Use Custom Notification Templates

As with every other aspect, Dolce comes with great default templates that are tailored specifically for each notifier. If you however want to customize the look or contents of the default, Dolce provides you with an easy way to override the templates that are used to generate the notifications.

Overriding a Template

When rendering a message, Dolce first checks if the template file exists inside DOLCE_CUSTOM_TEMPLATE_PATH. Only if this lookup fails the default template gets used, so to override the template for one or more notifier, create the following file:

./templates/<notifier>/<eventtype>.eta

where

• <notifier> is one of the built-in notifiers (smtp | discord | telegram | apprise) and
• <eventtype> is either event | reboot

depending on which notification you want to customise. The mount this folder to where DOLCE_CUSTOM_TEMPLATE_PATH points (by default this will be /var/dolce-custom-templates/):

docker-compose.yml

services:
  dolce:
    image: dangrie158/dolce:v3.2.0
    restart: unless-stopped
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - ./templates:/var/dolce-custom-templates # (1)!
    environment:
      ...

1. change the target path if you set DOLCE_CUSTOM_TEMPLATE_PATH to any other value.

Designing the Templates

As you can probably guess from the file extension, Dolce uses Eta as a templating engine to render the notification bodies so you can leverage the full power of JavaScript to generate the massge of you so choose.

Additionally some notifiers use the templates frontmatter in JSON format to specify additional attributes (e.g. EMail subject for SMTP notifier).

It is probably a good idea to to look at the default templates to get a starting point and work from there.

Template Context

Each template has access to a context object it that is populated with information that can be used inside the template.

Every template context contains the following global properties:

Name	Type	Description
hostname	string	Hostname of the machine running Dolce
newest_first	(DockerContainerEvent, DockerContainerEvent): number	See newest_first
get_event_class	(DockerContainerEvent): string	See get_event_class
get_event_symbol	(DockerContainerEvent): string	See get_event_symbol

For event templates the context additionally contains the following properties:

Name	Type	Description
events	DockerContainerEvent[]1	Events since the last notification
earliest_next_update	Date	Timestamp of the earliest next notification

For restart templates the context additionally contains the following properties:

Name	Type	Description
events_since_shutdown	DockerContainerEvent[]1	Events that happened while Dolce was not running
downtime_start	Date	Latest known timestamp where Dolce was still running
downtime_end	Date	Timestamp at which Dolce started again

Helper Functions

newest_first

This function takes two event arguments and returns the chronological order of the events so that newer events will be sorted first. This function is compatible with JavaScripts Array.sort and Array.toSorted which makes it perfect to iterate over a sorted array of events like this:

<% it.events.toSorted(it.newest_first).forEach(event => { %>
    <%= new Date(event.time * 1000).toLocaleString() %>: <%= event.Action %> <%= event.actor_name %>
<% }); %>

get_event_class

This function takes an event and returns one of success | warning | error depending on the event action. This is used to color the events in the default templates and can thus be used is custom templates to keep the same categorization that is used in the default templates:

event.Action	Class
start	success
die	error
kill	error
oom	error
stop	warning
pause	warning
unpause	success
health_status	warning

Example usage:

<span class="<%= it.get_event_class(event) %>"><%= event.Action %></span>

get_event_symbol

This function takes an event an returns a single UTF-8 glyph that can be used to represent the event based on the event action:

event.Action	Symbol
start	✅
die	❌
kill	❌
oom	❌
stop	⏹️
pause	⏸️
unpause	⏯️
health_status	❓

Example usage:

<%= event.actor_name %>: <%= it.get_event_symbol(event) %><%= event.Action %>

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1. DockerContainerEvent and DockerApiContainerEvent ↩↩