我的站点

一个系统软件工程师的随手涂鸦

Date: 十二月 9, 2015

Kubernetes笔记(1)—— hyperkube

k8s中用到一个hyperkube模块,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.

通俗地讲,hyperkube模块就是把各种功能集成到一个可执行文件,然后在运行时指定模块。比如km程序就用到了hyperkube

$ km --help
This is an all-in-one binary that can run any of the various Kubernetes-Mesos
servers.

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结构体定义:

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结构体的定义:

// 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
}

参看km程序的main函数:

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函数用到了hyperkube的一个重要方法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,在这个方法中,hk.servers[len(hk.servers)-1].hk = hk可以让Server结构体的hk字段指向同一个binary中的hyperkube,这样就把这些功能集成到一起。 接下来调用hyperkubeRunToExit运行相应的功能。

 

etcd简介

最近在搭建kubernetes on Mesos,用到了etcdetcd是一个分布式的,可靠的,key-value数据库。其项目主页在这里

etcd的搭建很简单,有现成的binary可以使用。不过让我感到与其它项目不同的是,它会为某项服务同时启动两个端口。比如:

-listen-peer-urls

List of URLs to listen on for peer traffic. This flag tells the etcd to accept incoming requests from its peers on the specified scheme://IP:port combinations. Scheme can be either http or https.If 0.0.0.0 is specified as the IP, etcd listens to the given port on all interfaces. If an IP address is given as well as a port, etcd will listen on the given port and interface. Multiple URLs may be used to specify a number of addresses and ports to listen on. The etcd will respond to requests from any of the listed addresses and ports.

default: “http://localhost:2380,http://localhost:7001”
env variable: ETCDLISTENPEER_URLS
example: “http://10.0.0.1:2380”
invalid example: “http://example.com:2380” (domain name is invalid for binding)

-listen-client-urls

List of URLs to listen on for client traffic. This flag tells the etcd to accept incoming requests from the clients on the specified scheme://IP:port combinations. Scheme can be either http or https. If 0.0.0.0 is specified as the IP, etcd listens to the given port on all interfaces. If an IP address is given as well as a port, etcd will listen on the given port and interface. Multiple URLs may be used to specify a number of addresses and ports to listen on. The etcd will respond to requests from any of the listed addresses and ports.
default: “http://localhost:2379,http://localhost:4001”
env variable: ETCDLISTENCLIENT_URLS
example: “http://10.0.0.1:2379”
invalid example: “http://example.com:2379” (domain name is invalid for binding)

-listen-peer-urls监听peer的请求,默认端口为23807001,而-listen-client-urls监听client的请求,默认端口为23794001

另外一个有趣的配置项是-advertise-client-urls,它是把当前运行的etcdclient URL地址通知给cluster中的其它成员。

-advertise-client-urls

List of this member’s client URLs to advertise to the rest of the cluster. These URLs can contain domain names. default: “http://localhost:2379,http://localhost:4001”
env variable: ETCDADVERTISECLIENT_URLS
example: “http://example.com:2379, http://10.0.0.1:2379”
Be careful if you are advertising URLs such as http://localhost:2379 from a cluster member and are using the proxy feature of etcd. This will cause loops, because the proxy will be forwarding requests to itself until its resources (memory, file descriptors) are eventually depleted.

参考资料:
Configuration Flags

 

Powered by WordPress & Theme by Anders Norén