1.8 KiB
Simplex.Messaging.Server.Prometheus
Prometheus text exposition format for router metrics, with histogram gap-filling and derived aggregations.
Source: Prometheus.hs
Histogram gap-filling
showTimeBuckets uses mapAccumL over sorted bucket keys. When the gap between consecutive buckets exceeds 60 seconds, it inserts a synthetic bucket at sec - 60 with the cumulative total up to that point. This fills sparse TimeBuckets maps into continuous Prometheus histograms. The 60-second gap threshold is hardcoded.
Bucket sum aggregation — filters by value, not key
showBucketSums intends to aggregate buckets into fixed time periods: 0-60s, 60-300s, 300-1200s, 1200-3600s, 3600+s. However, IM.filter (from Data.IntMap.Strict) filters by value (count), not by key (time). The predicate \sec -> minTime <= sec && sec < maxTime is applied to count values, not to the IntMap keys that represent seconds. This means buckets are selected based on whether their count falls in the range, not based on their time boundary. The aggregation boundaries are also independent of the bucketing thresholds in updateTimeBuckets (Stats.hs), which uses 5s/10s/30s/60s quantization.
Non-standard Prometheus timestamp output
The mstr function appends tsEpoch ts (millisecond-precision Unix timestamp) directly after metric values, which is valid Prometheus text exposition format.
Delivery histogram count/sum source
simplex_smp_delivery_ack_confirmed_time_count is _msgRecv + _msgRecvGet. simplex_smp_delivery_ack_confirmed_time_sum is sumTime from _msgRecvAckTimes. The count is accumulated separately from the histogram — if there's a code path that increments msgRecv without calling updateTimeBuckets, count and sum diverge.