filer: fetch only the part of a chunk the view covers

Replaces the PinRandomMode size heuristic with a per-chunk coverage rule.
ViewFromVisibleIntervals already clips chunk views to the request window,
so a view that is not IsFullChunk() is one the request only partially
needs; fetch it as a range regardless of the detected read pattern.

This closes the holes a request-size pin left open: ranges larger than
SeqTolerance no longer revert to whole-chunk downloads once their buffers
look sequential, and ranges that fully cover a chunk keep the shared
whole-chunk path instead of fetching 256KiB slices piecemeal. Prefetch
(MaybeCache) skips clipped views so it cannot amplify a range read either.

PinRandomMode is dropped: no caller needs it once coverage drives the
fetch choice. Range fetches route through fetchChunkDataFn so tests
observe them the same way as whole-chunk downloads.

weed/filer/filechunk_manifest.go

@@ -380,15 +380,6 @@ func fetchWholeChunk(ctx context.Context, bytesBuffer *bytes.Buffer, lookupFileI
 	})
 }
 
-func fetchChunkRange(ctx context.Context, buffer []byte, lookupFileIdFn wdclient.LookupFileIdFunctionType, fileId string, cipherKey []byte, isGzipped bool, offset int64, refreshUrls util_http.RefreshUrlsFunc) (int, error) {
-	urlStrings, err := lookupFileIdFn(ctx, fileId)
-	if err != nil {
-		glog.ErrorfCtx(ctx, "operation LookupFileId %s failed, err: %v", fileId, err)
-		return 0, err
-	}
-	return util_http.RetriedFetchChunkData(ctx, buffer, urlStrings, cipherKey, isGzipped, false, offset, fileId, refreshUrls)
-}
-
 // retriedStreamFetchChunkData streams a chunk from the first location that
 // answers. refreshUrls may be nil; when a location failed and a later one
 // answered, it is called so the reads that follow start from a fresh list.

weed/filer/reader_at.go

@@ -180,12 +180,6 @@ func (c *ChunkReadAt) ReleaseStream() {
 	c.readerCache.releaseStream(&c.stream)
 }
 
-// PinRandomMode pins this reader to range fetches; used by callers that
-// already know the request is a partial read, e.g. a small ranged GET.
-func (c *ChunkReadAt) PinRandomMode() {
-	c.readerPattern.PinRandomMode()
-}
-
 func (c *ChunkReadAt) ReadAt(p []byte, offset int64) (n int, err error) {
 
 	c.readerPattern.MonitorReadAt(offset, len(p))
@@ -355,14 +349,17 @@ func (c *ChunkReadAt) doReadAt(ctx context.Context, p []byte, offset int64) (n i
 
 func (c *ChunkReadAt) readChunkSliceAt(ctx context.Context, buffer []byte, chunkView *ChunkView, nextChunkViews *Interval[*ChunkView], offset uint64) (n int, err error) {
 
-	if c.readerPattern.IsRandomMode() {
+	// A view clipped to part of its chunk (e.g. the edge of a ranged GET,
+	// whose views ViewFromVisibleIntervals clips to the request) only ever
+	// needs that part: fetch it as a range no matter the detected pattern.
+	// Fetching the chunk whole would multiply volume-server reads.
+	if !chunkView.IsFullChunk() || c.readerPattern.IsRandomMode() {
 		c.readerCache.releaseStream(&c.stream)
 		n, err := c.readerCache.chunkCache.ReadChunkAt(buffer, chunkView.FileId, offset)
 		if n > 0 {
 			return n, err
 		}
-		return fetchChunkRange(ctx, buffer, c.readerCache.lookupFileIdFn, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped, int64(offset),
-			refreshUrls(ctx, c.readerCache.cacheInvalidator, c.readerCache.lookupFileIdFn, chunkView.FileId))
+		return c.readerCache.fetchChunkRange(ctx, buffer, chunkView, int64(offset))
 	}
 
