kratos源码分析系列(1)（kvm源码解析与应用 pdf）

https://github.com/go-kratos/kratos是b站开源的一个微服务框架，整体来看它结合grpc生态中的grpc-gateway，以及wire依赖注入和众多常用的trace，matrix，log等中间件提供了一套微服务框架。我先尝试一下使用。

安装

% go install github.com/go-kratos/kratos/cmd/kratos/v2@latest

创建demo

 % kratos new helloworld
 Creating service helloworld, layout repo is https://github.com/go-kratos/kratos-layout.git, please wait a moment.


当前分支没有跟踪信息。
请指定您要合并哪一个分支。
详见 git-pull(1)。


    git pull <远程> <分支>


如果您想要为此分支创建跟踪信息，您可以执行：


    git branch --set-upstream-to=origin/<分支> master




ERROR: Failed to create project(exit status 1)

这是由于国内环境拉项目模板会失败。可以换个源。

% kratos new helloworld -r https://gitee.com/go-kratos/kratos-layout.git


 Creating service helloworld, layout repo is https://gitee.com/go-kratos/kratos-layout.git, please wait a moment.


正克隆到 '/Users/xiazemin/.kratos/repo/gitee.com/go-kratos/kratos-layout@main'...


CREATED helloworld/.gitignore (528 bytes)
CREATED helloworld/Dockerfile (459 bytes)
CREATED helloworld/LICENSE (1066 bytes)
CREATED helloworld/Makefile (2399 bytes)
CREATED helloworld/README.md (1062 bytes)
CREATED helloworld/api/helloworld/v1/error_reason.pb.go (4991 bytes)
CREATED helloworld/api/helloworld/v1/error_reason.proto (289 bytes)
CREATED helloworld/api/helloworld/v1/greeter.pb.go (8074 bytes)
CREATED helloworld/api/helloworld/v1/greeter.proto (678 bytes)
CREATED helloworld/api/helloworld/v1/greeter_grpc.pb.go (3560 bytes)
CREATED helloworld/api/helloworld/v1/greeter_http.pb.go (2139 bytes)
CREATED helloworld/cmd/helloworld/main.go (1712 bytes)
CREATED helloworld/cmd/helloworld/wire.go (584 bytes)
CREATED helloworld/cmd/helloworld/wire_gen.go (1068 bytes)
CREATED helloworld/configs/config.yaml (266 bytes)
CREATED helloworld/go.mod (990 bytes)
CREATED helloworld/go.sum (18962 bytes)
CREATED helloworld/internal/biz/README.md (6 bytes)
CREATED helloworld/internal/biz/biz.go (128 bytes)
CREATED helloworld/internal/biz/greeter.go (1235 bytes)
CREATED helloworld/internal/conf/conf.pb.go (20782 bytes)
CREATED helloworld/internal/conf/conf.proto (761 bytes)
CREATED helloworld/internal/data/README.md (7 bytes)
CREATED helloworld/internal/data/data.go (472 bytes)
CREATED helloworld/internal/data/greeter.go (834 bytes)
CREATED helloworld/internal/server/grpc.go (825 bytes)
CREATED helloworld/internal/server/http.go (829 bytes)
CREATED helloworld/internal/server/server.go (150 bytes)
CREATED helloworld/internal/service/README.md (10 bytes)
CREATED helloworld/internal/service/greeter.go (688 bytes)
CREATED helloworld/internal/service/service.go (136 bytes)
CREATED helloworld/openapi.yaml (1130 bytes)
CREATED helloworld/third_party/README.md (14 bytes)
CREATED helloworld/third_party/errors/errors.proto (411 bytes)
CREATED helloworld/third_party/google/api/annotations.proto (1051 bytes)
CREATED helloworld/third_party/google/api/client.proto (3395 bytes)
CREATED helloworld/third_party/google/api/field_behavior.proto (3011 bytes)
CREATED helloworld/third_party/google/api/http.proto (15140 bytes)
CREATED helloworld/third_party/google/api/httpbody.proto (2671 bytes)
CREATED helloworld/third_party/google/protobuf/any.proto (5909 bytes)
CREATED helloworld/third_party/google/protobuf/api.proto (7734 bytes)
CREATED helloworld/third_party/google/protobuf/compiler/plugin.proto (8754 bytes)
CREATED helloworld/third_party/google/protobuf/descriptor.proto (38497 bytes)
CREATED helloworld/third_party/google/protobuf/duration.proto (4895 bytes)
CREATED helloworld/third_party/google/protobuf/empty.proto (2429 bytes)
CREATED helloworld/third_party/google/protobuf/field_mask.proto (8185 bytes)
CREATED helloworld/third_party/google/protobuf/source_context.proto (2341 bytes)
CREATED helloworld/third_party/google/protobuf/struct.proto (3779 bytes)
CREATED helloworld/third_party/google/protobuf/timestamp.proto (6459 bytes)
CREATED helloworld/third_party/google/protobuf/type.proto (6126 bytes)
CREATED helloworld/third_party/google/protobuf/wrappers.proto (4042 bytes)
CREATED helloworld/third_party/openapi/v3/annotations.proto (2196 bytes)
CREATED helloworld/third_party/openapi/v3/openapi.proto (22082 bytes)
CREATED helloworld/third_party/validate/README.md (81 bytes)
CREATED helloworld/third_party/validate/validate.proto (31270 bytes)


