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apply_systemd.go
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apply_systemd.go
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// +build linux
package systemd
import (
"fmt"
"io/ioutil"
"os"
"path/filepath"
"strconv"
"strings"
"sync"
"time"
systemd "github.com/coreos/go-systemd/dbus"
"github.com/docker/libcontainer/cgroups"
"github.com/docker/libcontainer/cgroups/fs"
"github.com/docker/libcontainer/configs"
"github.com/godbus/dbus"
)
type Manager struct {
Cgroups *configs.Cgroup
Paths map[string]string
}
type subsystem interface {
// Returns the stats, as 'stats', corresponding to the cgroup under 'path'.
GetStats(path string, stats *cgroups.Stats) error
// Set the cgroup represented by cgroup.
Set(path string, cgroup *configs.Cgroup) error
}
var subsystems = map[string]subsystem{
"devices": &fs.DevicesGroup{},
"memory": &fs.MemoryGroup{},
"cpu": &fs.CpuGroup{},
"cpuset": &fs.CpusetGroup{},
"cpuacct": &fs.CpuacctGroup{},
"blkio": &fs.BlkioGroup{},
"perf_event": &fs.PerfEventGroup{},
"freezer": &fs.FreezerGroup{},
}
const (
testScopeWait = 4
)
var (
connLock sync.Mutex
theConn *systemd.Conn
hasStartTransientUnit bool
hasTransientDefaultDependencies bool
)
func newProp(name string, units interface{}) systemd.Property {
return systemd.Property{
Name: name,
Value: dbus.MakeVariant(units),
}
}
func UseSystemd() bool {
s, err := os.Stat("/run/systemd/system")
if err != nil || !s.IsDir() {
return false
}
connLock.Lock()
defer connLock.Unlock()
if theConn == nil {
var err error
theConn, err = systemd.New()
if err != nil {
return false
}
// Assume we have StartTransientUnit
hasStartTransientUnit = true
// But if we get UnknownMethod error we don't
if _, err := theConn.StartTransientUnit("test.scope", "invalid"); err != nil {
if dbusError, ok := err.(dbus.Error); ok {
if dbusError.Name == "org.freedesktop.DBus.Error.UnknownMethod" {
hasStartTransientUnit = false
return hasStartTransientUnit
}
}
}
// Ensure the scope name we use doesn't exist. Use the Pid to
// avoid collisions between multiple libcontainer users on a
// single host.
scope := fmt.Sprintf("libcontainer-%d-systemd-test-default-dependencies.scope", os.Getpid())
testScopeExists := true
for i := 0; i <= testScopeWait; i++ {
if _, err := theConn.StopUnit(scope, "replace"); err != nil {
if dbusError, ok := err.(dbus.Error); ok {
if strings.Contains(dbusError.Name, "org.freedesktop.systemd1.NoSuchUnit") {
testScopeExists = false
break
}
}
}
time.Sleep(time.Millisecond)
}
// Bail out if we can't kill this scope without testing for DefaultDependencies
if testScopeExists {
return hasStartTransientUnit
}
// Assume StartTransientUnit on a scope allows DefaultDependencies
hasTransientDefaultDependencies = true
ddf := newProp("DefaultDependencies", false)
if _, err := theConn.StartTransientUnit(scope, "replace", ddf); err != nil {
if dbusError, ok := err.(dbus.Error); ok {
if strings.Contains(dbusError.Name, "org.freedesktop.DBus.Error.PropertyReadOnly") {
hasTransientDefaultDependencies = false
}
}
}
// Not critical because of the stop unit logic above.
theConn.StopUnit(scope, "replace")
}
return hasStartTransientUnit
}
func getIfaceForUnit(unitName string) string {
if strings.HasSuffix(unitName, ".scope") {
return "Scope"
}
if strings.HasSuffix(unitName, ".service") {
return "Service"
}
return "Unit"
}
func (m *Manager) Apply(pid int) error {
var (
c = m.Cgroups
unitName = getUnitName(c)
slice = "system.slice"
properties []systemd.Property
)
if c.Slice != "" {
slice = c.Slice
}
properties = append(properties,
systemd.PropSlice(slice),
systemd.PropDescription("docker container "+c.Name),
newProp("PIDs", []uint32{uint32(pid)}),
)
// Always enable accounting, this gets us the same behaviour as the fs implementation,
// plus the kernel has some problems with joining the memory cgroup at a later time.
