Add support for zstd compression (#249)

Co-authored-by: Michal Middleton <jafa81@gmail.com>

Dockerfile

@@ -1,7 +1,7 @@
 # Copyright 2021 - Offen Authors <hioffen@posteo.de>
 # SPDX-License-Identifier: MPL-2.0
 
-FROM golang:1.20-alpine as builder
+FROM golang:1.21-alpine as builder
 
 WORKDIR /app
 COPY . .
@@ -13,7 +13,7 @@ FROM alpine:3.18
 
 WORKDIR /root
 
-RUN apk add --no-cache ca-certificates busybox-extras
+RUN apk add --no-cache ca-certificates
 
 COPY --from=builder /app/cmd/backup/backup /usr/bin/backup
 COPY --chmod=755 ./entrypoint.sh /root/

README.md

@@ -148,13 +148,22 @@ You can populate below template according to your requirements and use it as you
 
 # BACKUP_CRON_EXPRESSION="0 2 * * *"
 
-# The name of the backup file including the `.tar.gz` extension.
+# The compression algorithm used in conjunction with tar.
+# Valid options are: "gz" (Gzip) and "zst" (Zstd).
+# Note that the selection affects the file extension.
+
+# BACKUP_COMPRESSION="gz"
+
+# The name of the backup file including the extension.
 # Format verbs will be replaced as in `strftime`. Omitting them
 # will result in the same filename for every backup run, which means previous
-# versions will be overwritten on subsequent runs. The default results
-# in filenames like `backup-2021-08-29T04-00-00.tar.gz`.
+# versions will be overwritten on subsequent runs.
+# Extension can be defined literally or via "{{ .Extension }}" template,
+# in which case it will become either "tar.gz" or "tar.zst" (depending
+# on your BACKUP_COMPRESSION setting).
+# The default results in filenames like: `backup-2021-08-29T04-00-00.tar.gz`.
 
-# BACKUP_FILENAME="backup-%Y-%m-%dT%H-%M-%S.tar.gz"
+# BACKUP_FILENAME="backup-%Y-%m-%dT%H-%M-%S.{{ .Extension }}"
 
 # Setting BACKUP_FILENAME_EXPAND to true allows for environment variable
 # placeholders in BACKUP_FILENAME, BACKUP_LATEST_SYMLINK and in

cmd/backup/archive.go

@@ -15,9 +15,11 @@ import (
 	"path"
 	"path/filepath"
 	"strings"
+
+	"github.com/klauspost/compress/zstd"
 )
 
-func createArchive(files []string, inputFilePath, outputFilePath string) error {
+func createArchive(files []string, inputFilePath, outputFilePath string, compression string) error {
 	inputFilePath = stripTrailingSlashes(inputFilePath)
 	inputFilePath, outputFilePath, err := makeAbsolute(inputFilePath, outputFilePath)
 	if err != nil {
@@ -27,7 +29,7 @@ func createArchive(files []string, inputFilePath, outputFilePath string) error {
 		return fmt.Errorf("createArchive: error creating output file path: %w", err)
 	}
 
-	if err := compress(files, outputFilePath, filepath.Dir(inputFilePath)); err != nil {
+	if err := compress(files, outputFilePath, filepath.Dir(inputFilePath), compression); err != nil {
 		return fmt.Errorf("createArchive: error creating archive: %w", err)
 	}
 
@@ -51,18 +53,30 @@ func makeAbsolute(inputFilePath, outputFilePath string) (string, string, error)
 	return inputFilePath, outputFilePath, err
 }
 
-func compress(paths []string, outFilePath, subPath string) error {
+func compress(paths []string, outFilePath, subPath string, algo string) error {
 	file, err := os.Create(outFilePath)
+	var compressWriter io.WriteCloser
 	if err != nil {
 		return fmt.Errorf("compress: error creating out file: %w", err)
 	}
 
 	prefix := path.Dir(outFilePath)
-	gzipWriter := gzip.NewWriter(file)
-	tarWriter := tar.NewWriter(gzipWriter)
+	switch algo {
+	case "gz":
+		compressWriter = gzip.NewWriter(file)
+	case "zst":
+		compressWriter, err = zstd.NewWriter(file)
+		if err != nil {
+			return fmt.Errorf("compress: zstd error: %w", err)
+		}
+	default:
+		return fmt.Errorf("compress: unsupported compression algorithm: %s", algo)
+	}
+
+	tarWriter := tar.NewWriter(compressWriter)
 
 	for _, p := range paths {
-		if err := writeTarGz(p, tarWriter, prefix); err != nil {
+		if err := writeTarball(p, tarWriter, prefix); err != nil {
 			return fmt.Errorf("compress: error writing %s to archive: %w", p, err)
 		}
 	}
@@ -72,9 +86,9 @@ func compress(paths []string, outFilePath, subPath string) error {
 		return fmt.Errorf("compress: error closing tar writer: %w", err)
 	}
 
