My alert is alerting when I don't want it to or my alert is not alerting when I want it to. How can I change the alert so that it does what I want?

There are a multiple factors that affect when an alert fires. The most common reasons for an alert firing too often and becoming noisy are when the thresholds for the alert are too close to the measured levels of data. The easiest way to change this is to set thresholds that are further away from generally measured levels. In the case of percent change alerts, where the alert is based on the amount of change in a metric, keep in mind that the percentages will increase the smaller the magnitudes of the metrics. For instance, a fast metric like DNS is measured in milliseconds as opposed to Onload measured in seconds. With smaller values, even a small change in the metric measurement can trigger a large percent change.

You may also experience an alert that hasn't been firing when it ought to. There can be a few more factors at play here when troubleshooting. Checking the thresholds for the alert is the first step. If there is too great of a distance between the alert thresholds and the generally measured values on your site, the alert may never fire. Another very influential factor is the interplay between the Evaluation Window and Minimum Sample Size in the "Scheduling" portion of configuration. If the Minimum Sample Size is too high in a short Evaluation Window, the alert may never fire due to insufficient measurements to trigger the alert. This typically affects smaller sites with lower volumes of traffic.