Merge pull request #3310 from pnasrat/cgroups-subpackage

Extract cgroups utilities to own submodule.

cgroups/MAINTAINERS

@@ -0,0 +1 @@
+Michael Crosby <michael@crosbymichael.com> (@crosbymichael)

cgroups/cgroups.go

@@ -0,0 +1,101 @@
+package cgroups
+
+import (
+	"bufio"
+	"fmt"
+	"github.com/dotcloud/docker/mount"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+// 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 "", fmt.Errorf("cgroup mountpoint not found for %s", subsystem)
+}
+
+// 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 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, ":")
+		if parts[1] == subsystem {
+			return parts[2], nil
+		}
+	}
+	return "", fmt.Errorf("cgroup '%s' not found in /proc/self/cgroup", subsystem)
+}
+
+// Returns a list of pids for the given container.
+func GetPidsForContainer(id string) ([]int, error) {
+	pids := []int{}
+
+	// memory is chosen randomly, any cgroup used by docker works
+	subsystem := "memory"
+
+	cgroupRoot, err := FindCgroupMountpoint(subsystem)
+	if err != nil {
+		return pids, err
+	}
+
+	cgroupDir, err := getThisCgroupDir(subsystem)
+	if err != nil {
+		return pids, err
+	}
+
+	filename := filepath.Join(cgroupRoot, cgroupDir, id, "tasks")
+	if _, err := os.Stat(filename); os.IsNotExist(err) {
+		// With more recent lxc versions use, cgroup will be in lxc/
+		filename = filepath.Join(cgroupRoot, cgroupDir, "lxc", id, "tasks")
+	}
+
+	output, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return pids, err
+	}
+	for _, p := range strings.Split(string(output), "\n") {
+		if len(p) == 0 {
+			continue
+		}
+		pid, err := strconv.Atoi(p)
+		if err != nil {
+			return pids, fmt.Errorf("Invalid pid '%s': %s", p, err)
+		}
+		pids = append(pids, pid)
+	}
+	return pids, nil
+}

cgroups/cgroups_test.go

@@ -0,0 +1,27 @@
+package cgroups
+
+import (
+	"bytes"
+	"testing"
+)
+
+const (
+	cgroupsContents = `11:hugetlb:/
+10:perf_event:/
+9:blkio:/
+8:net_cls:/
+7:freezer:/
+6:devices:/
+5:memory:/
+4:cpuacct,cpu:/
+3:cpuset:/
+2:name=systemd:/user.slice/user-1000.slice/session-16.scope`
+)
+
+func TestParseCgroups(t *testing.T) {
+	r := bytes.NewBuffer([]byte(cgroupsContents))
+	_, err := parseCgroupFile("blkio", r)
+	if err != nil {
+		t.Fatal(err)
+	}
+}

mount/mount.go

@@ -4,6 +4,10 @@ import (
 	"time"
 )
 
+func GetMounts() ([]*MountInfo, error) {
+	return parseMountTable()
+}
+
 // Looks at /proc/self/mountinfo to determine of the specified
 // mountpoint has been mounted
 func Mounted(mountpoint string) (bool, error) {
@@ -14,7 +18,7 @@ func Mounted(mountpoint string) (bool, error) {
 
 	// Search the table for the mountpoint
 	for _, e := range entries {
-		if e.mountpoint == mountpoint {
+		if e.Mountpoint == mountpoint {
 			return true, nil
 		}
 	}

mount/mountinfo.go

@@ -5,22 +5,35 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"strings"
 )
 
 const (
-	// We only parse upto the mountinfo because that is all we
-	// care about right now
-	mountinfoFormat = "%d %d %d:%d %s %s %s"
+	/* 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
+	   (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)
+
+	   (1) mount ID:  unique identifier of the mount (may be reused after umount)
+	   (2) parent ID:  ID of parent (or of self for the top of the mount tree)
+	   (3) major:minor:  value of st_dev for files on filesystem
+	   (4) root:  root of the mount within the filesystem
+	   (5) mount point:  mount point relative to the process's root
+	   (6) mount options:  per mount options
+	   (7) optional fields:  zero or more fields of the form "tag[:value]"
+	   (8) separator:  marks the end of the optional fields
+	   (9) filesystem type:  name of filesystem of the form "type[.subtype]"
+	   (10) mount source:  filesystem specific information or "none"
+	   (11) super options:  per super block options*/
+	mountinfoFormat = "%d %d %d:%d %s %s %s "
 )
 
