Captures Prometheus Alertmanager events into Discourse, and creates a topic for every group of alerts currently firing. It will continue to keep track of all alerts in the group in the same topic until the topic is closed (indicating that the "incident" is over). Future alerts for the same group will then create a new topic, linking to the previous one.

In addition, all newly created topics will be assigned to a randomly-selected member of a specified group.

Setup

1. Install this plugin in the usual fashion into your Discourse site. You will also need to install the discourse-assign plugin, which this plugin depends on.

2. The plugin makes extensive use of tags and creates multiple topics with the same name. As such, SiteSetting.allow_duplicate_topic_titles and SiteSetting.tagging_enabled will be enabled by the plugin upon installation.

3. Create a new receiver URL by POSTing (as an admin user, so probably using an API key) to /prometheus/receiver/generate, with a request body that includes category_id (the numeric ID of the site category to create all new topics in) and assignee_group_id (the numeric group ID of the group from which to select an initial assignee). Take note of the URL in the response body, you will need that to configure the Prometheus Alertmanager.

4. Configure the Alertmanager to send webhook requests to your receiver URL, with a config something like this:

    receivers:
      - name: discourse
        webhook_configs:
          - send_resolved: true
            url: 'https://discourse.example.com/prometheus/receiver/asdf1234<etc>'
   

   You can set a reasonable repeat_interval if you like, as the alert receiver will deal gracefully with repeated alerts.

5. For all alerts you send to Discourse, you can provide some annotations in the alert rule to customise the created topic. However, Prometheus templates are limited in what they can do, so there's a certain amount of hard-coding in the title.

   The recognised annotations are:

• topic_title -- the title to give to all newly-created topics for the alert. If you don't set this, you'll get a fairly gnarly-looking topic title.

• topic_body -- the opening paragraph(s) of the first post in all newly-created topics for the alert, in markdown format. It is useful to give a brief description of the problem, and potentially links to a runbook or other useful information.

• topic_assignee: Accepts User#username. Automatically assigns the created topic to the specified user. Note that the specified user has to be an admin or is a member of an assignable group given by the assign_allowed_on_groups site setting.

• topic_group_assignee: Accepts Group#name. Automatically assigns the created topic to the specified group. Note that the specified group has to at least be assignable by an admin. The assignability of a group can be configured at the /g/admins/manage/interaction path.

• description -- the description will be displayed under each alert.

TODO

1. Admin UI to generate a receiver URL for Prometheus Alertmanager webhook.