AGGREGATION_TEMPORALITY_CUMULATIVE

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:

1. The system starts receiving at time=t_0. 2. A request is received, the system measures 1 request. 3. A request is received, the system measures 1 request. 4. A request is received, the system measures 1 request. 5. The 1 second collection cycle ends. A metric is exported for the number of requests received over the interval of time t_0 to t_0+1 with a value of 3. 6. A request is received, the system measures 1 request. 7. A request is received, the system measures 1 request. 8. The 1 second collection cycle ends. A metric is exported for the number of requests received over the interval of time t_0 to t_0+2 with a value of 5. 9. The system experiences a fault and loses state. 10. The system recovers and resumes receiving at time=t_1. 11. A request is received, the system measures 1 request. 12. The 1 second collection cycle ends. A metric is exported for the number of requests received over the interval of time t_1 to t_0+1 with a value of 1.

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).