Heka 的配置文件加载逻辑

Posted on 2014-11-09 13:49 蝈蝈俊阅读(1690) 评论(0) 编辑收藏举报

Heka 使用的是 TOML 格式的配置文件，有关 golang 加载 TOML 配置文件的技术请参看： http://www.cnblogs.com/ghj1976/p/4082323.html

Heka用的读取 TOML 文件的Go库是： https://github.com/bbangert/toml 虽然跟上面文章的不是一个，但是基本差不多。

我们在hekad主进程的配置文件加载的逻辑如下：

在启动时，先读取hekad部分的配置内容，用于hekad的启动。
然后再去读其他配置节，把heka的管道启动起来。

github.com\mozilla-services\heka\cmd\hekad\main.go 文件中，我们摘要核心代码如下，就可以看到这个逻辑：

这里删除了一些跟这个逻辑过程无关的代码，方便阅读。

加载 hekad 部分配置

代码实现如下，注意，这里处理了配置文件内置支持环境变量的功能。

对环境变量支持的文档如下：

Using Environment Variables

If you wish to use environmental variables in your config files as a way to configure values, you can simply use %ENV[VARIABLE_NAME] and the text will be replaced with the value of the environmental variable VARIABLE_NAME.

Example:

[AMQPInput]
url = "amqp://%ENV[USER]:%ENV[PASSWORD]@rabbitmq/"
exchange = "testout"
exchangeType = "fanout"

加载插件相关的配置逻辑

加载插件配置的逻辑主要是下面代码：

每个Heka的TOML配置节，对应的实体类如下：

// The TOML spec for plugin configuration options that will be pulled out by
// Heka itself before the config is passed to the Plugin.Init method. Not all
// options apply to all plugin types.
type PluginGlobals struct {
    Typ        string `toml:"type"`
    Ticker     uint   `toml:"ticker_interval"`
    Matcher    string `toml:"message_matcher"` // Filter and Output only.
    Signer     string `toml:"message_signer"`  // Filter and Output only.
    Retries    RetryOptions
    Encoder    string // Output only.
    UseFraming *bool  `toml:"use_framing"` // Output only.
    CanExit    *bool  `toml:"can_exit"`
}

对应的解析时的逻辑如下：

func (self *PipelineConfig) loadPluginGlobals(section *ConfigSection) (err error) {
// Set up default retry policy.

    pGlobals := new(PluginGlobals)
    pGlobals.Retries = RetryOptions{
        MaxDelay:   "30s",
        Delay:      "250ms",
        MaxRetries: -1,
    }

    if err = toml.PrimitiveDecode(section.tomlSection, pGlobals); err != nil {
        err = fmt.Errorf("Unable to decode config for plugin '%s': %s",
            section.name, err)
        return
    }

    if pGlobals.Typ == "" {
        pGlobals.Typ = section.name
    }

    if _, ok := AvailablePlugins[pGlobals.Typ]; !ok {
        err = fmt.Errorf("No registered plugin type: %s", pGlobals.Typ)
    } else {
        section.globals = pGlobals
    }
    return
}

补充说明如下：

如果 type为空，则这个节的名字就是 type
插件要起作用，需要 RegisterPlugin ，参看 http://hekad.readthedocs.org/en/v0.8.0/developing/plugin.html

插件的类型有5种，都是在名字或者type上可以看出来的，对应的判断类型的代码如下：

var PluginTypeRegex = regexp.MustCompile("(Decoder|Encoder|Filter|Input|Output)$")

func getPluginCategory(pluginType string) string {
    pluginCats := PluginTypeRegex.FindStringSubmatch(pluginType)
    if len(pluginCats) < 2 {
        return ""
    }
    return pluginCats[1]
}

加载配置文件这里，代码在 LoadFromConfigFile 函数，这里其实就主要做了上面两个事情，外加不同类型插件的特殊处理。

// Loads all plugin configuration from a TOML configuration file. The
// PipelineConfig should be already initialized via the Init function before
// this method is called.
func (self *PipelineConfig) LoadFromConfigFile(filename string) (err error) {
    var configFile ConfigFile
    // 更新配置文件中，自定义变量（环境变量）
    contents, err := ReplaceEnvsFile(filename)
    if err != nil {
        return err
    }

