CA-411679: Runstate metrics return data over 100%

To handle deviations in CPU rates, Derive values exceeding the maximum
by up to 5% are capped at the maximum; others are marked as unknown.
This logic is specific to Derive data sources because they represent
rates derived from differences over time, which can occasionally
exceed expected bounds due to measurement inaccuracies.

Signed-off-by: Bengang Yuan <[email protected]>

Author: BengangY

ocaml/libs/xapi-rrd/lib/rrd.ml

@@ -468,11 +468,23 @@ let ds_update rrd timestamp valuesandtransforms new_rrd =
               in
               (* Apply the transform after the raw value has been calculated *)
               let raw = apply_transform_function transform raw in
+
               (* Make sure the values are not out of bounds after all the processing *)
-              if raw < ds.ds_min || raw > ds.ds_max then
-                (i, nan)
-              else
-                (i, raw)
+              match (ds.ds_ty, raw) with
+              | Derive, _ when raw > ds.ds_max && raw < ds.ds_max *. (1. +. 0.05)
+                ->
+                  (* CA-411679: To handle deviations in CPU rates, Derive values
+                     exceeding the maximum by up to 5% are capped at the maximum;
+                     others are marked as unknown. This logic is specific to
+                     Derive data sources because they represent rates derived
+                     from differences over time, which can occasionally exceed
+                     expected bounds due to measurement inaccuracies. *)
+                  (i, ds.ds_max)
+              | (Derive | Gauge | Absolute), _
+                when raw < ds.ds_min || raw > ds.ds_max ->
+                  (i, nan)
+              | (Derive | Gauge | Absolute), _ ->
+                  (i, raw)
           )
           valuesandtransforms
       in