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executor: stop joining executor to container cgroup #6839

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merged 3 commits into from
Dec 13, 2019
Merged

executor: stop joining executor to container cgroup #6839

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2f4b9da
drivers/exec: test all cgroups are destroyed
Dec 11, 2019
596d0be
executor: stop joining executor to container cgroup
Dec 11, 2019
f794b49
simplify cgroup path lookup
Dec 11, 2019
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88 changes: 22 additions & 66 deletions drivers/shared/executor/executor_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,6 @@ import (
"github.com/armon/circbuf"
"github.com/hashicorp/consul-template/signals"
hclog "github.com/hashicorp/go-hclog"
multierror "github.com/hashicorp/go-multierror"
"github.com/hashicorp/nomad/client/allocdir"
"github.com/hashicorp/nomad/client/stats"
cstructs "github.com/hashicorp/nomad/client/structs"
Expand All @@ -27,7 +26,6 @@ import (
"github.com/hashicorp/nomad/plugins/drivers"
"github.com/opencontainers/runc/libcontainer"
"github.com/opencontainers/runc/libcontainer/cgroups"
cgroupFs "github.com/opencontainers/runc/libcontainer/cgroups/fs"
lconfigs "github.com/opencontainers/runc/libcontainer/configs"
ldevices "github.com/opencontainers/runc/libcontainer/devices"
lutils "github.com/opencontainers/runc/libcontainer/utils"
Expand All @@ -36,7 +34,7 @@ import (
)

const (
defaultCgroupParent = "nomad"
defaultCgroupParent = "/nomad"
)

var (
Expand Down Expand Up @@ -92,15 +90,6 @@ func (l *LibcontainerExecutor) Launch(command *ExecCommand) (*ProcessState, erro

l.command = command

// Move to the root cgroup until process is started
subsystems, err := cgroups.GetAllSubsystems()
if err != nil {
return nil, err
}
if err := JoinRootCgroup(subsystems); err != nil {
return nil, err
}

// create a new factory which will store the container state in the allocDir
factory, err := libcontainer.New(
path.Join(command.TaskDir, "../alloc/container"),
Expand Down Expand Up @@ -194,15 +183,6 @@ func (l *LibcontainerExecutor) Launch(command *ExecCommand) (*ProcessState, erro
return nil, err
}

// Join process cgroups
containerState, err := container.State()
if err != nil {
l.logger.Error("error entering user process cgroups", "executor_pid", os.Getpid(), "error", err)
}
if err := cgroups.EnterPid(containerState.CgroupPaths, os.Getpid()); err != nil {
l.logger.Error("error entering user process cgroups", "executor_pid", os.Getpid(), "error", err)
}

// start a goroutine to wait on the process to complete, so Wait calls can
// be multiplexed
l.userProcExited = make(chan interface{})
Expand Down Expand Up @@ -287,15 +267,6 @@ func (l *LibcontainerExecutor) Shutdown(signal string, grace time.Duration) erro
return nil
}

// move executor to root cgroup
subsystems, err := cgroups.GetAllSubsystems()
if err != nil {
return err
}
if err := JoinRootCgroup(subsystems); err != nil {
return err
}

status, err := l.container.Status()
if err != nil {
return err
Expand Down Expand Up @@ -720,33 +691,40 @@ func configureBasicCgroups(cfg *lconfigs.Config) error {
id := uuid.Generate()

// Manually create freezer cgroup
cfg.Cgroups.Paths = map[string]string{}
root, err := cgroups.FindCgroupMountpointDir()
if err != nil {
return err
}

if _, err := os.Stat(root); err != nil {
return err
}
subsystem := "freezer"

freezer := cgroupFs.FreezerGroup{}
subsystem := freezer.Name()
path, err := cgroups.FindCgroupMountpoint("", subsystem)
path, err := getCgroupPathHelper(subsystem, filepath.Join(defaultCgroupParent, id))
if err != nil {
return fmt.Errorf("failed to find %s cgroup mountpoint: %v", subsystem, err)
}
// Sometimes subsystems can be mounted together as 'cpu,cpuacct'.
path = filepath.Join(root, filepath.Base(path), defaultCgroupParent, id)

if err = os.MkdirAll(path, 0755); err != nil {
return err
}

cfg.Cgroups.Paths[subsystem] = path
cfg.Cgroups.Paths = map[string]string{
subsystem: path,
}
return nil
}

func getCgroupPathHelper(subsystem, cgroup string) (string, error) {
mnt, root, err := cgroups.FindCgroupMountpointAndRoot("", subsystem)
if err != nil {
return "", err
}

