create a snapshot before creating tar archive (#32)

* create a snapshot before creating tar archive

* safeguard snapshot removal and make snapshot optional

* fix typo, make sure remove snapshot failure triggers failure hook

Co-authored-by: Schwannden Kuo <schwannden@mobagel.com>

README.md

@@ -126,6 +126,13 @@ You can populate below template according to your requirements and use it as you
 
 # BACKUP_LATEST_SYMLINK="backup.latest.tar.gz"
 
+# Wehter to copy the content of backup folder before creating archive.
+# In rare scenario where the content of the source backup volume is still
+# updating, but we do not wish to stop the container while performing backup,
+# this snapshot before archive ensures the integrity of the tar.gz file.
+
+# BACKUP_FROM_SNAPSHOT="false"
+
 ########### BACKUP STORAGE
 
 # The name of the remote bucket that should be used for storing backups. If

cmd/backup/main.go

@@ -26,6 +26,7 @@ import (
 	"github.com/m90/targz"
 	"github.com/minio/minio-go/v7"
 	"github.com/minio/minio-go/v7/pkg/credentials"
+	"github.com/otiai10/copy"
 	"github.com/sirupsen/logrus"
 	"golang.org/x/crypto/openpgp"
 )
@@ -95,6 +96,7 @@ type config struct {
 	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"`
 	AwsS3BucketName            string        `split_words:"true"`
 	AwsEndpoint                string        `split_words:"true" default:"s3.amazonaws.com"`
 	AwsEndpointProto           string        `split_words:"true" default:"https"`
@@ -326,14 +328,27 @@ func (s *script) stopContainers() (func() error, error) {
 	}, stopError
 }
 
+func (s *script) snapshotFolder() string {
+	return filepath.Join("/tmp", s.c.BackupSources)
+}
+
 // takeBackup creates a tar archive of the configured backup location and
 // saves it to disk.
 func (s *script) takeBackup() error {
 	s.file = timeutil.Strftime(&s.start, s.file)
-	if err := targz.Compress(s.c.BackupSources, s.file); err != nil {
+	backupSources := s.c.BackupSources
+	if s.c.BackupFromSnapshot {
+		backupSources = s.snapshotFolder()
+		s.logger.Infof("Created snapshot of `%s` at `%s`.", s.c.BackupSources, backupSources)
+		// copy before compressing guard against a situation where backup folder's content are still growing.
+		if err := copy.Copy(s.c.BackupSources, backupSources, copy.Options{ PreserveTimes: true }); err != nil {
+			return fmt.Errorf("takeBackup: error creating snapshot on backup folder: %w", err)
+		}
+	}
+	if err := targz.Compress(backupSources, s.file); err != nil {
 		return fmt.Errorf("takeBackup: error compressing backup folder: %w", err)
 	}
-	s.logger.Infof("Created backup of `%s` at `%s`.", s.c.BackupSources, s.file)
+	s.logger.Infof("Created backup of `%s` at `%s`.", backupSources, s.file)
 	return nil
 }
 
@@ -392,7 +407,7 @@ func (s *script) copyBackup() error {
 	}
 
 	if _, err := os.Stat(s.c.BackupArchive); !os.IsNotExist(err) {
-		if err := copy(s.file, path.Join(s.c.BackupArchive, name)); err != nil {
+		if err := copyFile(s.file, path.Join(s.c.BackupArchive, name)); err != nil {
 			return fmt.Errorf("copyBackup: error copying file to local archive: %w", err)
 		}
 		s.logger.Infof("Stored copy of backup `%s` in local archive `%s`.", s.file, s.c.BackupArchive)
@@ -410,8 +425,15 @@ func (s *script) copyBackup() error {
 	return nil
 }
 
-// removeArtifacts removes the backup file from disk.
+// removeArtifacts removes the backup file from disk. Also remove snapshot if snapshot was created
 func (s *script) removeArtifacts() error {
+	if s.c.BackupFromSnapshot {
+		snapshotFolder := s.snapshotFolder()
+		if err := os.RemoveAll(snapshotFolder); err != nil {
+			return fmt.Errorf("removeArtifacts: error removing snapshot folder %s: %w", snapshotFolder, err)
+		}
+		s.logger.Infof("Removed snapshot folder %s.", snapshotFolder)
+	}
 	_, err := os.Stat(s.file)
 	if err != nil {
 		if os.IsNotExist(err) {
@@ -628,7 +650,7 @@ func lock(lockfile string) func() error {
 }
 
