feat(filestore): add mmap reader option

CHANGELOG.md

@@ -66,6 +66,7 @@ The following emojis are used to highlight certain changes:
 - `routing/http/server`: added configurable routing timeout (`DefaultRoutingTimeout` being 30s) to prevent indefinite hangs during content/peer routing. Set custom duration via `WithRoutingTimeout`. [#720](https://github.com/ipfs/boxo/pull/720)
 - `routing/http/server`: exposes Prometheus metrics on `prometheus.DefaultRegisterer` and a custom one can be provided via `WithPrometheusRegistry` [#722](https://github.com/ipfs/boxo/pull/722)
 - `gateway`: `NewCacheBlockStore` and `NewCarBackend` will use `prometheus.DefaultRegisterer` when a custom one is not specified via `WithPrometheusRegistry` [#722](https://github.com/ipfs/boxo/pull/722)
+- `filestore`: add `WithMMapReader` option to `FileManager`
 
 ### Changed
 

filestore/filereader.go

@@ -0,0 +1,61 @@
+package filestore
+
+import (
+	"io"
+	"os"
+
+	"golang.org/x/exp/mmap"
+)
+
+type FileReader interface {
+	io.ReaderAt
+	io.Closer
+}
+
+var _ FileReader = (*stdReader)(nil)
+
+type stdReader struct {
+	f *os.File
+}
+
+// ReadAt implements the FileReader interface.
+func (r *stdReader) ReadAt(p []byte, off int64) (n int, err error) {
+	return r.f.ReadAt(p, off)
+}
+
+// Close implements the FileReader interface.
+func (r *stdReader) Close() error {
+	return r.f.Close()
+}
+
+func newStdReader(path string) (FileReader, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	return &stdReader{f: f}, nil
+}
+
+var _ FileReader = (*mmapReader)(nil)
+
+type mmapReader struct {
+	m *mmap.ReaderAt
+}
+
+// ReadAt implements the FileReader interface.
+func (r *mmapReader) ReadAt(p []byte, off int64) (n int, err error) {
+	return r.m.ReadAt(p, off)
+}
+
+// Close implements the FileReader interface.
+func (r *mmapReader) Close() error {
+	return r.m.Close()
+}
+
+func newMmapReader(path string) (FileReader, error) {
+	m, err := mmap.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	return &mmapReader{m: m}, nil
+}

filestore/filestore_test.go

@@ -18,14 +18,14 @@ import (
 
 var bg = context.Background()
 
-func newTestFilestore(t *testing.T) (string, *Filestore) {
+func newTestFilestore(t *testing.T, option ...Option) (string, *Filestore) {
 	mds := ds.NewMapDatastore()
 
 	testdir, err := os.MkdirTemp("", "filestore-test")
 	if err != nil {
 		t.Fatal(err)
 	}
-	fm := NewFileManager(mds, testdir)
+	fm := NewFileManager(mds, testdir, option...)
 	fm.AllowFiles = true
 
 	bs := blockstore.NewBlockstore(mds)
@@ -48,62 +48,74 @@ func makeFile(dir string, data []byte) (string, error) {
 }
 
 func TestBasicFilestore(t *testing.T) {
-	dir, fs := newTestFilestore(t)
-
-	buf := make([]byte, 1000)
-	rand.Read(buf)
-
-	fname, err := makeFile(dir, buf)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	var cids []cid.Cid
-	for i := 0; i < 100; i++ {
-		n := &posinfo.FilestoreNode{
-			PosInfo: &posinfo.PosInfo{
-				FullPath: fname,
-				Offset:   uint64(i * 10),
-			},
-			Node: dag.NewRawNode(buf[i*10 : (i+1)*10]),
-		}
-
-		err := fs.Put(bg, n)
-		if err != nil {
-			t.Fatal(err)
-		}
-		cids = append(cids, n.Node.Cid())
-	}
-
-	for i, c := range cids {
-		blk, err := fs.Get(bg, c)
-		if err != nil {
-			t.Fatal(err)
-		}
-
-		if !bytes.Equal(blk.RawData(), buf[i*10:(i+1)*10]) {
-			t.Fatal("data didnt match on the way out")
-		}
-	}
-
-	kch, err := fs.AllKeysChan(context.Background())
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	out := make(map[string]struct{})
-	for c := range kch {
-		out[c.KeyString()] = struct{}{}
-	}
-
-	if len(out) != len(cids) {
-		t.Fatal("mismatch in number of entries")
-	}
-
-	for _, c := range cids {
-		if _, ok := out[c.KeyString()]; !ok {
-			t.Fatal("missing cid: ", c)
-		}
+	cases := []struct {
+		name    string
+		options []Option
+	}{
+		{"default", nil},
+		{"mmap", []Option{WithMMapReader()}},
+	}
+
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			dir, fs := newTestFilestore(t, c.options...)
+
+			buf := make([]byte, 1000)
+			rand.Read(buf)
+
+			fname, err := makeFile(dir, buf)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			var cids []cid.Cid
+			for i := 0; i < 100; i++ {
+				n := &posinfo.FilestoreNode{
+					PosInfo: &posinfo.PosInfo{
+						FullPath: fname,
+						Offset:   uint64(i * 10),
+					},
+					Node: dag.NewRawNode(buf[i*10 : (i+1)*10]),
+				}
+
+				err := fs.Put(bg, n)
+				if err != nil {
+					t.Fatal(err)
+				}
+				cids = append(cids, n.Node.Cid())
+			}
+
+			for i, c := range cids {
+				blk, err := fs.Get(bg, c)
+				if err != nil {
+					t.Fatal(err)
+				}
+
+				if !bytes.Equal(blk.RawData(), buf[i*10:(i+1)*10]) {
+					t.Fatal("data didnt match on the way out")
+				}
+			}
+
+			kch, err := fs.AllKeysChan(context.Background())
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			out := make(map[string]struct{})
+			for c := range kch {
+				out[c.KeyString()] = struct{}{}
+			}
+
+			if len(out) != len(cids) {
+				t.Fatal("mismatch in number of entries")
+			}
+
+			for _, c := range cids {
+				if _, ok := out[c.KeyString()]; !ok {
+					t.Fatal("missing cid: ", c)
+				}
+			}
+		})
 	}
 }
 

