From f825a9de80f8be3b9721de4c680b08def52b6990 Mon Sep 17 00:00:00 2001
From: Roman Khavronenko <roman@victoriametrics.com>
Date: Mon, 7 Oct 2024 14:27:50 +0200
Subject: [PATCH] app/vmselect/promql: fix seriesFetched update logic (#7181)
### Describe Your Changes
evalInstantRollup could have overreport the number of fetched series if
`offset` checks will result into retry. This change updates fetched
series only if these checks were successful.
It also adds a comment to another potential place of over-reporting
series fetched. It doesn't fix it, because it would require spending
extra resources on such a check, while discrepancy in seriesFetched
doesn't affect calculations in any way.
Probably related to
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/7170
### Checklist
The following checks are **mandatory**:
- [x] My change adheres [VictoriaMetrics contributing
guidelines](https://docs.victoriametrics.com/contributing/).
Signed-off-by: hagen1778 <roman@victoriametrics.com>
(cherry picked from commit ebd393d8b334bdec6a938a5d4ff67135bb1dbfaa)
Signed-off-by: hagen1778 <roman@victoriametrics.com>
---
app/vmselect/promql/eval.go | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/app/vmselect/promql/eval.go b/app/vmselect/promql/eval.go
index 69825a40a2..a27685e49f 100644
--- a/app/vmselect/promql/eval.go
+++ b/app/vmselect/promql/eval.go
@@ -1123,7 +1123,6 @@ func evalInstantRollup(qt *querytracer.Tracer, ec *EvalConfig, funcName string,
again:
offset := int64(0)
tssCached := rollupResultCacheV.GetInstantValues(qt, at, expr, window, ec.Step, ec.EnforcedTagFilterss)
- ec.QueryStats.addSeriesFetched(len(tssCached))
if len(tssCached) == 0 {
// Cache miss. Re-populate the missing data.
start := int64(fasttime.UnixTimestamp()*1000) - cacheTimestampOffset.Milliseconds()
@@ -1167,6 +1166,7 @@ func evalInstantRollup(qt *querytracer.Tracer, ec *EvalConfig, funcName string,
deleteCachedSeries(qt)
goto again
}
+ ec.QueryStats.addSeriesFetched(len(tssCached))
return tssCached, offset, nil
}
@@ -1678,6 +1678,10 @@ func evalRollupFuncWithMetricExpr(qt *querytracer.Tracer, ec *EvalConfig, funcNa
ecNew = copyEvalConfig(ec)
ecNew.Start = start
}
+ // call to evalWithConfig also updates QueryStats.addSeriesFetched
+ // without checking whether tss has intersection with tssCached.
+ // So final number could be bigger than actual number of unique series.
+ // This discrepancy is acceptable, since seriesFetched stat is used as info only.
tss, err := evalWithConfig(ecNew)
if err != nil {
return nil, err