Real User (Performance) Monitoring for hover tooltips

Created by: tsenart

Background

Real User (Performance) Monitoring telemetry extends our ability to understand the user experience from the user perspective by capturing browser performance metrics such as DNS latency, Network transfer latency, DOM rendering, CSS repaints, Garbage Collection pauses, etc. The metrics available to us on the server side are not enough.

We already have Sentry to capture errors that happen in the browser extensions. We should look into integrating a RUM service to help us establish a real user performance baseline.

Once we have visibility into this baseline and the outliers, it'd be beneficial to come up with an internal SLO (Service Level Objective) for critical user operations. (e.g. hover load time 99p < 1s)

Slow performance, specially in the first interactions, is a big deterrent for new users to adopt Sourcegraph. Having an explicit SLO to measure and track is meant to manage that user satisfaction in regards to performance.