【kubernetes/k8s源码分析】calico node confd源码分析

github: https://github.com/kelseyhightower/confd

fork: https://github.com/projectcalico/confd

WHAT confd

     confd：根据etcd上状态信息，与本地模板，生成并更新BIRD配置

     通过lsdir获取当前目录下的所有子目录。第一层子目录为域名，根据域名即可生成acl规则、规则使用、后端名称等数据。
再重新通过瓶装域名目录，对域名目录执行lsdir，读取目录下的每个主机名，创建后端的server条目（一个域名下的负载均衡后段服务器），同时获取挂在这个目录下的属性键值对

WHY confd

       当系统变的复杂，配置项越来越多，一方面配置管理变得繁琐，另一方面配置修改后需要重新上线同样十分痛苦。这时候，需要有一套集中化配置管理系统，一方面提供统一的配置管理，另一方面提供配置变更的自动下发，及时生效。

      统一配置管理系统，常见的：zookeeper、etcd、consul、git等

1. InitConfig 函数

    首先初始化 confd 配置使用默认设置，从 confd 配置文件覆盖参数，从环境变量覆盖配置参数，最后从命令行参数覆盖配置参数

// InitConfig initializes the confd configuration by first setting defaults,
// then overriding settings from the confd config file, then overriding
// settings from environment variables, and finally overriding
// settings from flags set on the command line.
// It returns an error if any.
func InitConfig(ignoreFlags bool) (*Config, error) {
	if configFile == "" {
		if _, err := os.Stat(defaultConfigFile); !os.IsNotExist(err) {
			configFile = defaultConfigFile
		}
	}

    1.1 首先使用默认设置配置参数

// Set defaults.
config := Config{
	ConfDir:  "/etc/confd",
	Interval: 600,
	Prefix:   "",
	Typha: TyphaConfig{
		// Non-zero defaults copied from <felix>/config/config_params.go.
		K8sNamespace: "kube-system",
		ReadTimeout:  30 * time.Second,
		WriteTimeout: 10 * time.Second,
	},
}

    1.2 如果指定配置文件则从配置文件覆盖参数

// Update config from the TOML configuration file.
if configFile == "" {
	log.Info("Skipping confd config file.")
} else {
	log.Info("Loading " + configFile)
	configBytes, err := ioutil.ReadFile(configFile)
	if err != nil {
		return nil, err
	}
	_, err = toml.Decode(string(configBytes), &config)
	if err != nil {
		return nil, err
	}
}

    1.3 迭代从命令行参数读取配置参数进行覆盖

// processFlags iterates through each flag set on the command line and
// overrides corresponding configuration settings.
func processFlags(config *Config) {
	log.Info("Processing command line flags")
	v := ConfigVisitor{config: config}
	flag.Visit(v.setConfigFromFlag)
}

type ConfigVisitor struct {
	config *Config
}

func (c *ConfigVisitor) setConfigFromFlag(f *flag.Flag) {
	switch f.Name {
	case "confdir":
		c.config.ConfDir = confdir
	case "interval":
		c.config.Interval = interval
	case "noop":
		c.config.Noop = noop
	case "prefix":
		c.config.Prefix = prefix
	case "sync-only":
		c.config.SyncOnly = syncOnly
	case "calicoconfig":
		c.config.CalicoConfig = calicoconfig
	case "onetime":
		c.config.Onetime = onetime
	case "keep-stage-file":
		c.config.Onetime = keepStageFile
	}
}

    1.4 从环境变量获取参数进行配置覆盖

     环境变量前缀 CONFD_ FELIX_ CALICO_，中间 TYPHA

func readTyphaConfig(typhaConfig *TyphaConfig) {
	// When Typha is in use, there will already be variables prefixed with FELIX_, so it's
	// convenient if confd honours those too.  However there may use cases for confd to
	// have independent settings, so honour CONFD_ also.  Longer-term it would be nice to
	// coalesce around CALICO_, so support that as well.
	supportedPrefixes := []string{"CONFD_", "FELIX_", "CALICO_"}
	kind := reflect.TypeOf(*typhaConfig)
	for ii := 0; ii < kind.NumField(); ii++ {
		field := kind.Field(ii)
		nameUpper := strings.ToUpper(field.Name)
		for _, prefix := range supportedPrefixes {
			varName := prefix + "TYPHA" + nameUpper
			if value := os.Getenv(varName); value != "" && value != "none" {
				log.Infof("Found %v=%v", varName, value)
				if field.Type.Name() == "Duration" {
					seconds, err := strconv.ParseFloat(value, 64)
					if err != nil {
						log.Error("Invalid float")
					}
					duration := time.Duration(seconds * float64(time.Second))
					reflect.ValueOf(typhaConfig).Elem().FieldByName(field.Name).Set(reflect.ValueOf(duration))
				} else {
					reflect.ValueOf(typhaConfig).Elem().FieldByName(field.Name).Set(reflect.ValueOf(value))
				}
				break
			}
		}
	}
}

