flannel源码分析（一） 概述

 1 func main() {
 2     // glog will log to tmp files by default. override so all entries
 3     // can flow into journald (if running under systemd)
 4     flag.Set("logtostderr", "true")
 5     // now parse command line args
 6     flag.Parse()
 7     if flag.NArg() > 0 || opts.help {
 8         fmt.Fprintf(os.Stderr, "Usage: %s [OPTION]...\n", os.Args[0])
 9         flag.PrintDefaults()
10         os.Exit(0)
11     }
12     if opts.version {
13         fmt.Fprintln(os.Stderr, version.Version)
14         os.Exit(0)
15     }
16 
17     flagutil.SetFlagsFromEnv(flag.CommandLine, "FLANNELD")
18     
19     // 创建SubnetManager用于划分子网
20     sm, err := newSubnetManager()
21     if err != nil {
22         log.Error("Failed to create SubnetManager: ", err)
23         os.Exit(1)
24     }
25     // Register for SIGINT and SIGTERM
26     log.Info("Installing signal handlers")
27     sigs := make(chan os.Signal, 1)
28     signal.Notify(sigs, os.Interrupt, syscall.SIGTERM)
29     // 设置可以cancle的context
30     ctx, cancel := context.WithCancel(context.Background())
31     var runFunc func(ctx context.Context)
32     if opts.listen != "" {
33         if opts.remote != "" {
34             log.Error("--listen and --remote are mutually exclusive")
35             os.Exit(1)
36         }
37         log.Info("running as server")
38         runFunc = func(ctx context.Context) {
39             remote.RunServer(ctx, sm, opts.listen, opts.remoteCAFile, opts.remoteCertfile, opts.remoteKeyfile)
40         }
41     } else {
42         nm, err := network.NewNetworkManager(ctx, sm)
43         if err != nil {
44             log.Error("Failed to create NetworkManager: ", err)
45             os.Exit(1)
46         }
47         runFunc = func(ctx context.Context) {
48             nm.Run(ctx)
49         }
50     }
51     wg := sync.WaitGroup{}
52     wg.Add(1)
53     go func() {
54         runFunc(ctx)    // 在一个新的goroutine中运行NetworkManager的Run函数
55         wg.Done()
56     }()
57     <-sigs
58     // unregister to get default OS nuke behaviour in case we don‘t exit cleanly
59     signal.Stop(sigs)
60     log.Info("Exiting...")
61     
62     // 收到信号后，掉用cancle函数， 取消所有相关的子context
63     cancel()
64     wg.Wait()
65 }