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Telemetry Data Collection service overview
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The Telemetry Data Collection services provide the following functions:

* Efficiently polls metering data related to OpenStack services.

* Collects event and metering data by monitoring notifications sent
  from services.

* Publishes collected data to various targets including data stores and
  message queues.

The Telemetry service consists of the following components:

A compute agent (``ceilometer-agent-compute``)
  Runs on each compute node and polls for resource utilization
  statistics.

A central agent (``ceilometer-agent-central``)
  Runs on a central management server to poll for resource utilization
  statistics for resources not tied to instances or compute nodes.
  Multiple agents can be started to scale service horizontally.

A notification agent (``ceilometer-agent-notification``)
  Runs on a central management server(s) and consumes messages from
  the message queue(s) to build event and metering data. Data is then
  published to defined targets. By default, data is pushed to Gnocchi_.

These services communicate by using the OpenStack messaging bus. Ceilometer
data is designed to be published to various endpoints for storage and
analysis.

.. note::

   Ceilometer previously provided a storage and API solution. As of Newton,
   this functionality is officially deprecated and discouraged. For efficient
   storage and statistical analysis of Ceilometer data, Gnocchi_ is
   recommended.

.. _Gnocchi: http://gnocchi.xyz