drone的pipeline原理与代码分析

发布时间：2020-12-14 05:03:27 所属栏目：百科来源：网络整理

导读：最近的一个项目，需要实现一个工作任务流（task pipeline），基于之前CICD的经验，jenkins pipeline和drone的pipeline进入候

最近的一个项目，需要实现一个工作任务流（task pipeline），基于之前CICD的经验，jenkins pipeline和drone的pipeline进入候选。

drone是基于go的cicd解决方案，github上有1.6万+star，本文简单对比了其和jenkins的区别，重点介绍了drone的pipeline原理，并简单分析了代码。

jenkins 与 drone

对比项	jenkins	drone
pipeline定义	编写jenkinsfile	编写流程yml
运行方式	在一个pod里运行	每一步骤起对应的container，通过挂载volume实现数据共享
运行环境	物理机或者容器环境，包括K8S	docker容器环境
开发语言	java	golang

drone pipeline好处是相对更轻量级，yml定义也相对简洁清晰，按照功能来划分容器，可以方便的实现task的复用，而jenkins则是完全打包到一个镜像，会造成单个镜像体积过大，比如jenkins的单个镜像超过2G。

drone的pipeline，是基于https://github.com/cncd/pipeline 实现的，这里简单分析下其原理。

编译和执行 drone pipeline

要了解一个程序的原理，先从输入输出讲起。

先安装：

go get -u github.com/cncd/pipeline
go install github.com/cncd/pipeline/pipec

然后测试

cd $GOPATH/github.com/cncd/pipeline/samples/sample_1
# ll
total 28
drwxr-xr-x  2 root root 4096 Jan 22 11:44 ./
drwxr-xr-x 13 root root 4096 Jan 22 11:02 ../
-rw-r--r--  1 root root  549 Jan 22 11:02 .env
-rw-r--r--  1 root root 6804 Jan 22 16:30 pipeline.json
-rw-r--r--  1 root root  229 Jan 22 11:02 pipeline.yml
-rw-r--r--  1 root root  138 Jan 22 11:02 README.md

pipeline.yml 定义文件
pipeline.json 编译后的配置文件
.env 环境变量

先来查看pipeline.yml 定义

workspace:
  base: /go
  path: src/github.com/drone/envsubst

clone:
  git:
    image: plugins/git
    depth: 50

pipeline:
  build:
    image: golang:1.7
    commands:
      - go get -t ./...
      - go build
      - go test -v

上面的yml定义了：

工作目录workspace
初始化工作，git clone仓库,仓库地址在.env里定义
然后是定义pipeline，
- pipeline下面是step数组，这里只有一个build
- 使用golang:1.7镜像
- 构建命令在commands数组里定义

