Option
vitals of project
How much of the speed real visitors see is measured.
Value
{ share }: the share of the page views that are measured, from 0 to 1, 0.1 where it is left out; 0 measures none. A page that is measured loads a small part of the page code once the browser is idle, so it costs nothing at its start, and takes the browser's own measures: the time to the largest content, the delay of a press, the shift of the layout, the time to the first byte, and the time of each move between screens. It sends them once, when the page is hidden, to /_t/vitals.
The engine keeps them in the table vitals of its log, with the screen, the version, the kind of device by the width of the window, and the kind of connection: nothing that says whose visit it was. It takes them from a page of the app's own origin alone, holds each value to the range its measure can have, and takes limits.vitalsPerMinute (60) from one address. tent logs --vitals shows, for each screen, the 75th share of each measure over a day against the line of good for it, the screens furthest past their line first, each version beside the one before. With trace.otlp they are sent out as metrics too.
Example
export const shop = project('shop', { vitals: { share: 0.25 } })