-	err = gzipWriter.Close()
+	err = compressWriter.Close()
 	if err != nil {
-		return fmt.Errorf("compress: error closing gzip writer: %w", err)
+		return fmt.Errorf("compress: error closing compression writer: %w", err)
 	}
 
 	err = file.Close()
@@ -85,10 +99,10 @@ func compress(paths []string, outFilePath, subPath string) error {
 	return nil
 }
 
-func writeTarGz(path string, tarWriter *tar.Writer, prefix string) error {
+func writeTarball(path string, tarWriter *tar.Writer, prefix string) error {
 	fileInfo, err := os.Lstat(path)
 	if err != nil {
-		return fmt.Errorf("writeTarGz: error getting file infor for %s: %w", path, err)
+		return fmt.Errorf("writeTarball: error getting file infor for %s: %w", path, err)
 	}
 
 	if fileInfo.Mode()&os.ModeSocket == os.ModeSocket {
@@ -99,19 +113,19 @@ func writeTarGz(path string, tarWriter *tar.Writer, prefix string) error {
 	if fileInfo.Mode()&os.ModeSymlink == os.ModeSymlink {
 		var err error
 		if link, err = os.Readlink(path); err != nil {
-			return fmt.Errorf("writeTarGz: error resolving symlink %s: %w", path, err)
+			return fmt.Errorf("writeTarball: error resolving symlink %s: %w", path, err)
 		}
 	}
 
 	header, err := tar.FileInfoHeader(fileInfo, link)
 	if err != nil {
-		return fmt.Errorf("writeTarGz: error getting file info header: %w", err)
+		return fmt.Errorf("writeTarball: error getting file info header: %w", err)
 	}
 	header.Name = strings.TrimPrefix(path, prefix)
 
 	err = tarWriter.WriteHeader(header)
 	if err != nil {
-		return fmt.Errorf("writeTarGz: error writing file info header: %w", err)
+		return fmt.Errorf("writeTarball: error writing file info header: %w", err)
 	}
 
 	if !fileInfo.Mode().IsRegular() {
@@ -120,13 +134,13 @@ func writeTarGz(path string, tarWriter *tar.Writer, prefix string) error {
 
 	file, err := os.Open(path)
 	if err != nil {
-		return fmt.Errorf("writeTarGz: error opening %s: %w", path, err)
+		return fmt.Errorf("writeTarball: error opening %s: %w", path, err)
 	}
 	defer file.Close()
 
 	_, err = io.Copy(tarWriter, file)
 	if err != nil {
-		return fmt.Errorf("writeTarGz: error copying %s to tar writer: %w", path, err)
+		return fmt.Errorf("writeTarball: error copying %s to tar writer: %w", path, err)
 	}
 
