gvisor/runsc/container/container.go

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// Copyright 2018 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package container creates and manipulates containers.
package container
import (
"context"
"encoding/json"
"fmt"
"io/ioutil"
"os"
"os/exec"
"path/filepath"
"regexp"
"strconv"
"strings"
"syscall"
"time"
"github.com/cenkalti/backoff"
specs "github.com/opencontainers/runtime-spec/specs-go"
"gvisor.googlesource.com/gvisor/pkg/log"
"gvisor.googlesource.com/gvisor/pkg/sentry/control"
"gvisor.googlesource.com/gvisor/runsc/boot"
"gvisor.googlesource.com/gvisor/runsc/sandbox"
"gvisor.googlesource.com/gvisor/runsc/specutils"
)
// metadataFilename is the name of the metadata file relative to the container
// root directory that holds sandbox metadata.
const metadataFilename = "meta.json"
// validateID validates the container id.
func validateID(id string) error {
// See libcontainer/factory_linux.go.
idRegex := regexp.MustCompile(`^[\w+-\.]+$`)
if !idRegex.MatchString(id) {
return fmt.Errorf("invalid container id: %v", id)
}
return nil
}
// Container represents a containerized application. When running, the
// container is associated with a single Sandbox.
//
// Container metadata can be saved and loaded to disk. Within a root directory,
// we maintain subdirectories for each container named with the container id.
// The container metadata is stored as a json within the container directory
// in a file named "meta.json". This metadata format is defined by us and is
// not part of the OCI spec.
//
// Containers must write their metadata files after any change to their internal
// states. The entire container directory is deleted when the container is
// destroyed.
type Container struct {
// ID is the container ID.
ID string `json:"id"`
// Spec is the OCI runtime spec that configures this container.
Spec *specs.Spec `json:"spec"`
// BundleDir is the directory containing the container bundle.
BundleDir string `json:"bundleDir"`
// Root is the directory containing the container metadata file.
Root string `json:"root"`
// CreatedAt is the time the container was created.
CreatedAt time.Time `json:"createdAt"`
// Owner is the container owner.
Owner string `json:"owner"`
// ConsoleSocket is the path to a unix domain socket that will receive
// the console FD. It is only used during create, so we don't need to
// store it in the metadata.
ConsoleSocket string `json:"-"`
// Status is the current container Status.
Status Status `json:"status"`
// GoferPid is the pid of the gofer running along side the sandbox. May
// be 0 if the gofer has been killed or it's not being used.
GoferPid int `json:"goferPid"`
// Sandbox is the sandbox this container is running in. It will be nil
// if the container is not in state Running or Created.
Sandbox *sandbox.Sandbox `json:"sandbox"`
}
// Load loads a container with the given id from a metadata file. id may be an
// abbreviation of the full container id, in which case Load loads the
// container to which id unambiguously refers to.
// Returns ErrNotExist if container doesn't exist.
func Load(rootDir, id string) (*Container, error) {
log.Debugf("Load container %q %q", rootDir, id)
if err := validateID(id); err != nil {
return nil, fmt.Errorf("error validating id: %v", err)
}
cRoot, err := findContainerRoot(rootDir, id)
if err != nil {
// Preserve error so that callers can distinguish 'not found' errors.
return nil, err
}
metaFile := filepath.Join(cRoot, metadataFilename)
metaBytes, err := ioutil.ReadFile(metaFile)
if err != nil {
if os.IsNotExist(err) {
// Preserve error so that callers can distinguish 'not found' errors.
return nil, err
}
return nil, fmt.Errorf("error reading container metadata file %q: %v", metaFile, err)
}
var c Container
if err := json.Unmarshal(metaBytes, &c); err != nil {
return nil, fmt.Errorf("error unmarshaling container metadata from %q: %v", metaFile, err)
}
// If the status is "Running" or "Created", check that the sandbox
// process still exists, and set it to Stopped if it does not.
//
// This is inherently racey.
if c.Status == Running || c.Status == Created {
// Check if the sandbox process is still running.
if c.IsRunning() {
// TODO: Send a message into the sandbox to
// see if this particular container is still running.
