Retry on EOF errors in the SFTP backend

src/duplicacy_sftpstorage.go

@@ -14,6 +14,7 @@ import (
 	"runtime"
 	"strings"
 	"time"
+	"sync"
 
 	"github.com/pkg/sftp"
 	"golang.org/x/crypto/ssh"
@@ -23,9 +24,13 @@ type SFTPStorage struct {
 	StorageBase
 
 	client          *sftp.Client
+	clientLock      sync.Mutex
 	minimumNesting  int // The minimum level of directories to dive into before searching for the chunk file.
 	storageDir      string
 	numberOfThreads int
+	numberOfTries   int
+	serverAddress   string
+	sftpConfig      *ssh.ClientConfig
 }
 
 func CreateSFTPStorageWithPassword(server string, port int, username string, storageDir string,
@@ -86,6 +91,9 @@ func CreateSFTPStorage(server string, port int, username string, storageDir stri
 		storageDir:      storageDir,
 		minimumNesting:  minimumNesting,
 		numberOfThreads: threads,
+		numberOfTries:   6,
+		serverAddress:   serverAddress,
+		sftpConfig:      sftpConfig,
 	}
 
 	// Random number fo generating the temporary chunk file suffix.
@@ -99,13 +107,60 @@ func CreateSFTPStorage(server string, port int, username string, storageDir stri
 }
 
 func CloseSFTPStorage(storage *SFTPStorage) {
-	storage.client.Close()
+	if storage.client != nil {
+		storage.client.Close()
+		storage.client = nil
+	}
 }
 
+func (storage *SFTPStorage) getSFTPClient() *sftp.Client {
+	storage.clientLock.Lock()
+	defer storage.clientLock.Unlock()
+	return storage.client
+}
+
+func (storage *SFTPStorage) retry(f func () error) error {
+	delay := time.Second
+	for i := 0;; i++ {
+		err := f()
+		if err != nil && strings.Contains(err.Error(), "EOF") && i < storage.numberOfTries {
+			LOG_WARN("SFTP_RETRY", "Encountered an error (%v); retry after %d second(s)", err, delay/time.Second)
+			time.Sleep(delay)
+			delay *= 2
+
+			storage.clientLock.Lock()
+			if storage.client != nil {
+				storage.client.Close()
+				storage.client = nil
+			}
+
+			connection, err := ssh.Dial("tcp", storage.serverAddress, storage.sftpConfig)
+			if err != nil {
+				storage.clientLock.Unlock()
+				return err
+			}
+
+			client, err := sftp.NewClient(connection)
+			if err != nil {
+				connection.Close()
+				storage.clientLock.Unlock()
+				return err
+			}
+			storage.client = client
+			storage.clientLock.Unlock()
+			continue
+		}
+		return err
+	}
+}
 // ListFiles return the list of files and subdirectories under 'file' (non-recursively)
 func (storage *SFTPStorage) ListFiles(threadIndex int, dirPath string) (files []string, sizes []int64, err error) {
 
-	entries, err := storage.client.ReadDir(path.Join(storage.storageDir, dirPath))
+	var entries []os.FileInfo
+	err = storage.retry(func() error {
+		entries, err = storage.getSFTPClient().ReadDir(path.Join(storage.storageDir, dirPath))
+		return err
+	})
 	if err != nil {
 		return nil, nil, err
 	}
@@ -126,7 +181,11 @@ func (storage *SFTPStorage) ListFiles(threadIndex int, dirPath string) (files []
 // DeleteFile deletes the file or directory at 'filePath'.
 func (storage *SFTPStorage) DeleteFile(threadIndex int, filePath string) (err error) {
 	fullPath := path.Join(storage.storageDir, filePath)
-	fileInfo, err := storage.client.Stat(fullPath)
+	var fileInfo os.FileInfo
+	err = storage.retry(func() error {
+		fileInfo, err = storage.getSFTPClient().Stat(fullPath)
+		return err
+	})
 	if err != nil {
 		if os.IsNotExist(err) {
 			LOG_TRACE("SFTP_STORAGE", "File %s has disappeared before deletion", filePath)
@@ -137,33 +196,47 @@ func (storage *SFTPStorage) DeleteFile(threadIndex int, filePath string) (err er
 	if fileInfo == nil {
 		return nil
 	}
-	return storage.client.Remove(path.Join(storage.storageDir, filePath))
+	return storage.retry(func() error { return storage.getSFTPClient().Remove(path.Join(storage.storageDir, filePath)) })
 }
 
 // MoveFile renames the file.
 func (storage *SFTPStorage) MoveFile(threadIndex int, from string, to string) (err error) {
 	toPath := path.Join(storage.storageDir, to)
-	fileInfo, err := storage.client.Stat(toPath)
+	var fileInfo os.FileInfo
+	err = storage.retry(func() error {
+		fileInfo, err = storage.getSFTPClient().Stat(toPath)
+		return err
+	})
 	if fileInfo != nil {
 		return fmt.Errorf("The destination file %s already exists", toPath)
 	}
-	return storage.client.Rename(path.Join(storage.storageDir, from),
-		path.Join(storage.storageDir, to))
+	err = storage.retry(func() error { return storage.getSFTPClient().Rename(path.Join(storage.storageDir, from),
+		path.Join(storage.storageDir, to)) })
+	return err
 }
 
 // CreateDirectory creates a new directory.
 func (storage *SFTPStorage) CreateDirectory(threadIndex int, dirPath string) (err error) {
 	fullPath := path.Join(storage.storageDir, dirPath)
-	fileInfo, err := storage.client.Stat(fullPath)
+	var fileInfo os.FileInfo
+	err = storage.retry(func() error {
+		fileInfo, err = storage.getSFTPClient().Stat(fullPath)
+		return err
+	})
 	if fileInfo != nil && fileInfo.IsDir() {
 		return nil
 	}
-	return storage.client.Mkdir(path.Join(storage.storageDir, dirPath))
+	return storage.retry(func() error { return storage.getSFTPClient().Mkdir(path.Join(storage.storageDir, dirPath)) })
 }
 
