Requesting Statistics from vCenter Server

To request statistics, you must construct an appropriate request structure to filter statistics from the database.

To request data or metadata for a metric, you must supply the ID of the metric. You can get a list of metric IDs by using the list() method, which returns information on all available metrics.

When you query statistics, you provide a list of IDs to specify the metrics in which you are interested. You also supply a start time, an end time, a roll-up interval, and a roll-up function. These values interact as follows to determine the data returned to you.

• The response contains a list of data points for each metric ID you specified in the request.
• The start time and end time control the limits for the data you want in the response. The response contains data points only for statistics that have timestamps between those limits, inclusive of the endpoints. However, the start time is adjusted to a round number, in some cases. For more information, see Statistics Interval Adjustment in vCenter Server.
• The roll-up interval enables you to control the granularity of the data points in the response. Rather than a response with a data point for every statistic between the start time and end time, you get a response with a number of data points equal to the number of intervals between the start and end times. Generally, you should specify a time period that is an even multiple of the interval, so that each data point in the response represents the same number of statistics.
• The roll-up function specifies how the response summarizes the statistics that fall within each interval. The resulting data point can be the maximum statistic value within collection interval, or the mean of the statistics values within the interval, and so on.