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alloc_dir.go
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alloc_dir.go
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package allocdir
import (
"archive/tar"
"context"
"fmt"
"io"
"io/ioutil"
"os"
"path/filepath"
"sync"
"time"
hclog "github.com/hashicorp/go-hclog"
multierror "github.com/hashicorp/go-multierror"
cstructs "github.com/hashicorp/nomad/client/structs"
"github.com/hashicorp/nomad/nomad/structs"
"github.com/hpcloud/tail/watch"
tomb "gopkg.in/tomb.v1"
)
const (
// idUnsupported is what the uid/gid will be set to on platforms (eg
// Windows) that don't support integer ownership identifiers.
idUnsupported = -1
)
var (
// SnapshotErrorTime is the sentinel time that will be used on the
// error file written by Snapshot when it encounters as error.
SnapshotErrorTime = time.Date(2000, 0, 0, 0, 0, 0, 0, time.UTC)
// The name of the directory that is shared across tasks in a task group.
SharedAllocName = "alloc"
// Name of the directory where logs of Tasks are written
LogDirName = "logs"
// SharedDataDir is one of the shared allocation directories. It is
// included in snapshots.
SharedDataDir = "data"
// TmpDirName is the name of the temporary directory in each alloc and
// task.
TmpDirName = "tmp"
// The set of directories that exist inside each shared alloc directory.
SharedAllocDirs = []string{LogDirName, TmpDirName, SharedDataDir}
// The name of the directory that exists inside each task directory
// regardless of driver.
TaskLocal = "local"
// TaskSecrets is the name of the secret directory inside each task
// directory
TaskSecrets = "secrets"
// TaskDirs is the set of directories created in each tasks directory.
TaskDirs = map[string]os.FileMode{TmpDirName: os.ModeSticky | 0777}
)
// AllocDir allows creating, destroying, and accessing an allocation's
// directory. All methods are safe for concurrent use.
type AllocDir struct {
// AllocDir is the directory used for storing any state
// of this allocation. It will be purged on alloc destroy.
AllocDir string
// The shared directory is available to all tasks within the same task
// group.
SharedDir string
// TaskDirs is a mapping of task names to their non-shared directory.
TaskDirs map[string]*TaskDir
// built is true if Build has successfully run
built bool
mu sync.RWMutex
logger hclog.Logger
}
// AllocDirFS exposes file operations on the alloc dir
type AllocDirFS interface {
List(path string) ([]*cstructs.AllocFileInfo, error)
Stat(path string) (*cstructs.AllocFileInfo, error)
ReadAt(path string, offset int64) (io.ReadCloser, error)
Snapshot(w io.Writer) error
BlockUntilExists(ctx context.Context, path string) (chan error, error)
ChangeEvents(ctx context.Context, path string, curOffset int64) (*watch.FileChanges, error)
}
// NewAllocDir initializes the AllocDir struct with allocDir as base path for
// the allocation directory.
func NewAllocDir(logger hclog.Logger, allocDir string) *AllocDir {
logger = logger.Named("alloc_dir")
return &AllocDir{
AllocDir: allocDir,
SharedDir: filepath.Join(allocDir, SharedAllocName),
TaskDirs: make(map[string]*TaskDir),
logger: logger,
}
}
// Copy an AllocDir and all of its TaskDirs. Returns nil if AllocDir is
// nil.
func (d *AllocDir) Copy() *AllocDir {
d.mu.RLock()
defer d.mu.RUnlock()
if d == nil {
return nil
}
dcopy := &AllocDir{
AllocDir: d.AllocDir,
SharedDir: d.SharedDir,
TaskDirs: make(map[string]*TaskDir, len(d.TaskDirs)),
logger: d.logger,
}
for k, v := range d.TaskDirs {
dcopy.TaskDirs[k] = v.Copy()
}
return dcopy
}
// NewTaskDir creates a new TaskDir and adds it to the AllocDirs TaskDirs map.
