Brian, even better - great.
Now that you mentioned how count() returns no labels - it relates to
another alert rule I was trying to implement.
If I wanted to alert anytime a counter is incremented (and have it self
resolve after x time), this seems to do it:
*count(exception_total) - count(exception_total offset 1h) *
{} 0
above returns a zero value when it has been incremented but no labels or
useful results otherwise, but this other query I happened upon returns
labels and I don't understand why
*exception_total unless exception_total offset 1h*
exception_total{pod="x"} 1
exception_total{pod="y"} 1
exception_total{pod="z"} 1
--
Dan
On Mon, Oct 4, 2021 at 7:02 PM Brian Candler <[email protected]> wrote:
> count() returns no labels, and it also returns no timeseries when it has
> no input (rather than a timeseries with value zero, which I had naïvely
> expected). So this is simpler again:
>
> absent(jenkins_up) and count(up{job="jenkins"})
>
> On Monday, 4 October 2021 at 15:29:14 UTC+1 Dan S wrote:
>
>> Thanks Brian for the advice! I found the `absent() and absent()` seemed
>> to work well.
>>
>> Also Ben - thank you - I did take your advice as well re: making multiple
>> layers of alerts, and didn't know about
>> prometheus_target_scrape_pool_targets,
>> which could be useful in other ways as well.
>>
>> Appreciate it!
>>
>> Dan
>>
>>
>> On Mon, Oct 4, 2021 at 5:07 PM Brian Candler <[email protected]> wrote:
>>
>>> On Sunday, 3 October 2021 at 22:50:59 UTC+1 [email protected] wrote:
>>>
>>>> Trying to manipulate alerts with absent() tends to behave badly.
>>>>
>>>
>>> Aside: I found it a bit surprising at first that count() and sum()
>>> across an empty instant vector give an empty result, rather than 0. I
>>> don't see that behaviour explicitly called out here
>>> <https://prometheus.io/docs/prometheus/latest/querying/operators/#aggregation-operators>,
>>> but I guess it makes sense when you think about what "count by", "sum by"
>>> or "count_values" would have to do, when given no input.
>>>
>>> You can of course make it work the other way if required: e.g.
>>> "count(foo) or vector(0)"
>>>
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>>>
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