Merge pull request #12 from moov-io/support-larger-files

fix: allow Reader to stream larger files

client.go

@@ -5,6 +5,7 @@
 package go_ftp
 
 import (
+	"bufio"
 	"bytes"
 	"crypto/tls"
 	"crypto/x509"
@@ -179,37 +180,105 @@ func (cc *client) Open(path string) (*File, error) {
 	cc.mu.Lock()
 	defer cc.mu.Unlock()
 
-	resp, err := cc.openFilepath(path)
+	conn, err := cc.connection()
 	if err != nil {
 		return nil, err
 	}
+
+	dir, filename := filepath.Split(path)
+	if dir != "" {
+		// Jump to previous directory after command is done
+		wd, err := conn.CurrentDir()
+		if err != nil {
+			return nil, err
+		}
+		defer func(previous string) {
+			// Return to our previous directory when initially called
+			if cleanupErr := conn.ChangeDir(previous); cleanupErr != nil {
+				err = fmt.Errorf("FTP: problem with readFiles: %w", cleanupErr)
+			}
+		}(wd)
+
+		// Move into directory to run the command
+		if err := conn.ChangeDir(dir); err != nil {
+			return nil, err
+		}
+	}
+
+	resp, err := conn.Retr(filename)
+	if err != nil {
+		return nil, fmt.Errorf("retrieving %s failed: %w", path, err)
+	}
+
 	data, err := readResponse(resp)
 	if err != nil {
 		return nil, fmt.Errorf("reading %s failed: %w", path, err)
 	}
+
 	return &File{
 		Filename: filepath.Base(path),
 		Contents: data,
 	}, nil
 }
 
 // Reader will open the file at path and provide a reader to access its contents.
-// Callers need to close the returned Contents
+// Callers need to close the returned Contents.
 //
 // Callers should be aware that network errors while reading can occur since contents
-// are streamed from the FTP server. Having multiple open readers may not be supported.
+// are streamed from the FTP server. Having multiple open readers is not supported.
 func (cc *client) Reader(path string) (*File, error) {
 	cc.mu.Lock()
 	defer cc.mu.Unlock()
 
-	file, err := cc.openFilepath(path)
+	conn, err := cc.connection()
 	if err != nil {
 		return nil, err
 	}
-	return &File{
+
+	file := &File{
 		Filename: filepath.Base(path),
-		Contents: file,
-	}, nil
+	}
+
+	dir, filename := filepath.Split(path)
+	if dir != "" {
+		// Jump to previous directory after command is done
+		wd, err := conn.CurrentDir()
+		if err != nil {
+			return nil, err
+		}
+
+		// On file Close move back to the directory we were previously in
+		file.cleanup = func() error {
+			err := conn.ChangeDir(wd)
+			if err != nil {
+				return fmt.Errorf("returning to %s failed: %w", wd, err)
+			}
+			return nil
+		}
+
+		// Move into directory to run the command
+		if err := conn.ChangeDir(dir); err != nil {
+			return nil, err
+		}
+	}
+
+	resp, err := conn.Retr(filename)
+	if err != nil {
+		return nil, fmt.Errorf("retrieving %s failed: %w", path, err)
+	}
+	file.Contents = resp
+
+	prev := file.cleanup
+	file.cleanup = func() error {
+		if resp != nil {
+			if err := resp.Close(); err != nil {
+				return fmt.Errorf("closing RETR %s response failed: %w", path, err)
+			}
+		}
+		return prev()
+	}
+
+	return file, nil
 }
 
 func (cc *client) Delete(path string) error {
@@ -379,45 +448,11 @@ func (cc *client) Walk(dir string, fn fs.WalkDirFunc) error {
 	return nil
 }
 
-func (cc *client) openFilepath(path string) (resp *ftp.Response, err error) {
-	conn, err := cc.connection()
-	if err != nil {
-		return nil, err
-	}
-
-	dir, filename := filepath.Split(path)
-	if dir != "" {
-		// Jump to previous directory after command is done
-		wd, err := conn.CurrentDir()
-		if err != nil {
-			return nil, err
-		}
-		defer func(previous string) {
-			// Return to our previous directory when initially called
-			if cleanupErr := conn.ChangeDir(previous); cleanupErr != nil {
-				err = fmt.Errorf("FTP: problem with readFiles: %w", cleanupErr)
-			}
-		}(wd)
-
-		// Move into directory to run the command
-		if err := conn.ChangeDir(dir); err != nil {
-			return nil, err
-		}
-	}
-
-	resp, err = conn.Retr(filename)
-	if err != nil {
-		return nil, fmt.Errorf("retrieving %s failed: %w", path, err)
-	}
-
-	return resp, nil
-}
-
 func readResponse(resp *ftp.Response) (io.ReadCloser, error) {
 	defer resp.Close()
 