func (d *AllocDir) NewTaskDir(name string) *TaskDir {
d.mu.Lock()
defer d.mu.Unlock()
td := newTaskDir(d.logger, d.AllocDir, name)
d.TaskDirs[name] = td
return td
}
// Snapshot creates an archive of the files and directories in the data dir of
// the allocation and the task local directories
//
// Since a valid tar may have been written even when an error occurs, a special
// file "NOMAD-${ALLOC_ID}-ERROR.log" will be appended to the tar with the
// error message as the contents.
func (d *AllocDir) Snapshot(w io.Writer) error {
d.mu.RLock()
defer d.mu.RUnlock()
allocDataDir := filepath.Join(d.SharedDir, SharedDataDir)
rootPaths := []string{allocDataDir}
for _, taskdir := range d.TaskDirs {
rootPaths = append(rootPaths, taskdir.LocalDir)
}
tw := tar.NewWriter(w)
defer tw.Close()
walkFn := func(path string, fileInfo os.FileInfo, err error) error {
if err != nil {
return err
}
// Include the path of the file name relative to the alloc dir
// so that we can put the files in the right directories
relPath, err := filepath.Rel(d.AllocDir, path)
if err != nil {
return err
}
link := ""
if fileInfo.Mode()&os.ModeSymlink != 0 {
target, err := os.Readlink(path)
if err != nil {
return fmt.Errorf("error reading symlink: %v", err)
}
link = target
}
hdr, err := tar.FileInfoHeader(fileInfo, link)
if err != nil {
return fmt.Errorf("error creating file header: %v", err)
}
hdr.Name = relPath
if err := tw.WriteHeader(hdr); err != nil {
return err
}
// If it's a directory or symlink we just write the header into the tar
if fileInfo.IsDir() || (fileInfo.Mode()&os.ModeSymlink != 0) {
return nil
}
// Write the file into the archive
file, err := os.Open(path)
if err != nil {
return err
}
defer file.Close()
if _, err := io.Copy(tw, file); err != nil {
return err
}
return nil
}
// Walk through all the top level directories and add the files and
// directories in the archive
for _, path := range rootPaths {
if err := filepath.Walk(path, walkFn); err != nil {
allocID := filepath.Base(d.AllocDir)
if writeErr := writeError(tw, allocID, err); writeErr != nil {
// This could be bad; other side won't know
// snapshotting failed. It could also just mean
// the snapshotting side closed the connect
// prematurely and won't try to use the tar
// anyway.
d.logger.Warn("snapshotting failed and unable to write error marker", "error", writeErr)
}
return fmt.Errorf("failed to snapshot %s: %v", path, err)
}
}
return nil
}
// Move other alloc directory's shared path and local dir to this alloc dir.
func (d *AllocDir) Move(other *AllocDir, tasks []*structs.Task) error {
d.mu.RLock()
if !d.built {
// Enforce the invariant that Build is called before Move
d.mu.RUnlock()
return fmt.Errorf("unable to move to %q - alloc dir is not built", d.AllocDir)
}
// Moving is slow and only reads immutable fields, so unlock during heavy IO
d.mu.RUnlock()
// Move the data directory
otherDataDir := filepath.Join(other.SharedDir, SharedDataDir)
dataDir := filepath.Join(d.SharedDir, SharedDataDir)
if fileInfo, err := os.Stat(otherDataDir); fileInfo != nil && err == nil {
os.Remove(dataDir) // remove an empty data dir if it exists
if err := os.Rename(otherDataDir, dataDir); err != nil {
return fmt.Errorf("error moving data dir: %v", err)
}
}
// Move the task directories
for _, task := range tasks {
otherTaskDir := filepath.Join(other.AllocDir, task.Name)
otherTaskLocal := filepath.Join(otherTaskDir, TaskLocal)
fileInfo, err := os.Stat(otherTaskLocal)
if fileInfo != nil && err == nil {
// TaskDirs haven't been built yet, so create it
newTaskDir := filepath.Join(d.AllocDir, task.Name)
if err := os.MkdirAll(newTaskDir, 0777); err != nil {
return fmt.Errorf("error creating task %q dir: %v", task.Name, err)
}
localDir := filepath.Join(newTaskDir, TaskLocal)
os.Remove(localDir) // remove an empty local dir if it exists
if err := os.Rename(otherTaskLocal, localDir); err != nil {
return fmt.Errorf("error moving task %q local dir: %v", task.Name, err)
}
}
}
return nil
}
// Tears down previously build directory structure.
