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. This is actually the polling agent ceilometer-polling running with parameter --polling-namespace compute.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. This is actually the polling agent ceilometer-polling running with parameter --polling-namespace central.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.