 	return nil

cmd/backup/config.go

@@ -16,59 +16,60 @@ import (
 // Config holds all configuration values that are expected to be set
 // by users.
 type Config struct {
-	AwsS3BucketName               string        `split_words:"true"`
-	AwsS3Path                     string        `split_words:"true"`
-	AwsEndpoint                   string        `split_words:"true" default:"s3.amazonaws.com"`
-	AwsEndpointProto              string        `split_words:"true" default:"https"`
-	AwsEndpointInsecure           bool          `split_words:"true"`
-	AwsEndpointCACert             CertDecoder   `envconfig:"AWS_ENDPOINT_CA_CERT"`
-	AwsStorageClass               string        `split_words:"true"`
-	AwsAccessKeyID                string        `envconfig:"AWS_ACCESS_KEY_ID"`
-	AwsAccessKeyIDFile            string        `envconfig:"AWS_ACCESS_KEY_ID_FILE"`
-	AwsSecretAccessKey            string        `split_words:"true"`
-	AwsSecretAccessKeyFile        string        `split_words:"true"`
-	AwsIamRoleEndpoint            string        `split_words:"true"`
-	AwsPartSize                   int64         `split_words:"true"`
-	BackupSources                 string        `split_words:"true" default:"/backup"`
-	BackupFilename                string        `split_words:"true" default:"backup-%Y-%m-%dT%H-%M-%S.tar.gz"`
-	BackupFilenameExpand          bool          `split_words:"true"`
-	BackupLatestSymlink           string        `split_words:"true"`
-	BackupArchive                 string        `split_words:"true" default:"/archive"`
-	BackupRetentionDays           int32         `split_words:"true" default:"-1"`
-	BackupPruningLeeway           time.Duration `split_words:"true" default:"1m"`
-	BackupPruningPrefix           string        `split_words:"true"`
-	BackupStopContainerLabel      string        `split_words:"true" default:"true"`
-	BackupFromSnapshot            bool          `split_words:"true"`
-	BackupExcludeRegexp           RegexpDecoder `split_words:"true"`
-	GpgPassphrase                 string        `split_words:"true"`
-	NotificationURLs              []string      `envconfig:"NOTIFICATION_URLS"`
-	NotificationLevel             string        `split_words:"true" default:"error"`
-	EmailNotificationRecipient    string        `split_words:"true"`
-	EmailNotificationSender       string        `split_words:"true" default:"noreply@nohost"`
-	EmailSMTPHost                 string        `envconfig:"EMAIL_SMTP_HOST"`
-	EmailSMTPPort                 int           `envconfig:"EMAIL_SMTP_PORT" default:"587"`
-	EmailSMTPUsername             string        `envconfig:"EMAIL_SMTP_USERNAME"`
-	EmailSMTPPassword             string        `envconfig:"EMAIL_SMTP_PASSWORD"`
-	WebdavUrl                     string        `split_words:"true"`
-	WebdavUrlInsecure             bool          `split_words:"true"`
-	WebdavPath                    string        `split_words:"true" default:"/"`
-	WebdavUsername                string        `split_words:"true"`
-	WebdavPassword                string        `split_words:"true"`
-	SSHHostName                   string        `split_words:"true"`
-	SSHPort                       string        `split_words:"true" default:"22"`
-	SSHUser                       string        `split_words:"true"`
-	SSHPassword                   string        `split_words:"true"`
-	SSHIdentityFile               string        `split_words:"true" default:"/root/.ssh/id_rsa"`
-	SSHIdentityPassphrase         string        `split_words:"true"`
-	SSHRemotePath                 string        `split_words:"true"`
-	ExecLabel                     string        `split_words:"true"`
-	ExecForwardOutput             bool          `split_words:"true"`
-	LockTimeout                   time.Duration `split_words:"true" default:"60m"`
-	AzureStorageAccountName       string        `split_words:"true"`
-	AzureStoragePrimaryAccountKey string        `split_words:"true"`
-	AzureStorageContainerName     string        `split_words:"true"`
-	AzureStoragePath              string        `split_words:"true"`
-	AzureStorageEndpoint          string        `split_words:"true" default:"https://{{ .AccountName }}.blob.core.windows.net/"`
+	AwsS3BucketName               string          `split_words:"true"`
+	AwsS3Path                     string          `split_words:"true"`
+	AwsEndpoint                   string          `split_words:"true" default:"s3.amazonaws.com"`
+	AwsEndpointProto              string          `split_words:"true" default:"https"`
+	AwsEndpointInsecure           bool            `split_words:"true"`
+	AwsEndpointCACert             CertDecoder     `envconfig:"AWS_ENDPOINT_CA_CERT"`
+	AwsStorageClass               string          `split_words:"true"`
+	AwsAccessKeyID                string          `envconfig:"AWS_ACCESS_KEY_ID"`
+	AwsAccessKeyIDFile            string          `envconfig:"AWS_ACCESS_KEY_ID_FILE"`
+	AwsSecretAccessKey            string          `split_words:"true"`
+	AwsSecretAccessKeyFile        string          `split_words:"true"`
+	AwsIamRoleEndpoint            string          `split_words:"true"`
+	AwsPartSize                   int64           `split_words:"true"`
+	BackupCompression             CompressionType `split_words:"true" default:"gz"`
+	BackupSources                 string          `split_words:"true" default:"/backup"`
+	BackupFilename                string          `split_words:"true" default:"backup-%Y-%m-%dT%H-%M-%S.{{ .Extension }}"`
+	BackupFilenameExpand          bool            `split_words:"true"`
+	BackupLatestSymlink           string          `split_words:"true"`
+	BackupArchive                 string          `split_words:"true" default:"/archive"`
+	BackupRetentionDays           int32           `split_words:"true" default:"-1"`
+	BackupPruningLeeway           time.Duration   `split_words:"true" default:"1m"`
+	BackupPruningPrefix           string          `split_words:"true"`
+	BackupStopContainerLabel      string          `split_words:"true" default:"true"`
+	BackupFromSnapshot            bool            `split_words:"true"`
+	BackupExcludeRegexp           RegexpDecoder   `split_words:"true"`
+	GpgPassphrase                 string          `split_words:"true"`
+	NotificationURLs              []string        `envconfig:"NOTIFICATION_URLS"`
+	NotificationLevel             string          `split_words:"true" default:"error"`
+	EmailNotificationRecipient    string          `split_words:"true"`
+	EmailNotificationSender       string          `split_words:"true" default:"noreply@nohost"`
+	EmailSMTPHost                 string          `envconfig:"EMAIL_SMTP_HOST"`
+	EmailSMTPPort                 int             `envconfig:"EMAIL_SMTP_PORT" default:"587"`
+	EmailSMTPUsername             string          `envconfig:"EMAIL_SMTP_USERNAME"`
+	EmailSMTPPassword             string          `envconfig:"EMAIL_SMTP_PASSWORD"`
+	WebdavUrl                     string          `split_words:"true"`
+	WebdavUrlInsecure             bool            `split_words:"true"`
+	WebdavPath                    string          `split_words:"true" default:"/"`
+	WebdavUsername                string          `split_words:"true"`
+	WebdavPassword                string          `split_words:"true"`
+	SSHHostName                   string          `split_words:"true"`
+	SSHPort                       string          `split_words:"true" default:"22"`
+	SSHUser                       string          `split_words:"true"`
+	SSHPassword                   string          `split_words:"true"`
+	SSHIdentityFile               string          `split_words:"true" default:"/root/.ssh/id_rsa"`
+	SSHIdentityPassphrase         string          `split_words:"true"`
+	SSHRemotePath                 string          `split_words:"true"`
+	ExecLabel                     string          `split_words:"true"`
+	ExecForwardOutput             bool            `split_words:"true"`
+	LockTimeout                   time.Duration   `split_words:"true" default:"60m"`
+	AzureStorageAccountName       string          `split_words:"true"`
+	AzureStoragePrimaryAccountKey string          `split_words:"true"`
+	AzureStorageContainerName     string          `split_words:"true"`
+	AzureStoragePath              string          `split_words:"true"`
+	AzureStorageEndpoint          string          `split_words:"true" default:"https://{{ .AccountName }}.blob.core.windows.net/"`
 }
 