-// Represents one line from /proc/self/mountinfo
-type procEntry struct {
-	id, parent, major, minor int
-	source, mountpoint, opts string
+type MountInfo struct {
+	Id, Parent, Major, Minor int
+	Root, Mountpoint, Opts   string
+	Fstype, Source, VfsOpts  string
 }
 
 // Parse /proc/self/mountinfo because comparing Dev and ino does not work from bind mounts
-func parseMountTable() ([]*procEntry, error) {
+func parseMountTable() ([]*MountInfo, error) {
 	f, err := os.Open("/proc/self/mountinfo")
 	if err != nil {
 		return nil, err
@@ -30,10 +43,10 @@ func parseMountTable() ([]*procEntry, error) {
 	return parseInfoFile(f)
 }
 
-func parseInfoFile(r io.Reader) ([]*procEntry, error) {
+func parseInfoFile(r io.Reader) ([]*MountInfo, error) {
 	var (
 		s   = bufio.NewScanner(r)
-		out = []*procEntry{}
+		out = []*MountInfo{}
 	)
 
 	for s.Scan() {
@@ -42,14 +55,24 @@ func parseInfoFile(r io.Reader) ([]*procEntry, error) {
 		}
 
 		var (
-			p    = &procEntry{}
+			p    = &MountInfo{}
 			text = s.Text()
 		)
+
 		if _, err := fmt.Sscanf(text, mountinfoFormat,
-			&p.id, &p.parent, &p.major, &p.minor,
-			&p.source, &p.mountpoint, &p.opts); err != nil {
+			&p.Id, &p.Parent, &p.Major, &p.Minor,
+			&p.Root, &p.Mountpoint, &p.Opts); err != nil {
 			return nil, fmt.Errorf("Scanning '%s' failed: %s", text, err)
 		}
+		// Safe as mountinfo encodes mountpoints with spaces as \040.
+		index := strings.Index(text, " - ")
+		postSeparatorFields := strings.Fields(text[index+3:])
+		if len(postSeparatorFields) != 3 {
+			return nil, fmt.Errorf("Error did not find 3 fields post '-' in '%s'", text)
+		}
+		p.Fstype = postSeparatorFields[0]
+		p.Source = postSeparatorFields[1]
+		p.VfsOpts = postSeparatorFields[2]
 		out = append(out, p)
 	}
 	return out, nil

runtime.go

@@ -4,11 +4,12 @@ import (
 	"container/list"
 	"fmt"
 	"github.com/dotcloud/docker/archive"
-	"github.com/dotcloud/docker/pkg/graphdb"
+	"github.com/dotcloud/docker/cgroups"
 	"github.com/dotcloud/docker/graphdriver"
 	"github.com/dotcloud/docker/graphdriver/aufs"
 	_ "github.com/dotcloud/docker/graphdriver/devmapper"
 	_ "github.com/dotcloud/docker/graphdriver/vfs"
+	"github.com/dotcloud/docker/pkg/graphdb"
 	"github.com/dotcloud/docker/utils"
 	"io"
 	"io/ioutil"
@@ -332,7 +333,7 @@ func (runtime *Runtime) restore() error {
 
