Sensu Go Fatigue Check Filter
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.
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 sensu/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.gzFilter definition
---
type: EventFilter
api_version: core/v2
metadata:
name: fatigue_check
namespace: default
spec:
action: allow
expressions:
- fatigue_check(event)
runtime_assets:
- fatigue-check-filterHandler definition
---
type: Handler
api_version: core/v2
metadata:
namespace: default
name: email
spec:
type: pipe
command: sensu-email-handler -f [email protected] -t [email protected] -s smtp.example.com
-u emailuser -p sup3rs3cr3t
timeout: 10
filters:
- is_incident
- not_silenced
- fatigue_checkCheck 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
handlers:
- email
interval: 60
publish: true
runtime_assets:
subscriptions:
- linuxEntity definition
Via the agent.yml:
---
##
# agent configuration
##
#name: ""
#namespace: "default"
#subscriptions:
# - "localhost"
annotations:
fatigue_check/occurrences: "3"
fatigue_check/interval: "900"
fatigue_check/keepalive_occurrences: "1"
fatigue_check/keepalive_interval: "300"
fatigue_check/allow_resolution: "false"
[...]
Keepalives
Keepalives do not have check resources with annotations that can be used to tune
this filter. Using standard entity annotations would override the settings for
all other checks. To address this specific case, two additional tunables
exist for customizing this filter for keepalive events. These can be set as
arguments to the fatigue_check() function in the filter definition or as
entity annotations to override the defaults on a per entity basis.
Cron scheduled checks
Since cron scheduled checks do not provide an explicit interval, this filter has to compute the apparent interval using the history available in the event. In order for this to work, there has to be at least two entries in the event's check history. The only time there would be less than two history entries is during the first two check executions. By default this should not be an issue, but in the unlikely case the interval is set this low, a default interval of 60 seconds is used.
Annotations
The Fatigue Check Filter makes use of four annotations within the check and/or
entity metadata for normal checks with an additional two keepalive annotations
availalbe in the entity metadata. The entity annotations taking precedence over
check annotations. All annotations take precedence of the fatigue_check()
function arguments and defaults.
| Annotation | Default | Usage |
|---|---|---|
| fatigue_check/occurrences | 1 | On which occurrence to allow the initial event to pass through for normal checks |
| fatigue_check/interval | 1800 | In seconds, at what interval to allow subsequent events to pass through, ideally a multiple of the check interval for normal checks |
| fatigue_check/allow_resolution | true | Determines whether or not a resolution event is passed through |
| fatigue_check/suppress_flapping | true | Determines whether or not to suppress events for checks that are marked as flapping |
| fatigue_check/keepalive_occurrences | 1 | On which occurrence to allow the initial event to pass through for keepalives (entity only) |
| fatigue_check/keepalive_interval | 1800 | In seconds, at what interval to allow subsequent events to pass through, ideally a multiple of the check interval for keepalives (entity only) |
Arguments
The fatigue_check() function can take up to five arguments.
fatigue_check(event, occurrences, interval, keepalive_occurrences, keepalive_interval)The first one is the event and is required. The remaining four are optional and allow you to override the built-in defaults for occurrences, interval, keepalive_occurrences, and keepalive_interval, respectively. For example, if you'd like a version of the filter that, by default on non-keepalive checks, matches on the second occurrence instead of the first you could create a filter similar to below:
---
type: EventFilter
api_version: core/v2
metadata:
name: fatigue_check_two_occurrences
namespace: default
spec:
action: allow
expressions:
- fatigue_check(event, 2)
runtime_assets:
- fatigue-check-filterIf you'd like one that overrides the default 30 minute interval for non-keepalive checks with a 10 minute one you could create one similar to below (note that in order to specify the third argument, you have to provide the second):
---
type: EventFilter
api_version: core/v2
metadata:
name: fatigue_check_10m_interval
namespace: default
spec:
action: allow
expressions:
- fatigue_check(event, 1, 600)
runtime_assets:
- fatigue-check-filterIf you'd like one that overrides the default occurrences for keeaplives and alerts on the second occurrence rather than the first you could create one similar to below (note that in order to specify the fourth argument, you have to provide the second and third):
---
type: EventFilter
api_version: core/v2
metadata:
name: fatigue_check_two_occurrences
namespace: default
spec:
action: allow
expressions:
- fatigue_check(event, 1, 1800, 2)
runtime_assets:
- fatigue-check-filterIf you'd like one that overrides the default 30 minute interval for keepalives with a 10 minute one you could create one similar to below (note that in order to specify the fifth argument, you have to provide the second, third, and fourth as well, even if you want the defaults):
---
type: EventFilter
api_version: core/v2
metadata:
name: fatigue_check_10m_interval
namespace: default
spec:
action: allow
expressions:
- fatigue_check(event, 1, 1800, 1, 600)
runtime_assets:
- fatigue-check-filterNon-repeating alerts
If you need to have alerts which will not repeat, meaning the alert is only ever
sent on the first occurrence and none after (aside from the resolution, if
allow_resolution is true, which is the default), then you will need to set the
interval (or keepalive_interval) to zero (0) via an annotation.
Installation from source
Sensu Go
See the instructions above for asset registration.
Additional 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
Please submit an issue if you have problems or suggestions.
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