 func (c *Config) resolveSecret(envVar string, secretPath string) (string, error) {
@@ -82,6 +83,22 @@ func (c *Config) resolveSecret(envVar string, secretPath string) (string, error)
 	return string(data), nil
 }
 
+type CompressionType string
+
+func (c *CompressionType) Decode(v string) error {
+	switch v {
+	case "gz", "zst":
+		*c = CompressionType(v)
+		return nil
+	default:
+		return fmt.Errorf("config: error decoding compression type %s", v)
+	}
+}
+
+func (c *CompressionType) String() string {
+	return string(*c)
+}
+
 type CertDecoder struct {
 	Cert *x509.Certificate
 }

cmd/backup/exec.go

@@ -160,7 +160,7 @@ func (s *script) runLabeledCommands(label string) error {
 			userLabelName := fmt.Sprintf("%s.user", label)
 			user := c.Labels[userLabelName]
 
-			s.logger.Infof("Running %s command %s for container %s", label, cmd, strings.TrimPrefix(c.Names[0], "/"))
+			s.logger.Info(fmt.Sprintf("Running %s command %s for container %s", label, cmd, strings.TrimPrefix(c.Names[0], "/")))
 			stdout, stderr, err := s.exec(c.ID, cmd, user)
 			if s.c.ExecForwardOutput {
 				os.Stderr.Write(stderr)

cmd/backup/lock.go

@@ -41,9 +41,11 @@ func (s *script) lock(lockfile string) (func() error, error) {
 		}
 
 		if !s.encounteredLock {
-			s.logger.Infof(
-				"Exclusive lock was not available on first attempt. Will retry until it becomes available or the timeout of %s is exceeded.",
-				s.c.LockTimeout,
+			s.logger.Info(
+				fmt.Sprintf(
+					"Exclusive lock was not available on first attempt. Will retry until it becomes available or the timeout of %s is exceeded.",
+					s.c.LockTimeout,
+				),
 			)
 			s.encounteredLock = true
 		}

cmd/backup/main.go

@@ -4,6 +4,7 @@
 package main
 
 import (
+	"fmt"
 	"os"
 )
 
@@ -21,7 +22,9 @@ func main() {
 		if pArg := recover(); pArg != nil {
 			if err, ok := pArg.(error); ok {
 				if hookErr := s.runHooks(err); hookErr != nil {
-					s.logger.Errorf("An error occurred calling the registered hooks: %s", hookErr)
+					s.logger.Error(
+						fmt.Sprintf("An error occurred calling the registered hooks: %s", hookErr),
+					)
 				}
 				os.Exit(1)
 			}
@@ -29,9 +32,12 @@ func main() {
 		}
 
 		if err := s.runHooks(nil); err != nil {
-			s.logger.Errorf(
-				"Backup procedure ran successfully, but an error ocurred calling the registered hooks: %v",
-				err,
+			s.logger.Error(
+				fmt.Sprintf(
+
+					"Backup procedure ran successfully, but an error ocurred calling the registered hooks: %v",
+					err,
+				),
 			)
 			os.Exit(1)
 		}

