<p>We have a custom metric that gets exported only upon some error condition in app</p>
<p>Alert rule use that custom metric that gets registered with rule manager of Prometheus</p>
<p>Why Prometheus does not raise error, when this metric name is queried? Despite the metric is not available in Prometheus yet...</p>

overexchange
<p>It seems correct that the absence of a signal is not treated as an error.</p>
<p>However, it can cause problems with dashboards and alerting.</p>
<p>See this presentation by one of Prometheus' creators: <a href="https://promcon.io/2017-munich/slides/best-practices-and-beastly-pitfalls.pdf" rel="nofollow noreferrer">Best Practices &amp; Beastly Pitfalls</a></p>
