A sampled, structured decision log.

Writing to Logger, or anywhere else, from the request path would send a message or block for every request, so decisions are instead sampled into a fixed-size ring buffer: an ETS table indexed by an :atomics cursor, one per instance. Limen.DecisionLog.Flusher drains the buffer periodically and hands the decisions, in batches, to the instance's sink: by default Limen.DecisionLog.Logger, which writes each as a structured Logger report, or your own Limen.DecisionLog.Sink, to keep them in a database. When the buffer wraps faster than it is drained, the oldest entries are overwritten and the flusher logs how many were lost.

In tests, delivery: :inline hands each sampled decision to the sink at once, in the process that made it, instead (see the :decision_log options in Limen.Config); the buffer still keeps it for recent/2.

The same buffer backs recent/2, which the LiveDashboard page uses to show the latest decisions.

Sampling is configured with the :decision_log option, see Limen.Config.