cmd/backup/script.go

@@ -4,11 +4,13 @@
 package main
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"fmt"
 	"io"
 	"io/fs"
+	"log/slog"
 	"os"
 	"path"
 	"path/filepath"
@@ -32,7 +34,6 @@ import (
 	"github.com/kelseyhightower/envconfig"
 	"github.com/leekchan/timeutil"
 	"github.com/otiai10/copy"
-	"github.com/sirupsen/logrus"
 	"golang.org/x/crypto/openpgp"
 	"golang.org/x/sync/errgroup"
 )
@@ -42,7 +43,7 @@ import (
 type script struct {
 	cli       *client.Client
 	storages  []storage.Backend
-	logger    *logrus.Logger
+	logger    *slog.Logger
 	sender    *router.ServiceRouter
 	template  *template.Template
 	hooks     []hook
@@ -63,13 +64,8 @@ type script struct {
 func newScript() (*script, error) {
 	stdOut, logBuffer := buffer(os.Stdout)
 	s := &script{
-		c: &Config{},
-		logger: &logrus.Logger{
-			Out:       stdOut,
-			Formatter: new(logrus.TextFormatter),
-			Hooks:     make(logrus.LevelHooks),
-			Level:     logrus.InfoLevel,
-		},
+		c:      &Config{},
+		logger: slog.New(slog.NewTextHandler(stdOut, nil)),
 		stats: &Stats{
 			StartTime: time.Now(),
 			LogOutput: logBuffer,
@@ -94,6 +90,20 @@ func newScript() (*script, error) {
 	}
 
 	s.file = path.Join("/tmp", s.c.BackupFilename)
+
+	tmplFileName, tErr := template.New("extension").Parse(s.file)
+	if tErr != nil {
+		return nil, fmt.Errorf("newScript: unable to parse backup file extension template: %w", tErr)
+	}
+
+	var bf bytes.Buffer
+	if tErr := tmplFileName.Execute(&bf, map[string]string{
+		"Extension": fmt.Sprintf("tar.%s", s.c.BackupCompression),
+	}); tErr != nil {
+		return nil, fmt.Errorf("newScript: error executing backup file extension template: %w", tErr)
+	}
+	s.file = bf.String()
+
 	if s.c.BackupFilenameExpand {
 		s.file = os.ExpandEnv(s.file)
 		s.c.BackupLatestSymlink = os.ExpandEnv(s.c.BackupLatestSymlink)
@@ -114,12 +124,12 @@ func newScript() (*script, error) {
 	logFunc := func(logType storage.LogLevel, context string, msg string, params ...any) {
 		switch logType {
 		case storage.LogLevelWarning:
-			s.logger.Warnf("["+context+"] "+msg, params...)
+			s.logger.Warn(fmt.Sprintf("["+context+"] "+msg, params...))
 		case storage.LogLevelError:
-			s.logger.Errorf("["+context+"] "+msg, params...)
+			s.logger.Error(fmt.Sprintf("["+context+"] "+msg, params...))
 		case storage.LogLevelInfo:
 		default:
-			s.logger.Infof("["+context+"] "+msg, params...)
+			s.logger.Info(fmt.Sprintf("["+context+"] "+msg, params...))
 		}
 	}
 
@@ -306,11 +316,13 @@ func (s *script) stopContainers() (func() error, error) {
 		return noop, nil
 	}
 
-	s.logger.Infof(
-		"Stopping %d container(s) labeled `%s` out of %d running container(s).",
-		len(containersToStop),
-		containerLabel,
-		len(allContainers),
+	s.logger.Info(
+		fmt.Sprintf(
+			"Stopping %d container(s) labeled `%s` out of %d running container(s).",
+			len(containersToStop),
+			containerLabel,
+			len(allContainers),
+		),
 	)
 
 	var stoppedContainers []types.Container
@@ -382,9 +394,11 @@ func (s *script) stopContainers() (func() error, error) {
 				errors.Join(restartErrors...),
 			)
 		}
-		s.logger.Infof(
-			"Restarted %d container(s) and the matching service(s).",
-			len(stoppedContainers),
+		s.logger.Info(
+			fmt.Sprintf(
+				"Restarted %d container(s) and the matching service(s).",
+				len(stoppedContainers),
+			),
 		)
 		return nil
 	}, stopError
@@ -408,7 +422,9 @@ func (s *script) createArchive() error {
 			if err := remove(backupSources); err != nil {
 				return fmt.Errorf("createArchive: error removing snapshot: %w", err)
 			}
-			s.logger.Infof("Removed snapshot `%s`.", backupSources)
+			s.logger.Info(
+				fmt.Sprintf("Removed snapshot `%s`.", backupSources),
+			)
 			return nil
 		})
 		if err := copy.Copy(s.c.BackupSources, backupSources, copy.Options{
@@ -417,7 +433,9 @@ func (s *script) createArchive() error {
 		}); err != nil {
 			return fmt.Errorf("createArchive: error creating snapshot: %w", err)
 		}
-		s.logger.Infof("Created snapshot of `%s` at `%s`.", s.c.BackupSources, backupSources)
+		s.logger.Info(
+			fmt.Sprintf("Created snapshot of `%s` at `%s`.", s.c.BackupSources, backupSources),
+		)
 	}
 
