// StatusHandler (GET /status.json)
import (
- "bytes"
"container/list"
"crypto/md5"
"encoding/json"
}
}
- block, err := GetBlock(mux.Vars(req)["hash"], false)
+ block, err := GetBlock(mux.Vars(req)["hash"])
if err != nil {
// This type assertion is safe because the only errors
// GetBlock can return are DiskHashError or NotFoundError.
if err == nil {
resp.Write(jstat)
} else {
- log.Printf("json.Marshal: %s\n", err)
- log.Printf("NodeStatus = %v\n", &st)
+ log.Printf("json.Marshal: %s", err)
+ log.Printf("NodeStatus = %v", &st)
http.Error(resp, err.Error(), 500)
}
}
if body, err := json.Marshal(result); err == nil {
resp.Write(body)
} else {
- log.Printf("json.Marshal: %s (result = %v)\n", err, result)
+ log.Printf("json.Marshal: %s (result = %v)", err, result)
http.Error(resp, err.Error(), 500)
}
}
// which volume to check for fetching blocks, storing blocks, etc.
// ==============================
-// GetBlock fetches and returns the block identified by "hash". If
-// the update_timestamp argument is true, GetBlock also updates the
-// block's file modification time (for the sake of PutBlock, which
-// must update the file's timestamp when the block already exists).
+// GetBlock fetches and returns the block identified by "hash".
//
// On success, GetBlock returns a byte slice with the block data, and
// a nil error.
// DiskHashError.
//
-func GetBlock(hash string, update_timestamp bool) ([]byte, error) {
+func GetBlock(hash string) ([]byte, error) {
// Attempt to read the requested hash from a keep volume.
error_to_caller := NotFoundError
- var vols []Volume
- if update_timestamp {
- // Pointless to find the block on an unwritable volume
- // because Touch() will fail -- this is as good as
- // "not found" for purposes of callers who need to
- // update_timestamp.
- vols = KeepVM.AllWritable()
- } else {
- vols = KeepVM.AllReadable()
- }
-
- for _, vol := range vols {
+ for _, vol := range KeepVM.AllReadable() {
buf, err := vol.Get(hash)
if err != nil {
// IsNotExist is an expected error and may be
// volumes. If all volumes report IsNotExist,
// we return a NotFoundError.
if !os.IsNotExist(err) {
- log.Printf("GetBlock: reading %s: %s\n", hash, err)
+ log.Printf("%s: Get(%s): %s", vol, hash, err)
}
continue
}
if filehash != hash {
// TODO: Try harder to tell a sysadmin about
// this.
- log.Printf("%s: checksum mismatch for request %s (actual %s)\n",
+ log.Printf("%s: checksum mismatch for request %s (actual %s)",
vol, hash, filehash)
error_to_caller = DiskHashError
bufs.Put(buf)
log.Printf("%s: checksum mismatch for request %s but a good copy was found on another volume and returned",
vol, hash)
}
- if update_timestamp {
- if err := vol.Touch(hash); err != nil {
- error_to_caller = GenericError
- log.Printf("%s: Touch %s failed: %s",
- vol, hash, error_to_caller)
- bufs.Put(buf)
- continue
- }
- }
return buf, nil
}
return nil, error_to_caller
return RequestHashError
}
- // If we already have a block on disk under this identifier, return
- // success (but check for MD5 collisions). While fetching the block,
- // update its timestamp.
- // The only errors that GetBlock can return are DiskHashError and NotFoundError.
- // In either case, we want to write our new (good) block to disk,
- // so there is nothing special to do if err != nil.
- //
- if oldblock, err := GetBlock(hash, true); err == nil {
- defer bufs.Put(oldblock)
- if bytes.Compare(block, oldblock) == 0 {
- // The block already exists; return success.
- return nil
- } else {
- return CollisionError
- }
+ // If we already have this data, it's intact on disk, and we
+ // can update its timestamp, return success. If we have
+ // different data with the same hash, return failure.
+ if err := CompareAndTouch(hash, block); err == nil || err == CollisionError {
+ return err
}
// Choose a Keep volume to write to.
// write did not succeed. Report the
// error and continue trying.
allFull = false
- log.Printf("%s: Write(%s): %s\n", vol, hash, err)
+ log.Printf("%s: Write(%s): %s", vol, hash, err)
}
}
}
}
+// CompareAndTouch returns nil if one of the volumes already has the
+// given content and it successfully updates the relevant block's
+// modification time in order to protect it from premature garbage
+// collection.
+func CompareAndTouch(hash string, buf []byte) error {
+ var bestErr error = NotFoundError
+ for _, vol := range KeepVM.AllWritable() {
+ if err := vol.Compare(hash, buf); err == CollisionError {
+ // Stop if we have a block with same hash but
+ // different content. (It will be impossible
+ // to tell which one is wanted if we have
+ // both, so there's no point writing it even
+ // on a different volume.)
+ log.Printf("%s: Compare(%s): %s", vol, hash, err)
+ return err
+ } else if os.IsNotExist(err) {
+ // Block does not exist. This is the only
+ // "normal" error: we don't log anything.
+ continue
+ } else if err != nil {
+ // Couldn't open file, data is corrupt on
+ // disk, etc.: log this abnormal condition,
+ // and try the next volume.
+ log.Printf("%s: Compare(%s): %s", vol, hash, err)
+ continue
+ }
+ if err := vol.Touch(hash); err != nil {
+ log.Printf("%s: Touch %s failed: %s", vol, hash, err)
+ bestErr = err
+ continue
+ }
+ // Compare and Touch both worked --> done.
+ return nil
+ }
+ return bestErr
+}
+
var validLocatorRe = regexp.MustCompile(`^[0-9a-f]{32}$`)
// IsValidLocator
func IsExpired(timestamp_hex string) bool {
ts, err := strconv.ParseInt(timestamp_hex, 16, 0)
if err != nil {
- log.Printf("IsExpired: %s\n", err)
+ log.Printf("IsExpired: %s", err)
return true
}
return time.Unix(ts, 0).Before(time.Now())
projects / arvados.git / blobdiff