} else {
// Sandbox no longer exists, so this container definitely does not exist.
c.Status = Stopped
c.Sandbox = nil
}
}
return &c, nil
}
func findContainerRoot(rootDir, partialID string) (string, error) {
// Check whether the id fully specifies an existing container.
cRoot := filepath.Join(rootDir, partialID)
if _, err := os.Stat(cRoot); err == nil {
return cRoot, nil
}
// Now see whether id could be an abbreviation of exactly 1 of the
// container ids. If id is ambigious (it could match more than 1
// container), it is an error.
cRoot = ""
ids, err := List(rootDir)
if err != nil {
return "", err
}
for _, id := range ids {
if strings.HasPrefix(id, partialID) {
if cRoot != "" {
return "", fmt.Errorf("id %q is ambiguous and could refer to multiple containers: %q, %q", partialID, cRoot, id)
}
cRoot = id
}
}
if cRoot == "" {
return "", os.ErrNotExist
}
log.Debugf("abbreviated id %q resolves to full id %q", partialID, cRoot)
return filepath.Join(rootDir, cRoot), nil
}
// List returns all container ids in the given root directory.
func List(rootDir string) ([]string, error) {
log.Debugf("List containers %q", rootDir)
fs, err := ioutil.ReadDir(rootDir)
if err != nil {
return nil, fmt.Errorf("ReadDir(%s) failed: %v", rootDir, err)
}
var out []string
for _, f := range fs {
out = append(out, f.Name())
}
return out, nil
}
// Create creates the container in a new Sandbox process, unless the metadata
// indicates that an existing Sandbox should be used.
func Create(id string, spec *specs.Spec, conf *boot.Config, bundleDir, consoleSocket, pidFile string) (*Container, error) {
log.Debugf("Create container %q in root dir: %s", id, conf.RootDir)
if err := validateID(id); err != nil {
return nil, err
}
containerRoot := filepath.Join(conf.RootDir, id)
if _, err := os.Stat(containerRoot); err == nil {
return nil, fmt.Errorf("container with id %q already exists: %q", id, containerRoot)
} else if !os.IsNotExist(err) {
return nil, fmt.Errorf("error looking for existing container in %q: %v", containerRoot, err)
}
c := &Container{
ID: id,
Spec: spec,
ConsoleSocket: consoleSocket,
BundleDir: bundleDir,
Root: containerRoot,
Status: Creating,
Owner: os.Getenv("USER"),
}
// If the metadata annotations indicate that this container should be
// started in an existing sandbox, we must do so. The metadata will
// indicate the ID of the sandbox, which is the same as the ID of the
// init container in the sandbox.
if specutils.ShouldCreateSandbox(spec) || !conf.MultiContainer {
log.Debugf("Creating new sandbox for container %q", id)
ioFiles, err := c.createGoferProcess(spec, conf, bundleDir)
if err != nil {
return nil, err
}
// Start a new sandbox for this container. Any errors after this point
// must destroy the container.
s, err := sandbox.Create(id, spec, conf, bundleDir, consoleSocket, ioFiles)
if err != nil {
c.Destroy()
return nil, err
}
c.Sandbox = s
} else {
// This is sort of confusing. For a sandbox with a root
// container and a child container in it, runsc sees:
// * A container struct whose sandbox ID is equal to the
// container ID. This is the root container that is tied to
// the creation of the sandbox.
// * A container struct whose sandbox ID is equal to the above
// container/sandbox ID, but that has a different container
// ID. This is the child container.
sbid, ok := specutils.SandboxID(spec)
if !ok {
return nil, fmt.Errorf("no sandbox ID found when creating container")
}
log.Debugf("Creating new container %q in sandbox %q", c.ID, sbid)
// Find the sandbox associated with this ID.
sb, err := Load(conf.RootDir, sbid)
if err != nil {
c.Destroy()
return nil, err
}
c.Sandbox = sb.Sandbox
}
c.Status = Created
// Save the metadata file.
if err := c.save(); err != nil {
c.Destroy()
return nil, err
}
// Write the pid file. Containerd considers the create complete after
// this file is created, so it must be the last thing we do.
if pidFile != "" {
if err := ioutil.WriteFile(pidFile, []byte(strconv.Itoa(c.Pid())), 0644); err != nil {
c.Destroy()
return nil, fmt.Errorf("error writing pid file: %v", err)
}
}
return c, nil
}
// Start starts running the containerized process inside the sandbox.