 	tarFile := s.file
@@ -425,7 +443,9 @@ func (s *script) createArchive() error {
 		if err := remove(tarFile); err != nil {
 			return fmt.Errorf("createArchive: error removing tar file: %w", err)
 		}
-		s.logger.Infof("Removed tar file `%s`.", tarFile)
+		s.logger.Info(
+			fmt.Sprintf("Removed tar file `%s`.", tarFile),
+		)
 		return nil
 	})
 
@@ -449,11 +469,13 @@ func (s *script) createArchive() error {
 		return fmt.Errorf("createArchive: error walking filesystem tree: %w", err)
 	}
 
-	if err := createArchive(filesEligibleForBackup, backupSources, tarFile); err != nil {
+	if err := createArchive(filesEligibleForBackup, backupSources, tarFile, s.c.BackupCompression.String()); err != nil {
 		return fmt.Errorf("createArchive: error compressing backup folder: %w", err)
 	}
 
-	s.logger.Infof("Created backup of `%s` at `%s`.", backupSources, tarFile)
+	s.logger.Info(
+		fmt.Sprintf("Created backup of `%s` at `%s`.", backupSources, tarFile),
+	)
 	return nil
 }
 
@@ -470,7 +492,9 @@ func (s *script) encryptArchive() error {
 		if err := remove(gpgFile); err != nil {
 			return fmt.Errorf("encryptArchive: error removing gpg file: %w", err)
 		}
-		s.logger.Infof("Removed GPG file `%s`.", gpgFile)
+		s.logger.Info(
+			fmt.Sprintf("Removed GPG file `%s`.", gpgFile),
+		)
 		return nil
 	})
 
@@ -500,7 +524,9 @@ func (s *script) encryptArchive() error {
 	}
 
 	s.file = gpgFile
-	s.logger.Infof("Encrypted backup using given passphrase, saving as `%s`.", s.file)
+	s.logger.Info(
+		fmt.Sprintf("Encrypted backup using given passphrase, saving as `%s`.", s.file),
+	)
 	return nil
 }
 
@@ -572,7 +598,9 @@ func (s *script) pruneBackups() error {
 // is non-nil.
 func (s *script) must(err error) {
 	if err != nil {
-		s.logger.Errorf("Fatal error running backup: %s", err)
+		s.logger.Error(
+			fmt.Sprintf("Fatal error running backup: %s", err),
+		)
 		panic(err)
 	}
 }

entrypoint.sh

@@ -22,12 +22,5 @@ else
   done
 fi
 
-if [ ! -z "$SERVE_METRICS_PATH" ]; then
-  mkdir -p /var/www/html${SERVE_METRICS_PATH}
-  echo "ok" > /var/www/html${SERVE_METRICS_PATH}/metrics.txt
-  httpd -h /var/www/html -p "${SERVE_METRICS_PORT:-80}"
-  echo "Serving metrics on port ${SERVE_METRICS_PORT:-80}."
-fi
-
 echo "Starting cron in foreground."
 crond -f -d 8

go.mod

@@ -1,6 +1,6 @@
 module github.com/offen/docker-volume-backup
 
-go 1.19
+go 1.21
 
 require (
 	github.com/Azure/azure-sdk-for-go/sdk/azidentity v1.3.0
@@ -10,11 +10,11 @@ require (
 	github.com/docker/docker v24.0.5+incompatible
 	github.com/gofrs/flock v0.8.1
 	github.com/kelseyhightower/envconfig v1.4.0
+	github.com/klauspost/compress v1.16.7
 	github.com/leekchan/timeutil v0.0.0-20150802142658-28917288c48d
 	github.com/minio/minio-go/v7 v7.0.61
 	github.com/otiai10/copy v1.11.0
-	github.com/pkg/sftp v1.13.5
-	github.com/sirupsen/logrus v1.9.3
+	github.com/pkg/sftp v1.13.6
 	github.com/studio-b12/gowebdav v0.9.0
 	golang.org/x/crypto v0.11.0
 	golang.org/x/sync v0.3.0
@@ -34,7 +34,6 @@ require (
 	github.com/golang-jwt/jwt/v4 v4.5.0 // indirect
 	github.com/google/uuid v1.3.0 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
-	github.com/klauspost/compress v1.16.7 // indirect
 	github.com/klauspost/cpuid/v2 v2.2.5 // indirect
 	github.com/kr/fs v0.1.0 // indirect
 	github.com/kylelemons/godebug v1.1.0 // indirect
@@ -52,6 +51,7 @@ require (
 	github.com/pkg/browser v0.0.0-20210911075715-681adbf594b8 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/rs/xid v1.5.0 // indirect
+	github.com/sirupsen/logrus v1.9.3 // indirect
 	golang.org/x/net v0.12.0 // indirect
 	golang.org/x/sys v0.10.0 // indirect
 	golang.org/x/text v0.11.0 // indirect

