152,
"longitude": -743685054
},
"name": "13-17 Stanley Street, West Milford, NJ 07480, USA"
}, {
"location": {
"latitude": 408472324,
"longitude": -740726046
},
"name": "47 Industrial Avenue, Teterboro, NJ 07608, USA"
}, {
"location": {
"latitude": 412452168,
"longitude": -740214052
},
"name": "5 White Oak Lane, Stony Point, NY 10980, USA"
}, {
"location": {
"latitude": 409146138,
"longitude": -746188906
},
"name": "Berkshire Valley Management Area Trail, Jefferson, NJ, USA"
}, {
"location": {
"latitude": 404701380,
"longitude": -744781745
},
"name": "1007 Jersey Avenue, New Brunswick, NJ 08901, USA"
}, {
"location": {
"latitude": 409642566,
"longitude": -746017679
},
"name": "6 East Emerald Isle Drive, Lake Hopatcong, NJ 07849, USA"
}, {
"location": {
"latitude": 408031728,
"longitude": -748645385
},
"name": "1358-1474 New Jersey 57, Port Murray, NJ 07865, USA"
}, {
"location": {
"latitude": 413700272,
"longitude": -742135189
},
"name": "367 Prospect Road, Chester, NY 10918, USA"
}, {
"location": {
"latitude": 404310607,
"longitude": -740282632
},
"name": "10 Simon Lake Drive, Atlantic Highlands, NJ 07716, USA"
}, {
"location": {
"latitude": 409319800,
"longitude": -746201391
},
"name": "11 Ward Street, Mount Arlington, NJ 07856, USA"
}, {
"location": {
"latitude": 406685311,
"longitude": -742108603
},
"name": "300-398 Jefferson Avenue, Elizabeth, NJ 07201, USA"
}, {
"location": {
"latitude": 419018117,
"longitude": -749142781
},
"name": "43 Dreher Road, Roscoe, NY 12776, USA"
}, {
"location": {
"latitude": 412856162,
"longitude": -745148837
},
"name": "Swan Street, Pine Island, NY 10969, USA"
}, {
"location": {
"latitude": 416560744,
"longitude": -746721964
},
"name": "66 Pleasantview Avenue, Monticello, NY 12701, USA"
}, {
"location": {
"latitude": 405314270,
"longitude": -749836354
},
"name": ""
}, {
"location": {
"latitude": 414219548,
"longitude": -743327440
},
"name": ""
}, {
"location": {
"latitude": 415534177,
"longitude": -742900616
},
"name": "565 Winding Hills Road, Montgomery, NY 12549, USA"
}, {
"location": {
"latitude": 406898530,
"longitude": -749127080
},
"name": "231 Rocky Run Road, Glen Gardner, NJ 08826, USA"
}, {
"location": {
"latitude": 407586880,
"longitude": -741670168
},
"name": "100 Mount Pleasant Avenue, Newark, NJ 07104, USA"
}, {
"location": {
"latitude": 400106455,
"longitude": -742870190
},
"name": "517-521 Huntington Drive, Manchester Township, NJ 08759, USA"
}, {
"location": {
"latitude": 400066188,
"longitude": -746793294
},
"name": ""
}, {
"location": {
"latitude": 418803880,
"longitude": -744102673
},
"name": "40 Mountain Road, Napanoch, NY 12458, USA"
}, {
"location": {
"latitude": 414204288,
"longitude": -747895140
},
"name": ""
}, {
"location": {
"latitude": 414777405,
"longitude": -740615601
},
"name": ""
}, {
"location": {
"latitude": 415464475,
"longitude": -747175374
},
"name": "48 North Road, Forestburgh, NY 12777, USA"
}, {
"location": {
"latitude": 404062378,
"longitude": -746376177
},
"name": ""
}, {
"location": {
"latitude": 405688272,
"longitude": -749285130
},
"name": ""
}, {
"location": {
"latitude": 400342070,
"longitude": -748788996
},
"name": ""
}, {
"location": {
"latitude": 401809022,
"longitude": -744157964
},
"name": ""
}, {
"location": {
"latitude": 404226644,
"longitude": -740517141
},
"name": "9 Thompson Avenue, Leonardo, NJ 07737, USA"
}, {
"location": {
"latitude": 410322033,
"longitude": -747871659
},
"name": ""
}, {
"location": {
"latitude": 407100674,
"longitude": -747742727
},
"name": ""
}, {
"location": {
"latitude": 418811433,
"longitude": -741718005
},
"name": "213 Bush Road, Stone Ridge, NY 12484, USA"
}, {
"location": {
"latitude": 415034302,
"longitude": -743850945
},
"name": ""
}, {
"location": {
"latitude": 411349992,
"longitude": -743694161
},
"name": ""
}, {
"location": {
"latitude": 404839914,
"longitude": -744759616
},
"name": "1-17 Bergen Court, New Brunswick, NJ 08901, USA"
}, {
"location": {
"latitude": 414638017,
"longitude": -745957854
},
"name": "35 Oakland Valley Road, Cuddebackville, NY 12729, USA"
}, {
"location": {
"latitude": 412127800,
"longitude": -740173578
},
"name": ""
}, {
"location": {
"latitude": 401263460,
"longitude": -747964303
},
"name": ""
}, {
"location": {
"latitude": 412843391,
"longitude": -749086026
},
"name": ""
}, {
"location": {
"latitude": 418512773,
"longitude": -743067823
},
"name": ""
}, {
"location": {
"latitude": 404318328,
"longitude": -740835638
},
"name": "42-102 Main Street, Belford, NJ 07718, USA"
}, {
"location": {
"latitude": 419020746,
"longitude": -741172328
},
"name": ""
}, {
"location": {
"latitude": 404080723,
"longitude": -746119569
},
"name": ""
}, {
"location": {
"latitude": 401012643,
"longitude": -744035134
},
"name": ""
}, {
"location": {
"latitude": 404306372,
"longitude": -741079661
},
"name": ""
}, {
"location": {
"latitude": 403966326,
"longitude": -748519297
},
"name": ""
}, {
"location": {
"latitude": 405002031,
"longitude": -748407866
},
"name": ""
}, {
"location": {
"latitude": 409532885,
"longitude": -742200683
},
"name": ""
}, {
"location": {
"latitude": 416851321,
"longitude": -742674555
},
"name": ""
}, {
"location": {
"latitude": 406411633,
"longitude": -741722051
},
"name": "3387 Richmond Terrace, Staten Island, NY 10303, USA"
}, {
"location": {
"latitude": 413069058,
"longitude": -744597778
},
"name": "261 Van Sickle Road, Goshen, NY 10924, USA"
}, {
"location": {
"latitude": 418465462,
"longitude": -746859398
},
"name": ""
}, {
"location": {
"latitude": 411733222,
"longitude": -744228360
},
"name": ""
}, {
"location": {
"latitude": 410248224,
"longitude": -747127767
},
"name": "3 Hasta Way, Newton, NJ 07860, USA"
}]`)이제 서버측 구현은 완료되었고 클라이언트 측 구현을 해주도록 하자.
