# Notifications

Watchtower can send notifications when containers are updated. Notifications are sent via hooks in the logging
system, [logrus](http://github.com/sirupsen/logrus). The types of notifications to send are set by passing a
comma-separated list of values to the `--notifications` option
(or corresponding environment variable `WATCHTOWER_NOTIFICATIONS`), which has the following valid values:

-   `email` to send notifications via e-mail
-   `slack` to send notifications through a Slack webhook
-   `msteams` to send notifications via MSTeams webhook
-   `gotify` to send notifications via Gotify
-   `shoutrrr` to send notifications via [containrrr/shoutrrr](https://github.com/containrrr/shoutrrr)

!!! note "Using multiple notifications with environment variables"
    There is currently a bug in Viper (https://github.com/spf13/viper/issues/380), which prevents comma-separated slices to
    be used when using the environment variable.  
    A workaround is available where we instead put quotes around the environment variable value and replace the commas with
    spaces:
    ```
    WATCHTOWER_NOTIFICATIONS="slack msteams"
    ```
    If you're a `docker-compose` user, make sure to specify environment variables' values in your `.yml` file without double
    quotes (`"`). This prevents unexpected errors when watchtower starts.

## Settings

-   `--notifications-level` (env. `WATCHTOWER_NOTIFICATIONS_LEVEL`): Controls the log level which is used for the notifications. If omitted, the default log level is `info`. Possible values are: `panic`, `fatal`, `error`, `warn`, `info`, `debug` or `trace`.
-   `--notifications-hostname` (env. `WATCHTOWER_NOTIFICATIONS_HOSTNAME`): Custom hostname specified in subject/title. Useful to override the operating system hostname.
-   Watchtower will post a notification every time it is started. This behavior [can be changed](https://containrrr.github.io/watchtower/arguments/#without_sending_a_startup_message) with an argument.

## Available services

### Email

To receive notifications by email, the following command-line options, or their corresponding environment variables, can be set:

-   `--notification-email-from` (env. `WATCHTOWER_NOTIFICATION_EMAIL_FROM`): The e-mail address from which notifications will be sent.
-   `--notification-email-to` (env. `WATCHTOWER_NOTIFICATION_EMAIL_TO`): The e-mail address to which notifications will be sent.
-   `--notification-email-server` (env. `WATCHTOWER_NOTIFICATION_EMAIL_SERVER`): The SMTP server to send e-mails through.
-   `--notification-email-server-tls-skip-verify` (env. `WATCHTOWER_NOTIFICATION_EMAIL_SERVER_TLS_SKIP_VERIFY`): Do not verify the TLS certificate of the mail server. This should be used only for testing.
-   `--notification-email-server-port` (env. `WATCHTOWER_NOTIFICATION_EMAIL_SERVER_PORT`): The port used to connect to the SMTP server to send e-mails through. Defaults to `25`.
-   `--notification-email-server-user` (env. `WATCHTOWER_NOTIFICATION_EMAIL_SERVER_USER`): The username to authenticate with the SMTP server with.
-   `--notification-email-server-password` (env. `WATCHTOWER_NOTIFICATION_EMAIL_SERVER_PASSWORD`): The password to authenticate with the SMTP server with. Can also reference a file, in which case the contents of the file are used.
-   `--notification-email-delay` (env. `WATCHTOWER_NOTIFICATION_EMAIL_DELAY`): Delay before sending notifications expressed in seconds.
-   `--notification-email-subjecttag` (env. `WATCHTOWER_NOTIFICATION_EMAIL_SUBJECTTAG`): Prefix to include in the subject tag. Useful when running multiple watchtowers.

