profile kubectl using pprof

Question

In the kubernetes source code there is a block of code that handles the profiling part but I can not acces the endpoints:

in kubernetes/pkgs/kubelet/server/stats/server.go

func (s *Server) InstallProfilingHandler(enableProfilingLogHandler bool, enableContentionProfiling bool) {
    s.addMetricsBucketMatcher("debug")
    if !enableProfilingLogHandler {
        s.restfulCont.Handle(pprofBasePath, getHandlerForDisabledEndpoint("profiling endpoint is disabled."))
        return
    }

    handlePprofEndpoint := func(req *restful.Request, resp *restful.Response) {
        name := strings.TrimPrefix(req.Request.URL.Path, pprofBasePath)
        switch name {
        case "profile":
            pprof.Profile(resp, req.Request)
        case "symbol":
            pprof.Symbol(resp, req.Request)
        case "cmdline":
            pprof.Cmdline(resp, req.Request)
        case "trace":
            pprof.Trace(resp, req.Request)
        default:
            pprof.Index(resp, req.Request)
        }
    }

    // Setup pprof handlers.
    ws := new(restful.WebService).Path(pprofBasePath)
    ws.Route(ws.GET("/{subpath:*}").To(handlePprofEndpoint)).Doc("pprof endpoint")
    s.restfulCont.Add(ws)

    if enableContentionProfiling {
        goruntime.SetBlockProfileRate(1)
    }
}

I do not know the port used by the pprof tool but I found it using:

controller-0:/home/sysadmin/go/bin# netstat -atlpn | grep kubelet
tcp        0      0 127.0.0.1:10248         0.0.0.0:*               LISTEN      184856/kubelet      
tcp        0      0 192.168.206.2:49720     192.168.206.1:6443      ESTABLISHED 184856/kubelet      
tcp6       0      0 :::10250                :::*                    LISTEN      184856/kubelet 

Then I have tried

controller-0:/home/sysadmin/go/bin# ./go tool pprof  http://localhost:6443/debug/pprof/mutex
Fetching profile over HTTP from http://localhost:6443/debug/pprof/mutex
http://localhost:6443/debug/pprof/mutex: server response: 400 Bad Request
failed to fetch any source profiles

Is there anyone that knows what should I try to access the pprof endpoints? or how to try a different approach to profile the kubelet process?

Answer 1

Try:

$ kubectl proxy &
Starting to serve on 127.0.0.1:8001
$ go tool pprof "http://localhost:8001/api/v1/nodes/${NODE}/proxy/debug/pprof/profile"

When you start kubectl proxy, all requests to http://localhost:8001/api/v1/nodes/${NODE}/proxy/ go to the kubelet running on the ${NODE}. You can add any path you want and it. Let it be /debug/pprof/profile or debug/pprof/heap or whatever you want.