implement email notifications on failed backup runs

README.md

@@ -12,6 +12,7 @@ It handles __recurring or one-off backups of Docker volumes__ to a __local direc
 - [How to](#how-to)
   - [Stopping containers during backup](#stopping-containers-during-backup)
   - [Automatically pruning old backups](#automatically-pruning-old-backups)
+  - [Send email notifications on failed backup runs](#send-email-notifications-on-failed-backup-runs)
   - [Encrypting your backup using GPG](#encrypting-your-backup-using-gpg)
   - [Restoring a volume from a backup](#restoring-a-volume-from-a-backup)
   - [Using with Docker Swarm](#using-with-docker-swarm)
@@ -55,6 +56,10 @@ services:
       - docker-volume-backup.stop-during-backup=true
 
   backup:
+    # In production, it is advised to lock your image tag to a proper
+    # release version instead of using `latest`.
+    # Check https://github.com/offen/docker-volume-backup/releases
+    # for a list of available releases.
     image: offen/docker-volume-backup:latest
     restart: always
     env_file: ./backup.env # see below for configuration reference
@@ -188,6 +193,38 @@ You can populate below template according to your requirements and use it as you
 # override this default by specifying a different value here.
 
 # BACKUP_STOP_CONTAINER_LABEL="service1"
+
+########### EMAIL NOTIFICATIONS ON FAILED BACKUP RUNS
+
+# In case SMTP credentials are provided, notification emails can be sent out on
+# failed backup runs. These emails will contain the start time, the error
+# message and all log output prior to the failure.
+
+# The recipient(s) of the notification. Supply a comma separated list
+# of adresses if you want to notify multiple recipients. If this is
+# not set, no emails will be sent.
+
+# EMAIL_NOTIFICATION_RECIPIENT="you@example.com"
+
+# The "From" header of the sent email. Defaults to `noreply@nohost`.
+
+# EMAIL_NOTIFICATION_SENDER="no-reply@example.com"
+
+# The hostname of your SMTP server.
+
+# 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>"
 ```
 
 ## How to
@@ -247,6 +284,25 @@ volumes:
   data:
 ```
 
+### Send email notifications on failed backup runs
+
+To send out email notifications on failed backup runs, provide SMTP credentials, a sender and a recipient:
+
+```yml
+version: '3'
+
+services:
+  backup:
+    image: offen/docker-volume-backup:latest
+    environment:
+      # ... other configuration values go here
+      EMAIL_SMTP_HOST: "smtp.example.com"
+      EMAIL_SMTP_PASSWORD: "password"
+      EMAIL_SMTP_USERNAME: "username"
+      EMAIL_NOTIFICATION_SENDER: "noreply@example.com"
+      EMAIL_NOTIFICATION_RECIPIENT: "notifications@example.com"
+```
+
 ### Encrypting your backup using GPG
 
 The image supports encrypting backups using GPG out of the box.

cmd/backup/main.go

@@ -19,6 +19,7 @@ import (
 	"github.com/docker/docker/api/types/filters"
 	"github.com/docker/docker/api/types/swarm"
 	"github.com/docker/docker/client"
+	"github.com/go-gomail/gomail"
 	"github.com/gofrs/flock"
 	"github.com/kelseyhightower/envconfig"
 	"github.com/leekchan/timeutil"
@@ -88,6 +89,12 @@ type config struct {
 	AwsAccessKeyID             string        `envconfig:"AWS_ACCESS_KEY_ID"`
 	AwsSecretAccessKey         string        `split_words:"true"`
 	GpgPassphrase              string        `split_words:"true"`
+	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"`
 }
 
 // newScript creates all resources needed for the script to perform actions against
@@ -138,6 +145,28 @@ func newScript() (*script, error) {
 		s.mc = mc
 	}
 
