Reliable Insights

A blog on monitoring, scale and operational Sanity

July 23, 2018

Absent Alerting for Scraped Metrics

In the previous post we looked at dealing with when all the targets for a job had disappeared. What if you wanted to alert on specific metrics from one target disappearing?

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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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