Dapr源码解析-五分钟快速添加并构建你的自定义组件

今天跟大家分享一个小教程，如何自己动手写一个新组件，并加载到Dapr runtime。

前期准备

1. 关于Dapr runtime的启动过程，如何加载和实例化组件可以参考之前写的文章Dapr runtime 启动过程
2. Dapr开发环境配置，可以参考Dapr 开发环境配置

开始编码

克隆Dapr和 component-contrib

cd $GOPATH/src

# Clone dapr
mkdir -p github.com/dapr/dapr
git clone https://github.com/dapr/dapr.git github.com/dapr/dapr

# Clone component-contrib
mkdir -p github.com/dapr/components-contrib
git clone https://github.com/dapr/components-contrib.git github.com/dapr/components-contrib

编写组件

假设，我们组件名字叫：Mytest
首先在component-contrib项目下，创建mytest包。

1. 在mytest文件夹创建接口约束文件：github.com/dapr/components-contrib/mytest/mytest.go
   mytest组件提供两个方法，Init和Info

package mytest

type Mytest interface {
    // Init this component.
    Init(metadata Metadata)

    // Info show method
    Info(info string)
}

2. metadata.go：接收组件配置文件YAML中定义的Metadata字段

package mytest

type Metadata struct {
    Properties map[string]string `json:"properties"`
}

3.为mytest组件提供两种实现方式：demof和demos
在mytest包里创建demof包和demos包，分别在demof.go和demos.go实现Mytest组件
demof.go

package demof

import (
    "github.com/dapr/components-contrib/mytest"
    "github.com/dapr/kit/logger"
)

type Demof struct {
    logger logger.Logger
}

func NewDemof(logger logger.Logger) *Demof {
    d := &Demof{
        logger: logger,
    }

    return d
}

func (d *Demof) Init(metadata mytest.Metadata) {
    d.logger.Info(metadata)
}

func (d *Demof) Info(info string) {
    d.logger.Info("this is Demof, I received %s", info)
}

demos.go

package demos

import (
    "github.com/dapr/components-contrib/mytest"
    "github.com/dapr/kit/logger"
)

type Demos struct {
    logger logger.Logger
}

func NewDemos(logger logger.Logger) *Demos {
    d := &Demos{
        logger: logger,
    }

    return d
}

func (d *Demos) Init(metadata mytest.Metadata) {
    d.logger.Info(metadata)
}

func (d *Demos) Info(info string) {
    d.logger.Info("this is Demos, I received %s", info)
}

至此Mytest组件已经具备了可以执行的所有要素，目录解构如下

component-contrib
    |_mytest
        |_demof
            |_demof.go
        |_demos
            |_demos.go
        metadata.go
        mytest.go

将Mytest组件注册到Dapr runtime

1. 实现Mytest组件注册接口github.com/dapr/dapr/pkg/components/mytest/registry.go

package mytest

import (
    "strings"

    "github.com/pkg/errors"

    "github.com/dapr/components-contrib/mytest"
    "github.com/dapr/dapr/pkg/components"
)

type Mytest struct {
    Name          string
    FactoryMethod func() mytest.Mytest
}

func New(name string, factoryMethod func() mytest.Mytest) Mytest {
    return Mytest{
        Name:          name,
        FactoryMethod: factoryMethod,
    }
}

type Registry interface {
    Register(components ...Mytest)
    Create(name, version string) (mytest.Mytest, error)
}

type mytestRegistry struct {
    mytests map[string]func() mytest.Mytest
}

func NewRegistry() Registry {
    return &mytestRegistry{
        mytests: map[string]func() mytest.Mytest{},
    }
}

func (t *mytestRegistry) Register(components ...Mytest) {
    for _, component := range components {
        t.mytests[createFullName(component.Name)] = component.FactoryMethod
    }
}

func (t *mytestRegistry) Create(name, version string) (mytest.Mytest, error) {
    if method, ok := t.getMytest(name, version); ok {
        return method(), nil
    }
    return nil, errors.Errorf("couldn't find Mytest %s/%s", name, version)
}

func (t *mytestRegistry) getMytest(name, version string) (func() mytest.Mytest, bool) {
    nameLower := strings.ToLower(name)
    versionLower := strings.ToLower(version)
    mytestFn, ok := t.mytests[nameLower+"/"+versionLower]
    if ok {
        return mytestFn, true
    }
    if components.IsInitialVersion(versionLower) {
        mytestFn, ok = t.mytests[nameLower]
    }
    return mytestFn, ok
}

func createFullName(name string) string {
    return strings.ToLower("mytest." + name)
}

