In some instances, you might encounter a response that reports an empty data value, or even a series of empty data values. This might manifest as a list of data values containing some numeric values alternating with empty values.
- Empty data values can happen when the report time period is too short to be certain of containing any statistics. For instance, a time period of 30 seconds is half the length of the sample period for network metrics, so you have only a 50% chance of finding a network statistic during any 30-second reporting period.
- Empty data values can also happen when the interval is shorter than the sample period for a metric you have requested. In this case, some data points are present in the list, while others are empty because no statistic was collected during those intervals. For instance, an interval of 5 minutes is only half the length of the sample period for storage metrics, so every second data value is empty.
- Empty data values can also happen when the monitoring service has not finished collecting and writing the last sample to the database, even if the nominal sample timestamp falls within the report time period. For example, calculation of storage used can delay writing a storage statistic to the database. A request for the statistic during that delay time produces an empty data point in the response.
When a response contains an empty data value, this indicates that no statistics were collected during a collection interval. An appropriate action for the client in such a case depends on how the client is using the data. For example, if you are graphing a resource usage trend, you might choose to interpolate for the missing value to produce a smooth line.
