alerta-blackout-regex

Alerta <https://alerta.io/>_ plugin to enhance the blackout management, by
matching the alerts against blackouts with PCRE (Perl Compatible Regular
Expression) on attributes.

A blackout is considered matched when all its attributes are matched.

Once an alert is identified as matching a blackout, a special label is applied,
with the format: regex_blackout=<blackout id>, where blackout id is the
ID of the matched blackout, e.g.,
regex_blackout=d8ba1d3b-dbfd-4677-ab00-e7f8469d7ad3. This way, when the
alert is fired again, there's no need to verify the matching again, but simply
verify whether the blackout referenced is still active.

.. important::

Beginning with version 2.0.0, the behaviour has changed, and instead of 
evaluating the alert into the `post_receive` hook, this plugin now 
evaluates the alerts through the `pre_receive` hook. The reasoning was that 
`post_receive` would set the `blackout` status *after* the alert has been 
sent to other plugins, which has resulted in confusing behaviour.

That said, the plugin has been changed to process the alert in 
``pre_receive`` and therefore before the alert has been correlated. As the 
Blackouts are retrieved from the Alerta API as unfortunately there's no 
other way to gather the Blackouts from a plugin via other internal 
mechanisms, processing each and every alert throguh `pre_receive` would put 
a lot more workload on your Alerta API. To reduce this, the 
`blackout_regex` plugin now caches the Blackouts locally, into a file. To 
fine tune this behaviour for your own setup you are able to set a few 
environment variables. See more details below, under the _Configuration_ 
section.

.. note::

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.

Installation

This plugin is designed to be installed on the Alerta server; the package is
available on PyPI so you can install as:

.. code-block:: bash

pip install alerta-blackout-regex

Configuration

Add blackout_regex to the list of enabled PLUGINS in alertad.conf server
configuration file and set plugin-specific variables either in the server
configuration file or as environment variables.

.. code-block:: ini

PLUGINS = ['blackout_regex']

.. note::

To ensure this plugin won't affect the existing Blackouts you may have in 
place, it is recommended to list the `blackout_regex` plugin *after* the 
native ``blackout`` plugin in the ``PLUGINS`` configuration option or 
environment variable.

References

• Suppressing Alerts using Blackouts <https://docs.alerta.io/en/latest/gettingstarted/tutorial-5-blackouts.html>_

License

Copyright (c) 2020-2023 Mircea Ulinic. Available under the Apache License 2.0.