func (c *Container) Start(conf *boot.Config) error {
log.Debugf("Start container %q", c.ID)
if c.Status != Created {
return fmt.Errorf("cannot start container in state %s", c.Status)
}
// "If any prestart hook fails, the runtime MUST generate an error,
// stop and destroy the container" -OCI spec.
if c.Spec.Hooks != nil {
if err := executeHooks(c.Spec.Hooks.Prestart, c.State()); err != nil {
c.Destroy()
return err
}
}
if specutils.ShouldCreateSandbox(c.Spec) || !conf.MultiContainer {
if err := c.Sandbox.StartRoot(c.Spec, conf); err != nil {
c.Destroy()
return err
}
} else {
// Create the gofer process.
ioFiles, err := c.createGoferProcess(c.Spec, conf, c.BundleDir)
if err != nil {
return err
}
if err := c.Sandbox.Start(c.Spec, conf, c.ID, ioFiles); err != nil {
c.Destroy()
return err
}
}
// "If any poststart hook fails, the runtime MUST log a warning, but
// the remaining hooks and lifecycle continue as if the hook had
// succeeded" -OCI spec.
if c.Spec.Hooks != nil {
executeHooksBestEffort(c.Spec.Hooks.Poststart, c.State())
}
c.Status = Running
return c.save()
}
// Restore takes a container and replaces its kernel and file system
// to restore a container from its state file.
func (c *Container) Restore(spec *specs.Spec, conf *boot.Config, restoreFile string) error {
log.Debugf("Restore container %q", c.ID)
if c.Status != Created {
return fmt.Errorf("cannot restore container in state %s", c.Status)
}
if err := c.Sandbox.Restore(c.ID, spec, conf, restoreFile); err != nil {
return err
}
c.Status = Running
return c.save()
}
// Run is a helper that calls Create + Start + Wait.
func Run(id string, spec *specs.Spec, conf *boot.Config, bundleDir, consoleSocket, pidFile string) (syscall.WaitStatus, error) {
log.Debugf("Run container %q in root dir: %s", id, conf.RootDir)
c, err := Create(id, spec, conf, bundleDir, consoleSocket, pidFile)
if err != nil {
return 0, fmt.Errorf("error creating container: %v", err)
}
if err := c.Start(conf); err != nil {
return 0, fmt.Errorf("error starting container: %v", err)
}
return c.Wait()
}
// Execute runs the specified command in the container.
func (c *Container) Execute(e *control.ExecArgs) (syscall.WaitStatus, error) {
log.Debugf("Execute in container %q, args: %+v", c.ID, e)
if c.Status != Created && c.Status != Running {
return 0, fmt.Errorf("cannot exec in container in state %s", c.Status)
}
return c.Sandbox.Execute(c.ID, e)
}
// Event returns events for the container.
func (c *Container) Event() (*boot.Event, error) {
log.Debugf("Getting events for container %q", c.ID)
if c.Status != Running && c.Status != Created {
return nil, fmt.Errorf("cannot get events for container in state: %s", c.Status)
}
return c.Sandbox.Event(c.ID)
}
// Pid returns the Pid of the sandbox the container is running in, or -1 if the
// container is not running.
func (c *Container) Pid() int {
if c.Status != Running && c.Status != Created && c.Status != Paused {
return -1
}
return c.Sandbox.Pid
}
// Wait waits for the container to exit, and returns its WaitStatus.
func (c *Container) Wait() (syscall.WaitStatus, error) {
log.Debugf("Wait on container %q", c.ID)
if c.Status == Stopped {
return 0, fmt.Errorf("container is stopped")
}
return c.Sandbox.Wait(c.ID)
}
// WaitRootPID waits for process 'pid' in the sandbox's PID namespace and
// returns its WaitStatus.
func (c *Container) WaitRootPID(pid int32) (syscall.WaitStatus, error) {
log.Debugf("Wait on pid %d in sandbox %q", pid, c.Sandbox.ID)
if c.Status == Stopped {
return 0, fmt.Errorf("container is stopped")
}
return c.Sandbox.WaitPID(pid, c.Sandbox.ID)
}
// WaitPID waits for process 'pid' in the container's PID namespace and returns
// its WaitStatus.
func (c *Container) WaitPID(pid int32) (syscall.WaitStatus, error) {
log.Debugf("Wait on pid %d in container %q", pid, c.ID)
if c.Status == Stopped {
return 0, fmt.Errorf("container is stopped")
}
ws, err := c.Sandbox.WaitPID(pid, c.ID)
if err != nil {
return 0, err
}
if c.Sandbox.IsRootContainer(c.ID) {
// If waiting for the root, give some time for the sandbox process to exit
// to prevent races with resources that might still be in use.
