Meters

A meter is what a usage charge bills when an event name alone isn't enough: the signals of one event whose data passes its filters (a field equals a value, doesn't, or is present), counted or summed over a number in their data, such as the pages of document_uploaded signals whose type is claim. A meter belongs to a product; price one of the product's usage charges on it with pricing.meterId in place of eventName (UsagePerUnit, UsageGraduated, UsageVolume and the prepaid-credits types, where each signal spends its meter quantity × creditCost). Each signal's quantity on each meter is measured once, as it arrives (signals already sent are measured when a meter is created), and stored with it, so invoices and the credits ledger read the numbers measured then. Preview a meter over past signals before you price on it. Once an order bills on a meter, what it counts is fixed: create a new meter to count differently. Archiving a meter only stops new charges naming it.