 	shouldCache := (uint64(chunkView.ViewOffset) + chunkView.ChunkSize) <= c.readerCache.chunkCache.GetMaxFilePartSizeInCache()
@@ -386,6 +383,13 @@ func (c *ChunkReadAt) readChunkSliceAt(ctx context.Context, buffer []byte, chunk
 // readChunkSliceAtForParallel is a simplified version for parallel chunk fetching
 // It doesn't update lastChunkFid or trigger prefetch (handled by the caller)
 func (c *ChunkReadAt) readChunkSliceAtForParallel(ctx context.Context, buffer []byte, chunkView *ChunkView, offset uint64) (n int, err error) {
+	if !chunkView.IsFullChunk() {
+		n, err = c.readerCache.chunkCache.ReadChunkAt(buffer, chunkView.FileId, offset)
+		if n > 0 {
+			return n, err
+		}
+		return c.readerCache.fetchChunkRange(ctx, buffer, chunkView, int64(offset))
+	}
 	shouldCache := (uint64(chunkView.ViewOffset) + chunkView.ChunkSize) <= c.readerCache.chunkCache.GetMaxFilePartSizeInCache()
 	return c.readerCache.ReadChunkAt(ctx, buffer, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped, int64(offset), int(chunkView.ChunkSize), shouldCache)
 }

weed/filer/reader_at_shared_test.go

@@ -208,6 +208,143 @@ func TestChunkStreamConcurrentReadsOnOneReader(t *testing.T) {
 	}
 }
 
