101 lines
2.2 KiB
Go
101 lines
2.2 KiB
Go
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package cgroups
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import (
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"bufio"
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"fmt"
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"github.com/dotcloud/docker/pkg/mount"
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"io"
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"io/ioutil"
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"os"
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"path/filepath"
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"strconv"
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"strings"
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)
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// https://www.kernel.org/doc/Documentation/cgroups/cgroups.txt
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func FindCgroupMountpoint(subsystem string) (string, error) {
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mounts, err := mount.GetMounts()
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if err != nil {
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return "", err
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}
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for _, mount := range mounts {
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if mount.Fstype == "cgroup" {
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for _, opt := range strings.Split(mount.VfsOpts, ",") {
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if opt == subsystem {
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return mount.Mountpoint, nil
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}
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}
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}
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}
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return "", fmt.Errorf("cgroup mountpoint not found for %s", subsystem)
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}
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// Returns the relative path to the cgroup docker is running in.
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func getThisCgroupDir(subsystem string) (string, error) {
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f, err := os.Open("/proc/self/cgroup")
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if err != nil {
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return "", err
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}
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defer f.Close()
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return parseCgroupFile(subsystem, f)
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}
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func parseCgroupFile(subsystem string, r io.Reader) (string, error) {
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s := bufio.NewScanner(r)
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for s.Scan() {
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if err := s.Err(); err != nil {
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return "", err
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}
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text := s.Text()
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parts := strings.Split(text, ":")
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if parts[1] == subsystem {
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return parts[2], nil
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}
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}
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return "", fmt.Errorf("cgroup '%s' not found in /proc/self/cgroup", subsystem)
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}
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// Returns a list of pids for the given container.
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func GetPidsForContainer(id string) ([]int, error) {
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pids := []int{}
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// memory is chosen randomly, any cgroup used by docker works
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subsystem := "memory"
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cgroupRoot, err := FindCgroupMountpoint(subsystem)
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if err != nil {
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return pids, err
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}
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cgroupDir, err := getThisCgroupDir(subsystem)
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if err != nil {
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return pids, err
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}
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filename := filepath.Join(cgroupRoot, cgroupDir, id, "tasks")
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if _, err := os.Stat(filename); os.IsNotExist(err) {
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// With more recent lxc versions use, cgroup will be in lxc/
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filename = filepath.Join(cgroupRoot, cgroupDir, "lxc", id, "tasks")
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}
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output, err := ioutil.ReadFile(filename)
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if err != nil {
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return pids, err
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}
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for _, p := range strings.Split(string(output), "\n") {
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if len(p) == 0 {
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continue
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}
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pid, err := strconv.Atoi(p)
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if err != nil {
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return pids, fmt.Errorf("Invalid pid '%s': %s", p, err)
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}
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pids = append(pids, pid)
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}
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return pids, nil
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}
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