文章作者:jqpeng
原文链接: drone的pipeline原理与代码分析
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",
"alias": "git",
"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",
"alias": "build",
"image": "golang:1.7",
"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_SCRIPT": "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",
"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",
"HOME": "/root",
"SHELL": "/bin/sh"
},
"entrypoint": [
"/bin/sh",
"-c"
],
"command": [
"echo $CI_SCRIPT | base64 -d | /bin/sh -e"
],
"volumes": [
"pipeline_default:/go"
],
"networks": [
{
"name": "pipeline_default",
"aliases": [
"build"
]
}
],
"on_success": true,
"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.Engineif 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 enginestarted int64 // 开始时间
ctx context.Contexttracer Tracerlogger 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 envdefer func() { r.engine.Destroy(r.ctx, r.spec)}()// 初始化docker enginer.started = time.Now().Unix()if err := r.engine.Setup(r.ctx, r.spec); err != nil { return err}
// 依次运行stagefor _, 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.Groupdone := make(chan error)
// 遍历执行stepfor _, 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 nilcase 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, Code: wait.ExitCode, }}return nil
}
作者：Jadepeng
出处：jqpeng的技术记事本–http://www.cnblogs.com/xiaoqi
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