+type recordedFetch struct {
+	fileId      string
+	isFullChunk bool
+	offset      int64
+	size        int
+}
+
+// fetchRecorder stubs the volume fetch and records how each chunk was
+// requested: isFullChunk=false is a range fetch of just the view's slice,
+// isFullChunk=true is a whole-chunk download into the shared cache.
+func fetchRecorder(rc *ReaderCache) (fetches *[]recordedFetch) {
+	var mu sync.Mutex
+	recorded := &[]recordedFetch{}
+	rc.fetchChunkDataFn = func(_ context.Context, buffer []byte, _ []string, _ []byte, _ bool, isFullChunk bool, offset int64, fileId string, _ util_http.RefreshUrlsFunc) (int, error) {
+		mu.Lock()
+		*recorded = append(*recorded, recordedFetch{fileId, isFullChunk, offset, len(buffer)})
+		mu.Unlock()
+		for i := range buffer {
+			buffer[i] = fileId[len(fileId)-1]
+		}
+		return len(buffer), nil
+	}
+	return recorded
+}
+
+// A reader whose views are clipped to a request window — how the S3 gateway
+// builds a ranged GET — must fetch only the covered part of each chunk:
+// clipped edge views take range fetches, a fully covered chunk keeps the
+// shared whole-chunk path. This is what keeps a ranged GET larger than a
+// buffer from multiplying volume-server reads (issue #11564), without giving
+// up whole-chunk caching where the whole chunk is actually wanted.
+func TestChunkReadAtClippedViewsFetchOnlyCoveredParts(t *testing.T) {
+	const chunkSize = 64 << 10
+
+	rc := NewReaderCache(64, (*chunk_cache.TieredChunkCache)(nil), func(context.Context, string) ([]string, error) {
+		return []string{"unused"}, nil
+	}, nil)
+	defer rc.destroy()
+	fetches := fetchRecorder(rc)
+
+	// Window [56KiB, 136KiB): tail of chunk0, all of chunk1, head of chunk2.
+	views := NewIntervalList[*ChunkView]()
+	views.AppendInterval(&Interval[*ChunkView]{
+		StartOffset: chunkSize - 8<<10,
+		StopOffset:  chunkSize,
+		Value:       &ChunkView{FileId: "chunk0", OffsetInChunk: chunkSize - 8<<10, ViewSize: 8 << 10, ViewOffset: chunkSize - 8<<10, ChunkSize: chunkSize},
+	})
+	views.AppendInterval(&Interval[*ChunkView]{
+		StartOffset: chunkSize,
+		StopOffset:  2 * chunkSize,
+		Value:       &ChunkView{FileId: "chunk1", ViewSize: chunkSize, ViewOffset: chunkSize, ChunkSize: chunkSize},
+	})
+	views.AppendInterval(&Interval[*ChunkView]{
+		StartOffset: 2 * chunkSize,
+		StopOffset:  2*chunkSize + 8<<10,
+		Value:       &ChunkView{FileId: "chunk2", ViewSize: 8 << 10, ViewOffset: 2 * chunkSize, ChunkSize: chunkSize},
+	})
+
+	reader := NewChunkReaderAtFromClient(context.Background(), rc, views, 3*chunkSize, 0)
+	buf := make([]byte, chunkSize+16<<10)
+	if n, err := reader.ReadAt(buf, chunkSize-8<<10); err != nil || n != len(buf) {
+		t.Fatalf("window read: n=%d err=%v", n, err)
+	}
+	// buf holds [56KiB, 136KiB): chunk0's tail, chunk1, chunk2's head.
+	for i, b := range buf {
+		want := byte('1')
+		if i < 8<<10 {
+			want = '0'
+		} else if i >= 8<<10+chunkSize {
+			want = '2'
+		}
+		if b != want {
+			t.Fatalf("buf[%d]=%q, want %q", i, b, want)
+		}
+	}
+
+	want := []recordedFetch{
+		{fileId: "chunk0", isFullChunk: false, offset: chunkSize - 8<<10, size: 8 << 10},
+		{fileId: "chunk1", isFullChunk: true, offset: 0, size: chunkSize},
+		{fileId: "chunk2", isFullChunk: false, offset: 0, size: 8 << 10},
+	}
+	got := map[string]recordedFetch{}
+	for _, f := range *fetches {
+		if _, dup := got[f.fileId]; dup {
+			t.Fatalf("chunk %s fetched more than once: %+v", f.fileId, *fetches)
+		}
+		got[f.fileId] = f
+	}
+	for _, w := range want {
+		if g, ok := got[w.fileId]; !ok {
+			t.Fatalf("chunk %s never fetched: %+v", w.fileId, *fetches)
+		} else if g != w {
+			t.Fatalf("chunk %s fetched as %+v, want %+v", w.fileId, g, w)
+		}
+	}
+}
+
+// The regression from issue #11564: a ranged GET sitting inside one big
+// chunk. Every buffer of the request must stay a range fetch — none may
+// escalate into a whole-chunk download once the reads look sequential.
+func TestChunkReadAtRangeInsideOneChunkStaysRangeFetch(t *testing.T) {
+	const chunkSize = 1 << 20
+	const sliceSize = 16 << 10
+
+	rc := NewReaderCache(64, (*chunk_cache.TieredChunkCache)(nil), func(context.Context, string) ([]string, error) {
+		return []string{"unused"}, nil
+	}, nil)
+	defer rc.destroy()
+	fetches := fetchRecorder(rc)
+
+	// Range [32KiB, 96KiB) inside one 1MiB chunk: a single clipped view.
+	views := NewIntervalList[*ChunkView]()
+	views.AppendInterval(&Interval[*ChunkView]{
+		StartOffset: 32 << 10,
+		StopOffset:  96 << 10,
+		Value:       &ChunkView{FileId: "chunk0", OffsetInChunk: 32 << 10, ViewSize: 64 << 10, ViewOffset: 32 << 10, ChunkSize: chunkSize},
+	})
+
+	reader := NewChunkReaderAtFromClient(context.Background(), rc, views, chunkSize, 0)
+	for offset := int64(32 << 10); offset < 96<<10; offset += sliceSize {
+		buf := make([]byte, sliceSize)
+		if n, err := reader.ReadAt(buf, offset); err != nil || n != sliceSize {
+			t.Fatalf("read at %d: n=%d err=%v", offset, n, err)
+		}
+	}
+
+	if len(*fetches) != 4 {
+		t.Fatalf("got %d fetches, want 4 range fetches: %+v", len(*fetches), *fetches)
+	}
+	for i, f := range *fetches {
+		wantOffset := int64(32<<10) + int64(i)*sliceSize
+		if f.isFullChunk || f.offset != wantOffset || f.size != sliceSize {
+			t.Fatalf("fetch %d = %+v, want range fetch offset=%d size=%d", i, f, wantOffset, sliceSize)
+		}
+	}
+}
+
 // A chunk a stream is positioned in must outlast downloader-limit eviction:
 // otherwise a busy cache drops the buffer mid-stream and forces a refetch.
 func TestChunkReadAtPinnedChunkSurvivesEviction(t *testing.T) {

