Merge pull request #27 from offen/latest-symlink

Automatically create symlink to latest local backup if configured

README.md

@@ -3,11 +3,13 @@
 Backup Docker volumes locally or to any S3 compatible storage.
 
 The [offen/docker-volume-backup](https://hub.docker.com/r/offen/docker-volume-backup) Docker image can be used as a lightweight (below 15MB) sidecar container to an existing Docker setup.
-It handles __recurring or one-off backups of Docker volumes__ to a __local directory__ or __any S3 compatible storage__ (or both), and __rotates away old backups__ if configured. It also supports __encrypting your backups using GPG__.
+It handles __recurring or one-off backups of Docker volumes__ to a __local directory__ or __any S3 compatible storage__ (or both), and __rotates away old backups__ if configured. It also supports __encrypting your backups using GPG__ and __sending notifications for failed backup runs__.
 
 <!-- MarkdownTOC -->
 
 - [Quickstart](#quickstart)
+  - [Recurring backups in a compose setup](#recurring-backups-in-a-compose-setup)
+  - [One-off backups using Docker CLI](#one-off-backups-using-docker-cli)
 - [Configuration reference](#configuration-reference)
 - [How to](#how-to)
   - [Stopping containers during backup](#stopping-containers-during-backup)
@@ -38,6 +40,8 @@ Code and documentation for `v1` versions are found on [this branch][v1-branch].
 
 ## Quickstart
 
+### Recurring backups in a compose setup
+
 Add a `backup` service to your compose setup and mount the volumes you would like to see backed up:
 
 ```yml
@@ -78,6 +82,22 @@ volumes:
   data:
 ```
 
+### One-off backups using Docker CLI
+
+To run a one time backup, mount the volume you would like to see backed up into a container and run the `backup` command:
+
+```console
+docker run --rm \
+  -v data:/backup/data \
+  --env AWS_ACCESS_KEY_ID="<xxx>" \
+  --env AWS_SECRET_ACCESS_KEY="<xxx>" \
+  --env AWS_S3_BUCKET_NAME="<xxx>" \
+  --entrypoint backup \
+  offen/docker-volume-backup:latest
+```
+
+Alternatively, pass a `--env-file` in order to use a full config as described below.
+
 ## Configuration reference
 
 Backup targets, schedule and retention are configured in environment variables.
@@ -100,6 +120,11 @@ You can populate below template according to your requirements and use it as you
 
 # BACKUP_FILENAME="backup-%Y-%m-%dT%H-%M-%S.tar.gz"
 
+# When storing local backups, a symlink to the latest backup can be created
+# in case a value is given for this key. This has no effect on remote backups.
+
+# BACKUP_LATEST_SYMLINK="backup.latest.tar.gz"
+
 ########### BACKUP STORAGE
 
 # The name of the remote bucket that should be used for storing backups. If
@@ -114,6 +139,13 @@ You can populate below template according to your requirements and use it as you
 # AWS_ACCESS_KEY_ID="<xxx>"
 # AWS_SECRET_ACCESS_KEY="<xxx>"
 
+# Instead of providing static credentials, you can also use IAM instance profiles
+# or similar to provide authentication. Some possible configuration options on AWS:
+# - EC2: http://169.254.169.254
+# - ECS: http://169.254.170.2
+
+# AWS_IAM_ROLE_ENDPOINT="http://169.254.169.254"
+
 # This is the FQDN of your storage server, e.g. `storage.example.com`.
 # Do not set this when working against AWS S3 (the default value is 
 # `s3.amazonaws.com`). If you need to set a specific (non-https) protocol, you
@@ -210,20 +242,12 @@ You can populate below template according to your requirements and use it as you
 
 # EMAIL_NOTIFICATION_SENDER="no-reply@example.com"
 
-# The hostname of your SMTP server.
+# Configuration and credentials for the SMTP server to be used.
+# EMAIL_SMTP_PORT defaults to 587.
 