// This is needed for nested containers, because in /proc/self/cgroup we
// see paths from host, which don't exist in container.
relCgroup, err := filepath.Rel(root, cgroup)
if err != nil {
return "", err
}

return filepath.Join(mnt, relCgroup), nil
}

func newLibcontainerConfig(command *ExecCommand) (*lconfigs.Config, error) {
cfg := &lconfigs.Config{
Cgroups: &lconfigs.Cgroup{
Expand All @@ -771,28 +749,6 @@ func newLibcontainerConfig(command *ExecCommand) (*lconfigs.Config, error) {
return cfg, nil
}

// JoinRootCgroup moves the current process to the cgroups of the init process
func JoinRootCgroup(subsystems []string) error {
mErrs := new(multierror.Error)
paths := map[string]string{}
for _, s := range subsystems {
mnt, _, err := cgroups.FindCgroupMountpointAndRoot("", s)
if err != nil {
multierror.Append(mErrs, fmt.Errorf("error getting cgroup path for subsystem: %s", s))
continue
}

paths[s] = mnt
}

err := cgroups.EnterPid(paths, os.Getpid())
if err != nil {
multierror.Append(mErrs, err)
}

return mErrs.ErrorOrNil()
}

// cmdDevices converts a list of driver.DeviceConfigs into excutor.Devices.
func cmdDevices(devices []*drivers.DeviceConfig) ([]*lconfigs.Device, error) {
if len(devices) == 0 {
Expand Down
83 changes: 83 additions & 0 deletions drivers/shared/executor/executor_linux_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ import (
"github.com/hashicorp/nomad/nomad/mock"
"github.com/hashicorp/nomad/plugins/drivers"
tu "github.com/hashicorp/nomad/testutil"
"github.com/opencontainers/runc/libcontainer/cgroups"
lconfigs "github.com/opencontainers/runc/libcontainer/configs"
"github.com/stretchr/testify/require"
"golang.org/x/sys/unix"
Expand Down Expand Up @@ -217,6 +218,88 @@ func TestExecutor_CgroupPaths(t *testing.T) {
}, func(err error) { t.Error(err) })
}

// TestExecutor_CgroupPaths asserts that all cgroups created for a task
// are destroyed on shutdown
func TestExecutor_CgroupPathsAreDestroyed(t *testing.T) {
t.Parallel()
require := require.New(t)
testutil.ExecCompatible(t)

testExecCmd := testExecutorCommandWithChroot(t)
execCmd, allocDir := testExecCmd.command, testExecCmd.allocDir
execCmd.Cmd = "/bin/bash"
execCmd.Args = []string{"-c", "sleep 0.2; cat /proc/self/cgroup"}
defer allocDir.Destroy()

execCmd.ResourceLimits = true

executor := NewExecutorWithIsolation(testlog.HCLogger(t))
defer executor.Shutdown("SIGKILL", 0)

ps, err := executor.Launch(execCmd)
require.NoError(err)
require.NotZero(ps.Pid)

state, err := executor.Wait(context.Background())
require.NoError(err)
require.Zero(state.ExitCode)

var cgroupsPaths string
tu.WaitForResult(func() (bool, error) {
output := strings.TrimSpace(testExecCmd.stdout.String())
// sanity check that we got some cgroups
if !strings.Contains(output, ":devices:") {
return false, fmt.Errorf("was expected cgroup files but found:\n%v", output)
}
lines := strings.Split(output, "\n")
for _, line := range lines {
// Every cgroup entry should be /nomad/$ALLOC_ID
if line == "" {
continue
}

// Skip rdma subsystem; rdma was added in most recent kernels and libcontainer/docker
// don't isolate it by default.
if strings.Contains(line, ":rdma:") {
continue
}

if !strings.Contains(line, ":/nomad/") {
return false, fmt.Errorf("Not a member of the alloc's cgroup: expected=...:/nomad/... -- found=%q", line)
}
}

cgroupsPaths = output
return true, nil
}, func(err error) { t.Error(err) })

// shutdown executor and test that cgroups are destroyed
executor.Shutdown("SIGKILL", 0)

// test that the cgroup paths are not visible
tmpFile, err := ioutil.TempFile("", "")
require.NoError(err)
defer os.Remove(tmpFile.Name())

_, err = tmpFile.WriteString(cgroupsPaths)
require.NoError(err)
tmpFile.Close()

subsystems, err := cgroups.ParseCgroupFile(tmpFile.Name())
require.NoError(err)

for subsystem, cgroup := range subsystems {
if !strings.Contains(cgroup, "nomad/") {
// this should only be rdma at this point
continue
}

p, err := getCgroupPathHelper(subsystem, cgroup)
require.NoError(err)
require.Falsef(cgroups.PathExists(p), "cgroup for %s %s still exists", subsystem, cgroup)
}
}

func TestUniversalExecutor_LookupTaskBin(t *testing.T) {
t.Parallel()
require := require.New(t)
Expand Down