download: add inactivity monitor

if a download part is inactive for some time, restart it

server/download.go

@@ -25,6 +25,11 @@ import (
 	"github.com/jmorganca/ollama/format"
 )
 
+const maxRetries = 6
+
+var errMaxRetriesExceeded = errors.New("max retries exceeded")
+var errPartStalled = errors.New("part stalled")
+
 var blobDownloadManager sync.Map
 
 type blobDownload struct {
@@ -48,6 +53,7 @@ type blobDownloadPart struct {
 	Offset      int64
 	Size        int64
 	Completed   int64
+	lastUpdated time.Time
 
 	*blobDownload `json:"-"`
 }
@@ -72,6 +78,13 @@ func (p *blobDownloadPart) StopsAt() int64 {
 	return p.Offset + p.Size
 }
 
+func (p *blobDownloadPart) Write(b []byte) (n int, err error) {
+	n = len(b)
+	p.blobDownload.Completed.Add(int64(n))
+	p.lastUpdated = time.Now()
+	return n, nil
+}
+
 func (b *blobDownload) Prepare(ctx context.Context, requestURL *url.URL, opts *RegistryOptions) error {
 	partFilePaths, err := filepath.Glob(b.Name + "-partial-*")
 	if err != nil {
@@ -157,6 +170,9 @@ func (b *blobDownload) run(ctx context.Context, requestURL *url.URL, opts *Regis
 				case errors.Is(err, context.Canceled), errors.Is(err, syscall.ENOSPC):
 					// return immediately if the context is canceled or the device is out of space
 					return err
+				case errors.Is(err, errPartStalled):
+					try--
+					continue
 				case err != nil:
 					sleep := time.Second * time.Duration(math.Pow(2, float64(try)))
 					log.Printf("%s part %d attempt %d failed: %v, retrying in %s", b.Digest[7:19], part.N, try, err, sleep)
@@ -195,6 +211,8 @@ func (b *blobDownload) run(ctx context.Context, requestURL *url.URL, opts *Regis
 }
 
 func (b *blobDownload) downloadChunk(ctx context.Context, requestURL *url.URL, w io.Writer, part *blobDownloadPart, opts *RegistryOptions) error {
+	g, ctx := errgroup.WithContext(ctx)
+	g.Go(func() error {
 		headers := make(http.Header)
 		headers.Set("Range", fmt.Sprintf("bytes=%d-%d", part.StartsAt(), part.StopsAt()-1))
 		resp, err := makeRequestWithRetry(ctx, http.MethodGet, requestURL, headers, nil, opts)
@@ -203,7 +221,7 @@ func (b *blobDownload) downloadChunk(ctx context.Context, requestURL *url.URL, w
 		}
 		defer resp.Body.Close()
 
-	n, err := io.Copy(w, io.TeeReader(resp.Body, b))
+		n, err := io.Copy(w, io.TeeReader(resp.Body, part))
 		if err != nil && !errors.Is(err, context.Canceled) && !errors.Is(err, io.ErrUnexpectedEOF) {
 			// rollback progress
 			b.Completed.Add(-n)
@@ -217,6 +235,30 @@ func (b *blobDownload) downloadChunk(ctx context.Context, requestURL *url.URL, w
 
 		// return nil or context.Canceled or UnexpectedEOF (resumable)
 		return err
+	})
+
+	g.Go(func() error {
+		ticker := time.NewTicker(time.Second)
+		for {
+			select {
+			case <-ticker.C:
+				if part.Completed >= part.Size {
+					return nil
+				}
+
+				if !part.lastUpdated.IsZero() && time.Since(part.lastUpdated) > 5*time.Second {
+					log.Printf("%s part %d stalled; retrying", b.Digest[7:19], part.N)
+					// reset last updated
+					part.lastUpdated = time.Time{}
+					return errPartStalled
+				}
+			case <-ctx.Done():
+				return ctx.Err()
+			}
+		}
+	})
+
+	return g.Wait()
 }
 
 func (b *blobDownload) newPart(offset, size int64) error {
@@ -255,12 +297,6 @@ func (b *blobDownload) writePart(partName string, part *blobDownloadPart) error
 	return json.NewEncoder(partFile).Encode(part)
 }
 
-func (b *blobDownload) Write(p []byte) (n int, err error) {
-	n = len(p)
-	b.Completed.Add(int64(n))
-	return n, nil
-}
-
 func (b *blobDownload) acquire() {
 	b.references.Add(1)
 }
@@ -279,10 +315,6 @@ func (b *blobDownload) Wait(ctx context.Context, fn func(api.ProgressResponse))
 	for {
 		select {
 		case <-ticker.C:
-		case <-ctx.Done():
-			return ctx.Err()
-		}
-
 			fn(api.ProgressResponse{
 				Status:    fmt.Sprintf("pulling %s", b.Digest[7:19]),
 				Digest:    b.Digest,
@@ -293,6 +325,9 @@ func (b *blobDownload) Wait(ctx context.Context, fn func(api.ProgressResponse))
 			if b.done || b.err != nil {
 				return b.err
 			}
+		case <-ctx.Done():
+			return ctx.Err()
+		}
 	}
 }
 
@@ -303,10 +338,6 @@ type downloadOpts struct {
 	fn      func(api.ProgressResponse)
 }
 
-const maxRetries = 6
-
-var errMaxRetriesExceeded = errors.New("max retries exceeded")
-
 // downloadBlob downloads a blob from the registry and stores it in the blobs directory
 func downloadBlob(ctx context.Context, opts downloadOpts) error {
 	fp, err := GetBlobsPath(opts.digest)