helm源码分析之dependency update

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 目前刚开始写一个月，一共写了18篇原创文章，文章目录如下：

istio多集群探秘，部署了50次多集群后我得出的结论

istio多集群链路追踪，附实操视频

istio防故障利器，你知道几个,istio新手不要读，太难！

istio业务权限控制，原来可以这么玩

istio实现非侵入压缩，微服务之间如何实现压缩

不懂envoyfilter也敢说精通istio系列-http-rbac-不要只会用AuthorizationPolicy配置权限

不懂envoyfilter也敢说精通istio系列-02-http-corsFilter-不要只会vs

不懂envoyfilter也敢说精通istio系列-03-http-csrf filter-再也不用再代码里写csrf逻辑了

不懂envoyfilter也敢说精通istio系列http-jwt_authn-不要只会RequestAuthorization

不懂envoyfilter也敢说精通istio系列-05-fault-filter-故障注入不止是vs

不懂envoyfilter也敢说精通istio系列-06-http-match-配置路由不只是vs

不懂envoyfilter也敢说精通istio系列-07-负载均衡配置不止是dr

不懂envoyfilter也敢说精通istio系列-08-连接池和断路器

不懂envoyfilter也敢说精通istio系列-09-http-route filter

不懂envoyfilter也敢说精通istio系列-network filter-redis proxy

不懂envoyfilter也敢说精通istio系列-network filter-HttpConnectionManager

不懂envoyfilter也敢说精通istio系列-ratelimit-istio ratelimit完全手册

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func newDependencyUpdateCmd(out io.Writer) *cobra.Command {//创建dependecny update命令
	client := action.NewDependency()//初始化结构体

	cmd := &cobra.Command{//创建cobra命令
		Use:     "update CHART",
		Aliases: []string{"up"},
		Short:   "update charts/ based on the contents of Chart.yaml",
		Long:    dependencyUpDesc,
		Args:    require.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			chartpath := "."//设置chartpath为当前目录
			if len(args) > 0 {//如果参数大于0个，设置chart目录为第一个参数
				chartpath = filepath.Clean(args[0])
			}
			man := &downloader.Manager{//构造manager
				Out:              out,
				ChartPath:        chartpath,
				Keyring:          client.Keyring,
				SkipUpdate:       client.SkipRefresh,
				Getters:          getter.All(settings),
				RepositoryConfig: settings.RepositoryConfig,
				RepositoryCache:  settings.RepositoryCache,
				Debug:            settings.Debug,
			}
			if client.Verify {//判断是否verify
				man.Verify = downloader.VerifyAlways
			}
			return man.Update()//执行更新
		},
	}

	f := cmd.Flags()
	f.BoolVar(&client.Verify, "verify", false, "verify the packages against signatures")//verify选项
	f.StringVar(&client.Keyring, "keyring", defaultKeyring(), "keyring containing public keys")//keyring选项
	f.BoolVar(&client.SkipRefresh, "skip-refresh", false, "do not refresh the local repository cache")//skip-refresh选项

	return cmd
}

func (m *Manager) Update() error {//执行更新
	c, err := m.loadChartDir()//加载chart
	if err != nil {
		return err
	}

	// If no dependencies are found, we consider this a successful
	// completion.
	req := c.Metadata.Dependencies//获取chart的依赖
	if req == nil {
		return nil
	}

	// Check that all of the repos we're dependent on actually exist and
	// the repo index names.
	repoNames, err := m.resolveRepoNames(req)//解析仓库名称
	if err != nil {
		return err
	}

	// For each repo in the file, update the cached copy of that repo
	if !m.SkipUpdate {//如果不跳过update
		if err := m.UpdateRepositories(); err != nil {//更新仓库
			return err
		}
	}

	// Now we need to find out which version of a chart best satisfies the
	// dependencies in the Chart.yaml
	lock, err := m.resolve(req, repoNames)//解析依赖版本
	if err != nil {
		return err
	}

	// Now we need to fetch every package here into charts/
	if err := m.downloadAll(lock.Dependencies); err != nil {//下载依赖
		return err
	}

	// downloadAll might overwrite dependency version, recalculate lock digest
	newDigest, err := resolver.HashReq(req, lock.Dependencies)//计算依赖hash
	if err != nil {
		return err
	}
	lock.Digest = newDigest//设置hash

	// If the lock file hasn't changed, don't write a new one.
	oldLock := c.Lock
	if oldLock != nil && oldLock.Digest == lock.Digest {//如果新旧hash相同则直接返回
		return nil
	}

	// Finally, we need to write the lockfile.
	return writeLock(m.ChartPath, lock, c.Metadata.APIVersion == chart.APIVersionV1)//写依赖lock文件
}

//写依赖lock文件
func writeLock(chartpath string, lock *chart.Lock, legacyLockfile bool) error {
	data, err := yaml.Marshal(lock)//把lock文件内容转成yaml
	if err != nil {
		return err
	}
	lockfileName := "Chart.lock"//设置lock文件名称
	if legacyLockfile {//如果是老版本，设置lock文件名称
		lockfileName = "requirements.lock"
	}
	dest := filepath.Join(chartpath, lockfileName)//获取完成文件名称
	return ioutil.WriteFile(dest, data, 0644)//写数据到文件
}