Kube-scheduler 源码分析（二）：调度程序启动前逻辑

# 如果你的网络很给力，那么下面这个命令就够了；
go get -u github.com/spf13/cobra/cobra
# 如果你的网络不给力，那就下载cobra的zip包，丢到GOPATH下对应目录，然后解决依赖，再build

package main

import "myapp/cmd"

func main() {
        cmd.Execute()
}

//!FILENAME cmd/kube-scheduler/scheduler.go:34
func main() {
    command := app.NewSchedulerCommand()
    if err := command.Execute(); err != nil {
        fmt.Fprintf(os.Stderr, "%v\n", err)
        os.Exit(1)
    }
}

//!FILENAME cmd/kube-scheduler/app/server.go:70
// NewSchedulerCommand creates a *cobra.Command object with default parameters
func NewSchedulerCommand() *cobra.Command {
    cmd := &cobra.Command{
        Use: "kube-scheduler",
        Long: `The Kubernetes scheduler is a policy-rich, topology-aware,
workload-specific function that significantly impacts availability, performance,
and capacity. The scheduler needs to take into account individual and collective
resource requirements, quality of service requirements, hardware/software/policy
constraints, affinity and anti-affinity specifications, data locality, inter-workload
interference, deadlines, and so on. Workload-specific requirements will be exposed
through the API as necessary.`,
        Run: func(cmd *cobra.Command, args []string) {
            if err := runCommand(cmd, args, opts); err != nil {
                fmt.Fprintf(os.Stderr, "%v\n", err)
                os.Exit(1)
            }
        },
    }
    return cmd
}

//!FILENAME cmd/kube-scheduler/app/server.go:117
// runCommand runs the scheduler.
func runCommand(cmd *cobra.Command, args []string, opts *options.Options) error {
    c, err := opts.Config()
    stopCh := make(chan struct{})
    // Get the completed config
    cc := c.Complete()
    return Run(cc, stopCh)
}

//!FILENAME cmd/kube-scheduler/app/server.go:167
// Run executes the scheduler based on the given configuration. It only return on error or when stopCh is closed.
func Run(cc schedulerserverconfig.CompletedConfig, stopCh <-chan struct{}) error {
    // Create the scheduler.
    sched, err := scheduler.New(cc.Client,
        cc.InformerFactory.Core().V1().Nodes(),
        stopCh,
        scheduler.WithName(cc.ComponentConfig.SchedulerName))

    // Prepare a reusable runCommand function.
    run := func(ctx context.Context) {
        sched.Run()
        <-ctx.Done()
    }

    ctx, cancel := context.WithCancel(context.TODO()) 
    defer cancel()

    go func() {
        select {
        case <-stopCh:
            cancel()
        case <-ctx.Done():
        }
    }()

    // Leader election is disabled, so runCommand inline until done.
    run(ctx)
    return fmt.Errorf("finished without leader elect")
}

//!FILENAME pkg/scheduler/scheduler.go:58
// Scheduler watches for new unscheduled pods. It attempts to find
// nodes that they fit on and writes bindings back to the api server.
type Scheduler struct {
    config *factory.Config
}

//!FILENAME pkg/scheduler/factory/factory.go:96
// Config is an implementation of the Scheduler's configured input data.
type Config struct {
    // It is expected that changes made via SchedulerCache will be observed
    // by NodeLister and Algorithm.
    SchedulerCache schedulerinternalcache.Cache
    // Ecache is used for optimistically invalid affected cache items after
    // successfully binding a pod
    Ecache     *equivalence.Cache
    NodeLister algorithm.NodeLister
    Algorithm  algorithm.ScheduleAlgorithm
    GetBinder  func(pod *v1.Pod) Binder
    // PodConditionUpdater is used only in case of scheduling errors. If we succeed
    // with scheduling, PodScheduled condition will be updated in apiserver in /bind
    // handler so that binding and setting PodCondition it is atomic.
    PodConditionUpdater PodConditionUpdater
    // PodPreemptor is used to evict pods and update pod annotations.
    PodPreemptor PodPreemptor

    // NextPod should be a function that blocks until the next pod
    // is available. We don't use a channel for this, because scheduling
    // a pod may take some amount of time and we don't want pods to get
    // stale while they sit in a channel.
    NextPod func() *v1.Pod

    // SchedulingQueue holds pods to be scheduled
    SchedulingQueue internalqueue.SchedulingQueue
}