Changing retention period for metrics

You can change the retention period for metrics through an archive policy. By default, the ceilometer-low-rate and low policies are used to store metrics. Note that you cannot change the metering granularity for these policies.

To show the details of a particular archive policy

Use the gnocchi archive-policy show command. For example:

# gnocchi --insecure archive-policy show ceilometer-low-rate
+---------------------+---------------------------------------+
| Field               | Value                                 |
+---------------------+---------------------------------------+
| aggregation_methods | rate:mean, mean                       |
| back_window         | 0                                     |
| definition          | - points: 8640, granularity: 0:05:00, |
|                     |   timespan: 30 days, 0:00:00          |
| name                | ceilometer-low-rate                   |
+---------------------+---------------------------------------+

In the output:

• 8640 points shows how many aggregates will be retained
• the granularity of 5 minutes defines the time between two aggregates
• the timespan of 30 days specifies the retention period for aggregates

To sum it up, metrics with the ceilometer-low-rate policy will keep 8640 computed aggregates for one month with 5-minute granularity.

To change the policy definition

Use the gnocchi archive-policy update command. To calculate the correct number of points required for the desired timespan, refer to this formula:

points = timespan \ granularity

For example, to keep aggregates for 2 months with the 5-minute granularity, specify 17280 points:

# gnocchi --insecure archive-policy update ceilometer-low-rate \
-d points:17280,granularity:0:05:00,timespan:60d
+---------------------+----------------------------------------+
| Field               | Value                                  |
+---------------------+----------------------------------------+
| aggregation_methods | rate:mean, mean                        |
| back_window         | 0                                      |
| definition          | - points: 17280, granularity: 0:05:00, |
|                     |   timespan: 60 days, 0:00:00           |
| name                | ceilometer-low-rate                    |
+---------------------+----------------------------------------+