Server-side streaming RPC java 클라이언트 구현
java의 client 측 구현은 더욱 간단하다.
public class RouteGuideClient {
private final RouteGuideGrpc.RouteGuideBlockingStub blockingStub;
private final RouteGuideGrpc.RouteGuideStub asyncStub;
private Random random = new Random();
private TestHelper testHelper;
...
public void listFeatures(int lowLat, int lowLon, int hiLat, int hiLon) {
System.out.printf("*** ListFeatures: lowLat=%d lowLon=%d hiLat=%d hiLon={%d", lowLat, lowLon, hiLat, hiLon);
Rectangle request =
Rectangle.newBuilder()
.setLo(Point.newBuilder().setLatitude(lowLat).setLongitude(lowLon).build())
.setHi(Point.newBuilder().setLatitude(hiLat).setLongitude(hiLon).build()).build();
Iterator<Feature> features;
try {
features = blockingStub.listFeatures(request);
for (int i = 1; features.hasNext(); i++) {
Feature feature = features.next();
System.out.println("Result #" + i + ":" + feature);
if (testHelper != null) {
testHelper.onMessage(feature);
}
}
} catch (StatusRuntimeException e) {
System.out.println("RPC failed: " + e.getStatus());
if (testHelper != null) {
testHelper.onRpcError(e);
}
}
}
}blockingStub을 사용했기 때문에 모든 응답이 올 때까지 기다린다는 특징이 있다.
listFeatures를 호출하고 Iterator<Feature>로 받아내는 것을 볼 수 있다. grpc stub이 만들어낸 listFeatures 구현을 보면 다음과 같다.
...
public java.util.Iterator<com.grpc.javarouteguide.grpc.routeguide.Feature> listFeatures(
com.grpc.javarouteguide.grpc.routeguide.Rectangle request) {
return io.grpc.stub.ClientCalls.blockingServerStreamingCall(
getChannel(), getListFeaturesMethod(), getCallOptions(), request);
}
}
...blockingServerStreamingCall static 메서드를 호출하는 것을 볼 수 있다. 따라가면 다음의 메서드 형식이 나온다.
...
public static <ReqT, RespT> Iterator<RespT> blockingServerStreamingCall(Channel channel, MethodDescriptor<ReqT, RespT> method, CallOptions callOptions, ReqT req) {
ClientCall<ReqT, RespT> call = channel.newCall(method, callOptions.withOption(STUB_TYPE_OPTION, ClientCalls.StubType.BLOCKING));
BlockingResponseStream<RespT> result = new BlockingResponseStream<RespT>(call);
asyncUnaryRequestCall(call, req, result.listener());
return result;
}
...응답으로 Iterator<RespT> 을 반환하는 것을 볼 수 있다. 제네릭으로 <ReqT, RespT>를 받는데, ReqT는 Rectangle이고 RespT는 Feature이다.
iterator를 통해서 순회하면서 데이터를 읽는 코드인 것이다. 이제 코드를 실행시켜서 요청을 보내보도록 하자.
@SpringBootApplication
public class JavaRouteguideApplication {
public static void main(String[] args) throws InterruptedException {
SpringApplication.run(JavaRouteguideApplication.class, args);
String target = "localhost:50051";
List<Feature> features;
ManagedChannel channel = Grpc.newChannelBuilder(target, InsecureChannelCredentials.create()).build();
try {
RouteGuideClient client = new RouteGuideClient(channel);
client.listFeatures(400000000, -750000000, 420000000, -730000000);
} finally {
channel.shutdownNow().awaitTermination(5, TimeUnit.SECONDS);
}
}
}실행시켜보면 다음과 같은 결과가 나올 것이다.
*** ListFeatures: lowLat=400000000 lowLon=-750000000 hiLat=420000000 hiLon={-730000000Result #1:name: "Patriots Path, Mendham, NJ 07945, USA"
location {
latitude: 407838351
longitude: -746143763
}
...
Result #100:name: "3 Hasta Way, Newton, NJ 07860, USA"
location {
latitude: 410248224
longitude: -747127767
}클라이언트 측 java에서 gRPC로 위도 경도에 대한 데이터를 잘 보냈고, 서버는 이에 대해서 해당하는 stream 데이터 100개를 전달해준 것이다.
server-side streaming 예제를 보았으니 이번에는 client-side streaming을 보도록 하자.
R3의 망령