Example:

```bash
docker run -d \
  --name watchtower \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e WATCHTOWER_NOTIFICATIONS=email \
  -e WATCHTOWER_NOTIFICATION_EMAIL_FROM=fromaddress@gmail.com \
  -e WATCHTOWER_NOTIFICATION_EMAIL_TO=toaddress@gmail.com \
  -e WATCHTOWER_NOTIFICATION_EMAIL_SERVER=smtp.gmail.com \
  -e WATCHTOWER_NOTIFICATION_EMAIL_SERVER_PORT=587 \
  -e WATCHTOWER_NOTIFICATION_EMAIL_SERVER_USER=fromaddress@gmail.com \
  -e WATCHTOWER_NOTIFICATION_EMAIL_SERVER_PASSWORD=app_password \
  -e WATCHTOWER_NOTIFICATION_EMAIL_DELAY=2 \
  containrrr/watchtower
```

The previous example assumes, that you already have an SMTP server up and running you can connect to. If you don't or you want to bring up watchtower with your own simple SMTP relay the following `docker-compose.yml` might be a good start for you.

The following example assumes, that your domain is called `your-domain.com` and that you are going to use a certificate valid for `smtp.your-domain.com`. This hostname has to be used as `WATCHTOWER_NOTIFICATION_EMAIL_SERVER` otherwise the TLS connection is going to fail with `Failed to send notification email` or `connect: connection refused`. We also have to add a network for this setup in order to add an alias to it. If you also want to enable DKIM or other features on the SMTP server, you will find more information at [freinet/postfix-relay](https://hub.docker.com/r/freinet/postfix-relay).

Example including an SMTP relay:

```yaml
version: '3.8'
services:
  watchtower:
    image: containrrr/watchtower:latest
    container_name: watchtower
    environment:
      WATCHTOWER_MONITOR_ONLY: 'true'
      WATCHTOWER_NOTIFICATIONS: email
      WATCHTOWER_NOTIFICATION_EMAIL_FROM: from-address@your-domain.com
      WATCHTOWER_NOTIFICATION_EMAIL_TO: to-address@your-domain.com
      # you have to use a network alias here, if you use your own certificate
      WATCHTOWER_NOTIFICATION_EMAIL_SERVER: smtp.your-domain.com
      WATCHTOWER_NOTIFICATION_EMAIL_SERVER_PORT: 25
      WATCHTOWER_NOTIFICATION_EMAIL_DELAY: 2
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    networks:
      - watchtower
    depends_on:
      - postfix

  # SMTP needed to send out status emails
  postfix:
    image: freinet/postfix-relay:latest
    expose:
      - 25
    environment:
      MAILNAME: somename.your-domain.com
      TLS_KEY: '/etc/ssl/domains/your-domain.com/your-domain.com.key'
      TLS_CRT: '/etc/ssl/domains/your-domain.com/your-domain.com.crt'
      TLS_CA: '/etc/ssl/domains/your-domain.com/intermediate.crt'
    volumes:
      - /etc/ssl/domains/your-domain.com/:/etc/ssl/domains/your-domain.com/:ro
    networks:
      watchtower:
        # this alias is really important to make your certificate work
        aliases:
          - smtp.your-domain.com
networks:
  watchtower:
    external: false
```

### Slack

To receive notifications in Slack, add `slack` to the `--notifications` option or the `WATCHTOWER_NOTIFICATIONS` environment variable.

Additionally, you should set the Slack webhook URL using the `--notification-slack-hook-url` option or the `WATCHTOWER_NOTIFICATION_SLACK_HOOK_URL` environment variable. This option can also reference a file, in which case the contents of the file are used.

By default, watchtower will send messages under the name `watchtower`, you can customize this string through the `--notification-slack-identifier` option or the `WATCHTOWER_NOTIFICATION_SLACK_IDENTIFIER` environment variable.

Other, optional, variables include:

-   `--notification-slack-channel` (env. `WATCHTOWER_NOTIFICATION_SLACK_CHANNEL`): A string which overrides the webhook's default channel. Example: #my-custom-channel.

Example:

```bash
docker run -d \
  --name watchtower \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e WATCHTOWER_NOTIFICATIONS=slack \
  -e WATCHTOWER_NOTIFICATION_SLACK_HOOK_URL="https://hooks.slack.com/services/xxx/yyyyyyyyyyyyyyy" \
  -e WATCHTOWER_NOTIFICATION_SLACK_IDENTIFIER=watchtower-server-1 \
  -e WATCHTOWER_NOTIFICATION_SLACK_CHANNEL=#my-custom-channel \
  containrrr/watchtower
```

### Microsoft Teams

To receive notifications in MSTeams channel, add `msteams` to the `--notifications` option or the `WATCHTOWER_NOTIFICATIONS` environment variable.