 # EMAIL_SMTP_HOST="posteo.de"
-
-# The SMTP password.
-
 # EMAIL_SMTP_PASSWORD="<xxx>"
-
-# The SMTP username.
-
 # EMAIL_SMTP_USERNAME="no-reply@example.com"
-
-The port used when communicating with the server. Defaults to 587.
-
 # EMAIL_SMTP_PORT="<port>"
 ```
 
@@ -418,6 +442,9 @@ services:
   # ... define other services using the `data` volume here
   backup:
     image: offen/docker-volume-backup:latest
+    environment:
+      BACKUP_FILENAME: backup-%Y-%m-%dT%H-%M-%S.tar.gz
+      BACKUP_LATEST_SYMLINK: backup-latest.tar.gz
     volumes:
       - data:/backup/my-app-backup:ro
       - /var/run/docker.sock:/var/run/docker.sock:ro
@@ -555,7 +582,7 @@ volumes:
 
 ## Differences to `futurice/docker-volume-backup`
 
-This image is heavily inspired by the `futurice/docker-volume-backup`. We decided to publish this image as a simpler and more lightweight alternative because of the following requirements:
+This image is heavily inspired by `futurice/docker-volume-backup`. We decided to publish this image as a simpler and more lightweight alternative because of the following requirements:
 
 - The original image is based on `ubuntu` and requires additional tools, making it heavy.
 This version is roughly 1/25 in compressed size (it's ~12MB).

cmd/backup/main.go

@@ -39,6 +39,15 @@ func main() {
 		panic(err)
 	}
 
+	defer func() {
+		if err := recover(); err != nil {
+			if e, ok := err.(error); ok && strings.Contains(e.Error(), msgBackupFailed) {
+				os.Exit(1)
+			}
+			panic(err)
+		}
+	}()
+
 	s.must(func() error {
 		restartContainers, err := s.stopContainers()
 		defer func() {
@@ -50,9 +59,14 @@ func main() {
 		return s.takeBackup()
 	}())
 
-	s.must(s.encryptBackup())
+	s.must(func() error {
-	s.must(s.copyBackup())
+		defer func() {
-	s.must(s.removeArtifacts())
+			s.must(s.removeArtifacts())
+		}()
+		s.must(s.encryptBackup())
+		return s.copyBackup()
+	}())
+
 	s.must(s.pruneOldBackups())
 	s.logger.Info("Finished running backup tasks.")
 }
@@ -60,10 +74,10 @@ func main() {
 // script holds all the stateful information required to orchestrate a
 // single backup run.
 type script struct {
-	cli        *client.Client
+	cli    *client.Client
-	mc         *minio.Client
+	mc     *minio.Client
-	logger     *logrus.Logger
+	logger *logrus.Logger
-	errorHooks []errorHook
+	hooks  []hook
 
 	start  time.Time
 	file   string
@@ -72,11 +86,10 @@ type script struct {
 	c *config
 }
 
-type errorHook func(err error, start time.Time, logOutput string) error
-
 type config struct {
 	BackupSources              string        `split_words:"true" default:"/backup"`
 	BackupFilename             string        `split_words:"true" default:"backup-%Y-%m-%dT%H-%M-%S.tar.gz"`
+	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"`
@@ -88,6 +101,7 @@ type config struct {
 	AwsEndpointInsecure        bool          `split_words:"true"`
 	AwsAccessKeyID             string        `envconfig:"AWS_ACCESS_KEY_ID"`
 	AwsSecretAccessKey         string        `split_words:"true"`
+	AwsIamRoleEndpoint         string        `split_words:"true"`
 	GpgPassphrase              string        `split_words:"true"`
 	EmailNotificationRecipient string        `split_words:"true"`
 	EmailNotificationSender    string        `split_words:"true" default:"noreply@nohost"`
@@ -97,6 +111,8 @@ type config struct {
 	EmailSMTPPassword          string        `envconfig:"EMAIL_SMTP_PASSWORD"`
 }
 
+var msgBackupFailed = "backup run failed"
+
 // newScript creates all resources needed for the script to perform actions against