    // TOML 解析成 configFile
    if _, err = toml.Decode(contents, &configFile); err != nil {
        return fmt.Errorf("Error decoding config file: %s", err)
    }

    var (
        errcnt              uint
        protobufDRegistered bool
        protobufERegistered bool
    )
    sectionsByCategory := make(map[string][]*ConfigSection)

    // Load all the plugin globals and file them by category.
    for name, conf := range configFile {
        if name == HEKA_DAEMON {
            continue
        }
        log.Printf("Pre-loading: [%s]\n", name)
        section := &ConfigSection{
            name:        name,
            tomlSection: conf,
        }

        // 加载插件配置文件，这里面做了插件注册的检查
        if err = self.loadPluginGlobals(section); err != nil {
            self.log(err.Error())
            errcnt++
            continue
        }

        // 获取插件的类型
        category := getPluginCategory(section.globals.Typ)
        if category == "" {
            self.log(fmt.Sprintf("Type doesn't contain valid plugin name: %s\n",
                section.globals.Typ))
            errcnt++
            continue
        }

        // 特殊插件类型的处理
        section.category = category
        if section.globals.Typ == "MultiDecoder" {
            // Special case MultiDecoders so we can make sure they get
            // registered *after* all possible subdecoders.
            sectionsByCategory["MultiDecoder"] = append(sectionsByCategory["MultiDecoder"],
                section)
        } else {
            sectionsByCategory[category] = append(sectionsByCategory[category], section)
        }
        if name == "ProtobufDecoder" {
            protobufDRegistered = true
        }
        if name == "ProtobufEncoder" {
            protobufERegistered = true
        }
    }

    // Make sure ProtobufDecoder is registered.
    if !protobufDRegistered {
        var configDefault ConfigFile
        toml.Decode(protobufDecoderToml, &configDefault)
        log.Println("Pre-loading: [ProtobufDecoder]")
        section := &ConfigSection{
            name:        "ProtobufDecoder",
            category:    "Decoder",
            tomlSection: configDefault["ProtobufDecoder"],
        }
        if err = self.loadPluginGlobals(section); err != nil {
            // This really shouldn't happen.
            self.log(err.Error())
            errcnt++
        } else {
            sectionsByCategory["Decoder"] = append(sectionsByCategory["Decoder"],
                section)
        }
    }

    // Make sure ProtobufEncoder is registered.
    if !protobufERegistered {
        var configDefault ConfigFile
        toml.Decode(protobufEncoderToml, &configDefault)
        log.Println("Pre-loading: [ProtobufEncoder]")
        section := &ConfigSection{
            name:        "ProtobufEncoder",
            category:    "Encoder",
            tomlSection: configDefault["ProtobufEncoder"],
        }
        if err = self.loadPluginGlobals(section); err != nil {
            // This really shouldn't happen.
            self.log(err.Error())
            errcnt++
        } else {
            sectionsByCategory["Encoder"] = append(sectionsByCategory["Encoder"],
                section)
        }
    }

multiDecoders := make([]multiDecoderNode, len(sectionsByCategory["MultiDecoder"]))
multiConfigs := make(map[string]*ConfigSection)

for i, section := range sectionsByCategory["MultiDecoder"] {

multiConfigs[section.name] = section

multiDecoders[i] = newMultiDecoderNode(section.name, subsFromSection(section.tomlSection))

    }
    multiDecoders, err = orderDependencies(multiDecoders)
    if err != nil {
        return err
    }
    for i, d := range multiDecoders {
        sectionsByCategory["MultiDecoder"][i] = multiConfigs[d.name]
    }

    // Append MultiDecoders to the end of the Decoders list.
    sectionsByCategory["Decoder"] = append(sectionsByCategory["Decoder"],
        sectionsByCategory["MultiDecoder"]...)

    // Force decoders and encoders to be registered before the other plugin
    // types are initialized so we know they'll be there for inputs and
    // outputs to use during initialization.
    order := []string{"Decoder", "Encoder", "Input", "Filter", "Output"}
    for _, category := range order {
        for _, section := range sectionsByCategory[category] {
            log.Printf("Loading: [%s]\n", section.name)
            if err = self.loadSection(section); err != nil {
                self.log(err.Error())
                errcnt++
            }
        }
    }

    if errcnt != 0 {
        return fmt.Errorf("%d errors loading plugins", errcnt)
    }

return
}