Reliable Insights

A blog on monitoring, scale and operational Sanity

July 16, 2018

Absent Alerting for Jobs

Alerting on numbers being too big or small is easy with Prometheus. But what if the numbers go missing?

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May 28, 2018

Extracting raw samples from Prometheus

Sometimes you want the raw samples inside Prometheus for analysis or debugging. How do you get that?

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April 30, 2018

Identifying expensive alerting rules

Since Prometheus 2.1 there is a feature to view alerting rule evaluation times in the rules UI. In this blogpost we'll see an example of how this can be used to identify an expensive rule expression.

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April 23, 2018

Why can count(x > 5) not return 0?

When using the count aggregation operator you may have noticed that it sometimes returns nothing rather than 0. Why is this?

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March 19, 2018

Alerting on crash loops with Prometheus

If your applications are restarting regularly, whether due to segfaults or OOMs, it'd be nice to know.

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February 12, 2018

Alerting on gauges in Prometheus 2.0

One of the major changes introduced in Prometheus 2.0 was that of staleness handling. Previously for instant vectors, Prometheus would return a point up to 5 minutes in the past which caused a number of different issues.

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February 5, 2018

What percentage of time is my service down for?

Have you ever wondered what percentage of time a given service or application spends up or down?

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January 1, 2018

Rule groups for hierarchical aggregation

Prometheus 2.0 brought with it rule groups, making hierarchical aggregation easier than ever.

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December 11, 2017

Why are Prometheus histograms cumulative?

Have you ever wondered why the buckets in histograms are not just counters of events that fall into each bucket?

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December 4, 2017

Using time series as alert thresholds

Usually alert thresholds are hardcoded in the alert. In more sophisticated setups, it would be useful for it to be parameterised based on another time series.

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