Influxdb启动流程分析

Influxdb启动流程

1. Influxdb的启动代码实现在 cmd/influxd/main.go中
2. influxd支持下面几种启动命令

 backup               downloads a snapshot of a data node and saves it to disk 
 config               display the default configuration                        
 help                 display this help message                                
 restore              uses a snapshot of a data node to rebuild a cluster      
 run                  run node with existing configuration                     
 version              displays the InfluxDB version                            

我们启动的话通常是 influxd run -config [config file path]

3. 简单看一下run命令相关的代码:

func (m *Main) Run(args ...string) error {
    name, args := cmd.ParseCommandName(args)

    // Extract name from args.
    switch name {
    case "", "run":
        cmd := run.NewCommand()

        // Tell the server the build details.
        cmd.Version = version
        cmd.Commit = commit
        cmd.Branch = branch

        if err := cmd.Run(args...); err != nil {
            return fmt.Errorf("run: %s", err)
        }

        signalCh := make(chan os.Signal, 1)
        signal.Notify(signalCh, os.Interrupt, syscall.SIGTERM)
        cmd.Logger.Info("Listening for signals")

        // Block until one of the signals above is received
        <-signalCh
        cmd.Logger.Info("Signal received, initializing clean shutdown...")
        go cmd.Close()

        // Block again until another signal is received, a shutdown timeout elapses,
        // or the Command is gracefully closed
        cmd.Logger.Info("Waiting for clean shutdown...")
        select {
        case <-signalCh:
            cmd.Logger.Info("Second signal received, initializing hard shutdown")
        case <-time.After(time.Second * 30):
            cmd.Logger.Info("Time limit reached, initializing hard shutdown")
        case <-cmd.Closed:
            cmd.Logger.Info("Server shutdown completed")
        }
        ...
    }

    return nil
}

主要就是cmd := run.NewCommand()创建cmd对象，然后调用其Run方法

3. 我们来看一下Command.Run的实现

func (cmd *Command) Run(args ...string) error {
    // 解析参数
    options, err := cmd.ParseFlags(args...)

    ...
    
    // 解析配置文件，初始化各组件的配置信息
    config, err := cmd.ParseConfig(options.GetConfigPath())
     
    // 初始化logger
    if cmd.Logger, logErr = config.Logging.New(cmd.Stderr); logErr != nil {
        // assign the default logger
        cmd.Logger = logger.New(cmd.Stderr)
    }
    
    // 如果配置了pid file path, 就写pud
    cmd.writePIDFile(options.PIDFile)
    
    // 创建Server对象，并调用Open方法将 Server运行起来
    s, err := NewServer(config, buildInfo)
    ...
    if err := s.Open(); err != nil {
        return fmt.Errorf("open server: %s", err)
    }

    // 开如monitor server error信息
    go cmd.monitorServerErrors()
}

4. 我们来过一下NewServer的实现， 它主要的功能就是依据配置Server对象和它管理的各个组件, 主要包括

Monitor
MetaClient
TSDBStore
Subscriber
PoinitsWriter
QueryExecutor
...

5. 紧接着会调用Server.Open添加各种service,让各个组件运行起来

// Open opens the meta and data store and all services.
func (s *Server) Open() error {
    // 创建并运行一个tcp的连接复用器
    ln, err := net.Listen("tcp", s.BindAddress)
    if err != nil {
        return fmt.Errorf("listen: %s", err)
    }
    s.Listener = ln

    // Multiplex listener.
    mux := tcp.NewMux()
    go mux.Serve(ln)

    // 添加各种service
    s.appendMonitorService()  // 
    s.appendPrecreatorService(s.config.Precreator) //预创建ShardGroup
    s.appendSnapshotterService() //使用上面的tcp连接复用器，处理snapshot相关的请求
    s.appendContinuousQueryService(s.config.ContinuousQuery) // 连续query服务
    s.appendHTTPDService(s.config.HTTPD) //http服务，接收并处理所有客户端的请求
    s.appendRetentionPolicyService(s.config.Retention) //依据RetentionPolicy周期性的作清理
    
    // Graphite, Collectd, OpenTSDB都会对其实TSDB数据格式的支持
    for _, i := range s.config.GraphiteInputs {
        if err := s.appendGraphiteService(i); err != nil {
            return err
        }
    }
    for _, i := range s.config.CollectdInputs {
        s.appendCollectdService(i)
    }
    for _, i := range s.config.OpenTSDBInputs {
        if err := s.appendOpenTSDBService(i); err != nil {
            return err
        }
    }
    for _, i := range s.config.UDPInputs {
        s.appendUDPService(i)
    }

    ...
    
    // Open TSDB store.
    if err := s.TSDBStore.Open(); err != nil {
        return fmt.Errorf("open tsdb store: %s", err)
    }

    // Open the subscriber service
    if err := s.Subscriber.Open(); err != nil {
        return fmt.Errorf("open subscriber: %s", err)
    }

    // Open the points writer service
    if err := s.PointsWriter.Open(); err != nil {
        return fmt.Errorf("open points writer: %s", err)
    }

    s.PointsWriter.AddWriteSubscriber(s.Subscriber.Points())

    for _, service := range s.Services {
        if err := service.Open(); err != nil {
            return fmt.Errorf("open service: %s", err)
        }
    }

    ...

    return nil
}

图解Influxd的启动流程

influxdb_run.png