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rrd: Fix absolute rate calculations #6646

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Merged
merged 1 commit into from
Sep 3, 2025
Merged

rrd: Fix absolute rate calculations #6646

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10 changes: 6 additions & 4 deletions ocaml/libs/xapi-rrd/lib/rrd.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -342,9 +342,9 @@ let rra_update rrd proc_pdp_st elapsed_pdp_st pdps =

(* We assume that the data being given is of the form of a rate; that is,
it's dependent on the time interval between updates.
Gauge and Absolute data sources are simply kept as is without any
time-based calculations, while Derive data sources will be changed according
to the time passed since the last measurement. (see CA-404597) *)
Gauge data sources are simply kept as is without any time-based
calculations, while Absolute and Derive data sources will be changed
according to the time passed since the last measurement. (see CA-404597) *)
let process_ds_value ds value interval new_rrd =
if interval > ds.ds_mrhb then
nan
Expand All @@ -361,8 +361,10 @@ let process_ds_value ds value interval new_rrd =

let rate =
match (ds.ds_ty, new_rrd) with
| Absolute, _ | Derive, true | Gauge, _ ->
| Derive, true | Gauge, _ ->
value_raw
| Absolute, _ ->
value_raw /. interval
| Derive, false -> (
match (ds.ds_last, value) with
| VT_Int64 x, VT_Int64 y ->
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42 changes: 9 additions & 33 deletions ocaml/libs/xapi-rrd/lib_test/unit_tests.ml
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Expand Up @@ -147,46 +147,22 @@ let absolute_rrd =

let absolute_rrd_CA_404597 () =
let rra = rra_create CF_Average 100 1 0.5 in
let rra2 = rra_create CF_Average 100 10 0.5 in
let rra3 = rra_create CF_Average 100 100 0.5 in
let rra4 = rra_create CF_Average 100 1000 0.5 in
let ts = 1000000000.0 in
let ts = 0.0 in
let ds =
ds_create "foo" Absolute ~mrhb:10.0 ~min:0. ~max:infinity (VT_Float 0.0)
ds_create "foo" Absolute ~mrhb:1000.0 ~min:0. ~max:infinity (VT_Float 0.0)
in
let ds2 =
ds_create "bar" Absolute ~mrhb:10.0 ~min:0. ~max:infinity (VT_Float 0.0)
in
let ds3 =
ds_create "baz" Absolute ~mrhb:10.0 ~min:0. ~max:infinity (VT_Float 0.0)
in
let ds4 =
ds_create "boo" Absolute ~mrhb:10.0 ~min:0. ~max:infinity (VT_Float 0.0)
in
let rrd = rrd_create [|ds; ds2; ds3; ds4|] [|rra; rra2; rra3; rra4|] 1L ts in
let rrd = rrd_create [|ds|] [|rra|] 1L ts in
let id = Identity in
for i = 1 to 100000 do
let t = 1000000.0 +. (0.7 *. float_of_int i) in
let t = 300. *. float_of_int i in
let ((_, val1) as v1) =
(0, {value= VT_Float (0.5 +. (0.5 *. sin (t /. 10.0))); transform= id})
(0, {value= VT_Float (300. *. float_of_int i); transform= id})
in
let ((_, val2) as v2) =
(1, {value= VT_Float (1.5 +. (0.5 *. cos (t /. 80.0))); transform= id})
in
let ((_, val3) as v3) =
(2, {value= VT_Float (3.5 +. (0.5 *. sin (t /. 700.0))); transform= id})
in
let ((_, val4) as v4) =
(3, {value= VT_Float (6.5 +. (0.5 *. cos (t /. 5000.0))); transform= id})
in
ds_update rrd t [|v1; v2; v3; v4|] false ;
ds_update rrd t [|v1|] false ;

Array.iter2
(fun ds value ->
compare_float __LOC__ ds.ds_value
(float_of_string (ds_value_to_string value.value))
)
rrd.rrd_dss [|val1; val2; val3; val4|]
compare_float __LOC__
(float_of_string (ds_value_to_string val1.value) /. 300.)
rrd.rrd_dss.(0).ds_value
done

(** Verify that Gauge data soruce values are correctly handled by the RRD lib
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