E Examples Of Metrics - HP HPE VAN SDN Controller 2.7 Administrator's Manual

E Examples of Metrics

The SDN controller has a subsystem for tracking metric values over time. Metric values are held
as a time series which becomes available to the user via JMX or may be persisted to disk. For
metric values that are persisted to disk the time-series values for each individual metric may be
persisted at intervals of 1, 5, or 15 minutes; the component or application creating the metric
may choose to use the default persistence. Each persisted value represents the value of the
metric over the elapsed interval represented by the metric. Persisted metric values are retained
on the controller disk for the period of time configured via the metric manager configuration.
Persisted metric values may be extracted from the controller using a series of REST calls.
Example 7 Persisted value
Consider the value of a counter that incremented from 100 to 145 during a 5 minute interval. By
taking the value at the end of the interval (145), less the value at the start of the interval (100)
the value persisted for the interval would be 45.
The amount of time during the interval over which the metric value was accrued is also persisted.
If the counter value was accrued over only the last 3 minutes of the 5 minute interval, then the
normalized rate of accrual over the interval would be 15 counts per minute or 75 counts for the
entire 5 minute interval.
The user can inspect the most recent value of the exposed metric using any JMX client (e.g.
jconsole). The values exposed will show the absolute value of each such metric. Metric values
that are retained only in memory and not exposed to the user via persistence and/or JMX may
be used internally by a component or application.
The metric REST API consists of several distinct commands that may be used in combination
to determine which metrics have persisted time-series values resident on the controller, what
each metric represents, and to retrieve time series values for specific metrics of interest. Note
this API operates only on a single controller at a time; it is not team-aware and does not return
values that span a controller team. The metrics applications commands will display the application
IDs – including the controller itself – that have persisted metrics to disk.
Figure 71 Metrics options
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