 // remote resources like the Docker engine or remote storage locations. All
 // reading from env vars or other configuration sources is expected to happen
@@ -131,12 +147,21 @@ func newScript() (*script, error) {
 	}
 
 	if s.c.AwsS3BucketName != "" {
-		mc, err := minio.New(s.c.AwsEndpoint, &minio.Options{
+		var creds *credentials.Credentials
-			Creds: credentials.NewStaticV4(
+		if s.c.AwsAccessKeyID != "" && s.c.AwsSecretAccessKey != "" {
+			creds = credentials.NewStaticV4(
 				s.c.AwsAccessKeyID,
 				s.c.AwsSecretAccessKey,
 				"",
-			),
+			)
+		} else if s.c.AwsIamRoleEndpoint != "" {
+			creds = credentials.NewIAM(s.c.AwsIamRoleEndpoint)
+		} else {
+			return nil, errors.New("newScript: AWS_S3_BUCKET_NAME is defined, but no credentials were provided")
+		}
+
+		mc, err := minio.New(s.c.AwsEndpoint, &minio.Options{
+			Creds:  creds,
 			Secure: !s.c.AwsEndpointInsecure && s.c.AwsEndpointProto == "https",
 		})
 		if err != nil {
@@ -146,7 +171,7 @@ func newScript() (*script, error) {
 	}
 
 	if s.c.EmailNotificationRecipient != "" {
-		s.errorHooks = append(s.errorHooks, func(err error, start time.Time, logOutput string) error {
+		s.hooks = append(s.hooks, hook{hookLevelFailure, func(err error, start time.Time, logOutput string) error {
 			mailer := gomail.NewDialer(
 				s.c.EmailSMTPHost, s.c.EmailSMTPPort, s.c.EmailSMTPUsername, s.c.EmailSMTPPassword,
 			)
@@ -155,7 +180,7 @@ func newScript() (*script, error) {
 				"Failure running docker-volume-backup at %s", start.Format(time.RFC3339),
 			)
 			body := fmt.Sprintf(
-				"Running docker-volume-backup failed with error: %s\n\nLog output before the error occurred:\n\n%s\n", err, logOutput,
+				"Running docker-volume-backup failed with error: %s\n\nLog output of the failed run was:\n\n%s\n", err, logOutput,
 			)
 
 			message := gomail.NewMessage()
@@ -164,7 +189,7 @@ func newScript() (*script, error) {
 			message.SetHeader("Subject", subject)
 			message.SetBody("text/plain", body)
 			return mailer.DialAndSend(message)
-		})
+		}})
 	}
 
 	return s, nil
@@ -356,16 +381,33 @@ func (s *script) copyBackup() error {
 			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)
+		if s.c.BackupLatestSymlink != "" {
+			symlink := path.Join(s.c.BackupArchive, s.c.BackupLatestSymlink)
+			if _, err := os.Lstat(symlink); err == nil {
+				os.Remove(symlink)
+			}
+			if err := os.Symlink(name, symlink); err != nil {
+				return fmt.Errorf("copyBackup: error creating latest symlink: %w", err)
+			}
+			s.logger.Infof("Created/Updated symlink `%s` for latest backup.", s.c.BackupLatestSymlink)
+		}
 	}
 	return nil
 }
 
 // removeArtifacts removes the backup file from disk.
 func (s *script) removeArtifacts() error {
-	if err := os.Remove(s.file); err != nil {
+	_, err := os.Stat(s.file)
-		return fmt.Errorf("removeArtifacts: error removing file: %w", err)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return fmt.Errorf("removeArtifacts: error calling stat on file %s: %w", s.file, err)
 	}
-	s.logger.Info("Removed local artifacts.")
+	if err := os.Remove(s.file); err != nil {
+		return fmt.Errorf("removeArtifacts: error removing file %s: %w", s.file, err)
+	}
+	s.logger.Infof("Removed local artifacts %s.", s.file)
 	return nil
 }
 
@@ -466,7 +508,7 @@ func (s *script) pruneOldBackups() error {
 				)
 			}
 
-			if fi.ModTime().Before(deadline) {
+			if fi.Mode() != os.ModeSymlink && fi.ModTime().Before(deadline) {
 				matches = append(matches, candidate)
 			}
 		}
@@ -504,17 +546,35 @@ func (s *script) pruneOldBackups() error {
 	return nil
 }
 
