Docker Swarm代码分析笔记（11）——Engine.Connect

Engine.Connect()方法用来完成对Docker engine的连接工作：

// Connect will initialize a connection to the Docker daemon running on the
// host, gather machine specs (memory, cpu, ...) and monitor state changes.
func (e *Engine) Connect(config *tls.Config) error {
    host, _, err := net.SplitHostPort(e.Addr)
    if err != nil {
        return err
    }

    addr, err := net.ResolveIPAddr("ip4", host)
    if err != nil {
        return err
    }
    e.IP = addr.IP.String()

    c, err := dockerclient.NewDockerClientTimeout("tcp://"+e.Addr, config, time.Duration(requestTimeout), setTCPUserTimeout)
    if err != nil {
        return err
    }
    // Use HTTP Client used by dockerclient to create engine-api client
    apiClient, err := engineapi.NewClient("tcp://"+e.Addr, "", c.HTTPClient, nil)
    if err != nil {
        return err
    }

    return e.ConnectWithClient(c, apiClient)
}

Engine.Connect()利用了另外两个Docker项目：dockerclient和engine-api。首先调用dockerclient.NewDockerClientTimeout("tcp://"+e.Addr, config, time.Duration(requestTimeout), setTCPUserTimeout)生成一个DockerClient结构体：

type DockerClient struct {
    URL           *url.URL
    HTTPClient    *http.Client
    TLSConfig     *tls.Config
    monitorStats  int32
    eventStopChan chan (struct{})
}

再把DockerClient.HTTPClient传入engineapi.NewClient()函数，作为engine-api的http.Client，作为HTTP请求的传输载体。最后调用Engine.ConnectWithClient()连接Docker engine，获得Docker信息。

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