 // FIXME: comment please!
 func (runtime *Runtime) UpdateCapabilities(quiet bool) {
-	if cgroupMemoryMountpoint, err := utils.FindCgroupMountpoint("memory"); err != nil {
+	if cgroupMemoryMountpoint, err := cgroups.FindCgroupMountpoint("memory"); err != nil {
 		if !quiet {
 			log.Printf("WARNING: %s\n", err)
 		}

server.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"github.com/dotcloud/docker/archive"
 	"github.com/dotcloud/docker/auth"
+	"github.com/dotcloud/docker/cgroups"
 	"github.com/dotcloud/docker/engine"
 	"github.com/dotcloud/docker/pkg/graphdb"
 	"github.com/dotcloud/docker/registry"
@@ -702,7 +703,7 @@ func (srv *Server) ContainerTop(name, psArgs string) (*APITop, error) {
 		if !container.State.IsRunning() {
 			return nil, fmt.Errorf("Container %s is not running", name)
 		}
-		pids, err := utils.GetPidsForContainer(container.ID)
+		pids, err := cgroups.GetPidsForContainer(container.ID)
 		if err != nil {
 			return nil, err
 		}

utils/utils.go

@@ -583,28 +583,6 @@ func CompareKernelVersion(a, b *KernelVersionInfo) int {
 	return 0
 }
 
-func FindCgroupMountpoint(cgroupType string) (string, error) {
-	output, err := ioutil.ReadFile("/proc/mounts")
-	if err != nil {
-		return "", err
-	}
-
-	// /proc/mounts has 6 fields per line, one mount per line, e.g.
-	// cgroup /sys/fs/cgroup/devices cgroup rw,relatime,devices 0 0
-	for _, line := range strings.Split(string(output), "\n") {
-		parts := strings.Split(line, " ")
-		if len(parts) == 6 && parts[2] == "cgroup" {
-			for _, opt := range strings.Split(parts[3], ",") {
-				if opt == cgroupType {
-					return parts[1], nil
-				}
-			}
-		}
-	}
-
-	return "", fmt.Errorf("cgroup mountpoint not found for %s", cgroupType)
-}
-
 func GetKernelVersion() (*KernelVersionInfo, error) {
 	var (
 		err error
@@ -1157,59 +1135,3 @@ func CopyFile(src, dst string) (int64, error) {
 	defer df.Close()
 	return io.Copy(df, sf)
 }
-
-// Returns the relative path to the cgroup docker is running in.
-func GetThisCgroup(cgroupType string) (string, error) {
-	output, err := ioutil.ReadFile("/proc/self/cgroup")
-	if err != nil {
-		return "", err
-	}
-	for _, line := range strings.Split(string(output), "\n") {
-		parts := strings.Split(line, ":")
-		// any type used by docker should work
-		if parts[1] == cgroupType {
-			return parts[2], nil
-		}
-	}
-	return "", fmt.Errorf("cgroup '%s' not found in /proc/self/cgroup", cgroupType)
-}
-
-// Returns a list of pids for the given container.
-func GetPidsForContainer(id string) ([]int, error) {
-	pids := []int{}
-
-	// memory is chosen randomly, any cgroup used by docker works
-	cgroupType := "memory"
-
-	cgroupRoot, err := FindCgroupMountpoint(cgroupType)
-	if err != nil {
-		return pids, err
-	}
-
-	cgroupThis, err := GetThisCgroup(cgroupType)
-	if err != nil {
-		return pids, err
-	}
-
-	filename := filepath.Join(cgroupRoot, cgroupThis, id, "tasks")
-	if _, err := os.Stat(filename); os.IsNotExist(err) {
-		// With more recent lxc versions use, cgroup will be in lxc/
-		filename = filepath.Join(cgroupRoot, cgroupThis, "lxc", id, "tasks")
-	}
-
-	output, err := ioutil.ReadFile(filename)
-	if err != nil {
-		return pids, err
-	}
-	for _, p := range strings.Split(string(output), "\n") {
-		if len(p) == 0 {
-			continue
-		}
-		pid, err := strconv.Atoi(p)
-		if err != nil {
-			return pids, fmt.Errorf("Invalid pid '%s': %s", p, err)
-		}
-		pids = append(pids, pid)
-	}
-	return pids, nil
-}