AggregationTemporality defines how a metric aggregator reports aggregated values. It describes how those values relate to the time interval over which they are aggregated.
CUMULATIVE is an AggregationTemporality for a metric aggregator which reports changes since a fixed start time. This means that current values of a CUMULATIVE metric depend on all previous measurements since the start time. Because of this, the sender is required to retain this state in some form. If this state is lost or invalidated, the CUMULATIVE metric values MUST be reset and a new fixed start time following the last reported measurement time sent MUST be used.
For example, consider a system measuring the number of requests that it receives and reports the sum of these requests every second as a CUMULATIVE metric:
Note: Even though, when reporting changes since last report time, using CUMULATIVE is valid, it is not recommended. This may cause problems for systems that do not use start_time to determine when the aggregation value was reset (e.g. Prometheus).
DELTA is an AggregationTemporality for a metric aggregator which reports changes since last report time. Successive metrics contain aggregation of values from continuous and non-overlapping intervals.
The values for a DELTA metric are based only on the time interval associated with one measurement cycle. There is no dependency on previous measurements like is the case for CUMULATIVE metrics.
For example, consider a system measuring the number of requests that it receives and reports the sum of these requests every second as a DELTA metric:
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