+	if s.c.EmailNotificationRecipient != "" {
+		s.errorHooks = append(s.errorHooks, func(err error, start time.Time, logOutput string) error {
+			mailer := gomail.NewDialer(
+				s.c.EmailSMTPHost, s.c.EmailSMTPPort, s.c.EmailSMTPUsername, s.c.EmailSMTPPassword,
+			)
+
+			subject := fmt.Sprintf(
+				"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,
+			)
+
+			message := gomail.NewMessage()
+			message.SetHeader("From", s.c.EmailNotificationSender)
+			message.SetHeader("To", s.c.EmailNotificationRecipient)
+			message.SetHeader("Subject", subject)
+			message.SetBody("text/plain", body)
+			return mailer.DialAndSend(message)
+		})
+	}
+
 	return s, nil
 }
 
@@ -482,7 +511,7 @@ func (s *script) must(err error) {
 	if err != nil {
 		for _, hook := range s.errorHooks {
 			if hookErr := hook(err, s.start, s.output.String()); hookErr != nil {
-				s.logger.Errorf("An error occurred calling an error hook: %s", err)
+				s.logger.Errorf("An error occurred calling an error hook: %s", hookErr)
 			}
 		}
 		s.logger.Fatalf("Fatal error running backup: %s", err)

go.mod

@@ -20,6 +20,7 @@ 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
@@ -41,5 +42,6 @@ require (
 	google.golang.org/genproto v0.0.0-20201110150050-8816d57aaa9a // indirect
 	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/ini.v1 v1.57.0 // indirect
 )

go.sum

@@ -254,6 +254,8 @@ github.com/ghodss/yaml v1.0.0/go.mod h1:4dBDuWmgqj2HViK6kFavaiC9ZROes6MMH2rRYeME
 github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1/go.mod h1:vR7hzQXu2zJy9AVAgeJqvqgH9Q5CA+iKCZ2gyEVpxRU=
 github.com/go-gl/glfw/v3.3/glfw v0.0.0-20191125211704-12ad95a8df72/go.mod h1:tQ2UAYgL5IevRw8kRxooKSPJfGvJ9fJQFa0TUsXzTg8=
 github.com/go-gl/glfw/v3.3/glfw v0.0.0-20200222043503-6f7a984d4dc4/go.mod h1:tQ2UAYgL5IevRw8kRxooKSPJfGvJ9fJQFa0TUsXzTg8=
+github.com/go-gomail/gomail v0.0.0-20160411212932-81ebce5c23df h1:Bao6dhmbTA1KFVxmJ6nBoMuOJit2yjEgLJpIMYpop0E=
+github.com/go-gomail/gomail v0.0.0-20160411212932-81ebce5c23df/go.mod h1:GJr+FCSXshIwgHBtLglIg9M2l2kQSi6QjVAngtzI08Y=
 github.com/go-ini/ini v1.25.4/go.mod h1:ByCAeIL28uOIIG0E3PJtZPDL8WnHpFKFOtgjp+3Ies8=
 github.com/go-kit/kit v0.8.0/go.mod h1:xBxKIO96dXMWWy0MnWVtmwkA9/13aqxPnvrjFYMA2as=
 github.com/go-kit/kit v0.9.0/go.mod h1:xBxKIO96dXMWWy0MnWVtmwkA9/13aqxPnvrjFYMA2as=
@@ -908,6 +910,8 @@ google.golang.org/protobuf v1.26.0 h1:bxAC2xTBsZGibn2RTntX0oH50xLsqy1OxA9tTL3p/l
 google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
 gopkg.in/airbrake/gobrake.v2 v2.0.9/go.mod h1:/h5ZAUhDkGaJfjzjKLSjv6zCL6O0LLBxU4K+aSYdM/U=
 gopkg.in/alecthomas/kingpin.v2 v2.2.6/go.mod h1:FMv+mEhP44yOT+4EoQTLFTRgOQ1FBLkstjWtayDeSgw=
+gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc h1:2gGKlE2+asNV9m7xrywl36YYNnBG5ZQ0r/BOOxqPpmk=
+gopkg.in/alexcesaro/quotedprintable.v3 v3.0.0-20150716171945-2caba252f4dc/go.mod h1:m7x9LTH6d71AHyAX77c9yqWCCa3UKHcVEj9y7hAtKDk=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20141024133853-64131543e789/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=