properties = append(properties,
newProp("MemoryAccounting", true),
newProp("CPUAccounting", true),
newProp("BlockIOAccounting", true))
if hasTransientDefaultDependencies {
properties = append(properties,
newProp("DefaultDependencies", false))
}
if c.Memory != 0 {
properties = append(properties,
newProp("MemoryLimit", uint64(c.Memory)))
}
// TODO: MemoryReservation and MemorySwap not available in systemd
if c.CpuShares != 0 {
properties = append(properties,
newProp("CPUShares", uint64(c.CpuShares)))
}
if c.BlkioWeight != 0 {
properties = append(properties,
newProp("BlockIOWeight", uint64(c.BlkioWeight)))
}
if _, err := theConn.StartTransientUnit(unitName, "replace", properties...); err != nil {
return err
}
if err := joinDevices(c, pid); err != nil {
return err
}
// TODO: CpuQuota and CpuPeriod not available in systemd
// we need to manually join the cpu.cfs_quota_us and cpu.cfs_period_us
if err := joinCpu(c, pid); err != nil {
return err
}
// -1 disables memorySwap
if c.MemorySwap >= 0 && c.Memory != 0 {
if err := joinMemory(c, pid); err != nil {
return err
}
}
// we need to manually join the freezer and cpuset cgroup in systemd
// because it does not currently support it via the dbus api.
if err := joinFreezer(c, pid); err != nil {
return err
}
if err := joinCpuset(c, pid); err != nil {
return err
}
// FIXME: Systemd does have `BlockIODeviceWeight` property, but we got problem
// using that (at least on systemd 208, see https://github.com/docker/libcontainer/pull/354),
// so use fs work around for now.
if err := joinBlkio(c, pid); err != nil {
return err
}
paths := make(map[string]string)
for sysname := range subsystems {
subsystemPath, err := getSubsystemPath(m.Cgroups, sysname)
if err != nil {
// Don't fail if a cgroup hierarchy was not found, just skip this subsystem
if cgroups.IsNotFound(err) {
continue
}
return err
}
paths[sysname] = subsystemPath
}
m.Paths = paths
return nil
}
func (m *Manager) Destroy() error {
return cgroups.RemovePaths(m.Paths)
}
func (m *Manager) GetPaths() map[string]string {
return m.Paths
}
func writeFile(dir, file, data string) error {
return ioutil.WriteFile(filepath.Join(dir, file), []byte(data), 0700)
}
func join(c *configs.Cgroup, subsystem string, pid int) (string, error) {
path, err := getSubsystemPath(c, subsystem)
if err != nil {
return "", err
}
if err := os.MkdirAll(path, 0755); err != nil && !os.IsExist(err) {
return "", err
}
if err := writeFile(path, "cgroup.procs", strconv.Itoa(pid)); err != nil {
return "", err
}
return path, nil
}
func joinCpu(c *configs.Cgroup, pid int) error {
path, err := getSubsystemPath(c, "cpu")
if err != nil {
return err
}
if c.CpuQuota != 0 {
if err = ioutil.WriteFile(filepath.Join(path, "cpu.cfs_quota_us"), []byte(strconv.FormatInt(c.CpuQuota, 10)), 0700); err != nil {
return err
}
}
if c.CpuPeriod != 0 {
if err = ioutil.WriteFile(filepath.Join(path, "cpu.cfs_period_us"), []byte(strconv.FormatInt(c.CpuPeriod, 10)), 0700); err != nil {
return err
}
}
return nil
}
func joinFreezer(c *configs.Cgroup, pid int) error {
if _, err := join(c, "freezer", pid); err != nil {
return err
}
return nil
}
func getSubsystemPath(c *configs.Cgroup, subsystem string) (string, error) {
mountpoint, err := cgroups.FindCgroupMountpoint(subsystem)
if err != nil {
return "", err
}
initPath, err := cgroups.GetInitCgroupDir(subsystem)
if err != nil {
return "", err
}
slice := "system.slice"
if c.Slice != "" {