通过pipec compilecompile配置文件：

# pipec compile
Successfully compiled pipeline.yml to pipeline.json

查看编译后的pipeline.json

{
  "pipeline": [
    {
      "name": "pipeline_clone_0","alias": "git","steps": [
        {
          "name": "pipeline_clone_0","image": "plugins/git:latest","working_dir": "/go/src/github.com/drone/envsubst","environment": {
            "CI": "drone","CI_BUILD_CREATED": "1486119586","CI_BUILD_EVENT": "push","CI_BUILD_NUMBER": "6","CI_BUILD_STARTED": "1486119585","CI_COMMIT_AUTHOR": "bradrydzewski","CI_COMMIT_AUTHOR_NAME": "bradrydzewski","CI_COMMIT_BRANCH": "master","CI_COMMIT_MESSAGE": "added a few more test cases for escaping behavior","CI_COMMIT_REF": "refs/heads/master","CI_COMMIT_SHA": "d0876d3176965f9552a611cbd56e24a9264355e6","CI_REMOTE_URL": "https://github.com/drone/envsubst.git","CI_REPO": "drone/envsubst","CI_REPO_LINK": "https://github.com/drone/envsubst","CI_REPO_NAME": "drone/envsubst","CI_REPO_REMOTE": "https://github.com/drone/envsubst.git","CI_SYSTEM": "pipec","CI_SYSTEM_ARCH": "linux/amd64","CI_SYSTEM_LINK": "https://github.com/cncd/pipec","CI_SYSTEM_NAME": "pipec","CI_WORKSPACE": "/go/src/github.com/drone/envsubst","DRONE": "true","DRONE_ARCH": "linux/amd64","DRONE_BRANCH": "master","DRONE_BUILD_CREATED": "1486119586","DRONE_BUILD_EVENT": "push","DRONE_BUILD_LINK": "https://github.com/cncd/pipec/drone/envsubst/6","DRONE_BUILD_NUMBER": "6","DRONE_BUILD_STARTED": "1486119585","DRONE_COMMIT": "d0876d3176965f9552a611cbd56e24a9264355e6","DRONE_COMMIT_AUTHOR": "bradrydzewski","DRONE_COMMIT_BRANCH": "master","DRONE_COMMIT_MESSAGE": "added a few more test cases for escaping behavior","DRONE_COMMIT_REF": "refs/heads/master","DRONE_COMMIT_SHA": "d0876d3176965f9552a611cbd56e24a9264355e6","DRONE_JOB_STARTED": "1486119585","DRONE_REMOTE_URL": "https://github.com/drone/envsubst.git","DRONE_REPO": "drone/envsubst","DRONE_REPO_LINK": "https://github.com/drone/envsubst","DRONE_REPO_NAME": "envsubst","DRONE_REPO_OWNER": "drone","DRONE_REPO_SCM": "git","DRONE_WORKSPACE": "/go/src/github.com/drone/envsubst","PLUGIN_DEPTH": "50"
          },"volumes": [
            "pipeline_default:/go"
          ],"networks": [
            {
              "name": "pipeline_default","aliases": [
                "git"
              ]
            }
          ],"on_success": true,"auth_config": {}
        }
      ]
    },{
      "name": "pipeline_stage_0","alias": "build","steps": [
        {
          "name": "pipeline_step_0","image": "golang:1.7","CI_SCRIPT": "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","HOME": "/root","SHELL": "/bin/sh"
          },"entrypoint": [
            "/bin/sh","-c"
          ],"command": [
            "echo $CI_SCRIPT | base64 -d | /bin/sh -e"
          ],"aliases": [
                "build"
              ]
            }
          ],"auth_config": {}
        }
      ]
    }
  ],"networks": [
    {
      "name": "pipeline_default","driver": "bridge"
    }
  ],"volumes": [
    {
      "name": "pipeline_default","driver": "local"
    }
  ],"secrets": null
}

简单分析结构：

pipeline 定义了执行的stage，每个stage有一个或者多个step
networks、volumes、secrets 分别定义网络、存储和secrets
- 通过network，实现container互通
- 通过volumes实现数据共享

最后执行，通过pipec exec：

# pipec exec
proc "pipeline_clone_0" started
+ git init
Initialized empty Git repository in /go/src/github.com/drone/envsubst/.git/
+ git remote add origin https://github.com/drone/envsubst.git
+ git fetch --no-tags --depth=50 origin +refs/heads/master:
From https://github.com/drone/envsubst
 * branch            master     -> FETCH_HEAD
 * [new branch]      master     -> origin/master
+ git reset --hard -q d0876d3176965f9552a611cbd56e24a9264355e6
+ git submodule update --init --recursive
proc "pipeline_clone_0" exited with status 0
proc "pipeline_step_0" started
+ go get -t ./...
+ go build
+ go test -v
=== RUN   TestExpand
--- PASS: TestExpand (0.00s)
=== RUN   TestFuzz
--- PASS: TestFuzz (0.01s)
=== RUN   Test_len
--- PASS: Test_len (0.00s)
=== RUN   Test_lower
--- PASS: Test_lower (0.00s)
=== RUN   Test_lowerFirst
--- PASS: Test_lowerFirst (0.00s)
=== RUN   Test_upper
--- PASS: Test_upper (0.00s)
=== RUN   Test_upperFirst
--- PASS: Test_upperFirst (0.00s)
=== RUN   Test_default
--- PASS: Test_default (0.00s)
PASS
ok      github.com/drone/envsubst   0.009s
proc "pipeline_step_0" exited with status 0

pipeline 原理分析

编译过程

可以形象的理解为 .env+pipeline.yml --> pipeline.json

编译过程不复杂，主要是解析pipeline.yml为Config:

Config struct {
        Cache     libcompose.Stringorslice
        Platform  string
        Branches  Constraint
        Workspace Workspace
        Clone     Containers
        Pipeline  Containers
        Services  Containers
        Networks  Networks
        Volumes   Volumes
        Labels    libcompose.SliceorMap
    }

然后转换为json对应的config：

Config struct {
        Stages   []*Stage   `json:"pipeline"` // pipeline stages
        Networks []*Network `json:"networks"` // network definitions
        Volumes  []*Volume  `json:"volumes"`  // volume definitions
        Secrets  []*Secret  `json:"secrets"`  // secret definitions
    }

该部分主要代码在pipeline/frontend里

执行过程

我们主要关注执行过程，主要代码在pipeline/backend里。

首先是读取配置文件为backend.Config

config,err := pipeline.Parse(reader)
    if err != nil {
        return err
    }