filestore/fsrefstore.go

@@ -25,6 +25,8 @@ import (
 // FilestorePrefix identifies the key prefix for FileManager blocks.
 var FilestorePrefix = ds.NewKey("filestore")
 
+type Option func(*FileManager)
+
 // FileManager is a blockstore implementation which stores special
 // blocks FilestoreNode type. These nodes only contain a reference
 // to the actual location of the block data in the filesystem
@@ -34,6 +36,7 @@ type FileManager struct {
 	AllowUrls  bool
 	ds         ds.Batching
 	root       string
+	makeReader func(path string) (FileReader, error)
 }
 
 // CorruptReferenceError implements the error interface.
@@ -51,11 +54,32 @@ func (c CorruptReferenceError) Error() string {
 	return c.Err.Error()
 }
 
+// WithMMapReader sets the FileManager's reader factory to use memory-mapped file I/O.
+// On Windows, when reading and writing to a file simultaneously, the system would consume
+// a significant amount of memory due to caching. This memory usage is not reflected in
+// the application but in the system. Using memory-mapped files (implemented with
+// CreateFileMapping on Windows) avoids this issue.
+func WithMMapReader() Option {
+	return func(f *FileManager) {
+		f.makeReader = newMmapReader
+	}
+}
+
 // NewFileManager initializes a new file manager with the given
 // datastore and root. All FilestoreNodes paths are relative to the
 // root path given here, which is prepended for any operations.
-func NewFileManager(ds ds.Batching, root string) *FileManager {
-	return &FileManager{ds: dsns.Wrap(ds, FilestorePrefix), root: root}
+func NewFileManager(ds ds.Batching, root string, options ...Option) *FileManager {
+	f := &FileManager{
+		ds:         dsns.Wrap(ds, FilestorePrefix),
+		root:       root,
+		makeReader: newStdReader,
+	}
+
+	for _, option := range options {
+		option(f)
+	}
+
+	return f
 }
 
 // AllKeysChan returns a channel from which to read the keys stored in
@@ -175,21 +199,16 @@ func (f *FileManager) readFileDataObj(m mh.Multihash, d *pb.DataObj) ([]byte, er
 	p := filepath.FromSlash(d.GetFilePath())
 	abspath := filepath.Join(f.root, p)
 
-	fi, err := os.Open(abspath)
+	fi, err := f.makeReader(abspath)
 	if os.IsNotExist(err) {
 		return nil, &CorruptReferenceError{StatusFileNotFound, err}
 	} else if err != nil {
 		return nil, &CorruptReferenceError{StatusFileError, err}
 	}
 	defer fi.Close()
 
-	_, err = fi.Seek(int64(d.GetOffset()), io.SeekStart)
-	if err != nil {
-		return nil, &CorruptReferenceError{StatusFileError, err}
-	}
-
 	outbuf := make([]byte, d.GetSize_())
-	_, err = io.ReadFull(fi, outbuf)
+	_, err = fi.ReadAt(outbuf, int64(d.GetOffset()))
 	if err == io.EOF || err == io.ErrUnexpectedEOF {
 		return nil, &CorruptReferenceError{StatusFileChanged, err}
 	} else if err != nil {

go.mod

@@ -75,6 +75,7 @@ require (
 	go.opentelemetry.io/otel/trace v1.31.0
 	go.uber.org/multierr v1.11.0
 	go.uber.org/zap v1.27.0
+	golang.org/x/exp v0.0.0-20241009180824-f66d83c29e7c
 	golang.org/x/oauth2 v0.23.0
 	golang.org/x/sync v0.8.0
 	golang.org/x/sys v0.26.0
@@ -185,7 +186,6 @@ require (
 	go.uber.org/fx v1.23.0 // indirect
 	go.uber.org/mock v0.5.0 // indirect
 	golang.org/x/crypto v0.28.0 // indirect
-	golang.org/x/exp v0.0.0-20241009180824-f66d83c29e7c // indirect
 	golang.org/x/mod v0.21.0 // indirect
 	golang.org/x/net v0.30.0 // indirect
 	golang.org/x/text v0.19.0 // indirect