go.sum

@@ -188,6 +188,7 @@ github.com/Azure/azure-sdk-for-go/sdk/azidentity v1.3.0/go.mod h1:OQeznEEkTZ9Orh
 github.com/Azure/azure-sdk-for-go/sdk/internal v1.3.0 h1:sXr+ck84g/ZlZUOZiNELInmMgOsuGwdjjVkEIde0OtY=
 github.com/Azure/azure-sdk-for-go/sdk/internal v1.3.0/go.mod h1:okt5dMMTOFjX/aovMlrjvvXoPMBVSPzk9185BT0+eZM=
 github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/storage/armstorage v1.2.0 h1:Ma67P/GGprNwsslzEH6+Kb8nybI8jpDTm4Wmzu2ReK8=
+github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/storage/armstorage v1.2.0/go.mod h1:c+Lifp3EDEamAkPVzMooRNOK6CZjNSdEnf1A7jsI9u4=
 github.com/Azure/azure-sdk-for-go/sdk/storage/azblob v1.1.0 h1:nVocQV40OQne5613EeLayJiRAJuKlBGy+m22qWG+WRg=
 github.com/Azure/azure-sdk-for-go/sdk/storage/azblob v1.1.0/go.mod h1:7QJP7dr2wznCMeqIrhMgWGf7XpAQnVrJqDm9nvV3Cu4=
 github.com/Azure/go-ansiterm v0.0.0-20170929234023-d6e3b3328b78 h1:w+iIsaOQNcT7OZ575w+acHgRric5iCyQh+xv+KJ4HB8=
@@ -247,6 +248,7 @@ github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSs
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dnaeon/go-vcr v1.2.0 h1:zHCHvJYTMh1N7xnV7zf1m1GPBF9Ad0Jk/whtQ1663qI=
+github.com/dnaeon/go-vcr v1.2.0/go.mod h1:R4UdLID7HZT3taECzJs4YgbbH6PIGXB6W/sc5OLb6RQ=
 github.com/docker/distribution v2.8.2+incompatible h1:T3de5rq0dB1j30rp0sA2rER+m322EBzniBPB6ZIzuh8=
 github.com/docker/distribution v2.8.2+incompatible/go.mod h1:J2gT2udsDAN96Uj4KfcMRqY0/ypR+oyYUYmja8H+y+w=
 github.com/docker/docker v24.0.5+incompatible h1:WmgcE4fxyI6EEXxBRxsHnZXrO1pQ3smi0k/jho4HLeY=
@@ -543,6 +545,7 @@ github.com/opencontainers/image-spec v1.0.3-0.20211202183452-c5a74bcca799/go.mod
 github.com/otiai10/copy v1.11.0 h1:OKBD80J/mLBrwnzXqGtFCzprFSGioo30JcmR4APsNwc=
 github.com/otiai10/copy v1.11.0/go.mod h1:rSaLseMUsZFFbsFGc7wCJnnkTAvdc5L6VWxPE4308Ww=
 github.com/otiai10/mint v1.5.1 h1:XaPLeE+9vGbuyEHem1JNk3bYc7KKqyI/na0/mLd/Kks=
+github.com/otiai10/mint v1.5.1/go.mod h1:MJm72SBthJjz8qhefc4z1PYEieWmy8Bku7CjcAqyUSM=
 github.com/pascaldekloe/goe v0.0.0-20180627143212-57f6aae5913c/go.mod h1:lzWF7FIEvWOWxwDKqyGYQf6ZUaNfKdP144TG7ZOy1lc=
 github.com/pascaldekloe/goe v0.1.0/go.mod h1:lzWF7FIEvWOWxwDKqyGYQf6ZUaNfKdP144TG7ZOy1lc=
 github.com/pelletier/go-toml v1.9.5/go.mod h1:u1nR/EPcESfeI/szUZKdtJ0xRNbUoANCkoOuaOx1Y+c=
@@ -554,8 +557,8 @@ github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINE
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/sftp v1.13.1/go.mod h1:3HaPG6Dq1ILlpPZRO0HVMrsydcdLt6HRDccSgb87qRg=
-github.com/pkg/sftp v1.13.5 h1:a3RLUqkyjYRtBTZJZ1VRrKbN3zhuPLlUc3sphVz81go=
-github.com/pkg/sftp v1.13.5/go.mod h1:wHDZ0IZX6JcBYRK1TH9bcVq8G7TLpVHYIGJRFnmPfxg=
+github.com/pkg/sftp v1.13.6 h1:JFZT4XbOU7l77xGSpOdW+pwIMqP044IyjXX6FGyEKFo=
+github.com/pkg/sftp v1.13.6/go.mod h1:tz1ryNURKu77RL+GuCzmoJYxQczL3wLNNpPWagdg4Qk=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/posener/complete v1.1.1/go.mod h1:em0nMJCgc9GFtwrmVmEMR/ZL6WyhyjMBndrE9hABlRI=
@@ -657,7 +660,6 @@ golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPh
 golang.org/x/crypto v0.0.0-20210421170649-83a5a9bb288b/go.mod h1:T9bdIzuCu7OtxOm1hfPfRQxPLYneinmdGuTeoZ9dtd4=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/crypto v0.0.0-20211108221036-ceb1ce70b4fa/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
-golang.org/x/crypto v0.0.0-20211215153901-e495a2d5b3d3/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
 golang.org/x/crypto v0.0.0-20220525230936-793ad666bf5e/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
 golang.org/x/crypto v0.1.0/go.mod h1:RecgLatLF4+eUMCP1PoPZQb+cVrJcOPbHkTkbkB9sbw=
 golang.org/x/crypto v0.11.0 h1:6Ewdq3tDic1mg5xRO4milcWCfMVQhI4NkqWWvqejpuA=
@@ -903,6 +905,7 @@ golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9sn
 golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/term v0.1.0/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/term v0.10.0 h1:3R7pNqamzBraeqj/Tj8qt1aQ2HpmlC+Cx/qL/7hn4/c=
+golang.org/x/term v0.10.0/go.mod h1:lpqdcUyK/oCiQxvxVrppt5ggO2KCZ5QblwqPnfZ6d5o=
 golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

