System architecture¶

The Telemetry service uses an agent-based architecture. Several modules combine their responsibilities to collect data, store samples in a database, or provide an API service for handling incoming requests.

The Telemetry service is built from the following agents and services:

ceilometer-api (deprecated in Ocata)

Presents aggregated metering data to consumers (such as billing engines and analytics tools). Alarm, Meter and Event APIs are now handled by aodh, gnocchi, and panko services respectively.

ceilometer-polling

Polls for different kinds of meter data by using the polling plug-ins (pollsters) registered in different namespaces. It provides a single polling interface across different namespaces. The compute namespace polls the local hypervisor to acquire performance data of local instances. The central namespace polls the public RESTful APIs of other OpenStack services such as Compute service and Image service. The ipmi namespace polls the local node with IPMI support, in order to acquire IPMI sensor data and Intel Node Manager datahost-level information.

ceilometer-agent-notification

Consumes AMQP messages from other OpenStack services, normalizes messages, and publishes them to configured targets.

ceilometer-collector (deprecated in Ocata)

Consumes AMQP notifications from the agents, then dispatches these data to the appropriate data store.

Note

1. The ceilometer-polling service provides polling support on any namespace but many distributions continue to provide namespace-scoped agents: ceilometer-agent-central, ceilometer-agent-compute, and ceilometer-agent-ipmi.
2. The ceilometer-api and ceilometer-collector are no longer supported since the Ocata release. Storage and API are provided by gnocchi, aodh, and panko services.

Except for the ceilometer-polling agents polling the compute or ipmi namespaces, all the other services are placed on one or more controller nodes.

The Telemetry architecture highly depends on the AMQP service both for consuming notifications coming from OpenStack services and internal communication.