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utils.go
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/
utils.go
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package cgroups
import (
"bufio"
"fmt"
"io"
"io/ioutil"
"os"
"path/filepath"
"strconv"
"strings"
"time"
"github.com/docker/docker/pkg/mount"
)
// https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt
func FindCgroupMountpoint(subsystem string) (string, error) {
mounts, err := mount.GetMounts()
if err != nil {
return "", err
}
for _, mount := range mounts {
if mount.Fstype == "cgroup" {
for _, opt := range strings.Split(mount.VfsOpts, ",") {
if opt == subsystem {
return mount.Mountpoint, nil
}
}
}
}
return "", NewNotFoundError(subsystem)
}
func FindCgroupMountpointDir() (string, error) {
mounts, err := mount.GetMounts()
if err != nil {
return "", err
}
for _, mount := range mounts {
if mount.Fstype == "cgroup" {
return filepath.Dir(mount.Mountpoint), nil
}
}
return "", NewNotFoundError("cgroup")
}
type Mount struct {
Mountpoint string
Subsystems []string
}
func (m Mount) GetThisCgroupDir() (string, error) {
if len(m.Subsystems) == 0 {
return "", fmt.Errorf("no subsystem for mount")
}
return GetThisCgroupDir(m.Subsystems[0])
}
func GetCgroupMounts() ([]Mount, error) {
mounts, err := mount.GetMounts()
if err != nil {
return nil, err
}
all, err := GetAllSubsystems()
if err != nil {
return nil, err
}
allMap := make(map[string]bool)
for _, s := range all {
allMap[s] = true
}
res := []Mount{}
for _, mount := range mounts {
if mount.Fstype == "cgroup" {
m := Mount{Mountpoint: mount.Mountpoint}
for _, opt := range strings.Split(mount.VfsOpts, ",") {
if strings.HasPrefix(opt, "name=") {
m.Subsystems = append(m.Subsystems, opt)
}
if allMap[opt] {
m.Subsystems = append(m.Subsystems, opt)
}
}
res = append(res, m)
}
}
return res, nil
}
// Returns all the cgroup subsystems supported by the kernel
func GetAllSubsystems() ([]string, error) {
f, err := os.Open("/proc/cgroups")
if err != nil {
return nil, err
}
defer f.Close()
subsystems := []string{}
s := bufio.NewScanner(f)
for s.Scan() {
if err := s.Err(); err != nil {
return nil, err
}
text := s.Text()
if text[0] != '#' {
parts := strings.Fields(text)
if len(parts) >= 4 && parts[3] != "0" {
subsystems = append(subsystems, parts[0])
}
}
}
return subsystems, nil
}
// Returns the relative path to the cgroup docker is running in.
func GetThisCgroupDir(subsystem string) (string, error) {
f, err := os.Open("/proc/self/cgroup")
if err != nil {
return "", err
}
defer f.Close()
return ParseCgroupFile(subsystem, f)
}
func GetInitCgroupDir(subsystem string) (string, error) {
f, err := os.Open("/proc/1/cgroup")
if err != nil {
return "", err
}
defer f.Close()
return ParseCgroupFile(subsystem, f)
}
func ReadProcsFile(dir string) ([]int, error) {
f, err := os.Open(filepath.Join(dir, "cgroup.procs"))
if err != nil {
return nil, err
}
defer f.Close()
var (
s = bufio.NewScanner(f)
out = []int{}
)
for s.Scan() {
if t := s.Text(); t != "" {
pid, err := strconv.Atoi(t)
if err != nil {
return nil, err
}
out = append(out, pid)
}
}
return out, nil
}
func ParseCgroupFile(subsystem string, r io.Reader) (string, error) {
s := bufio.NewScanner(r)
for s.Scan() {
if err := s.Err(); err != nil {
return "", err
}
text := s.Text()
parts := strings.Split(text, ":")
for _, subs := range strings.Split(parts[1], ",") {
if subs == subsystem {
return parts[2], nil
}
}
}
return "", NewNotFoundError(subsystem)
}
func PathExists(path string) bool {
if _, err := os.Stat(path); err != nil {
return false
}
return true
}
func EnterPid(cgroupPaths map[string]string, pid int) error {
for _, path := range cgroupPaths {
if PathExists(path) {
if err := ioutil.WriteFile(filepath.Join(path, "cgroup.procs"),
[]byte(strconv.Itoa(pid)), 0700); err != nil {
return err
}
}
}
return nil
}
// RemovePaths iterates over the provided paths removing them.
// We trying to remove all paths five times with increasing delay between tries.
// If after all there are not removed cgroups - appropriate error will be
// returned.
func RemovePaths(paths map[string]string) (err error) {
delay := 10 * time.Millisecond
for i := 0; i < 5; i++ {
if i != 0 {
time.Sleep(delay)
delay *= 2
}
for s, p := range paths {
os.RemoveAll(p)
// TODO: here probably should be logging
_, err := os.Stat(p)
// We need this strange way of checking cgroups existence because
// RemoveAll almost always returns error, even on already removed
// cgroups
if os.IsNotExist(err) {
delete(paths, s)
}
}
if len(paths) == 0 {
return nil
}
}
return fmt.Errorf("Failed to remove paths: %s", paths)
}