test/cli-zstd/run.sh

@@ -0,0 +1,66 @@
+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)
+. ../util.sh
+current_test=$(basename $(pwd))
+
+docker network create test_network
+docker volume create backup_data
+docker volume create app_data
+# This volume is created to test whether empty directories are handled
+# correctly. It is not supposed to hold any data.
+docker volume create empty_data
+
+docker run -d \
+  --name minio \
+  --network test_network \
+  --env MINIO_ROOT_USER=test \
+  --env MINIO_ROOT_PASSWORD=test \
+  --env MINIO_ACCESS_KEY=test \
+  --env MINIO_SECRET_KEY=GMusLtUmILge2by+z890kQ \
+  -v backup_data:/data \
+  minio/minio:RELEASE.2020-08-04T23-10-51Z server /data
+
+docker exec minio mkdir -p /data/backup
+
+docker run -d \
+  --name offen \
+  --network test_network \
+  -v app_data:/var/opt/offen/ \
+  offen/offen:latest
+
+sleep 10
+
+docker run --rm \
+  --network test_network \
+  -v app_data:/backup/app_data \
+  -v empty_data:/backup/empty_data \
+  -v /var/run/docker.sock:/var/run/docker.sock \
+  --env AWS_ACCESS_KEY_ID=test \
+  --env AWS_SECRET_ACCESS_KEY=GMusLtUmILge2by+z890kQ \
+  --env AWS_ENDPOINT=minio:9000 \
+  --env AWS_ENDPOINT_PROTO=http \
+  --env AWS_S3_BUCKET_NAME=backup \
+  --env BACKUP_COMPRESSION=zst \
+  --env BACKUP_FILENAME='test.{{ .Extension }}' \
+  --env "BACKUP_FROM_SNAPSHOT=true" \
+  --entrypoint backup \
+  offen/docker-volume-backup:${TEST_VERSION:-canary}
+
+# Have to install tar and zstd on Alpine because the plain image comes with very
+# basic tar from busybox and it does not seem to support zstd
+docker run --rm \
+  -v backup_data:/data alpine \
+  ash -c 'apk add --no-cache zstd tar && tar -xvf /data/backup/test.tar.zst --zstd && test -f /backup/app_data/offen.db && test -d /backup/empty_data'
+
+pass "Found relevant files in untared remote backup."
+
+# This test does not stop containers during backup. This is happening on
+# purpose in order to cover this setup as well.
+expect_running_containers "2"
+
+docker rm $(docker stop minio offen)
+docker volume rm backup_data app_data
+docker network rm test_network