Remove kubelet dependency on pidof

Issue #26093 identified pidof as one of the dependencies of kublet
which could be worked around. In this PR, we just look at /proc
to construct the list of pids we need for a specified process
instead of running "pidof" executable

Related to #26093

pkg/util/procfs/procfs.go

@@ -17,12 +17,17 @@ limitations under the License.
 package procfs
 
 import (
+	"bytes"
 	"fmt"
 	"io/ioutil"
 	"os"
 	"path"
+	"path/filepath"
 	"strconv"
 	"strings"
+	"unicode"
+
+	"github.com/golang/glog"
 )
 
 type ProcFS struct{}
@@ -56,3 +61,46 @@ func (pfs *ProcFS) GetFullContainerName(pid int) (string, error) {
 	}
 	return containerNameFromProcCgroup(string(content))
 }
+
+func PidOf(name string) []int {
+	pids := []int{}
+	filepath.Walk("/proc", func(path string, info os.FileInfo, err error) error {
+		base := filepath.Base(path)
+		// Traverse only the directories we are interested in
+		if info.IsDir() && path != "/proc" {
+			// If the directory is not a number (i.e. not a PID), skip it
+			if _, err := strconv.Atoi(base); err != nil {
+				return filepath.SkipDir
+			}
+		}
+		if base != "cmdline" {
+			return nil
+		}
+		cmdline, err := ioutil.ReadFile(path)
+		if err != nil {
+			glog.V(4).Infof("Error reading file %s: %+v", path, err)
+			return nil
+		}
+		// The bytes we read have '\0' as a separator for the command line
+		parts := bytes.SplitN(cmdline, []byte{0}, 2)
+		if len(parts) == 0 {
+			return nil
+		}
+		// Split the command line itself we are interested in just the first part
+		exe := strings.FieldsFunc(string(parts[0]), func(c rune) bool {
+			return unicode.IsSpace(c) || c == ':'
+		})
+		if len(exe) == 0 {
+			return nil
+		}
+		// Check if the name of the executable is what we are looking for
+		if filepath.Base(exe[0]) == name {
+			dirname := filepath.Base(filepath.Dir(path))
+			// Grab the PID from the directory path
+			pid, _ := strconv.Atoi(dirname)
+			pids = append(pids, pid)
+		}
+		return nil
+	})
+	return pids
+}

pkg/util/procfs/procfs_test.go

@@ -18,7 +18,12 @@ package procfs
 
 import (
 	"io/ioutil"
+	"os"
+	"path/filepath"
+	"runtime"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func verifyContainerName(procCgroupText, expectedName string, expectedErr bool, t *testing.T) {
@@ -56,3 +61,12 @@ func TestContainerNameFromProcCgroup(t *testing.T) {
 	procCgroupInvalid := "devices:docker/kubelet\ncpuacct:pkg/kubectl"
 	verifyContainerName(procCgroupInvalid, "", true, t)
 }
+
+func TestPidOf(t *testing.T) {
+	if runtime.GOOS == "darwin" || runtime.GOOS == "windows" {
+		t.Skipf("not supported on GOOS=%s", runtime.GOOS)
+	}
+	pids := PidOf(filepath.Base(os.Args[0]))
+	assert.NotZero(t, pids)
+	assert.Contains(t, pids, os.Getpid())
+}