Latency Improvements, or, Yet Another Satisfying Graph

This is the third in my ongoing series of posts containing satisfying graphs.

Today’s feature: a plot of the mean and 95th percentile submission delays of “main” pings received by Firefox Telemetry from users running Firefox Beta.

Screenshot-2017-7-12 Beta _Main_ Ping Submission Delay in hours (mean, 95th %ile)

We went from receiving 95% of pings after about, say, 130 hours (or 5.5 days) down to getting them within about 55 hours (2 days and change). And the numbers will continue to fall as more beta users get the modern beta builds with lower latency ping sending thanks to pingsender.

What does this mean? This means that you should no longer have to wait a week to get a decently-rigorous count of data that comes in via “main” pings (which is most of our data). Instead, you only have to wait a couple of days.

Some teams were using the rule-of-thumb of ten (10) days before counting anything that came in from “main” pings. We should be able to reduce that significantly.

How significantly? Time, and data, will tell. This quarter I’m looking into what guarantees we might be able to extend about our data quality, which includes timeliness… so stay tuned.

For a more rigorous take on this, partake in any of dexter’s recent reports on RTMO. He’s been tracking the latency improvements and possible increases in duplicate ping rates as these changes have ridden the trains towards release. He’s blogged about it if you want all the rigour but none of Python.

:chutten

FINE PRINT: Yes, due to how these graphs work they will always look better towards the end because the really delayed stuff hasn’t reached us yet. However, even by the standards of the pre-pingsender mean and 95th percentiles we are far enough after the massive improvement for it to be exceedingly unlikely to change much as more data is received. By the post-pingsender standards, it is almost impossible. So there.

FINER PRINT: These figures include adjustments for client clocks having skewed relative to server clocks. Time is a really hard problem when even on a single computer and trying to reconcile it between many computers separated by oceans both literal and metaphorical is the subject of several dissertations and, likely, therapy sessions. As I mentioned above, for rigour and detail about this and other aspects, see RTMO.