func (d *AllocDir) Destroy() error {
// Unmount all mounted shared alloc dirs.
var mErr multierror.Error
if err := d.UnmountAll(); err != nil {
mErr.Errors = append(mErr.Errors, err)
}
if err := os.RemoveAll(d.AllocDir); err != nil {
mErr.Errors = append(mErr.Errors, fmt.Errorf("failed to remove alloc dir %q: %v", d.AllocDir, err))
}
// Unset built since the alloc dir has been destroyed.
d.mu.Lock()
d.built = false
d.mu.Unlock()
return mErr.ErrorOrNil()
}
// UnmountAll linked/mounted directories in task dirs.
func (d *AllocDir) UnmountAll() error {
d.mu.RLock()
defer d.mu.RUnlock()
var mErr multierror.Error
for _, dir := range d.TaskDirs {
// Check if the directory has the shared alloc mounted.
if pathExists(dir.SharedTaskDir) {
if err := unlinkDir(dir.SharedTaskDir); err != nil {
mErr.Errors = append(mErr.Errors,
fmt.Errorf("failed to unmount shared alloc dir %q: %v", dir.SharedTaskDir, err))
} else if err := os.RemoveAll(dir.SharedTaskDir); err != nil {
mErr.Errors = append(mErr.Errors,
fmt.Errorf("failed to delete shared alloc dir %q: %v", dir.SharedTaskDir, err))
}
}
if pathExists(dir.SecretsDir) {
if err := removeSecretDir(dir.SecretsDir); err != nil {
mErr.Errors = append(mErr.Errors,
fmt.Errorf("failed to remove the secret dir %q: %v", dir.SecretsDir, err))
}
}
// Unmount dev/ and proc/ have been mounted.
if err := dir.unmountSpecialDirs(); err != nil {
mErr.Errors = append(mErr.Errors, err)
}
}
return mErr.ErrorOrNil()
}
// Build the directory tree for an allocation.
func (d *AllocDir) Build() error {
// Make the alloc directory, owned by the nomad process.
if err := os.MkdirAll(d.AllocDir, 0755); err != nil {
return fmt.Errorf("Failed to make the alloc directory %v: %v", d.AllocDir, err)
}
// Make the shared directory and make it available to all user/groups.
if err := os.MkdirAll(d.SharedDir, 0777); err != nil {
return err
}
// Make the shared directory have non-root permissions.
if err := dropDirPermissions(d.SharedDir, os.ModePerm); err != nil {
return err
}
// Create shared subdirs
for _, dir := range SharedAllocDirs {
p := filepath.Join(d.SharedDir, dir)
if err := os.MkdirAll(p, 0777); err != nil {
return err
}
if err := dropDirPermissions(p, os.ModePerm); err != nil {
return err
}
}
// Mark as built
d.mu.Lock()
d.built = true
d.mu.Unlock()
return nil
}
// List returns the list of files at a path relative to the alloc dir
func (d *AllocDir) List(path string) ([]*cstructs.AllocFileInfo, error) {
if escapes, err := structs.PathEscapesAllocDir("", path); err != nil {
return nil, fmt.Errorf("Failed to check if path escapes alloc directory: %v", err)
} else if escapes {
return nil, fmt.Errorf("Path escapes the alloc directory")
}
p := filepath.Join(d.AllocDir, path)
finfos, err := ioutil.ReadDir(p)
if err != nil {
return []*cstructs.AllocFileInfo{}, err
}
files := make([]*cstructs.AllocFileInfo, len(finfos))
for idx, info := range finfos {
files[idx] = &cstructs.AllocFileInfo{
Name: info.Name(),
IsDir: info.IsDir(),
Size: info.Size(),
FileMode: info.Mode().String(),
ModTime: info.ModTime(),
}
}
return files, err
}
// Stat returns information about the file at a path relative to the alloc dir
func (d *AllocDir) Stat(path string) (*cstructs.AllocFileInfo, error) {
