Message Types

Kitex supports message types of PingPong、Oneway、Streaming.

Protocols

The table below is message types, codecs and transports supported by Kitex.

Message Types Codec Transport
PingPong Thrift / Protobuf TTHeader / HTTP2(gRPC)
Oneway Thrift TTHeader
Streaming Protobuf HTTP2(gRPC)
  • PingPong: the client always waits for a response after sending a request
  • Oneway: the client does not expect any response after sending a request
  • Streaming: the client can send one or more requests while receiving one or more responses.

Thrift

When the codec is thrift, Kitex supports PingPong and Oneway. The streaming on thrift is under development.

Example

Given an IDL:

namespace go echo

struct Request {
    1: string Msg
}

struct Response {
    1: string Msg
}

service EchoService {
    Response Echo(1: Request req); // pingpong method
    oneway void VisitOneway(1: Request req); // oneway method
}

The layout of generated code might be:

.
└── kitex_gen
    └── echo
        ├── echo.go
        ├── echoservice
        │   ├── client.go
        │   ├── echoservice.go
        │   ├── invoker.go
        │   └── server.go
        └── k-echo.go

The handler code in server side might be:

package main

import (
    "xx/echo"
    "xx/echo/echoservice"
)

type handler struct {}

func (handler) Echo(ctx context.Context, req *echo.Request) (r *echo.Response, err error) {
    //...
    return &echo.Response{ Msg: "world" }
}

func (handler) VisitOneway(ctx context.Context, req *echo.Request) (err error) {
    //...
    return nil
}

func main() {
    svr, err := echoservice.NewServer(handler{})
    if err != nil {
        panic(err)
    }
    svr.Run()
}

PingPong

The code in client side might be:

package main

import (
    "xx/echo"
    "xx/echo/echoservice"
)

func main() {
    cli, err := echoservice.NewClient("destServiceName")
    if err != nil {
        panic(err)
    }
    req := echo.NewRequest()
    req.Msg = "hello"
    resp, err := cli.Echo(req)
    if err != nil {
        panic(err)
    }
    // resp.Msg == "world"
}

Oneway

The code in client side might be:

package main

import (
    "xx/echo"
    "xx/echo/echoservice"
)

func main() {
    cli, err := echoservice.NewClient("destServiceName")
    if err != nil {
        panic(err)
    }
    req := echo.NewRequest()
    req.Msg = "hello"
    err = cli.VisitOneway(req)
    if err != nil {
        panic(err)
    }
    // no response return
}

Protobuf

Kitex supports two kind of protocols that carries Protobuf payload:

  • Kitex Protobuf
    • Only supports the PingPong type of messages. If any streaming method is defined in the IDL, the protocol will switch to gRPC.
  • The gRPC Protocol
    • The protocol that shipped with gRPC.

Example

The following is an example showing how to use the streaming types.

Given an IDL:

syntax = "proto3";

option go_package = "echo";

package echo;

message Request {
  string msg = 1;
}

message Response {
  string msg = 1;
}

service EchoService {
  rpc ClientSideStreaming(stream Request) returns (Response) {} // client streaming
  rpc ServerSideStreaming(Request) returns (stream Response) {} // server streaming
  rpc BidiSideStreaming(stream Request) returns (stream Response) {} // bidirectional streaming
}

The generated code might be:

.
└── kitex_gen
    └── echo
        ├── echo.pb.go
        └── echoservice
            ├── client.go
            ├── echoservice.go
            ├── invoker.go
            └── server.go

The handler code in server side:

package main

import (
    "sync"

    "xx/echo"
    "xx/echo/echoservice"
}

type handler struct{}

func (handler) ClientSideStreaming(stream echo.EchoService_ClientSideStreamingServer) (err error) {
    for {
        req, err := stream.Recv()
        if err != nil {
            return err
        }
    }
}

func (handler) ServerSideStreaming(req *echo.Request, stream echo.EchoService_ServerSideStreamingServer) (err error) {
      _ = req
      for {
          resp := &echo.Response{Msg: "world"}
          if err := stream.Send(resp); err != nil {
              return err
          }
      }
}

func (handler) BidiSideStreaming(stream echo.EchoService_BidiSideStreamingServer) (err error) {
    var once sync.Once
	go func() {
		for {
			req, err2 := stream.Recv()
			log.Println("received:", req.GetMsg())
			if err2 != nil {
				once.Do(func() {
					err = err2
				})
				break
			}
		}
	}()
	for {
		resp := &echo.Response{Msg: "world"}
		if err2 := stream.Send(resp); err2 != nil {
			once.Do(func() {
				err = err2
			})
			return
		}
	}
	return
}

func main() {
    svr, err := echoservice.NewServer(handler{})
    if err != nil {
        panic(err)
    }
    svr.Run()
}

Streaming

ClientSideStreaming:

package main

import (
    "xx/echo"
    "xx/echo/echoservice"
}

func main() {
    cli, err := echoservice.NewClient("destServiceName")
    if err != nil {
        panic(err)
    }
    cliStream, err := cli.ClientSideStreaming(context.Background())
    if err != nil {
        panic(err)
    }
    for {
        req := &echo.Request{Msg: "hello"}
        if err := cliStream.Send(req); err != nil {
            panic(err)
        }
    }

}

ServerSideStreaming:

package main

import (
    "xx/echo"
    "xx/echo/echoservice"
}

func main() {
    cli, err := echoseervice.NewClient("destServiceName")
    if err != nil {
        panic(err)
    }
    req := &echo.Request{Msg: "hello"}
    svrStream, err := cli.ServerSideStreaming(context.Background(), req)
    if err != nil {
        panic(err)
    }
    for {
        resp, err := svrStream.Recv()
        if err != nil {
            panic(err)
        }
        // resp.Msg == "world"
    }

}

BidiSideStreaming:

package main

import (
    "xx/echo"
    "xx/echo/echoservice"
}

func main() {
    cli, err := echoseervice.NewClient("destServiceName")
    if err != nil {
        panic(err)
    }
    req := &echo.Request{Msg: "hello"}
    bidiStream, err := cli.BidiSideStreaming(context.Background())
    if err != nil {
        panic(err)
    }
    go func() {
        for {
            req := &echo.Request{Msg: "hello"}
            err := bidiStream.Send(req)
            if err != nil {
                panic(err)
            }
        }
    }()
    for {
        resp, err := bidiStream.Recv()
        if err != nil {
            panic(err)
        }
        // resp.Msg == "world"
    }
}

Last modified July 13, 2023 : docs: update code example in kitex-generic call (#711) (f80b346)