 // copy creates a copy of the file located at `dst` at `src`.
-func copy(src, dst string) error {
+func copyFile(src, dst string) error {
 	in, err := os.Open(src)
 	if err != nil {
 		return err

go.mod

@@ -4,11 +4,13 @@ go 1.17
 
 require (
 	github.com/docker/docker v20.10.8+incompatible
+	github.com/go-gomail/gomail v0.0.0-20160411212932-81ebce5c23df
 	github.com/gofrs/flock v0.8.1
 	github.com/kelseyhightower/envconfig v1.4.0
 	github.com/leekchan/timeutil v0.0.0-20150802142658-28917288c48d
 	github.com/m90/targz v0.0.0-20210904082215-2e9a4529a615
 	github.com/minio/minio-go/v7 v7.0.12
+	github.com/otiai10/copy v1.6.0
 	github.com/sirupsen/logrus v1.8.1
 	golang.org/x/crypto v0.0.0-20210817164053-32db794688a5
 )
@@ -20,7 +22,6 @@ require (
 	github.com/docker/go-connections v0.4.0 // indirect
 	github.com/docker/go-units v0.4.0 // indirect
 	github.com/dustin/go-humanize v1.0.0 // indirect
-	github.com/go-gomail/gomail v0.0.0-20160411212932-81ebce5c23df // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/golang/protobuf v1.5.0 // indirect
 	github.com/google/uuid v1.2.0 // indirect
@@ -43,5 +44,6 @@ require (
 	google.golang.org/grpc v1.33.2 // indirect
 	google.golang.org/protobuf v1.26.0 // indirect
 	gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc // indirect
+	gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df // indirect
 	gopkg.in/ini.v1 v1.57.0 // indirect
 )

go.sum

@@ -494,6 +494,13 @@ github.com/opencontainers/runtime-tools v0.0.0-20181011054405-1d69bd0f9c39/go.mo
 github.com/opencontainers/selinux v1.6.0/go.mod h1:VVGKuOLlE7v4PJyT6h7mNWvq1rzqiriPsEqVhc+svHE=
 github.com/opencontainers/selinux v1.8.0/go.mod h1:RScLhm78qiWa2gbVCcGkC7tCGdgk3ogry1nUQF8Evvo=
 github.com/opencontainers/selinux v1.8.2/go.mod h1:MUIHuUEvKB1wtJjQdOyYRgOnLD2xAPP8dBsCoU0KuF8=
+github.com/otiai10/copy v1.6.0 h1:IinKAryFFuPONZ7cm6T6E2QX/vcJwSnlaA5lfoaXIiQ=
+github.com/otiai10/copy v1.6.0/go.mod h1:XWfuS3CrI0R6IE0FbgHsEazaXO8G0LpMp9o8tos0x4E=
+github.com/otiai10/curr v0.0.0-20150429015615-9b4961190c95/go.mod h1:9qAhocn7zKJG+0mI8eUu6xqkFDYS2kb2saOteoSB3cE=
+github.com/otiai10/curr v1.0.0/go.mod h1:LskTG5wDwr8Rs+nNQ+1LlxRjAtTZZjtJW4rMXl6j4vs=
+github.com/otiai10/mint v1.3.0/go.mod h1:F5AjcsTsWUqX+Na9fpHb52P8pcRX2CI6A3ctIT91xUo=
+github.com/otiai10/mint v1.3.2 h1:VYWnrP5fXmz1MXvjuUvcBrXSjGE6xjON+axB/UrpO3E=
+github.com/otiai10/mint v1.3.2/go.mod h1:/yxELlJQ0ufhjUwhshSj+wFjZ78CnZ48/1wtmBH1OTc=
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
 github.com/pelletier/go-toml v1.8.1/go.mod h1:T2/BmBdy8dvIRq1a/8aqjN41wvWlN4lrapLU/GW4pbc=
 github.com/peterbourgon/diskv v2.0.1+incompatible/go.mod h1:uqqh8zWWbv1HBMNONnaR/tNboyR3/BZd58JJSHlUSCU=
@@ -921,6 +928,8 @@ gopkg.in/cheggaaa/pb.v1 v1.0.25/go.mod h1:V/YB90LKu/1FcN3WVnfiiE5oMCibMjukxqG/qS
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/fsnotify.v1 v1.4.7/go.mod h1:Tz8NjZHkW78fSQdbUxIjBTcgA1z1m8ZHf0WmKUhAMys=
 gopkg.in/gemnasium/logrus-airbrake-hook.v2 v2.1.2/go.mod h1:Xk6kEKp8OKb+X14hQBKWaSkCsqBpgog8nAV2xsGOxlo=
+gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df h1:n7WqCuqOuCbNr617RXOY0AWRXxgwEyPp2z+p0+hgMuE=
+gopkg.in/gomail.v2 v2.0.0-20160411212932-81ebce5c23df/go.mod h1:LRQQ+SO6ZHR7tOkpBDuZnXENFzX8qRjMDMyPD6BRkCw=
 gopkg.in/inf.v0 v0.9.1/go.mod h1:cWUDdTG/fYaXco+Dcufb5Vnc6Gp2YChqWtbxRZE0mXw=
 gopkg.in/ini.v1 v1.57.0 h1:9unxIsFcTt4I55uWluz+UmL95q4kdJ0buvQ1ZIqVQww=
 gopkg.in/ini.v1 v1.57.0/go.mod h1:pNLf8WUiyNEtQjuu5G5vTm06TEv9tsIgeAvK8hOrP4k=