if escapes, err := structs.PathEscapesAllocDir("", path); err != nil {
return nil, fmt.Errorf("Failed to check if path escapes alloc directory: %v", err)
} else if escapes {
return nil, fmt.Errorf("Path escapes the alloc directory")
}
p := filepath.Join(d.AllocDir, path)
info, err := os.Stat(p)
if err != nil {
return nil, err
}
return &cstructs.AllocFileInfo{
Size: info.Size(),
Name: info.Name(),
IsDir: info.IsDir(),
FileMode: info.Mode().String(),
ModTime: info.ModTime(),
}, nil
}
// ReadAt returns a reader for a file at the path relative to the alloc dir
func (d *AllocDir) ReadAt(path string, offset int64) (io.ReadCloser, error) {
if escapes, err := structs.PathEscapesAllocDir("", path); err != nil {
return nil, fmt.Errorf("Failed to check if path escapes alloc directory: %v", err)
} else if escapes {
return nil, fmt.Errorf("Path escapes the alloc directory")
}
p := filepath.Join(d.AllocDir, path)
// Check if it is trying to read into a secret directory
d.mu.RLock()
for _, dir := range d.TaskDirs {
if filepath.HasPrefix(p, dir.SecretsDir) {
d.mu.RUnlock()
return nil, fmt.Errorf("Reading secret file prohibited: %s", path)
}
}
d.mu.RUnlock()
f, err := os.Open(p)
if err != nil {
return nil, err
}
if _, err := f.Seek(offset, 0); err != nil {
return nil, fmt.Errorf("can't seek to offset %q: %v", offset, err)
}
return f, nil
}
// BlockUntilExists blocks until the passed file relative the allocation
// directory exists. The block can be cancelled with the passed context.
func (d *AllocDir) BlockUntilExists(ctx context.Context, path string) (chan error, error) {
if escapes, err := structs.PathEscapesAllocDir("", path); err != nil {
return nil, fmt.Errorf("Failed to check if path escapes alloc directory: %v", err)
} else if escapes {
return nil, fmt.Errorf("Path escapes the alloc directory")
}
// Get the path relative to the alloc directory
p := filepath.Join(d.AllocDir, path)
watcher := getFileWatcher(p)
returnCh := make(chan error, 1)
t := &tomb.Tomb{}
go func() {
<-ctx.Done()
t.Kill(nil)
}()
go func() {
returnCh <- watcher.BlockUntilExists(t)
close(returnCh)
}()
return returnCh, nil
}
// ChangeEvents watches for changes to the passed path relative to the
// allocation directory. The offset should be the last read offset. The context is
// used to clean up the watch.
func (d *AllocDir) ChangeEvents(ctx context.Context, path string, curOffset int64) (*watch.FileChanges, error) {
if escapes, err := structs.PathEscapesAllocDir("", path); err != nil {
return nil, fmt.Errorf("Failed to check if path escapes alloc directory: %v", err)
} else if escapes {
return nil, fmt.Errorf("Path escapes the alloc directory")
}
t := &tomb.Tomb{}
go func() {
<-ctx.Done()
t.Kill(nil)
}()
// Get the path relative to the alloc directory
p := filepath.Join(d.AllocDir, path)
watcher := getFileWatcher(p)
return watcher.ChangeEvents(t, curOffset)
}
// getFileWatcher returns a FileWatcher for the given path.
func getFileWatcher(path string) watch.FileWatcher {
return watch.NewPollingFileWatcher(path)
}
// fileCopy from src to dst setting the permissions and owner (if uid & gid are
// both greater than 0)
func fileCopy(src, dst string, uid, gid int, perm os.FileMode) error {
// Do a simple copy.