if err := c.waitForStopped(); err != nil {
return 0, err
}
}
return ws, nil
}
// Signal sends the signal to the container.
func (c *Container) Signal(sig syscall.Signal) error {
log.Debugf("Signal container %q", c.ID)
if c.Status == Stopped {
log.Warningf("container %q not running, not sending signal %v", c.ID, sig)
return nil
}
return c.Sandbox.Signal(c.ID, sig)
}
// Checkpoint sends the checkpoint call to the container.
// The statefile will be written to f, the file at the specified image-path.
func (c *Container) Checkpoint(f *os.File) error {
log.Debugf("Checkpoint container %q", c.ID)
if c.Status == Stopped {
log.Warningf("container %q not running, not checkpointing", c.ID)
return nil
}
return c.Sandbox.Checkpoint(c.ID, f)
}
// Pause suspends the container and its kernel.
// The call only succeeds if the container's status is created or running.
func (c *Container) Pause() error {
log.Debugf("Pausing container %q", c.ID)
switch c.Status {
case Created, Running:
if err := c.Sandbox.Pause(c.ID); err != nil {
return fmt.Errorf("error pausing container: %v", err)
}
c.Status = Paused
return c.save()
default:
return fmt.Errorf("container %q not created or running, not pausing", c.ID)
}
}
// Resume unpauses the container and its kernel.
// The call only succeeds if the container's status is paused.
func (c *Container) Resume() error {
log.Debugf("Resuming container %q", c.ID)
switch c.Status {
case Paused:
if err := c.Sandbox.Resume(c.ID); err != nil {
return fmt.Errorf("error resuming container: %v", err)
}
c.Status = Running
return c.save()
default:
return fmt.Errorf("container %q not paused, not resuming", c.ID)
}
}
// State returns the metadata of the container.
func (c *Container) State() specs.State {
return specs.State{
Version: specs.Version,
ID: c.ID,
Status: c.Status.String(),
Pid: c.Pid(),
Bundle: c.BundleDir,
}
}
// Processes retrieves the list of processes and associated metadata inside a
// container.
func (c *Container) Processes() ([]*control.Process, error) {
if c.Status != Running && c.Status != Paused {
return nil, fmt.Errorf("cannot get processes of container %q because it isn't running. It is in state %v", c.ID, c.Status)
}
return c.Sandbox.Processes(c.ID)
}
// Destroy frees all resources associated with the container.
func (c *Container) Destroy() error {
log.Debugf("Destroy container %q", c.ID)
// First stop the container.
if c.Sandbox != nil {
if err := c.Sandbox.Stop(c.ID); err != nil {
return err
}
}
// "If any poststop hook fails, the runtime MUST log a warning, but the
// remaining hooks and lifecycle continue as if the hook had succeeded" -OCI spec.
if c.Spec.Hooks != nil && (c.Status == Created || c.Status == Running) {
executeHooksBestEffort(c.Spec.Hooks.Poststop, c.State())
}
// If we are the first container in the sandbox, take the sandbox down
// as well.
if c.Sandbox != nil && c.Sandbox.IsRootContainer(c.ID) {
if err := c.Sandbox.Destroy(); err != nil {
log.Warningf("Failed to destroy sandbox %q: %v", c.Sandbox.ID, err)
}
}
c.Sandbox = nil
if c.GoferPid != 0 {
log.Debugf("Killing gofer for container %q, PID: %d", c.ID, c.GoferPid)
if err := syscall.Kill(c.GoferPid, syscall.SIGKILL); err != nil {
log.Warningf("error sending signal %d to pid %d: %v", syscall.SIGKILL, c.GoferPid, err)
} else {
c.GoferPid = 0
}
}
if err := destroyFS(c.Spec); err != nil {
return fmt.Errorf("error destroying container fs: %v", err)
}
if err := os.RemoveAll(c.Root); err != nil && !os.IsNotExist(err) {
return fmt.Errorf("error deleting container root directory %q: %v", c.Root, err)
}
c.Status = Stopped
return nil
}
// IsRunning returns true if the sandbox or gofer process is running.