然后创建执行环境，目前的代码仅docker可用，k8s是空代码。

var engine backend.Engine
    if c.Bool("kubernetes") {
        engine = kubernetes.New(
            c.String("kubernetes-namepsace"),c.String("kubernetes-endpoint"),c.String("kubernetes-token"),)
    } else {
        engine,err = docker.NewEnv()
        if err != nil {
            return err
        }
    }

接着开始执行

ctx,cancel := context.WithTimeout(context.Background(),c.Duration("timeout"))
    defer cancel()
    ctx = interrupt.WithContext(ctx)

    return pipeline.New(config,pipeline.WithContext(ctx),pipeline.WithLogger(defaultLogger),pipeline.WithTracer(defaultTracer),pipeline.WithEngine(engine),).Run()

其中pipeline.NEW创建了Runtime对象;

type Runtime struct {
    err     error  // 错误信息
    spec    *backend.Config  // 配置信息
    engine  backend.Engine  // docker engine
    started int64 // 开始时间

    ctx    context.Context
    tracer Tracer
    logger Logger
}

其中Engine，操作容器的interface，目前仅docker可用。

// Engine defines a container orchestration backend and is used
// to create and manage container resources.
type Engine interface {
    // Setup the pipeline environment.
    Setup(context.Context,*Config) error
    // Start the pipeline step.
    Exec(context.Context,*Step) error
    // Kill the pipeline step.
    Kill(context.Context,*Step) error
    // Wait for the pipeline step to complete and returns
    // the completion results.
    Wait(context.Context,*Step) (*State,error)
    // Tail the pipeline step logs.
    Tail(context.Context,*Step) (io.ReadCloser,error)
    // Destroy the pipeline environment.
    Destroy(context.Context,*Config) error
}

关注Run：

// Run starts the runtime and waits for it to complete.
func (r *Runtime) Run() error {
    
    // 延迟函数，用于销毁docker env
    defer func() {
        r.engine.Destroy(r.ctx,r.spec)
    }()
    
    // 初始化docker engine
    r.started = time.Now().Unix()
    if err := r.engine.Setup(r.ctx,r.spec); err != nil {
        return err
    }
   
   // 依次运行stage
    for _,stage := range r.spec.Stages {
        select {
        case <-r.ctx.Done():
            return ErrCancel
        // 执行
        case err := <-r.execAll(stage.Steps):
            if err != nil {
                r.err = err
            }
        }
    }

    return r.err
}

重点在于使用errgroup.Group通过协程方式运行step：

// 执行所有steps
func (r *Runtime) execAll(procs []*backend.Step) <-chan error {
    var g errgroup.Group
    done := make(chan error)
    // 遍历执行step
    for _,proc := range procs {
       // 协程 exec
        proc := proc
        g.Go(func() error {
            return r.exec(proc)
        })
    }

    go func() {
        done <- g.Wait()
        close(done)
    }()
    return done
}

// 执行单个step
func (r *Runtime) exec(proc *backend.Step) error {
    switch {
    case r.err != nil && proc.OnFailure == false:
        return nil
    case r.err == nil && proc.OnSuccess == false:
        return nil
    }
    
    // trace日志
    if r.tracer != nil {
        state := new(State)
        state.Pipeline.Time = r.started
        state.Pipeline.Error = r.err
        state.Pipeline.Step = proc
        state.Process = new(backend.State) // empty
        if err := r.tracer.Trace(state); err == ErrSkip {
            return nil
        } else if err != nil {
            return err
        }
    }
   
   // docker engine执行
    if err := r.engine.Exec(r.ctx,proc); err != nil {
        return err
    }
   
   // 记录日志信息
    if r.logger != nil {
        rc,err := r.engine.Tail(r.ctx,proc)
        if err != nil {
            return err
        }

        go func() {
            r.logger.Log(proc,multipart.New(rc))
            rc.Close()
        }()
    }

    if proc.Detached {
        return nil
    }

   // 等待docker engine执行完成
    wait,err := r.engine.Wait(r.ctx,proc)
    if err != nil {
        return err
    }

    if r.tracer != nil {
        state := new(State)
        state.Pipeline.Time = r.started
        state.Pipeline.Error = r.err
        state.Pipeline.Step = proc
        state.Process = wait
        if err := r.tracer.Trace(state); err != nil {
            return err
        }
    }
   
    if wait.OOMKilled {
        return &OomError{
            Name: proc.Name,Code: wait.ExitCode,}
    } else if wait.ExitCode != 0 {
        return &ExitError{
            Name: proc.Name,}
    }
    return nil
}

作者：Jadepeng
出处：jqpeng的技术记事本--http://www.cnblogs.com/xiaoqi 您的支持是对博主最大的鼓励，感谢您的认真阅读。本文版权归作者所有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。

（编辑：李大同）

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