Additionally, you should set the MSTeams webhook URL using the `--notification-msteams-hook` option or the `WATCHTOWER_NOTIFICATION_MSTEAMS_HOOK_URL` environment variable. This option can also reference a file, in which case the contents of the file are used.

MSTeams notifier could send keys/values filled by `log.WithField` or `log.WithFields` as MSTeams message facts. To enable this feature add `--notification-msteams-data` flag or set `WATCHTOWER_NOTIFICATION_MSTEAMS_USE_LOG_DATA=true` environment variable.

Example:

```bash
docker run -d \
  --name watchtower \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e WATCHTOWER_NOTIFICATIONS=msteams \
  -e WATCHTOWER_NOTIFICATION_MSTEAMS_HOOK_URL="https://outlook.office.com/webhook/xxxxxxxx@xxxxxxx/IncomingWebhook/yyyyyyyy/zzzzzzzzzz" \
  -e WATCHTOWER_NOTIFICATION_MSTEAMS_USE_LOG_DATA=true \
  containrrr/watchtower
```

### Gotify

To push a notification to your Gotify instance, register a Gotify app and specify the Gotify URL and app token:

```bash
docker run -d \
  --name watchtower \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e WATCHTOWER_NOTIFICATIONS=gotify \
  -e WATCHTOWER_NOTIFICATION_GOTIFY_URL="https://my.gotify.tld/" \
  -e WATCHTOWER_NOTIFICATION_GOTIFY_TOKEN="SuperSecretToken" \
  containrrr/watchtower
```

`-e WATCHTOWER_NOTIFICATION_GOTIFY_TOKEN` or `--notification-gotify-token` can also reference a file, in which case the contents of the file are used.

If you want to disable TLS verification for the Gotify instance, you can use either `-e WATCHTOWER_NOTIFICATION_GOTIFY_TLS_SKIP_VERIFY=true` or `--notification-gotify-tls-skip-verify`.

### [containrrr/shoutrrr](https://github.com/containrrr/shoutrrr)

To send notifications via shoutrrr, the following command-line options, or their corresponding environment variables, can be set:

-   `--notification-url` (env. `WATCHTOWER_NOTIFICATION_URL`): The shoutrrr service URL to be used.

Go to [containrrr.github.io/shoutrrr/services/overview](https://containrrr.github.io/shoutrrr/services/overview) to
learn more about the different service URLs you can use. You can define multiple services by space separating the
URLs. (See example below)

You can customize the message posted by setting a template.

-   `--notification-template` (env. `WATCHTOWER_NOTIFICATION_TEMPLATE`): The template used for the message.

The template is a Go [template](https://golang.org/pkg/text/template/) and that format a list
of [log entries](https://pkg.go.dev/github.com/sirupsen/logrus?tab=doc#Entry).

The default value if not set is `{{range .}}{{.Message}}{{println}}{{end}}`. The example below uses a template that also
outputs timestamp and log level.

!!! tip "Custom date format"
    If you want to adjust the date/time format it must show how the
    [reference time](https://golang.org/pkg/time/#pkg-constants) (_Mon Jan 2 15:04:05 MST 2006_) would be displayed in your
    custom format.  
    i.e., The day of the year has to be 1, the month has to be 2 (february), the hour 3 (or 15 for 24h time) etc.

Example:

```bash
docker run -d \
  --name watchtower \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e WATCHTOWER_NOTIFICATIONS=shoutrrr \
  -e WATCHTOWER_NOTIFICATION_URL="discord://token@channel slack://watchtower@token-a/token-b/token-c" \
  -e WATCHTOWER_NOTIFICATION_TEMPLATE="{{range .}}{{.Time.Format \"2006-01-02 15:04:05\"}} ({{.Level}}): {{.Message}}{{println}}{{end}}" \
  containrrr/watchtower
```