Design: show application alerts #8261

Applications will be able to provide their own alert rules (#8100), for example when a phone trunk is down or a mail queue grows. Today the cluster-admin UI shows only node alerts, without telling which ones concern an application, so administrators cannot see at a glance which application needs attention.

The purpose of this issue is the UI design of application alerts.

Proposed solution

Design where and how alerts are shown:

• count active alerts in the Cluster Status page, separating node alerts from application alerts
• show the active alerts of an application in its page, and a badge in the Applications list
• link each alert to the page where the problem can be checked or fixed, like the application settings or the System logs
• show the severity, the start time, and a short description written by the application developer, with translations

The design output is a mockup. Implementation issues follow.

Alternative solutions

• Show alerts only in Grafana: requires the Metrics application and gives no hint in the cluster-admin UI.
• Show alerts only by email: already available for critical alerts, but easy to miss.

Additional context

#8100 provides the backend: this design does not block it.

See also

• Allow applications to provide their own alert rules: Allow applications to provide their own alert rules #8100
• Discussion https://mattermost.nethesis.it/nethesis/pl/hb94wc6eb3r35bgdyp5kymirre
• Discussion (Lucia) https://mattermost.nethesis.it/nethesis/pl/eyeu9urua7fpuknmou3s4gf4xr