slice = c.Slice
}
return filepath.Join(mountpoint, initPath, slice, getUnitName(c)), nil
}
func (m *Manager) Freeze(state configs.FreezerState) error {
path, err := getSubsystemPath(m.Cgroups, "freezer")
if err != nil {
return err
}
prevState := m.Cgroups.Freezer
m.Cgroups.Freezer = state
freezer := subsystems["freezer"]
err = freezer.Set(path, m.Cgroups)
if err != nil {
m.Cgroups.Freezer = prevState
return err
}
return nil
}
func (m *Manager) GetPids() ([]int, error) {
path, err := getSubsystemPath(m.Cgroups, "cpu")
if err != nil {
return nil, err
}
return cgroups.ReadProcsFile(path)
}
func (m *Manager) GetStats() (*cgroups.Stats, error) {
stats := cgroups.NewStats()
for name, path := range m.Paths {
sys, ok := subsystems[name]
if !ok || !cgroups.PathExists(path) {
continue
}
if err := sys.GetStats(path, stats); err != nil {
return nil, err
}
}
return stats, nil
}
func (m *Manager) Set(container *configs.Config) error {
panic("not implemented")
}
func getUnitName(c *configs.Cgroup) string {
return fmt.Sprintf("%s-%s.scope", c.Parent, c.Name)
}
// Atm we can't use the systemd device support because of two missing things:
// * Support for wildcards to allow mknod on any device
// * Support for wildcards to allow /dev/pts support
//
// The second is available in more recent systemd as "char-pts", but not in e.g. v208 which is
// in wide use. When both these are availalable we will be able to switch, but need to keep the old
// implementation for backwards compat.
//
// Note: we can't use systemd to set up the initial limits, and then change the cgroup
// because systemd will re-write the device settings if it needs to re-apply the cgroup context.
// This happens at least for v208 when any sibling unit is started.
func joinDevices(c *configs.Cgroup, pid int) error {
path, err := join(c, "devices", pid)
if err != nil {
return err
}
devices := subsystems["devices"]
if err := devices.Set(path, c); err != nil {
return err
}
return nil
}
// Symmetrical public function to update device based cgroups. Also available
// in the fs implementation.
func ApplyDevices(c *configs.Cgroup, pid int) error {
return joinDevices(c, pid)
}
func joinMemory(c *configs.Cgroup, pid int) error {
memorySwap := c.MemorySwap
if memorySwap == 0 {
// By default, MemorySwap is set to twice the size of RAM.
memorySwap = c.Memory * 2
}
path, err := getSubsystemPath(c, "memory")
if err != nil {
return err
}
return ioutil.WriteFile(filepath.Join(path, "memory.memsw.limit_in_bytes"), []byte(strconv.FormatInt(memorySwap, 10)), 0700)
}
// systemd does not atm set up the cpuset controller, so we must manually
// join it. Additionally that is a very finicky controller where each
// level must have a full setup as the default for a new directory is "no cpus"
func joinCpuset(c *configs.Cgroup, pid int) error {
path, err := getSubsystemPath(c, "cpuset")
if err != nil {
return err
}
s := &fs.CpusetGroup{}
return s.ApplyDir(path, c, pid)
}
// `BlockIODeviceWeight` property of systemd does not work properly, and systemd
// expects device path instead of major minor numbers, which is also confusing
// for users. So we use fs work around for now.
func joinBlkio(c *configs.Cgroup, pid int) error {
path, err := getSubsystemPath(c, "blkio")
if err != nil {
return err
}
if c.BlkioWeightDevice != "" {
if err := writeFile(path, "blkio.weight_device", c.BlkioWeightDevice); err != nil {
return err
}
}
return nil
}