-// A UnixVolume is a Volume backed by a locally mounted disk.
-//
package main
import (
+ "bytes"
"fmt"
+ "io"
"io/ioutil"
"log"
"os"
"path/filepath"
+ "regexp"
"strconv"
"strings"
+ "sync"
"syscall"
"time"
)
-// IORequests are encapsulated Get or Put requests. They are used to
-// implement serialized I/O (i.e. only one read/write operation per
-// volume). When running in serialized mode, the Keep front end sends
-// IORequests on a channel to an IORunner, which handles them one at a
-// time and returns an IOResponse.
-//
-type IOMethod int
-
-const (
- KeepGet IOMethod = iota
- KeepPut
-)
-
-type IORequest struct {
- method IOMethod
- loc string
- data []byte
- reply chan *IOResponse
-}
-
-type IOResponse struct {
- data []byte
- err error
-}
-
-// A UnixVolume has the following properties:
-//
-// root
-// the path to the volume's root directory
-// queue
-// A channel of IORequests. If non-nil, all I/O requests for
-// this volume should be queued on this channel; the result
-// will be delivered on the IOResponse channel supplied in the
-// request.
-//
+// A UnixVolume stores and retrieves blocks in a local directory.
type UnixVolume struct {
- root string // path to this volume
- queue chan *IORequest
-}
-
-func (v *UnixVolume) IOHandler() {
- for req := range v.queue {
- var result IOResponse
- switch req.method {
- case KeepGet:
- result.data, result.err = v.Read(req.loc)
- case KeepPut:
- result.err = v.Write(req.loc, req.data)
- }
- req.reply <- &result
- }
-}
-
-func MakeUnixVolume(root string, serialize bool) (v UnixVolume) {
- if serialize {
- v = UnixVolume{root, make(chan *IORequest)}
- go v.IOHandler()
- } else {
- v = UnixVolume{root, nil}
- }
- return
-}
-
-func (v *UnixVolume) Get(loc string) ([]byte, error) {
- if v.queue == nil {
- return v.Read(loc)
- }
- reply := make(chan *IOResponse)
- v.queue <- &IORequest{KeepGet, loc, nil, reply}
- response := <-reply
- return response.data, response.err
-}
-
-func (v *UnixVolume) Put(loc string, block []byte) error {
- if v.queue == nil {
- return v.Write(loc, block)
- }
- reply := make(chan *IOResponse)
- v.queue <- &IORequest{KeepPut, loc, block, reply}
- response := <-reply
- return response.err
+ // path to the volume's root directory
+ root string
+ // something to lock during IO, typically a sync.Mutex (or nil
+ // to skip locking)
+ locker sync.Locker
+ readonly bool
}
+// Touch sets the timestamp for the given locator to the current time
func (v *UnixVolume) Touch(loc string) error {
+ if v.readonly {
+ return MethodDisabledError
+ }
p := v.blockPath(loc)
f, err := os.OpenFile(p, os.O_RDWR|os.O_APPEND, 0644)
if err != nil {
return err
}
defer f.Close()
+ if v.locker != nil {
+ v.locker.Lock()
+ defer v.locker.Unlock()
+ }
if e := lockfile(f); e != nil {
return e
}
return syscall.Utime(p, &utime)
}
+// Mtime returns the stored timestamp for the given locator.
func (v *UnixVolume) Mtime(loc string) (time.Time, error) {
p := v.blockPath(loc)
- if fi, err := os.Stat(p); err != nil {
+ fi, err := os.Stat(p)
+ if err != nil {
return time.Time{}, err
- } else {
- return fi.ModTime(), nil
}
+ return fi.ModTime(), nil
+}
+
+// Lock the locker (if one is in use), open the file for reading, and
+// call the given function if and when the file is ready to read.
+func (v *UnixVolume) getFunc(path string, fn func(io.Reader) error) error {
+ if v.locker != nil {
+ v.locker.Lock()
+ defer v.locker.Unlock()
+ }
+ f, err := os.Open(path)
+ if err != nil {
+ return err
+ }
+ defer f.Close()
+ return fn(f)
+}
+
+// stat is os.Stat() with some extra sanity checks.
+func (v *UnixVolume) stat(path string) (os.FileInfo, error) {
+ stat, err := os.Stat(path)
+ if err == nil {
+ if stat.Size() < 0 {
+ err = os.ErrInvalid
+ } else if stat.Size() > BlockSize {
+ err = TooLongError
+ }
+ }
+ return stat, err
}
-// Read retrieves a block identified by the locator string "loc", and
+// Get retrieves a block identified by the locator string "loc", and
// returns its contents as a byte slice.
//
-// If the block could not be opened or read, Read returns a nil slice
-// and the os.Error that was generated.