func (c *Container) IsRunning() bool {
if c.Status == Stopped {
return false
}
if c.Sandbox != nil && c.Sandbox.IsRunning() {
return true
}
if c.GoferPid != 0 {
// Send a signal 0 to the gofer process.
if err := syscall.Kill(c.GoferPid, 0); err == nil {
log.Warningf("Found orphan gofer process, pid: %d", c.GoferPid)
// Attempt to kill gofer if it's orphan.
syscall.Kill(c.GoferPid, syscall.SIGKILL)
// Don't wait for gofer to die. Return 'running' and hope gofer is dead
// next time around.
return true
}
}
return false
}
// DestroyAndWait frees all resources associated with the container
// and waits for destroy to finish before returning.
//
// TODO: This only works for single container.
func (c *Container) DestroyAndWait() error {
if err := c.Destroy(); err != nil {
return fmt.Errorf("error destroying container %v: %v", c, err)
}
return c.waitForStopped()
}
// save saves the container metadata to a file.
func (c *Container) save() error {
log.Debugf("Save container %q", c.ID)
if err := os.MkdirAll(c.Root, 0711); err != nil {
return fmt.Errorf("error creating container root directory %q: %v", c.Root, err)
}
meta, err := json.Marshal(c)
if err != nil {
return fmt.Errorf("error marshaling container metadata: %v", err)
}
metaFile := filepath.Join(c.Root, metadataFilename)
if err := ioutil.WriteFile(metaFile, meta, 0640); err != nil {
return fmt.Errorf("error writing container metadata: %v", err)
}
return nil
}
func (c *Container) waitForStopped() error {
ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
defer cancel()
b := backoff.WithContext(backoff.NewConstantBackOff(100*time.Millisecond), ctx)
op := func() error {
if !c.IsRunning() {
return fmt.Errorf("container is still running")
}
return nil
}
return backoff.Retry(op, b)
}
func (c *Container) createGoferProcess(spec *specs.Spec, conf *boot.Config, bundleDir string) ([]*os.File, error) {
if conf.FileAccess == boot.FileAccessDirect {
// Don't start a gofer. The sandbox will access host FS directly.
return nil, nil
}
if err := setupFS(spec, conf, bundleDir); err != nil {
return nil, fmt.Errorf("failed to setup mounts: %v", err)
}
// Start with the general config flags.
args := conf.ToFlags()
args = append(args, "gofer", "--bundle", bundleDir)
if conf.Overlay {
args = append(args, "--panic-on-write=true")
}
// Add root mount and then add any other additional mounts.
mountCount := 1
// Add additional mounts.
for _, m := range spec.Mounts {
if specutils.Is9PMount(m) {
mountCount++
}
}
sandEnds := make([]*os.File, 0, mountCount)
goferEnds := make([]*os.File, 0, mountCount)
// nextFD is the next available file descriptor for the gofer process.
// It starts at 3 because 0-2 are used by stdin/stdout/stderr.
nextFD := 3
for ; nextFD-3 < mountCount; nextFD++ {
fds, err := syscall.Socketpair(syscall.AF_UNIX, syscall.SOCK_STREAM|syscall.SOCK_CLOEXEC, 0)
if err != nil {
return nil, err
}
sandEnds = append(sandEnds, os.NewFile(uintptr(fds[0]), "sandbox io fd"))
goferEnd := os.NewFile(uintptr(fds[1]), "gofer io fd")
defer goferEnd.Close()
goferEnds = append(goferEnds, goferEnd)
args = append(args, fmt.Sprintf("--io-fds=%d", nextFD))
}
binPath, err := specutils.BinPath()
if err != nil {
return nil, err
}
cmd := exec.Command(binPath, args...)
cmd.ExtraFiles = goferEnds
// Setup any uid/gid mappings, and create or join the configured user
// namespace so the gofer's view of the filesystem aligns with the
// users in the sandbox.
specutils.SetUIDGIDMappings(cmd, spec)
nss := specutils.FilterNS([]specs.LinuxNamespaceType{specs.UserNamespace}, spec)
// Start the gofer in the given namespace.
log.Debugf("Starting gofer: %s %v", binPath, args)
if err := specutils.StartInNS(cmd, nss); err != nil {
return nil, err
}
log.Infof("Gofer started, pid: %d", cmd.Process.Pid)
c.GoferPid = cmd.Process.Pid
return sandEnds, nil
}