 	var buf bytes.Buffer
-	n, err := io.Copy(&buf, resp)
+	n, err := io.Copy(&buf, bufio.NewReader(resp))
 	// If there was nothing downloaded and no error then assume it's a directory.
 	//
 	// The FTP client doesn't have a STAT command, so we can't quite ensure this

client_test.go

@@ -11,7 +11,9 @@ import (
 	"io/fs"
 	"math/rand"
 	"os"
+	"path/filepath"
 	"strings"
+	"sync"
 	"testing"
 	"time"
 
@@ -43,6 +45,30 @@ func TestClient(t *testing.T) {
 		require.Equal(t, "hello world", strings.TrimSpace(buf.String()))
 	})
 
+	t.Run("open larger files", func(t *testing.T) {
+		largerFileSize := size(t, filepath.Join("testdata", "ftp-server", "bigdata", "large.txt"))
+
+		const iterations = 10
+		var wg sync.WaitGroup
+		wg.Add(iterations)
+		for i := 0; i < iterations; i++ {
+			go func(wg *sync.WaitGroup) {
+				defer wg.Done()
+
+				file, err := client.Open("/bigdata/large.txt")
+				require.NoError(t, err)
+
+				var buf bytes.Buffer
+				_, err = io.Copy(&buf, file)
+				require.NoError(t, err)
+
+				require.NoError(t, file.Close())
+				require.Equal(t, largerFileSize, len(buf.Bytes()))
+			}(&wg)
+		}
+		wg.Wait()
+	})
+
 	t.Run("reader", func(t *testing.T) {
 		file, err := client.Reader("archive/old.txt")
 		require.NoError(t, err)
@@ -53,6 +79,23 @@ func TestClient(t *testing.T) {
 		require.Equal(t, "previous data", strings.TrimSpace(buf.String()))
 	})
 
+	t.Run("read larger files", func(t *testing.T) {
+		largerFileSize := size(t, filepath.Join("testdata", "ftp-server", "bigdata", "large.txt"))
+
+		// reader must process files in sequence
+		for i := 0; i < 10; i++ {
+			file, err := client.Reader("/bigdata/large.txt")
+			require.NoError(t, err)
+
+			var buf bytes.Buffer
+			_, err = io.Copy(&buf, file)
+			require.NoError(t, err)
+
+			require.NoError(t, file.Close())
+			require.Equal(t, largerFileSize, len(buf.Bytes()))
+		}
+	})
+
 	t.Run("upload and delete", func(t *testing.T) {
 		body := io.NopCloser(strings.NewReader("example data"))
 		err := client.UploadFile("new.txt", body)
@@ -151,7 +194,7 @@ func TestClient(t *testing.T) {
 		})
 		require.NoError(t, err)
 		require.ElementsMatch(t, found, []string{
-			"Upper/names.txt",
+			"Upper/names.txt", "bigdata/large.txt",
 			"first.txt", "second.txt", "empty.txt",
 			"archive/old.txt", "archive/empty2.txt",
 			"with-empty/EMPTY1.txt", "with-empty/empty_file2.txt",
@@ -256,3 +299,15 @@ func TestClient__tlsDialOption(t *testing.T) {
 	require.NotNil(t, client)
 	require.NoError(t, client.Close())
 }
+
+func size(t *testing.T, where string) int {
+	t.Helper()
+
+	fd, err := os.Open(where)
+	require.NoError(t, err)
+
+	info, err := fd.Stat()
+	require.NoError(t, err)
+
+	return int(info.Size())
+}

file.go

@@ -22,6 +22,8 @@ type File struct {
 	ModTime time.Time
 
 	fileinfo fs.FileInfo
+
+	cleanup func() error
 }
 
 var _ fs.File = (&File{})
@@ -31,7 +33,14 @@ func (f *File) Close() error {
 		return nil
 	}
 	if f.Contents != nil {
-		return f.Contents.Close()
+		if err := f.Contents.Close(); err != nil {
+			return err
+		}
+	}
+	if f.cleanup != nil {
+		if err := f.cleanup(); err != nil {
+			return err
+		}
 	}
 	return nil
 }