weed/filer/reader_cache.go

@@ -100,6 +100,11 @@ func (rc *ReaderCache) MaybeCache(chunkViews *Interval[*ChunkView], count int) {
 			// abort when slots are filled
 			return
 		}
+		if !chunkView.IsFullChunk() {
+			// the view is clipped to part of the chunk, so the rest is never
+			// read; prefetching it whole would download bytes nobody needs
+			continue
+		}
 
 		// glog.V(4).Infof("prefetch %s offset %d", chunkView.FileId, chunkView.ViewOffset)
 		// cache this chunk if not yet
@@ -114,6 +119,20 @@ func (rc *ReaderCache) MaybeCache(chunkViews *Interval[*ChunkView], count int) {
 	return
 }
 
+// fetchChunkRange downloads only [offset, offset+len(buffer)) of a chunk,
+// for views clipped to part of their chunk and for random-mode reads. It
+// goes through fetchChunkDataFn so tests observe range fetches the same way
+// they observe whole-chunk downloads.
+func (rc *ReaderCache) fetchChunkRange(ctx context.Context, buffer []byte, chunkView *ChunkView, offset int64) (int, error) {
+	urlStrings, err := rc.lookupFileIdFn(ctx, chunkView.FileId)
+	if err != nil {
+		glog.ErrorfCtx(ctx, "operation LookupFileId %s failed, err: %v", chunkView.FileId, err)
+		return 0, err
+	}
+	return rc.fetchChunkDataFn(ctx, buffer, urlStrings, chunkView.CipherKey, chunkView.IsGzipped, false, offset, chunkView.FileId,
+		refreshUrls(ctx, rc.cacheInvalidator, rc.lookupFileIdFn, chunkView.FileId))
+}
+
 // chunkStream is one sequential reader's position in a shared ReaderCache.
 // The chunk it is reading stays pinned until the stream reads it to the end or
 // moves elsewhere, so another stream finishing or leaving the same chunk does

weed/filer/reader_cache_memory_test.go

@@ -72,7 +72,7 @@ func TestReaderCacheBudgetInFlight(t *testing.T) {
 					return len(buffer), nil
 				}
 				if prefetch {
-					rc.MaybeCache(&Interval[*ChunkView]{Value: &ChunkView{FileId: "chunk", ChunkSize: 3 << 10}}, 1)
+					rc.MaybeCache(&Interval[*ChunkView]{Value: &ChunkView{FileId: "chunk", ViewSize: 3 << 10, ChunkSize: 3 << 10}}, 1)
 				} else {
 					readers.Add(1)
 					go func() {
@@ -180,7 +180,7 @@ func TestReaderCacheFailedPrefetchReleasesBudget(t *testing.T) {
 			rc.fetchChunkDataFn = func(_ context.Context, _ []byte, _ []string, _ []byte, _ bool, _ bool, _ int64, _ string, _ util_http.RefreshUrlsFunc) (int, error) {
 				return 0, fmt.Errorf("fetch failed")
 			}
-			rc.MaybeCache(&Interval[*ChunkView]{Value: &ChunkView{FileId: "failed", ChunkSize: 1024}}, 1)
+			rc.MaybeCache(&Interval[*ChunkView]{Value: &ChunkView{FileId: "failed", ViewSize: 1024, ChunkSize: 1024}}, 1)
 			deadline := time.Now().Add(5 * time.Second)
 			for {
 				rc.Lock()
@@ -278,7 +278,7 @@ func TestReaderCachePrefetchBufferDroppedAfterRead(t *testing.T) {
 		buffer[0] = 42
 		return len(buffer), nil
 	}
-	rc.MaybeCache(&Interval[*ChunkView]{Value: &ChunkView{FileId: "chunk", ChunkSize: 4 << 10}}, 1)
+	rc.MaybeCache(&Interval[*ChunkView]{Value: &ChunkView{FileId: "chunk", ViewSize: 4 << 10, ChunkSize: 4 << 10}}, 1)
 