2.更新runtime 组件发现和注册机制
github.com/dapr/dapr/pkg/runtime/options.go
扩展runtimeOpts

import(
"github.com/dapr/dapr/pkg/components/mytest"
)
runtimeOpts struct {
    ...
    mytests     []mytest.Mytest
}

添加runtime组件注册函数

func WithMytests(mytests ...mytest.Mytest) Option {
    return func(o *runtimeOpts) {
        o.mytests = append(o.mytests, mytests...)
    }
}

更新runtime启动流程，注册Mytest组件
github.com/dapr/dapr/pkg/runtime/runtime.go

import(
....
"github.com/dapr/components-contrib/mytest"
    mytest_loader "github.com/dapr/dapr/pkg/components/mytest"
)

...
//更新变量声明
const (
    mytestComponent             ComponentCategory = "mytest"
)
var componentCategoriesNeedProcess = []ComponentCategory{
    ...
    mytestComponent,
}
...
// 扩展 DaprRuntime  components of the runtime.
type DaprRuntime struct {
    ...
    mytestRegistry mytest_loader.Registry
    mytests        map[string]mytest.Mytest
}

// NewDaprRuntime returns a new runtime with the given runtime config and global config.
func NewDaprRuntime(runtimeConfig *Config, globalConfig *config.Configuration, accessControlList *config.AccessControlList, resiliencyProvider resiliency.Provider) *DaprRuntime {
    ctx, cancel := context.WithCancel(context.Background())
    return &DaprRuntime{
        ...
        mytestRegistry: mytest_loader.NewRegistry(),
        mytests:        map[string]mytest.Mytest{},
    }
}

...
//初始化runtime
func (a *DaprRuntime) initRuntime(opts *runtimeOpts) error {
    ...
    a.mytestRegistry.Register(opts.mytests...)
    ...
}

//本示例仅以http api接口为例
func (a *DaprRuntime) startHTTPServer(port int, publicPort *int, profilePort int, allowedOrigins string, pipeline http_middleware.Pipeline) error {
    a.daprHTTPAPI = http.NewAPI(a.runtimeConfig.ID,
        a.appChannel,
        a.directMessaging,
        a.getComponents,
        a.resiliency,
        a.stateStores,
        a.lockStores,
        a.secretStores,
        a.secretsConfiguration,
        a.configurationStores,
        a.getPublishAdapter(),
        a.actor,
        a.sendToOutputBinding,
        a.globalConfig.Spec.TracingSpec,
        a.ShutdownWithWait,
        a.getComponentsCapabilitesMap,
        a.mytests,
    )
...
}

//runtime初始化过程从components目录 发现并初始化组件
func (a *DaprRuntime) doProcessOneComponent(category ComponentCategory, comp components_v1alpha1.Component) error {
    switch category {
    ...
    case mytestComponent:
        return a.initMytest(comp)
    }
    return nil
}

func (a *DaprRuntime) initMytest(c components_v1alpha1.Component) error {
    mytestIns, err := a.mytestRegistry.Create(c.Spec.Type, c.Spec.Version)
    if err != nil {
        log.Errorf("error create component %s: %s", c.ObjectMeta.Name, err)
    }
    a.mytests[c.ObjectMeta.Name] = mytestIns
    properties := a.convertMetadataItemsToProperties(c.Spec.Metadata)
    log.Debug("properties is ", properties)
    mytestIns.Init(mytest.Metadata{
        Properties: properties,
    })
    return err
}

实现Dapr http api调用接口

github.com/dapr/dapr/pkg/http/api.go

import (
"github.com/dapr/components-contrib/mytest"
)

type api struct {
    ....
    mytests              map[string]mytest.Mytest
}

const (
    ...
    mytestParam          = "mytestName"
)

// NewAPI returns a new API.
func NewAPI(
    ...
    mytests map[string]mytest.Mytest,
) API {
    ...
    api := &api{
        ...
        mytests:              mytests,
    }
    ...
    api.endpoints = append(api.endpoints, api.constructMytestEndpoints()...)

    return api
}
/**
 * regist Mytest component api
 */
func (a *api) constructMytestEndpoints() []Endpoint {
    return []Endpoint{
        {
            Methods: []string{fasthttp.MethodGet, fasthttp.MethodPost},
            Route:   "mytest/{mytestName}/info",
            Version: apiVersionV1,
            Handler: a.onMytestInfo,
        },
    }
}