 // GetFileInfo returns the information about the file or directory at 'filePath'.
 func (storage *SFTPStorage) GetFileInfo(threadIndex int, filePath string) (exist bool, isDir bool, size int64, err error) {
-	fileInfo, err := storage.client.Stat(path.Join(storage.storageDir, filePath))
+	var fileInfo os.FileInfo
+	err = storage.retry(func() error {
+		fileInfo, err = storage.getSFTPClient().Stat(path.Join(storage.storageDir, filePath))
+		return err
+	})
+
 	if err != nil {
 		if os.IsNotExist(err) {
 			return false, false, 0, nil
@@ -181,18 +254,19 @@ func (storage *SFTPStorage) GetFileInfo(threadIndex int, filePath string) (exist
 
 // DownloadFile reads the file at 'filePath' into the chunk.
 func (storage *SFTPStorage) DownloadFile(threadIndex int, filePath string, chunk *Chunk) (err error) {
-	file, err := storage.client.Open(path.Join(storage.storageDir, filePath))
+	return storage.retry(func() error {
+		file, err := storage.getSFTPClient().Open(path.Join(storage.storageDir, filePath))
 
-	if err != nil {
-		return err
-	}
+		if err != nil {
+			return err
+		}
 
-	defer file.Close()
-	if _, err = RateLimitedCopy(chunk, file, storage.DownloadRateLimit/storage.numberOfThreads); err != nil {
-		return err
-	}
-
-	return nil
+		defer file.Close()
+		if _, err = RateLimitedCopy(chunk, file, storage.DownloadRateLimit/storage.numberOfThreads); err != nil {
+			return err
+		}
+		return nil
+	})
 }
 
 // UploadFile writes 'content' to the file at 'filePath'.
@@ -203,20 +277,26 @@ func (storage *SFTPStorage) UploadFile(threadIndex int, filePath string, content
 	dirs := strings.Split(filePath, "/")
 	if len(dirs) > 1 {
 		fullDir := path.Dir(fullPath)
-		_, err := storage.client.Stat(fullDir)
+		err = storage.retry(func() error {
+			_, err := storage.getSFTPClient().Stat(fullDir)
+			return err
+		})
 		if err != nil {
 			// The error may be caused by a non-existent fullDir, or a broken connection.  In either case,
 			// we just assume it is the former because there isn't a way to tell which is the case.
 			for i, _ := range dirs[1 : len(dirs)-1] {
 				subDir := path.Join(storage.storageDir, path.Join(dirs[0:i+2]...))
 				// We don't check the error; just keep going blindly but always store the last err
-				err = storage.client.Mkdir(subDir)
+				err = storage.getSFTPClient().Mkdir(subDir)
 			}
 
 			// If there is an error creating the dirs, we check fullDir one more time, because another thread
 			// may happen to create the same fullDir ahead of this thread
 			if err != nil {
-				_, err := storage.client.Stat(fullDir)
+				err = storage.retry(func() error {
+					_, err := storage.getSFTPClient().Stat(fullDir)
+					return err
+				})
 				if err != nil {
 					return err
 				}
@@ -224,39 +304,41 @@ func (storage *SFTPStorage) UploadFile(threadIndex int, filePath string, content
 		}
 	}
 
-	letters := "abcdefghijklmnopqrstuvwxyz"
-	suffix := make([]byte, 8)
-	for i := range suffix {
-		suffix[i] = letters[rand.Intn(len(letters))]
-	}
+	return storage.retry(func() error {
 
-	temporaryFile := fullPath + "." + string(suffix) + ".tmp"
-
-	file, err := storage.client.OpenFile(temporaryFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC)
-	if err != nil {
-		return err
-	}
-
-	reader := CreateRateLimitedReader(content, storage.UploadRateLimit/storage.numberOfThreads)
-	_, err = io.Copy(file, reader)
-	if err != nil {
-		file.Close()
-		return err
-	}
-	file.Close()
-
-	err = storage.client.Rename(temporaryFile, fullPath)
-	if err != nil {
-
-		if _, err = storage.client.Stat(fullPath); err == nil {
-			storage.client.Remove(temporaryFile)
-			return nil
-		} else {
-			return fmt.Errorf("Uploaded file but failed to store it at %s: %v", fullPath, err)
+		letters := "abcdefghijklmnopqrstuvwxyz"
+		suffix := make([]byte, 8)
+		for i := range suffix {
+			suffix[i] = letters[rand.Intn(len(letters))]
 		}
-	}
 
-	return nil
+		temporaryFile := fullPath + "." + string(suffix) + ".tmp"
+
+		file, err := storage.getSFTPClient().OpenFile(temporaryFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC)
+		if err != nil {
+			return err
+		}
+
+		reader := CreateRateLimitedReader(content, storage.UploadRateLimit/storage.numberOfThreads)
+		_, err = io.Copy(file, reader)
+		if err != nil {
+			file.Close()
+			return err
+		}
+		file.Close()
+
+		err = storage.getSFTPClient().Rename(temporaryFile, fullPath)
+		if err != nil {
+			if _, err = storage.getSFTPClient().Stat(fullPath); err == nil {
+				storage.getSFTPClient().Remove(temporaryFile)
+				return nil
+			} else {
+				return fmt.Errorf("Uploaded file but failed to store it at %s: %v", fullPath, err)
+			}
+		}
+
+		return nil
+	})
 }
 
 // If a local snapshot cache is needed for the storage to avoid downloading/uploading chunks too often when