-//
-// If the block is present but its content hash does not match loc,
-// Read returns the block and a CorruptError. It is the caller's
-// responsibility to decide what (if anything) to do with the
-// corrupted data block.
-//
-func (v *UnixVolume) Read(loc string) ([]byte, error) {
- buf, err := ioutil.ReadFile(v.blockPath(loc))
- return buf, err
+// Get returns a nil buffer IFF it returns a non-nil error.
+func (v *UnixVolume) Get(loc string) ([]byte, error) {
+ path := v.blockPath(loc)
+ stat, err := v.stat(path)
+ if err != nil {
+ return nil, err
+ }
+ buf := bufs.Get(int(stat.Size()))
+ err = v.getFunc(path, func(rdr io.Reader) error {
+ _, err = io.ReadFull(rdr, buf)
+ return err
+ })
+ if err != nil {
+ bufs.Put(buf)
+ return nil, err
+ }
+ return buf, nil
+}
+
+// Compare returns nil if Get(loc) would return the same content as
+// expect. It is functionally equivalent to Get() followed by
+// bytes.Compare(), but uses less memory.
+func (v *UnixVolume) Compare(loc string, expect []byte) error {
+ path := v.blockPath(loc)
+ stat, err := v.stat(path)
+ if err != nil {
+ return err
+ }
+ bufLen := 1 << 20
+ if int64(bufLen) > stat.Size() {
+ bufLen = int(stat.Size())
+ }
+ cmp := expect
+ buf := make([]byte, bufLen)
+ return v.getFunc(path, func(rdr io.Reader) error {
+ // Loop invariants: all data read so far matched what
+ // we expected, and the first N bytes of cmp are
+ // expected to equal the next N bytes read from
+ // reader.
+ for {
+ n, err := rdr.Read(buf)
+ if n > len(cmp) || bytes.Compare(cmp[:n], buf[:n]) != 0 {
+ return collisionOrCorrupt(loc[:32], expect[:len(expect)-len(cmp)], buf[:n], rdr)
+ }
+ cmp = cmp[n:]
+ if err == io.EOF {
+ if len(cmp) != 0 {
+ return collisionOrCorrupt(loc[:32], expect[:len(expect)-len(cmp)], nil, nil)
+ }
+ return nil
+ } else if err != nil {
+ return err
+ }
+ }
+ })
}
-// Write stores a block of data identified by the locator string
+// Put stores a block of data identified by the locator string
// "loc". It returns nil on success. If the volume is full, it
// returns a FullError. If the write fails due to some other error,
// that error is returned.
-//
-func (v *UnixVolume) Write(loc string, block []byte) error {
+func (v *UnixVolume) Put(loc string, block []byte) error {
+ if v.readonly {
+ return MethodDisabledError
+ }
if v.IsFull() {
return FullError
}
}
bpath := v.blockPath(loc)
+ if v.locker != nil {
+ v.locker.Lock()
+ defer v.locker.Unlock()
+ }
if _, err := tmpfile.Write(block); err != nil {
log.Printf("%s: writing to %s: %s\n", v, bpath, err)
+ tmpfile.Close()
+ os.Remove(tmpfile.Name())
return err
}
if err := tmpfile.Close(); err != nil {
}
// Status returns a VolumeStatus struct describing the volume's
-// current state.
+// current state, or nil if an error occurs.
//
func (v *UnixVolume) Status() *VolumeStatus {
var fs syscall.Statfs_t
return &VolumeStatus{v.root, devnum, free, used}
}
-// Index returns a list of blocks found on this volume which begin with
-// the specified prefix. If the prefix is an empty string, Index returns
-// a complete list of blocks.
+var blockDirRe = regexp.MustCompile(`^[0-9a-f]+$`)
+
+// IndexTo writes (to the given Writer) a list of blocks found on this
+// volume which begin with the specified prefix. If the prefix is an
+// empty string, IndexTo writes a complete list of blocks.
//
-// The return value is a multiline string (separated by
-// newlines). Each line is in the format
+// Each block is given in the format
//
-// locator+size modification-time
+// locator+size modification-time {newline}
//
// e.g.:
//
// e4d41e6fd68460e0e3fc18cc746959d2+67108864 1377796043
// e4de7a2810f5554cd39b36d8ddb132ff+67108864 1388701136
//
-func (v *UnixVolume) Index(prefix string) (output string) {
- filepath.Walk(v.root,
- func(path string, info os.FileInfo, err error) error {
- // This WalkFunc inspects each path in the volume
- // and prints an index line for all files that begin
- // with prefix.
- if err != nil {
- log.Printf("IndexHandler: %s: walking to %s: %s",
- v, path, err)
- return nil
- }
- locator := filepath.Base(path)
- // Skip directories that do not match prefix.
