Alerta-blackout-regex

headphonejames optimised to pull the Blackouts via the Alerta model, instead of DB query. See 21.
deesel Added support for multitenant deployments. See 23.

Starting with version 3.0.0 onwards, the plugin will gather the list of Blackouts straight from the database (instead of using the API, as previously). This should normally improve reliability, but as there's no caching involved, every alert notification coming in (before being evaluated and correlated) will cause a DB query.

The configuration options for caching are therefore no longer required.

Additionally, you can now have regular expressions on the environment name (athough via the Alerta UI you are only able to select the environments that have produced alerts, you can use whatever environment name via the API).

We currently act on the every alert in the `post_receive` which
evaluates the alert _after_ it has been correlated et al. While this is
an optimal approach from some perspectives, it introduces some confusion
and the alert risks to be thrown to other plugins before it's been acted
on (for example displayed in Slack).
To work around this unfortunate design choice, moving the code to be
executed in `pre_receive`; this has the major disadvantage that every
alert would request the Blackouts API endpoint - but caching the results
into a file would alleviate this.

Fix 6: Don't override the alerts status to blackout when it's 'closed' 7