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:

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

The handler code on server side:

package main

import (
    "context"

    "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" }, err
}

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

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

PingPong

The code on client side:

package main

import (
    "context"
    "fmt"

    "xx/echo"
    "xx/echo/echoservice"
	
	"github.com/cloudwego/kitex/client"
)

func main() {
    cli, err := echoservice.NewClient("destServiceName", client.WithHostPorts("0.0.0.0:8888"))
    if err != nil {
        panic(err)
    }
    req := echo.NewRequest()
    req.Msg = "hello"
    resp, err := cli.Echo(context.Background(), req)
    if err != nil {
        panic(err)
    }

    fmt.Println(resp.Msg)
    // resp.Msg == "world"
}

Oneway

The code on client side:

package main

import (
    "context"

    "xx/echo"
    "xx/echo/echoservice"
    
    "github.com/cloudwego/kitex/client"
)

func main() {
    cli, err := echoservice.NewClient("destServiceName", client.WithHostPorts("0.0.0.0:8888"))
    if err != nil {
        panic(err)
    }
    req := echo.NewRequest()
    req.Msg = "hello"
    err = cli.VisitOneway(context.Background(), req)
    if err != nil {
        panic(err)
    }
    // no response return
}

Protobuf

Kitex supports two kinds of protocols that carry 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
    • Be able to interoperate with gRPC. Use the same definition as gRPC service, and supports Unary (PingPong) and Streaming calls.

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:

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

The handler code on server side:

package main

import (
	"log"
	"time"
    "context"

    "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
        }
        log.Println("received:" , req.GetMsg())
    }
}

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) {
	ctx, cancel := context.WithCancel(context.Background())
	errChan := make(chan error, 1)

	go func() {
		for {
			select {
			case <- ctx.Done():
				return
			default:
				req,err := stream.Recv()
				if err != nil {
					errChan <- err
					cancel()
					return
				}
				log.Println("received:", req.GetMsg())
			}
		}
	}()
	go func() {
		for {
			select {
			case <- ctx.Done():
				return
			default:
				resp := &echo.Response{Msg: "world"}
				if err := stream.Send(resp); err != nil {
					errChan <- err
					cancel()
					return
				}
			}
			time.Sleep(time.Second)
		}
	}()
	
	err = <-errChan
	cancel()
	return err
}

func main() {
    svr := echo.NewServer(handler{})

	err := svr.Run()

	if err != nil {
		log.Println(err.Error())
	}
}

Streaming

ClientSideStreaming:

package main

import (
    "context"
	"time"

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

    "github.com/cloudwego/kitex/client"
}

func main() {
    cli, err := echoservice.NewClient("destServiceName", client.WithHostPorts("0.0.0.0:8888"))
    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)
        }
        time.Sleep(time.Second)
    }

}

ServerSideStreaming:

package main

import (
    "context"
	"log"
	"time"

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

    "github.com/cloudwego/kitex/client"
}

func main() {
    cli, err := echoseervice.NewClient("destServiceName", client.WithHostPorts("0.0.0.0:8888"))
    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()
        log.Println("response:",resp.GetMsg())
        if err != nil {
            panic(err)
        }
        time.Sleep(time.Second)
        // resp.Msg == "world"
    }

}

BidiSideStreaming:

package main

import (
    "context"
	"log"
	"time"

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

    "github.com/cloudwego/kitex/client"
}

func main() {
    cli, err := echoservice.NewClient("destServiceName", client.WithHostPorts("0.0.0.0:8888"))
    if err != nil {
        panic(err)
    }
    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)
            }
            time.Sleep(time.Second)
        }
    }()
    for {
        resp, err := bidiStream.Recv()
        if err != nil {
            panic(err)
        }
        log.Println(resp.GetMsg())
        // resp.Msg == "world"
    }
}

Last modified March 20, 2024 : docs: fix the code of kitex tutorials (#1038) (d39106c)