 Project creation succeeded helloworld
 Use the following command to start the project :


$ cd helloworld
$ go generate ./...
$ go build -o ./bin/ ./...
$ ./bin/helloworld -conf ./configs


       Thanks for using Kratos
   Tutorial: https://go-kratos.dev/docs/getting-started/start

可以发现模板生成成功了

 %  cd helloworld
 % go mod download

安装wire

% go get github.com/google/wire/cmd/wire@v0.5.0
go get: installing executables with 'go get' in module mode is deprecated.
  To adjust and download dependencies of the current module, use 'go get -d'.
  To install using requirements of the current module, use 'go install'.
  To install ignoring the current module, use 'go install' with a version,
  like 'go install example.com/cmd@latest'.
  For more information, see https://golang.org/doc/go-get-install-deprecation
  or run 'go help get' or 'go help install'.

生成依赖

% go generate ./...
wire: helloworld/cmd/helloworld: wrote /Users/xiazemin/bilibili/kratos/helloworld/cmd/helloworld/wire_gen.go

启动服务

 % kratos run
DEBUG msg=config loaded: config.yaml format: yaml
INFO ts=2022-09-04T21:36:08+08:00 caller=server.go:276 service.id=xiazemindeMacBook-Pro.local service.name= service.version= trace.id= span.id= msg=[HTTP] server listening on: [::]:8000
INFO ts=2022-09-04T21:36:08+08:00 caller=server.go:193 service.id=xiazemindeMacBook-Pro.local service.name= service.version= trace.id= span.id= msg=[gRPC] server listening on: [::]:9000
INFO ts=2022-09-04T21:36:25+08:00 caller=greeter.go:43 service.id=xiazemindeMacBook-Pro.local service.name= service.version= trace.id= span.id= msg=CreateGreeter: kratos
^@^@^@^@^CINFO ts=2022-09-04T21:42:10+08:00 caller=server.go:291 service.id=xiazemindeMacBook-Pro.local service.name= service.version= trace.id= span.id= msg=[HTTP] server stopping


INFO ts=2022-09-04T21:42:10+08:00 caller=server.go:202 service.id=xiazemindeMacBook-Pro.local service.name= service.version= trace.id= span.id= msg=[gRPC] server stopping
INFO ts=2022-09-04T21:42:10+08:00 caller=data.go:20 service.id=xiazemindeMacBook-Pro.local service.name= service.version= trace.id= span.id= msg=closing the data resources

测试

 % curl 'http://127.0.0.1:8000/helloworld/kratos'
{"message":"Hello kratos"}

接着我们看下目录结构

% tree
.
|____cmd
| |____helloworld
| | |____wire_gen.go
| | |____wire.go
| | |____main.go
|____go.mod
|____LICENSE
|____Dockerfile
|____Makefile
|____internal
| |____biz
| | |____README.md
| | |____greeter.go
| | |____biz.go
| |____server
| | |____server.go
| | |____grpc.go
| | |____http.go
| |____service
| | |____service.go
| | |____README.md
| | |____greeter.go
| |____data
| | |____README.md
| | |____data.go
| | |____greeter.go
| |____conf
| | |____conf.proto
| | |____conf.pb.go
|____go.sum
|____README.md
|____third_party
| |____validate
| | |____README.md
| | |____validate.proto
| |____google
| | |____api
| | | |____client.proto
| | | |____http.proto
| | | |____annotations.proto
| | | |____field_behavior.proto
| | | |____httpbody.proto
| | |____protobuf
| | | |____timestamp.proto
| | | |____field_mask.proto
| | | |____api.proto
| | | |____duration.proto
| | | |____struct.proto
| | | |____wrappers.proto
| | | |____source_context.proto
| | | |____any.proto
| | | |____type.proto
| | | |____empty.proto
| | | |____compiler
| | | | |____plugin.proto
| | | |____descriptor.proto
| |____openapi
| | |____v3
| | | |____annotations.proto
| | | |____openapi.proto
| |____README.md
| |____errors
| | |____errors.proto
|____.gitignore
|____configs
| |____config.yaml
|____api
| |____helloworld
| | |____v1
| | | |____greeter_http.pb.go
| | | |____error_reason.proto
| | | |____error_reason.pb.go
| | | |____greeter.pb.go
| | | |____greeter.proto
| | | |____greeter_grpc.pb.go
|____openapi.yaml