- // We know there is nothing interesting inside.
- if info.IsDir() &&
- !strings.HasPrefix(locator, prefix) &&
- !strings.HasPrefix(prefix, locator) {
- return filepath.SkipDir
- }
- // Skip any file that is not apparently a locator, e.g. .meta files
- if !IsValidLocator(locator) {
- return nil
+func (v *UnixVolume) IndexTo(prefix string, w io.Writer) error {
+ var lastErr error = nil
+ rootdir, err := os.Open(v.root)
+ if err != nil {
+ return err
+ }
+ defer rootdir.Close()
+ for {
+ names, err := rootdir.Readdirnames(1)
+ if err == io.EOF {
+ return lastErr
+ } else if err != nil {
+ return err
+ }
+ if !strings.HasPrefix(names[0], prefix) && !strings.HasPrefix(prefix, names[0]) {
+ // prefix excludes all blocks stored in this dir
+ continue
+ }
+ if !blockDirRe.MatchString(names[0]) {
+ continue
+ }
+ blockdirpath := filepath.Join(v.root, names[0])
+ blockdir, err := os.Open(blockdirpath)
+ if err != nil {
+ log.Print("Error reading ", blockdirpath, ": ", err)
+ lastErr = err
+ continue
+ }
+ for {
+ fileInfo, err := blockdir.Readdir(1)
+ if err == io.EOF {
+ break
+ } else if err != nil {
+ log.Print("Error reading ", blockdirpath, ": ", err)
+ lastErr = err
+ break
}
- // Print filenames beginning with prefix
- if !info.IsDir() && strings.HasPrefix(locator, prefix) {
- output = output + fmt.Sprintf(
- "%s+%d %d\n", locator, info.Size(), info.ModTime().Unix())
+ name := fileInfo[0].Name()
+ if !strings.HasPrefix(name, prefix) {
+ continue
}
- return nil
- })
-
- return
+ _, err = fmt.Fprint(w,
+ name,
+ "+", fileInfo[0].Size(),
+ " ", fileInfo[0].ModTime().Unix(),
+ "\n")
+ }
+ blockdir.Close()
+ }
}
+// Delete deletes the block data from the unix storage
func (v *UnixVolume) Delete(loc string) error {
+ // Touch() must be called before calling Write() on a block. Touch()
+ // also uses lockfile(). This avoids a race condition between Write()
+ // and Delete() because either (a) the file will be deleted and Touch()
+ // will signal to the caller that the file is not present (and needs to
+ // be re-written), or (b) Touch() will update the file's timestamp and
+ // Delete() will read the correct up-to-date timestamp and choose not to
+ // delete the file.
+
+ if v.readonly {
+ return MethodDisabledError
+ }
+ if v.locker != nil {
+ v.locker.Lock()
+ defer v.locker.Unlock()
+ }
p := v.blockPath(loc)
f, err := os.OpenFile(p, os.O_RDWR|os.O_APPEND, 0644)
if err != nil {
}
defer unlockfile(f)
- // If the block has been PUT more recently than -permission_ttl,
- // return success without removing the block. This guards against
- // a race condition where a block is old enough that Data Manager
- // has added it to the trash list, but the user submitted a PUT
- // for the block since then.
+ // If the block has been PUT in the last blob_signature_ttl
+ // seconds, return success without removing the block. This
+ // protects data from garbage collection until it is no longer
+ // possible for clients to retrieve the unreferenced blocks
+ // anyway (because the permission signatures have expired).
if fi, err := os.Stat(p); err != nil {
return err
} else {
- if time.Since(fi.ModTime()) < permission_ttl {
+ if time.Since(fi.ModTime()) < blob_signature_ttl {
return nil
}
}
}
// IsFull returns true if the free space on the volume is less than
-// MIN_FREE_KILOBYTES.
+// MinFreeKilobytes.
//
func (v *UnixVolume) IsFull() (isFull bool) {
fullSymlink := v.root + "/full"
}
if avail, err := v.FreeDiskSpace(); err == nil {
- isFull = avail < MIN_FREE_KILOBYTES
+ isFull = avail < MinFreeKilobytes
} else {
log.Printf("%s: FreeDiskSpace: %s\n", v, err)
isFull = false
return fmt.Sprintf("[UnixVolume %s]", v.root)
}
+// Writable returns false if all future Put, Mtime, and Delete calls are expected to fail.
+func (v *UnixVolume) Writable() bool {
+ return !v.readonly
+}
+
// lockfile and unlockfile use flock(2) to manage kernel file locks.
func lockfile(f *os.File) error {
return syscall.Flock(int(f.Fd()), syscall.LOCK_EX)
projects / arvados.git / blobdiff