-// must exits the script run non-zero and prematurely in case the given error
+// runHooks runs all hooks that have been registered using the
-// is non-nil. If error hooks are present on the script object, they
+// given level. In case executing a hook returns an error, the following
+// hooks will still be run before the function returns an error.
+func (s *script) runHooks(err error, targetLevel string) error {
+	var actionErrors []error
+	for _, hook := range s.hooks {
+		if hook.level != targetLevel {
+			continue
+		}
+		if err := hook.action(err, s.start, s.output.String()); err != nil {
+			actionErrors = append(actionErrors, err)
+		}
+	}
+	if len(actionErrors) != 0 {
+		return join(actionErrors...)
+	}
+	return nil
+}
+
+// must exits the script run prematurely in case the given error
+// is non-nil. If failure hooks have been registered on the script object, they
 // will be called, passing the failure and previous log output.
 func (s *script) must(err error) {
 	if err != nil {
-		for _, hook := range s.errorHooks {
+		s.logger.Errorf("Fatal error running backup: %s", err)
-			if hookErr := hook(err, s.start, s.output.String()); hookErr != nil {
+		if hookErr := s.runHooks(err, hookLevelFailure); hookErr != nil {
-				s.logger.Errorf("An error occurred calling an error hook: %s", hookErr)
+			s.logger.Errorf("An error occurred calling the registered failure hooks: %s", hookErr)
-			}
 		}
-		s.logger.Fatalf("Fatal error running backup: %s", err)
+		panic(errors.New(msgBackupFailed))
 	}
 }
 
@@ -587,3 +647,14 @@ func (b *bufferingWriter) Write(p []byte) (n int, err error) {
 	}
 	return b.writer.Write(p)
 }
+
+// hook contains a queued action that can be trigger them when the script
+// reaches a certain point (e.g. unsuccessful backup)
+type hook struct {
+	level  string
+	action func(err error, start time.Time, logOutput string) error
+}
+
+const (
+	hookLevelFailure = "failure"
+)

test/cli/run.sh

@@ -29,8 +29,7 @@ docker run -d \
 
 sleep 10
 
-docker run -d \
+docker run --rm \
-  --name backup \
   --network test_network \
   -v app_data:/backup/app_data \
   -v /var/run/docker.sock:/var/run/docker.sock \
@@ -40,18 +39,16 @@ docker run -d \
   --env AWS_ENDPOINT_PROTO=http \
   --env AWS_S3_BUCKET_NAME=backup \
   --env BACKUP_FILENAME=test.tar.gz \
-  --env BACKUP_CRON_EXPRESSION="0 0 5 31 2 ?" \
+  --entrypoint backup \
   offen/docker-volume-backup:$TEST_VERSION
 
-docker exec backup backup
-
 docker run --rm -it \
   -v backup_data:/data alpine \
   ash -c 'tar -xvf /data/backup/test.tar.gz && test -f /backup/app_data/offen.db'
 
 echo "[TEST:PASS] Found relevant files in untared backup."
 
-if [ "$(docker ps -q | wc -l)" != "3" ]; then
+if [ "$(docker ps -q | wc -l)" != "2" ]; then
   echo "[TEST:FAIL] Expected all containers to be running post backup, instead seen:"
   docker ps
   exit 1

test/compose/docker-compose.yml

@@ -24,6 +24,7 @@ services:
       AWS_ENDPOINT_PROTO: http
       AWS_S3_BUCKET_NAME: backup
       BACKUP_FILENAME: test.tar.gz
+      BACKUP_LATEST_SYMLINK: test.latest.tar.gz.gpg
       BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
       BACKUP_RETENTION_DAYS: ${BACKUP_RETENTION_DAYS:-7}
       BACKUP_PRUNING_LEEWAY: 5s

test/compose/run.sh

@@ -18,6 +18,7 @@ docker run --rm -it \
 
 echo "[TEST:PASS] Found relevant files in untared remote backup."
 
+test -L ./local/test.latest.tar.gz.gpg
 echo 1234secret | gpg -d --yes --passphrase-fd 0 ./local/test.tar.gz.gpg > ./local/decrypted.tar.gz
 tar -xf ./local/decrypted.tar.gz -C /tmp && test -f /tmp/backup/app_data/offen.db
 rm ./local/decrypted.tar.gz