扫描二维码关注公众号，回复： 8728796 查看本文章

2. Run 函数

func Run(config *config.Config) {
	log.Info("Starting calico-confd")
	storeClient, err := calico.NewCalicoClient(config)
	if err != nil {
		log.Fatal(err.Error())
	}

    2.1 NewCalicoClient

      路径 kelseyhightower/confd/pkg/backends/calico/client.go

     2.1.1 loadClientConfig 

      如果指定配置文件则从配置文件读取配置参数，未指定则从环境变量获取配置参数

// LoadClientConfig loads the ClientConfig from the specified file (if specified)
// or from environment variables (if the file is not specified).
func LoadClientConfig(filename string) (*CalicoAPIConfig, error) {

	// Override / merge with values loaded from the specified file.
	if filename != "" {
		b, err := ioutil.ReadFile(filename)
		if err != nil {
			return nil, err
		}

		c, err := LoadClientConfigFromBytes(b)
		if err != nil {
			return nil, fmt.Errorf("syntax error in %s: %v", filename, err)
		}
		return c, nil
	}
	return LoadClientConfigFromEnvironment()
}

    2.1.2 使用 etcdv3 或者 kubernetes 作为 backend

// Query the current BGP configuration to determine if the node to node mesh is enabled or
// not.  If it is we need to monitor all node configuration.  If it is not enabled then we
// only need to monitor our own node.  If this setting changes, we terminate confd (so that
// when restarted it will start watching the correct resources).
cc, err := clientv3.New(*config)
if err != nil {
	log.Errorf("Failed to create main Calico client: %v", err)
	return nil, err
}

    2.1.3 查询名为 default 资源为 bgpconfigurations

cfg, err := cc.BGPConfigurations().Get(
	context.Background(),
	"default",
	options.GetOptions{},
)
if _, ok := err.(lerr.ErrorResourceDoesNotExist); err != nil && !ok {
	// Failed to get the BGP configuration (and not because it doesn't exist).
	// Exit.
	log.Errorf("Failed to query current BGP settings: %v", err)
	return nil, err
}

    2.1.4 实例化模板配置 Config

templateConfig := template.Config{
	ConfDir:       config.ConfDir,
	ConfigDir:     filepath.Join(config.ConfDir, "conf.d"),
	KeepStageFile: config.KeepStageFile,
	Noop:          config.Noop,
	Prefix:        config.Prefix,
	SyncOnly:      config.SyncOnly,
	TemplateDir:   filepath.Join(config.ConfDir, "templates"),
	StoreClient:   storeClient,
}

3. WatchProcessor 实例化

func WatchProcessor(config Config, stopChan, doneChan chan bool, errChan chan error) Processor {
	return &watchProcessor{config, stopChan, doneChan, errChan, sync.WaitGroup{}}
}

4. sync 函数

    监控同步配置，如果更新过则重新 reload 命令

// sync compares the staged and dest config files and attempts to sync them
// if they differ. sync will run a config check command if set before
// overwriting the target config file. Finally, sync will run a reload command
// if set to have the application or service pick up the changes.
// It returns an error if any.
func (t *TemplateResource) sync() error {
	staged := t.StageFile.Name()
	if t.keepStageFile {
		log.Info("Keeping staged file: " + staged)
	} else {
		defer func() {
			if e := os.Remove(staged); e != nil {
				if !os.IsNotExist(e) {
					// Just log the error but don't carry it up the calling stack.
					log.WithError(e).WithField("filename", staged).Error("error removing file")
				} else {
					log.Debugf("Ignore not exists err. %s", e.Error())
				}
			}
		}()
	}