Glossary

agent

Software service running on the OpenStack infrastructure measuring usage and sending the results to the collector.

alarm

An action triggered whenever a meter reaches a certain threshold.

API server

HTTP REST API service for ceilometer.

ceilometer

From Wikipedia [1]:

A ceilometer is a device that uses a laser or other light source to determine the height of a cloud base.

central agent

Software service running on a central management node within the OpenStack infrastructure measuring usage and sending the results to the collector.

collector

Software service running on the OpenStack infrastructure monitoring notifications from other OpenStack components and samples from the ceilometer agent and recording the results in the database.

compute agent

Software service running on a compute node within the OpenStack infrastructure measuring usage and sending the results to the collector.

data store

Storage system for recording data collected by ceilometer.

meter

The measurements tracked for a resource. For example, an instance has a number of meters, such as duration of instance, CPU time used, number of disk io requests, etc. Three types of meters are defined in ceilometer:

• Cumulative: Increasing over time (e.g. disk I/O)
• Gauge: Discrete items (e.g. floating IPs, image uploads) and fluctuating values (e.g. number of Swift objects)
• Delta: Incremental change to a counter over time (e.g. bandwidth delta)

notification

A message sent via an external OpenStack system (e.g Nova, Glance, etc) using the Oslo notification mechanism [2]. These notifications are usually sent to and received by Ceilometer through the notifier RPC driver.

non-repudiable

From Wikipedia [3]:

Non-repudiation refers to a state of affairs where the purported maker of a statement will not be able to successfully challenge the validity of the statement or contract. The term is often seen in a legal setting wherein the authenticity of a signature is being challenged. In such an instance, the authenticity is being “repudiated”.

project

The OpenStack tenant or project.

resource

The OpenStack entity being metered (e.g. instance, volume, image, etc).

sample

Data sample for a particular meter.

source

The origin of metering data. This field is set to “openstack” by default. It can be configured to a different value using the sample_source field in the ceilometer.conf file.

user

An OpenStack user.

[1]	http://en.wikipedia.org/wiki/Ceilometer

[2]	https://git.openstack.org/cgit/openstack/ceilometer/tree/ceilometer/openstack/common/notifier

[3]	http://en.wikipedia.org/wiki/Non-repudiation