ac3cc4be6e
Update the 'measurements' reference in samples.py to refer to the section that describes the supported sample types. Change-Id: I75913cdac6780d2cb6498999830ebb3734a8457e
3.9 KiB
New measurements
Ceilometer is designed to collect measurements from OpenStack services and from other external components. If you would like to add new meters to the currently existing ones, you need to follow the guidelines given in this section.
Types
Three type of meters are defined in Ceilometer:
double: meter; cumulative double: meter; gauge double: meter; delta
| Type | Definition |
|---|---|
| Cumulative | Increasing over time (instance hours) |
| Gauge | Discrete items (floating IPs, image uploads) and fluctuating values (disk I/O) |
| Delta | Changing over time (bandwidth) |
When you're about to add a new meter choose one type from the above list, which is applicable.
Units
- Whenever a volume is to be measured, SI approved units and their approved symbols or abbreviations should be used. Information units should be expressed in bits ('b') or bytes ('B').
- For a given meter, the units should NEVER, EVER be changed.
- When the measurement does not represent a volume, the unit description should always describe WHAT is measured (ie: apples, disk, routers, floating IPs, etc.).
- When creating a new meter, if another meter exists measuring something similar, the same units and precision should be used.
- Meters and samples should always document their units in Ceilometer (API and Documentation) and new sampling code should not be merged without the appropriate documentation.
| Dimension | Unit | Abbreviations | Note |
|---|---|---|---|
None Volume Time |
N/A byte seconds |
B s |
Dimension-less variable |
Meters
Naming convention
If you plan on adding meters, please follow the convention below:
- Always use '.' as separator and go from least to most discriminant word. For example, do not use ephemeral_disk_size but disk.ephemeral.size
- When a part of the name is a variable, it should always be at the end and start with a ':'. For example do not use <type>.image but image:<type>, where type is your variable name.
- If you have any hesitation, come and ask in #openstack-ceilometer
Non-metric meters and events
Ceilometer supports collecting notifications as events. It is highly recommended to use events for capturing if something happened in the system or not as opposed to defining meters of which volume will be constantly '1'. Events enable better representation and querying of metadata rather than statistical aggregations required for Samples. When the event support is turned on for Ceilometer, event type meters are collected into the event database too, which can lead to the duplication of a huge amount of data.
In order to learn more about events see the events section.