mikejihbe/metrics

Standard deviation is Nan

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#51 opened on Oct 3, 2017

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help wanted

Description

My service is outputting metrics to Grafana but it's end points are never called. What I'm finding is that the standard deviation value is NaN, output via:

send(util.format('%s.%s', histogram.name, 'stddev'), histogram.stdDev(), timestamp);

in graphite-reporter.js. I suspect this should output zero.

Contributor guide

Tech stack
javascriptnodejs
Domain
backendobservability
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
basic JavaScriptunderstanding of standard deviation
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
90
Research direction
Look at the `graphite reporter.js` file in the repository, specifically the line that calls `histogram.stdDev()` and then formats the output. The standard deviation calculation likely returns NaN when there are no data points or all values are equal. Modify the code to output 0 when the result is NaN, e.g., by using `isNaN()` check before sending the metric. Test with a histogram that has no observations to verify the fix.