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Прозрачный gRPC-proxy один-ко-многим - Андрей С...

Прозрачный gRPC-proxy один-ко-многим - Андрей Смирнов

GopherCon Russia

April 23, 2021
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Transcript

  1. Agenda Why gRPC? Why API gateway? Why Go? First iteration

    in Go, problems and solutions. Transparent proxying in Go using gRPC. Cutting and concatenating protobuf messages.
  2. Use Cases for gRPC API Gateway Migrating from monolith to

    smaller services (or vice versa) Migrating to new API version Common authentication or authorization layer Logging, traceability, … Non-trivial proxy logic: send one request to many backends, combine responses
  3. Ping-pong gRPC service message Ping { string value = 1;

    } message Pong { string value = 1; } service TestService { rpc PingPong(Ping) returns (Pong) {} }
  4. Easy! (?) func (s *Proxy) connect() { s.conn = grpc.Dial(...)

    s.client = pb.NewTestServiceClient(conn) } func (s *Proxy) PingPong(ctx context.Context, ping *pb.Ping) (*pb.Pong, error) { return s.client.PingPong(ctx, ping) }
  5. gRPC metadata gRPC metadata: headers, trailers Go gRPC Client Metadata:

    Metadata Go gRPC Server Metadata: Headers Trailers
  6. Metadata handling md, _ := metadata.FromIncomingContext(ctx) outCtx := metadata.NewOutgoingContext(ctx, md)

    var header, trailer metadata.MD resp, err := s.client.Ping(outCtx, ping, grpc.Header(&header), grpc.Trailer(&trailer)) grpc.SendHeader(ctx, header) grpc.SetTrailer(ctx, trailer) return resp, err
  7. Streaming Service message Counter { int32 counter = 1; }

    service TestService { rpc Counter(Empty) returns (stream Counter) {} }
  8. Streaming Proxy (½) ctx, cancel := context.WithCancel(srv.Context()) defer cancel() cli,

    err := s.client.Counter(ctx, in) if err != nil { return err } ...
  9. Streaming Proxy (½) for { msg, err := cli.Recv() switch

    { case err == io.EOF: return nil case err != nil: return err } err = srv.Send(msg) if err != nil { return err } }
  10. Protobuf Update (v2) message Ping { string value = 1;

    int counter = 2; } message Pong { string value = 1; int counter = 2; } service TestService { rpc PingPong(Ping) returns (Pong) {} }
  11. Version Mismatch gRPC backend API Gateway v1 v2 Ping value:

    “foo” counter: 42 Ping value: “foo” counter: 42 Pong value: “bar” counter: 24 Pong value: “bar” counter: 24
  12. grpc.Codec type Codec interface { // Marshal returns the wire

    format of v. Marshal(v interface{}) ([]byte, error) // Unmarshal parses the wire format into v. Unmarshal(data []byte, v interface{}) error }
  13. Raw Codec type frame struct { payload []byte } func

    (c *rawCodec) Marshal(v interface{}) ([]byte, error) { out, ok := v.(*frame) if !ok { return fmt.Errorf("expected frame") } return out.payload, nil } func (c *rawCodec) Unmarshal(data []byte, v interface{}) error { dst, ok := v.(*frame) if !ok { return fmt.Errorf("expected frame")} dst.payload = data return nil }
  14. grpc.NewClientStream func handler(srv interface{}, serverStream grpc.ServerStream) error { conn, err

    = grpc.Dial(addr, grpc.WithCodec(proxy.Codec())) clientStream, err = grpc.NewClientStream( ctx, &grpc.StreamDesc{ ServerStreams: true, ClientStreams: true, }, conn, fullMethodName) // copy clientStream <> serverStream }
  15. Response Metadata message ResponseMetadata { string upstream_node = 1; string

    upstream_error = 2; } message Pong { ResponseMetadata metadata = 99; string value = 1; }
  16. Enriching Response gRPC backend node-1 API Gateway Pong value: “bar”

    Pong value: “bar” metadata: upstream_node: node_1
  17. Protobuf Glue Pong value: “bar” (1) Pong value: “bar” (1)

    metadata: (99) upstream_node: node_1 (1) Pong metadata: (99) upstream_node: node_1 (1) (type: bytes, field: 1, length: 3): “bar” (type: bytes, field: 99, length: N): [(type: bytes, field: 1, length: 6): “node_1”] (type: bytes, field: 1, length: 3): “bar” (type: bytes, field: 99, length: N): [(type: bytes, field: 1, length: 6): “node_1”] protobuf serialization: messages:
  18. Embedding Errors gRPC backend API Gateway Ping value: “foo” Pong

    metadata: upstream_node: node_1 upstream_error: ECONNREFUSED connection refused
  19. Server Streaming API Gateway Ping value: “foo” Pong metadata: upstream_node:

    node_1 upstream_error: ECONNREFUSED Pong value: “bar” metadata: upstream_node: node_2
  20. Unary Calls API Gateway Ping value: “foo” Pong metadata: upstream_node:

    node_1 upstream_error: ECONNREFUSED Pong value: “bar” metadata: upstream_node: node_2
  21. Unary Protobuf Definition message ResponseMetadata { string upstream_node = 99;

    string upstream_error = 100; } message Pong { ResponseMetadata metadata = 99; string value = 1; } message PongResponse { repeated Pong messages = 1; }
  22. Protobuf Scissors PongResponse messages: (1) - Pong: value: “bar” (1)

    (type: bytes, field: 1, length: N): [(type: bytes, field: 1, length: 3): bar] PongResponse messages: (1) - Pong: value: “bar” (1) metadata: (99) u_node: node_1 (1) (type: bytes, field: 1, length: N’): [(type: bytes, field: 1, length: 3): bar (type: bytes: field: 99, length: K): [(type: bytes: field: 1, length: 6): node_1 ]
  23. Q&A