The Telemetry module is the metering service in OpenStack.

Even in the cloud industry, providers must use a multi-step process for billing. The required steps to bill for usage in a cloud environment are metering, rating, and billing. Because the provider's requirements may be far too specific for a shared solution, rating and billing solutions cannot be designed a common module that satisfies all. Providing users with measurements on cloud services is required to meet the "measured service" definition of cloud computing. The Telemetry module was originally designed to support billing systems for OpenStack cloud resources. This project only covers the metering portion of the required processing for billing. This module collects information about the system and stores it in the form of samples in order to provide data about anything that can be billed. The list of meters is continuously growing, which makes it possible to use the data collected by Telemetry for different purposes, other than billing. For example, the autoscaling feature in the Orchestration module can be triggered by alarms this module sets and then gets notified within Telemetry. The sections in this document contain information about the architecture and usage of Telemetry. The first section contains a brief summary about the system architecture used in a typical OpenStack deployment. The second section describes the data collection mechanisms. You can also read about alarming to understand how alarm definitions can be posted to Telemetry and what actions can happen if an alarm is raised. The last section contains a troubleshooting guide, which mentions error situations and possible solutions for the problems. You can retrieve the collected samples three different ways: with the REST API, with the command line interface, or with the Metering tab on an OpenStack dashboard.