Message Types

Kitex supports message types of PingPong、Oneway、Streaming.

Protocols

The table below is message types, serializations and transport protocols supported by Kitex:

Message Types	Serialization	Transport Protocol
PingPong	Thrift / Protobuf	TTHeader / HTTP2(gRPC)
Oneway	Thrift	TTHeader
Streaming	Thrift / 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

Kitex supports PingPong and Oneway message types based on Thrift protocol; Simultaneously supporting Thrift Streaming over HTTP2.

The interface definitions for PingPong and Oneway are shown in the following example, and the usage of Thrift Streaming please see Thrift Streaming

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 := echoservice.NewServer(new(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"
    }
}

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Last modified September 6, 2024 : doc(xds): add xds feature document (#1126) (6235b19)