As resources are being managed within the OpenStack cluster, there are certain types of things that are being measured by Ceilometer. These types of things are called meters in Ceilometer. Each of these types of measurements gathers samples. Samples are single measurements or data points of a certain meter. The definition of how often to sample a meter is called a pipeline. Once enough samples are collected, they can be aggregated into statistics. Ceilometer statistics show a collection of samples over time for a particular meter. Ceilometer also has the ability to set alarms that will monitor statistics and is able to respond to matching criteria.