# Rollups¶

A rollup is a simple mathematical function that takes all of the datapoints received over a period of time and produces a single output datapoint for that period. Rollups are a way to summarize data, and they enable SignalFx to render charts or perform computations for longer time ranges quickly, without compromising the accuracy of the results.

When SignalFx receives datapoints for a given time series, it accumulates them for specific periods of time and stores five rollups for each interval, as follows:

- Sum - The sum of all the values of the datapoints received during each interval
- Min - The lowest value from among the datapoints received during each interval
- Max -The highest value from among the datapoints received during each interval
- Count - The number of datapoints received during each interval
- Latest - The value of the most recent datapoint received during each interval

For example, if SignalFx receives the datapoint values 40, 50, 30, 10, and 20 (in that order) for a given time series in a 1-minute window, the 1-minute rollups will be stored as shown in the following table.

Rollup type | Value |
---|---|

Sum | 150 |

Count | 5 |

Min | 10 |

Max | 50 |

Latest | 20 |

In addition to the 5 rollups described above, additional rollup options are available for use when displaying chart data:

- Average - Calculates the mean of datapoint values received during each interval.
- Lag - Represents the difference between the time the measurement was taken (timestamp on the datapoint) and the time SignalFx received it, in milliseconds.
- Delta - For cumulative counters, summarizes data by calculating the difference between datapoints at successive intervals. Equivalent to Sum for counters.
- Rate per second - For cumulative counters, divides delta by the length of the interval. For counters, divides sum by length of the interval. Useful for showing running totals (e.g. error count) as a rate (e.g. number of errors per second).

For visualizing data in charts, SignalFx chooses a default rollup (displayed as “Auto”) that is appropriate to how you typically want to view the data; the default depends on the metric type, as shown in the following table.

Metric type | Default rollup | Other rollups available* |
---|---|---|

Gauge | Average | None |

Counter | Rate per second | None |

Cumulative counter | Rate per second | Delta |

* In addition to the rollups that are available for all metric types: Sum, Count, Min, Max, Latest, Average, and Lag.

You can change the rollup being used for a metric, and choose whether to display the rollup time on the plot line in the chart builder, in the plot configuration panel.

In some cases, you may see “Multiple” as the default rollup. If so, it is because your selected metric has more than one metric type, either because of a wildcard query, or because it is an AWS CloudWatch metric where the stat dimension has not been specified.

You can view and change the metric type in the Metrics Catalog; see Signals in Using the Metrics Catalog to Find Metrics.