srcFile, err := os.Open(src)
if err != nil {
return fmt.Errorf("Couldn't open src file %v: %v", src, err)
}
defer srcFile.Close()
dstFile, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE, perm)
if err != nil {
return fmt.Errorf("Couldn't create destination file %v: %v", dst, err)
}
defer dstFile.Close()
if _, err := io.Copy(dstFile, srcFile); err != nil {
return fmt.Errorf("Couldn't copy %q to %q: %v", src, dst, err)
}
if uid != idUnsupported && gid != idUnsupported {
if err := dstFile.Chown(uid, gid); err != nil {
return fmt.Errorf("Couldn't copy %q to %q: %v", src, dst, err)
}
}
return nil
}
// pathExists is a helper function to check if the path exists.
func pathExists(path string) bool {
if _, err := os.Stat(path); err != nil {
if os.IsNotExist(err) {
return false
}
}
return true
}
// pathEmpty returns true if a path exists, is listable, and is empty. If the
// path does not exist or is not listable an error is returned.
func pathEmpty(path string) (bool, error) {
f, err := os.Open(path)
if err != nil {
return false, err
}
defer f.Close()
entries, err := f.Readdir(1)
if err != nil && err != io.EOF {
return false, err
}
return len(entries) == 0, nil
}
// createDir creates a directory structure inside the basepath. This functions
// preserves the permissions of each of the subdirectories in the relative path
// by looking up the permissions in the host.
func createDir(basePath, relPath string) error {
filePerms, err := splitPath(relPath)
if err != nil {
return err
}
// We are going backwards since we create the root of the directory first
// and then create the entire nested structure.
for i := len(filePerms) - 1; i >= 0; i-- {
fi := filePerms[i]
destDir := filepath.Join(basePath, fi.Name)
if err := os.MkdirAll(destDir, fi.Perm); err != nil {
return err
}
if fi.Uid != idUnsupported && fi.Gid != idUnsupported {
if err := os.Chown(destDir, fi.Uid, fi.Gid); err != nil {
return err
}
}
}
return nil
}
// fileInfo holds the path and the permissions of a file
type fileInfo struct {
Name string
Perm os.FileMode
// Uid and Gid are unsupported on Windows
Uid int
Gid int
}
// splitPath stats each subdirectory of a path. The first element of the array
// is the file passed to this function, and the last element is the root of the
// path.
func splitPath(path string) ([]fileInfo, error) {
var mode os.FileMode
fi, err := os.Stat(path)
// If the path is not present in the host then we respond with the most
// flexible permission.
uid, gid := idUnsupported, idUnsupported
if err != nil {
mode = os.ModePerm
} else {
uid, gid = getOwner(fi)
mode = fi.Mode()
}
var dirs []fileInfo
dirs = append(dirs, fileInfo{Name: path, Perm: mode, Uid: uid, Gid: gid})
currentDir := path
for {
dir := filepath.Dir(filepath.Clean(currentDir))
if dir == currentDir {
break
}
// We try to find the permission of the file in the host. If the path is not
// present in the host then we respond with the most flexible permission.
uid, gid := idUnsupported, idUnsupported
fi, err := os.Stat(dir)
if err != nil {
mode = os.ModePerm
} else {
uid, gid = getOwner(fi)
mode = fi.Mode()
}
dirs = append(dirs, fileInfo{Name: dir, Perm: mode, Uid: uid, Gid: gid})
currentDir = dir
}
return dirs, nil
}
// SnapshotErrorFilename returns the filename which will exist if there was an
// error snapshotting a tar.
func SnapshotErrorFilename(allocID string) string {
return fmt.Sprintf("NOMAD-%s-ERROR.log", allocID)
}
// writeError writes a special file to a tar archive with the error encountered
// during snapshotting. See Snapshot().
func writeError(tw *tar.Writer, allocID string, err error) error {
contents := []byte(fmt.Sprintf("Error snapshotting: %v", err))
hdr := tar.Header{
Name: SnapshotErrorFilename(allocID),
Mode: 0666,
Size: int64(len(contents)),
AccessTime: SnapshotErrorTime,
ChangeTime: SnapshotErrorTime,
ModTime: SnapshotErrorTime,
Typeflag: tar.TypeReg,
}
if err := tw.WriteHeader(&hdr); err != nil {
return err
}
_, err = tw.Write(contents)
return err
}