具体分层含义可以参考官方文档：
https://go-kratos.dev/docs/intro/layout

  .
├── Dockerfile  
├── LICENSE
├── Makefile  
├── README.md
├── api // 下面维护了微服务使用的proto文件以及根据它们所生成的go文件
│   └── helloworld
│       └── v1
│           ├── error_reason.pb.go
│           ├── error_reason.proto
│           ├── error_reason.swagger.json
│           ├── greeter.pb.go
│           ├── greeter.proto
│           ├── greeter.swagger.json
│           ├── greeter_grpc.pb.go
│           └── greeter_http.pb.go
├── cmd  // 整个项目启动的入口文件
│   └── server
│       ├── main.go
│       ├── wire.go  // 我们使用wire来维护依赖注入
│       └── wire_gen.go
├── configs  // 这里通常维护一些本地调试用的样例配置文件
│   └── config.yaml
├── generate.go
├── go.mod
├── go.sum
├── internal  // 该服务所有不对外暴露的代码，通常的业务逻辑都在这下面，使用internal避免错误引用
│   ├── biz   // 业务逻辑的组装层，类似 DDD 的 domain 层，data 类似 DDD 的 repo，而 repo 接口在这里定义，使用依赖倒置的原则。
│   │   ├── README.md
│   │   ├── biz.go
│   │   └── greeter.go
│   ├── conf  // 内部使用的config的结构定义，使用proto格式生成
│   │   ├── conf.pb.go
│   │   └── conf.proto
│   ├── data  // 业务数据访问，包含 cache、db 等封装，实现了 biz 的 repo 接口。我们可能会把 data 与 dao 混淆在一起，data 偏重业务的含义，它所要做的是将领域对象重新拿出来，我们去掉了 DDD 的 infra层。
│   │   ├── README.md
│   │   ├── data.go
│   │   └── greeter.go
│   ├── server  // http和grpc实例的创建和配置
│   │   ├── grpc.go
│   │   ├── http.go
│   │   └── server.go
│   └── service  // 实现了 api 定义的服务层，类似 DDD 的 application 层，处理 DTO 到 biz 领域实体的转换(DTO -> DO)，同时协同各类 biz 交互，但是不应处理复杂逻辑
│       ├── README.md
│       ├── greeter.go
│       └── service.go
└── third_party  // api 依赖的第三方proto
    ├── README.md
    ├── google
    │   └── api
    │       ├── annotations.proto
    │       ├── http.proto
    │       └── httpbody.proto
    └── validate
        ├── README.md
        └── validate.proto

首先看下api目录它以
api/helloworld/v1/greeter.proto为模板生成了对应的grpc pb文件和http pb文件，前者是通过proto-gen-go生成的，后者是通过grpc gateway生成的。

我们从main函数开始读下这个模板 cmd/helloworld/main.go核心代码下面两行

app, cleanup, err := wireApp(bc.Server, bc.Data, logger)
if err := app.Run(); err != nil {

wireApp进行了依赖注入，看下wire.go里面声明的依赖

func wireApp(*conf.Server, *conf.Data, log.Logger) (*kratos.App, func(), error) {
  panic(wire.Build(server.ProviderSet, data.ProviderSet, biz.ProviderSet, service.ProviderSet, newApp))
}

最后一个参数newApp函数是在main.go里声明的。它new里一个kratos.App对象

func newApp(logger log.Logger, gs *grpc.Server, hs *http.Server) *kratos.App {
  return kratos.New(
    kratos.ID(id),
    kratos.Name(Name),
    kratos.Version(Version),
    kratos.Metadata(map[string]string{}),
    kratos.Logger(logger),
    kratos.Server(
      gs,
      hs,
    ),
  )
}

最后就是通过app.Run启动server进行端口监听的。具体代码实现在
github.com/go-kratos/kratos/v2@v2.4.1/app.go中，可以看到它时结合waitGroup和errorGroup来控制多个server的起动和停止的。

func (a *App) Run() error {
    wg := sync.WaitGroup{}
    for _, srv := range a.opts.servers {
      srv := srv
      eg.Go(func() error {
        <-ctx.Done() // wait for stop signal
        stopCtx, cancel := context.WithTimeout(NewContext(a.opts.ctx, a), a.opts.stopTimeout)
        defer cancel()
        return srv.Stop(stopCtx)
      })
      wg.Add(1)
      eg.Go(func() error {
        wg.Done()
        return srv.Start(NewContext(a.opts.ctx, a))
      })
    }
    wg.Wait()

可以看到核心代码是通过waitGroup等待所有的的server停止服务。但是对于每一个服务通过errorGroup来等待当前服务的超时或者完成服务正常结束的。

以上就是main服务的整体流程。下一讲我们分析依赖注入的server，biz，data和serverice。