The logic of those calculations is the same for Composite SLOs as for regular (standard) objectives and SLOs. For more information on Error Budget Burn Rate, refer to the Glossary | Nobl9 Documentation.
The only differences in the calculations are as follows:
SLI comes from the N9 app, not from the Agent or Direct. Possible SLIs are:
burn rate for Occurrences (the same as on the charts on SLO Details)
good or bad minute for Time Slices - those values are not presented on any chart; they are used to calculate burn rates and error budgets
burnRateCondition used for determining if the error budget will burn
Does it matter for Composite SLO if there is one or many objectives with a burn rate greater than the burn rate condition?
No. One objective satisfying burn rate condition causes the budget for Composite SLO to burn at the same rate.
Do objective calculations restart when I change the SLO type to Composite SLO?
No, calculations for the objectives are not restarted. Enabling Composite SLO does not cause any loss of results or chart data.
Changing the burn rate condition causes the charts for Composite SLO to reset the calculations as for a standard objective when the objective value is changed.
Is objective's historical data included in calculations for Composite SLO charts?
Nobl9 does not calculate data for Composite SLOs charts by using objective's historical data. Creating Composite SLO is similar to creating a new objective - only new incoming data is used during calculations.