import (
"fmt"
+ "io"
"io/ioutil"
"log"
"os"
// request.
//
type UnixVolume struct {
- root string // path to this volume
- queue chan *IORequest
+ root string // path to this volume
+ queue chan *IORequest
+ readonly bool
}
func (v *UnixVolume) IOHandler() {
}
}
-func MakeUnixVolume(root string, serialize bool) (v UnixVolume) {
+func MakeUnixVolume(root string, serialize bool, readonly bool) *UnixVolume {
+ v := &UnixVolume{
+ root: root,
+ queue: nil,
+ readonly: readonly,
+ }
if serialize {
- v = UnixVolume{root, make(chan *IORequest)}
+ v.queue = make(chan *IORequest)
go v.IOHandler()
- } else {
- v = UnixVolume{root, nil}
}
- return
+ return v
}
func (v *UnixVolume) Get(loc string) ([]byte, error) {
}
func (v *UnixVolume) Put(loc string, block []byte) error {
+ if v.readonly {
+ return MethodDisabledError
+ }
if v.queue == nil {
return v.Write(loc, block)
}
}
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 e := lockfile(f); e != nil {
return e
}
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.
+// 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 (v *UnixVolume) IndexTo(prefix string, w io.Writer) error {
+ return 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",
+ log.Printf("%s: IndexTo Walk error at %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.
+ basename := filepath.Base(path)
if info.IsDir() &&
- !strings.HasPrefix(locator, prefix) &&
- !strings.HasPrefix(prefix, locator) {
+ !strings.HasPrefix(basename, prefix) &&
+ !strings.HasPrefix(prefix, basename) {
+ // Skip directories that do not match
+ // prefix. We know there is nothing
+ // interesting inside.
return filepath.SkipDir
}
- // Skip any file that is not apparently a locator, e.g. .meta files
- if !IsValidLocator(locator) {
+ if info.IsDir() ||
+ !IsValidLocator(basename) ||
+ !strings.HasPrefix(basename, prefix) {
return nil
}
- // 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())
- }
- return nil
+ _, err = fmt.Fprintf(w, "%s+%d %d\n",
+ basename, info.Size(), info.ModTime().Unix())
+ return err
})
-
- return
}
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
+ }
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 e := lockfile(f); e != nil {
return e
}
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
}
}
return fmt.Sprintf("[UnixVolume %s]", v.root)
}
+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