1.why

kubernetes是使用go语言编写的，对于很多同学来说，可能对这种语言机制不甚熟悉。掌握调试方法，一方面能够精准定位问题，另一方面对学习相关语言也有反向促进机制。摩刀不误砍柴功。只要有源码，任何问题都是可以解决的，剩下的只是时间问题。

2.准备工作

1. 安装delve
   delve是目前最方便用于调试golang的工具，安装delve有两种方法:

• 使用go命令:

go get -u github.com/derekparker/delve/cmd/dlv

• 使用源码

https://github.com/derekparker/delve
make install

2.编译kubernetes组件

• 通过make help查看如何编译带调试信息的kubernetes组件

[newcent@localhost kubernetes-1.9.2]$ make help
--------------------------------------------------------------------------------
all
# Build code.
#
# Args:
#   WHAT: Directory names to build.  If any of these directories has a 'main'
#     package, the build will produce executable files under _output/go/bin.
#     If not specified, "everything" will be built.
#   GOFLAGS: Extra flags to pass to 'go' when building.
#   GOLDFLAGS: Extra linking flags passed to 'go' when building.
#   GOGCFLAGS: Additional go compile flags passed to 'go' when building.
#
# Example:
#   make
#   make all
#   make all WHAT=cmd/kubelet GOFLAGS=-v
#   make all GOGCFLAGS="-N -l"
#     Note: Use the -N -l options to disable compiler optimizations an inlining.
#           Using these build options allows you to subsequently use source
#           debugging tools like delve.
---------------------------------------------------------------------------------
......

• 使用make all GOGCFLAGS="-N -l"编译kubernetes组件

3.调试kubelet

• 将编译kubelet拷贝到相应的node上
• 在node上通过dlv启动kubelet

 dlv exec ./kubelet --headless -l 192.168.122.12:1234 -- --logtostderr=true --v=0 --allow-privileged=false --address=0.0.0.0 --hostname-override=node1 --pod-infra-container-image=gcr.io/google_ctainers/pause-amd64:3.0 --kubeconfig=/etc/kubernetes/kubelet.kubeconfig --cgroup-driver=systemd

--headless -l 192.168.122.12:1234指定启动一个调试server端，因为编译kubernetes组件往往不会在node上编译，node上也没有相应的源码，通过这一机制，可以在编译节点上启动dlv client，调试相关代码。

• 在编译节点上连接server端

[newcent@localhost kubernetes-1.9.2]$ dlv connect 192.168.122.12:1234
Type 'help' for list of commands.
(dlv) b main.main
Breakpoint 1 set at 0x394496b for main.main() ./_output/local/go/src/k8s.io/kubernetes/cmd/kubelet/kubelet.go:44
(dlv) c
> main.main() ./_output/local/go/src/k8s.io/kubernetes/cmd/kubelet/kubelet.go:44 (hits goroutine(1):1 total:1) (PC: 0x394496b)
Warning: debugging optimized function
Warning: listing may not match stale executable
    39: func die(err error) {
    40:     fmt.Fprintf(os.Stderr, "error: %v\n", err)
    41:     os.Exit(1)
    42: }
    43: 
=>  44: func main() {
    45:     // construct KubeletFlags object and register command line flags mapping
    46:     kubeletFlags := options.NewKubeletFlags()
    47:     kubeletFlags.AddFlags(pflag.CommandLine)
    48: 
    49:     fmt.Printf("args: %s\n", os.Args[0])
(dlv) 

4.delve使用方法(附)