# Telemetry Alarming service overview

The Telemetry Alarming services trigger alarms when the collected metering or event data break the defined rules.

The Telemetry Alarming service consists of the following components:

An API server (`aodh-api`)

  Runs on one or more central management servers to provide access to the alarm information stored in the data store.

An alarm evaluator (`aodh-evaluator`)

  Runs on one or more central management servers to determine when alarms fire due to the associated statistic trend crossing a threshold over a sliding time window.

A notification listener (`aodh-listener`)

  Runs on a central management server and determines when to fire alarms. The alarms are generated based on defined rules against events, which are captured by the Telemetry Data Collection service’s notification agents.

An alarm notifier (`aodh-notifier`)

  Runs on one or more central management servers to allow alarms to be set based on the threshold evaluation for a collection of samples.

These services communicate by using the OpenStack messaging bus.

this page last updated: 2026-04-01 16:27:05

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