Kubernetes筆記（1）—— hyperkube

這是一個建立於 的文章，其中的資訊可能已經有所發展或是發生改變。

k8s中用到一個hyperkube模組，其功能如下：

// Package hyperkube is a framework for kubernetes server components. It
// allows us to combine all of the kubernetes server components into a single
// binary where the user selects which components to run in any individual
// process.
//
// Currently, only one server component can be run at once. As such there is
// no need to harmonize flags or identify logs across the various servers. In
// the future we will support launching and running many servers — either by
// managing processes or running in-proc.
//
// This package is inspired by https://github.com/spf13/cobra. However, as
// the eventual goal is to run multiple servers from one call, a new package
// was needed.

通俗地講，hyperkube模組就是把各種功能整合到一個可執行檔，然後在運行時指定模組。比如km程式就用到了hyperkube：

$ km --helpThis is an all-in-one binary that can run any of the various Kubernetes-Mesosservers.Usage  km <server> [flags]Servers  apiserver    The main API entrypoint and interface to the storage system. The API server    is also the focal point for all authorization decisions.......

hyperkube結構體定義：

type HyperKube struct {    Name string // The executable name, used for help and soft-link invocation    Long string // A long description of the binary.  It will be world wrapped before output.    servers     []Server    baseFlags   *pflag.FlagSet    out         io.Writer    helpFlagVal bool}

其中用到的Server結構體的定義：

// Server describes a server that this binary can morph into.type Server struct {    SimpleUsage string        // One line description of the server.    Long        string        // Longer free form description of the server    Run         serverRunFunc // Run the server.  This is not expected to return.    flags *pflag.FlagSet // Flags for the command (and all dependents)    name  string    hk    *HyperKube}

參看km程式的main函數：

func main() {    hk := HyperKube{        Name: "km",        Long: "This is an all-in-one binary that can run any of the various Kubernetes-Mesos servers.",    }    hk.AddServer(NewKubeAPIServer())    hk.AddServer(NewControllerManager())    hk.AddServer(NewScheduler())    hk.AddServer(NewKubeletExecutor())    hk.AddServer(NewKubeProxy())    hk.AddServer(NewMinion())    hk.RunToExit(os.Args)}

main函數用到了hyperkube的一個重要方法AddServer：

// AddServer adds a server to the HyperKube object.func (hk *HyperKube) AddServer(s *Server) {    hk.servers = append(hk.servers, *s)    hk.servers[len(hk.servers)-1].hk = hk}

可以看到，在這個方法中，hk.servers[len(hk.servers)-1].hk = hk可以讓Server結構體的hk欄位指向同一個binary中的hyperkube，這樣就把這些功能整合到一起。 接下來調用hyperkube的RunToExit運行相應的功能。