 	buf := make([]byte, 4<<10)
 	n, err := rc.ReadChunkAt(context.Background(), buf, "chunk", nil, false, 0, 4<<10, false)

weed/filer/reader_pattern.go

@@ -7,7 +7,6 @@ import (
 type ReaderPattern struct {
 	isSequentialCounter int64
 	readFrontier        int64 // highest (offset+size) observed across reads
-	pinnedRandom        int64 // set when the caller already knows the reads are a partial range
 }
 
 const ModeChangeLimit = 3
@@ -66,12 +65,5 @@ func (rp *ReaderPattern) MonitorReadAt(offset int64, size int) {
 }
 
 func (rp *ReaderPattern) IsRandomMode() bool {
-	return atomic.LoadInt64(&rp.pinnedRandom) != 0 || atomic.LoadInt64(&rp.isSequentialCounter) < 0
-}
-
-// PinRandomMode pins the pattern to random for readers that already know
-// they serve a partial range, e.g. a small ranged GET: contiguous buffer
-// reads within the request must not escalate into whole-chunk fetches.
-func (rp *ReaderPattern) PinRandomMode() {
-	atomic.StoreInt64(&rp.pinnedRandom, 1)
+	return atomic.LoadInt64(&rp.isSequentialCounter) < 0
 }

weed/filer/reader_pattern_test.go

@@ -122,17 +122,3 @@ func TestReaderPatternRangedReadStaysRandom(t *testing.T) {
 		t.Fatal("sustained sequential reads should restore sequential mode")
 	}
 }
-
-
-// A reader pinned random (a known small ranged request) must stay random
-// for every buffer of the request, near or far.
-func TestReaderPatternPinnedRandom(t *testing.T) {
-	rp := NewReaderPattern()
-	rp.PinRandomMode()
-	for i := int64(0); i < 10; i++ {
-		rp.MonitorReadAt(i*256*1024, 256*1024) // contiguous from the start
-		if !rp.IsRandomMode() {
-			t.Fatalf("pinned reader flipped to sequential at read %d", i+1)
-		}
-	}
-}

weed/s3api/s3api_object_handlers.go

@@ -1104,12 +1104,6 @@ func (s3a *S3ApiServer) streamFromVolumeServers(w http.ResponseWriter, r *http.R
 	chunkViews := filer.ViewFromVisibleIntervals(visibleIntervals, offset, size)
 	reader := filer.NewChunkReaderAtFromClient(ctx, s3a.readerCache, chunkViews, totalSize, filer.DefaultPrefetchCount)
 	defer reader.ReleaseStream()
-	// A small ranged request reads back less than a whole chunk; pin random
-	// mode so every buffer fetch stays a range read instead of downloading
-	// each covered chunk in full.
-	if isRangeRequest && size <= filer.SeqTolerance {
-		reader.PinRandomMode()
-	}
 	streamPrepTime = time.Since(tStreamPrep)
 
 	// A cached chunk whose volume server is down, or whose needle was evicted and