/**
 * switch Mytest component instance
 */
func (a *api) getMytestWithRequestValidation(reqCtx *fasthttp.RequestCtx) (mytest.Mytest, string, error) {
    if a.mytests == nil || len(a.mytests) == 0 {
        msg := NewErrorResponse("ERR_MYTEST_NOT_CONFIGURED", messages.ErrMytestNotFound)
        respond(reqCtx, withError(fasthttp.StatusInternalServerError, msg))
        log.Debug(msg)
        return nil, "", errors.New(msg.Message)
    }

    mytestName := a.getMytestName(reqCtx)
    if a.mytests[mytestName] == nil {
        msg := NewErrorResponse("ERR_MYTEST_NOT_CONFIGURED", fmt.Sprintf(messages.ErrMytestNotFound, mytestName))
        respond(reqCtx, withError(fasthttp.StatusBadRequest, msg))
        log.Debug(msg)
        return nil, "", errors.New(msg.Message)
    }
    return a.mytests[mytestName], mytestName, nil
}

func (a *api) getMytestName(reqCtx *fasthttp.RequestCtx) string {
    return reqCtx.UserValue(mytestParam).(string)
}

func (a *api) onMytestInfo(reqCtx *fasthttp.RequestCtx) {
    log.Debug("calling mytest components")
    mytestInstance, _, err := a.getMytestWithRequestValidation(reqCtx)
    if err != nil {
        log.Debug(err)
        return
    }

    mytestInstance.Info()
    respond(reqCtx, withEmpty())
}

Dapr runtime初始化入口

github.com/dapr/dapr/cmd/daprd/main.go

import (
    //mytest demo
    "github.com/dapr/components-contrib/mytest"
    mytest_demof "github.com/dapr/components-contrib/mytest/demof"
    mytest_demos "github.com/dapr/components-contrib/mytest/demos"
    mytest_loader "github.com/dapr/dapr/pkg/components/mytest"
)
...

runtime.WithSecretStores(
...
        runtime.WithMytests(
            mytest_loader.New("demof", func() mytest.Mytest {
                return mytest_demof.NewDemof(logContrib)
            }),
            mytest_loader.New("demos", func() mytest.Mytest {
                return mytest_demos.NewDemos(logContrib)
            }),
        ),
...
)
....

在component目录中添加mytest.yaml 配置文件

默认是在.dapr/components目录

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: demof
spec:
  type: mytest.demof
  version: v1
  metadata:
  - name: mName
    value: mValue

编译并运行Dapr

go mod edit -replace github.com/dapr/components-contrib=../components-contrib

go mod tidy

make DEBUG=1 build

# Back up the current daprd
cp ~/.dapr/bin/daprd ~/.dapr/bin/daprd.bak
cp ./dist/darwin_amd64/debug/daprd ~/.dapr/bin

dapr run --app-id myapp --dapr-http-port 3500  --log-level debug

观察Dapr启动日志

DEBU[0000] loading component. name: demof, type: mytest.demof/v1  app_id=myapp instance=MacBook-Pro-3.local scope=dapr.runtime type=log ver=edge
INFO[0000] component loaded. name: demof, type: mytest.demof/v1  app_id=myapp instance=MacBook-Pro-3.local scope=dapr.runtime type=log ver=edge
INFO[0000] {map[mName:mValue]}                           app_id=myapp instance=MacBook-Pro-3.local scope=dapr.contrib type=log ver=edge

demof组件已经加载成功，接下来使用http api接口尝试调用demof info接口

curl http://localhost:3500/v1.0/mytest/demof/info

日志记录到了我们在组件中打印的信息

INFO[0126] this is Demof, I'm working                    app_id=myapp instance=MacBook-Pro-3.local scope=dapr.contrib type=log ver=edge

修改一下mytest.yaml 配置文件，实例化demos

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: demos
spec:
  type: mytest.demos
  version: v1
  metadata:
  - name: mName
    value: mValue

尝试调用demos info接口

curl http://localhost:3500/v1.0/mytest/demos/info

INFO[0058] this is Demos, I'm working                    app_id=myapp instance=MacBook-Pro-3.local scope=dapr.contrib type=log ver=edge

组件正常工作。

以上示例代码已经放在github上
https://github.com/RcXu/dapr.git
https://github.com/RcXu/components-contrib.git
分支名为：dev-demo

多谢阅读，敬请斧正！