Incident #210


Complete, one action item outstanding.


Sentinel consumed by wolf after repeated false alarms.


Loss of sentinel. No flock impact.

Root causes

Sentinel generated noisy alerts due to premature deployment, incomplete training, and overly monotonous task. Oncalls failed to respond to true positive due to alert fatigue.




Gathered flock. Deployed replacement sentinel.


Sentinel did not report at end of shift.

Action Items

Priority Action Item Type Status
P0 Gather flock mitigate complete
P0 Deploy replacement sentinel mitigate complete
P1 Update playbook for wolf alerts prevent complete
P2 Update remaining sentinels prevent complete
P2 Revise sentinel training program prevent complete
P2 Investigate equipping sentinels with flutes or slings prevent in progress

Lessons Learned

What went well

  • Flock gathering proceeded without issues.
  • No flock injuries or losses.
  • Replacement sentinel did not exhibit false positive alerts.

What went wrong

  • Noisy alerts not addressed.
  • Alerts silenced contrary to playbook.
  • Loss of sentinel.

Where we got lucky

  • Only one wolf.
  • Wolf sated after sentinel consumption.
  • Replacement sentinel available.


All times local

March 3rd:

  • 16:32 Oncalls paged "wolf".
  • 16:34 First oncall arrives at sentinel location.
  • 16:34 Alert diagnosed as false positive. No corrective action performed.

March 4th:

  • 14:15 Oncalls paged "wolf".
  • 14:19 First oncall arrives at sentinel location.
  • 14:19 Alert diagnosed as false positive. No corrective action performed.

March 5th:

  • 17:03 (Reconstructed) Outage begins, sentinel notices wolf.
  • 17:03 Oncalls paged "wolf".
  • 17:04 Oncalls paged "wolf".
  • 17:04 Oncalls paged "real wolf".
  • 17:05 (Reconstructed) Wolf consumes sentinel.
  • 18:45 Sentinel does not report at end of shift.
  • 19:05 Primary oncall dispatched to field.
  • 19:10 Oncall diagnoses issue.
  • 19:10 Incident begins, secondary and tertiary oncalls paged.
  • 19:15 First sheep located.
  • 19:52 Last sheep located.
  • 20:05 Flock safe in pens.
  • 20:05 Outage ends, flock protection fully restored.
  • 20:45 Replacement sentinel identified.
March 6th:
  • 07:38 Replacement sentinel deployed
  • 18:45 Replacement sentinel reports at end of shift
  • 18:45 Incident ends, 24hr without wolf alerts or activity (exit criterion).

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13 comments, sorted by Click to highlight new comments since:

Man this is some fuckin' poetry.

This historical incident report fails to mention the true root cause, which has since been addressed: Wolves were not yet locally driven to extinction.


I thought the true root cause was that people were still raising animals for human consumption?

in sufficiently complex systems, there is often no single root cause, even if you could see the entire causal graph. This seems like a case where that applies to me.

... but also, what jeff said

I don't understand what I just read.

It's the "Boy who cried wolf" fable in the format of an incident report such as what might be written in the wake of an industrial disaster. Whether the fictional report writer has learned the right lessons I suppose is an exercise left for the reader.

See also: Swiss cheese model

tl;dr: don't overanalyze the final cause of disaster; usually it was preceded by serial failure of prevention mechanisms, any one or all of which can be improved for risk reduction.


Yeah but false positive. Every time anyone mentions all the ignored warnings they never try to calculate how many times the same warning occurred and everything was fine?

It's easy to point to O rings after the space shuttle is lost. But how many thousand other weak links were NASA/contractor engineers concerned about?

OK, but why equip sentinels with flutes?

To make the task less monotonous. This is also a major benefit of slings.

(Epistemic status: lyrics)

I’m not too clear about what you just spoke. Is that a parable, or a very subtle joke?

If you're making false claims of your incomprehension, it's clear that you've missed the moral dimension. When you truly can't get what someone is saying, remember today and the games you were playing. It takes people effort to give added proof...and they won't put that in for the boy who cries wolf.

Oh boy, this is terrifyingly familiar from my oncall days!