}
}
- block, err := GetBlock(mux.Vars(req)["hash"])
+ // TODO: Probe volumes to check whether the block _might_
+ // exist. Some volumes/types could support a quick existence
+ // check without causing other operations to suffer. If all
+ // volumes support that, and assure us the block definitely
+ // isn't here, we can return 404 now instead of waiting for a
+ // buffer.
+
+ buf, err := getBufferForResponseWriter(resp, bufs, BlockSize)
if err != nil {
- // This type assertion is safe because the only errors
- // GetBlock can return are DiskHashError or NotFoundError.
- http.Error(resp, err.Error(), err.(*KeepError).HTTPCode)
+ http.Error(resp, err.Error(), http.StatusServiceUnavailable)
return
}
- defer bufs.Put(block)
+ defer bufs.Put(buf)
- resp.Header().Set("Content-Length", strconv.Itoa(len(block)))
+ size, err := GetBlock(mux.Vars(req)["hash"], buf, resp)
+ if err != nil {
+ code := http.StatusInternalServerError
+ if err, ok := err.(*KeepError); ok {
+ code = err.HTTPCode
+ }
+ http.Error(resp, err.Error(), code)
+ return
+ }
+
+ resp.Header().Set("Content-Length", strconv.Itoa(size))
resp.Header().Set("Content-Type", "application/octet-stream")
- resp.Write(block)
+ resp.Write(buf[:size])
+}
+
+// Get a buffer from the pool -- but give up and return a non-nil
+// error if resp implements http.CloseNotifier and tells us that the
+// client has disconnected before we get a buffer.
+func getBufferForResponseWriter(resp http.ResponseWriter, bufs *bufferPool, bufSize int) ([]byte, error) {
+ var closeNotifier <-chan bool
+ if resp, ok := resp.(http.CloseNotifier); ok {
+ closeNotifier = resp.CloseNotify()
+ }
+ var buf []byte
+ bufReady := make(chan []byte)
+ go func() {
+ bufReady <- bufs.Get(bufSize)
+ close(bufReady)
+ }()
+ select {
+ case buf = <-bufReady:
+ return buf, nil
+ case <-closeNotifier:
+ go func() {
+ // Even if closeNotifier happened first, we
+ // need to keep waiting for our buf so we can
+ // return it to the pool.
+ bufs.Put(<-bufReady)
+ }()
+ return nil, ErrClientDisconnect
+ }
}
// PutBlockHandler is a HandleFunc to address Put block requests.
return
}
- buf := bufs.Get(int(req.ContentLength))
- _, err := io.ReadFull(req.Body, buf)
+ buf, err := getBufferForResponseWriter(resp, bufs, int(req.ContentLength))
+ if err != nil {
+ http.Error(resp, err.Error(), http.StatusServiceUnavailable)
+ return
+ }
+
+ _, err = io.ReadFull(req.Body, buf)
if err != nil {
http.Error(resp, err.Error(), 500)
bufs.Put(buf)
}
}
-// ==============================
// GetBlock and PutBlock implement lower-level code for handling
// blocks by rooting through volumes connected to the local machine.
// Once the handler has determined that system policy permits the
// should be the only part of the code that cares about which volume a
// block is stored on, so it should be responsible for figuring out
// which volume to check for fetching blocks, storing blocks, etc.
-// ==============================
-// GetBlock fetches and returns the block identified by "hash".
-//
-// On success, GetBlock returns a byte slice with the block data, and
-// a nil error.
+// GetBlock fetches the block identified by "hash" into the provided
+// buf, and returns the data size.
//
// If the block cannot be found on any volume, returns NotFoundError.
//
// If the block found does not have the correct MD5 hash, returns
// DiskHashError.
//
-func GetBlock(hash string) ([]byte, error) {
+func GetBlock(hash string, buf []byte, resp http.ResponseWriter) (int, error) {
// Attempt to read the requested hash from a keep volume.
errorToCaller := NotFoundError
for _, vol := range KeepVM.AllReadable() {
- buf, err := vol.Get(hash)
+ size, err := vol.Get(hash, buf)
if err != nil {
// IsNotExist is an expected error and may be
// ignored. All other errors are logged. In
}
// Check the file checksum.
//
- filehash := fmt.Sprintf("%x", md5.Sum(buf))
+ filehash := fmt.Sprintf("%x", md5.Sum(buf[:size]))
if filehash != hash {
// TODO: Try harder to tell a sysadmin about
// this.
log.Printf("%s: checksum mismatch for request %s (actual %s)",
vol, hash, filehash)
errorToCaller = DiskHashError
- bufs.Put(buf)
continue
}
if errorToCaller == DiskHashError {
log.Printf("%s: checksum mismatch for request %s but a good copy was found on another volume and returned",
vol, hash)
}
- return buf, nil
+ return size, nil
}
- return nil, errorToCaller
+ return 0, errorToCaller
}
// PutBlock Stores the BLOCK (identified by the content id HASH) in Keep.
projects / arvados.git / blobdiff