Sensu Go Fatigue Check Filter

• Overview
• Files
• Usage examples
• Configuration
  • Sensu Go
    • Asset registration
    • Asset definition
    • Filter definition
    • Handler definition
    • Check definition
    • Entity definition
• Sensu Core
• Installation from source
• Additional notes
• Contributing

Overview

The Sensu Go Fatigue Check Filter is a Sensu Event Filter for managing alert fatigue.

A typical use of filters is to reduce alert fatigue. One of the most typical examples of this is create the following filter that only passes through events on their first occurrence and every hour after that.

{
  "type": "EventFilter",
  "api_version": "core/v2",
  "metadata": {
    "name": "hourly",
    "namespace": "default"
  },
  "spec": {
    "action": "allow",
    "expressions": [
      "event.check.occurrences == 1 || event.check.occurrences % (3600 / event.check.interval) == 0"
    ],
    "runtime_assets": []
  }
}

However, the use of the filter above creates some limitations. Suppose you have one check in particular that you want to change to only alert after three (3) occurrences. Typically that might mean creating another handler and filter pair to assign to that check. If you have to do this often enough and you start to have an unwieldy mass of handlers and filters.

That's where this Fatigue Check Filter comes in. Using annotations, it makes the number of occurrences and the interval tunable on a per-check or per-entity basis. It also allows you to control whether or not resolution events are passed through.

Files

N/A

Usage examples

N/A

Configuration

Sensu Go

Asset registration

Assets are the best way to make use of this plugin. If you're not using an asset, please consider doing so! If you're using sensuctl 5.13 or later, you can use the following command to add the asset:

sensuctl asset add nixwiz/sensu-go-fatigue-check-filter --rename fatigue-check-filter

Note that the --rename is not necessary, but references to the runtime asset in the filter definition as in the example below would need to be updated to match.

If you're using an earlier version of sensuctl, you can download the asset definition from this project's Bonsai asset index page.

You can create your own asset by creating a tar file containing lib/fatigue_check.js and creating your asset definition accordingly.

Asset definition

If not using sensuctl asset add:

{
  "type": "Asset",
  "api_version": "core/v2",
  "metadata": {
    "name": "fatigue-check-filter",
    "namespace": "default"
  },
  "spec": {
    "sha512": "2e67975df7d993492cd5344edcb9eaa23b38c1eef7000576b396804fc2b33362b02a1ca2f7311651c175c257b37d8bcbbce1e18f6dca3ca04520e27fda552856",
    "url": "http://example.com/sensu/assets/fatigue-check.tar.gz"
  }
}

Filter definition

{
  "type": "EventFilter",
  "api_version": "core/v2",
  "metadata": {
    "name": "fatigue_check",
    "namespace": "default"
  },
  "spec": {
    "action": "allow",
    "expressions": [
      "fatigue_check(event)"
    ],
    "runtime_assets": [
      "fatigue-check-filter"
    ]
  }
}

Handler definition

{
    "api_version": "core/v2",
    "type": "Handler",
    "metadata": {
        "namespace": "default",
        "name": "email"
    },
    "spec": {
        "type": "pipe",
        "command": "sensu-email-handler -f from@example.com -t to@example.com -s smtp.example.com -u emailuser -p sup3rs3cr3t",
        "timeout": 10,
        "filters": [
            "is_incident",
            "not_silenced",
            "fatigue_check"
        ]
    }
}

Check definition

{
  "type": "CheckConfig",
  "api_version": "core/v2",
  "metadata": {
    "name": "linux-cpu-check",
    "namespace": "default",
    "annotations": {
      "fatigue_check/occurrences": "3",
      "fatigue_check/interval": "900",
      "fatigue_check/allow_resolution": "false"
    }
  },
  "spec": {
    "command": "check-cpu -w 90 c 95",
    "env_vars": null,
    "handlers": [
      "email"
    ],
    "high_flap_threshold": 0,
    "interval": 60,
    "low_flap_threshold": 0,
    "output_metric_format": "",
    "output_metric_handlers": null,
    "proxy_entity_name": "",
    "publish": true,
    "round_robin": false,
    "runtime_assets": null,
    "stdin": false,
    "subdue": null,
    "subscriptions": [
      "linux"
    ],
    "timeout": 0,
    "ttl": 0
  }
}

Entity definition

Via the agent.yml:

---
##
# agent configuration
##

#name: ""

#namespace: "default"

#subscriptions: 
#  - "localhost"

annotations:
  fatigue_check/occurrences: "3"
  fatigue_check/interval: "900"
  fatigue_check/allow_resolution: "false"

[...]

Sensu Core

N/A

Installation from source

Sensu Go

See the instructions above for asset registration.

Sensu Core

Install and setup plugins on Sensu Core.

Additional notes

Configuration

The Fatigue Check Filter makes use of four annotations within the check and/or entity metadata, with the entity annotations taking precedence.

Notes:

• This filter makes use of the occurrences_watermark attribute that was buggy up until Sensu Go 5.9. Your mileage may vary on prior versions.
• If the interval is not a multiple of the check's interval, then the actual interval is computed by rounding up the result of dividing the interval by the check's interval. For example, an interval of 180s with a check interval of 25s would pass the event through on every 8 occurrences (200s).

Contributing

N/A