Deduplicate metamonitoring queries (thanos-io#6121)

* Deduplicate metamonitoring queries

Signed-off-by: Andre Baptista Aguas <andre.aguas@protonmail.com>
Signed-off-by: Andre Baptista Aguas <andre.agua@protonmail.com>

* Update CHANGELOG

Signed-off-by: Andre Baptista Aguas <andre.aguas@protonmail.com>
Signed-off-by: Andre Baptista Aguas <andre.agua@protonmail.com>

* do not remove empty line from CHANGELOG

Signed-off-by: Andre Baptista Aguas <andre.agua@protonmail.com>

---------

Signed-off-by: Andre Baptista Aguas <andre.aguas@protonmail.com>
Signed-off-by: Andre Baptista Aguas <andre.agua@protonmail.com>
Co-authored-by: Andre Baptista Aguas <andre.agua@protonmail.com>

CHANGELOG.md

@@ -31,6 +31,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 - [#6082](https://github.com/thanos-io/thanos/pull/6082) Store: Don't error when no stores are matched.
 - [#6098](https://github.com/thanos-io/thanos/pull/6098) Cache/Redis: upgrade `rueidis` to v0.0.93 to fix potential panic when the client-side caching is disabled.
 - [#6103](https://github.com/thanos-io/thanos/pull/6103) Mixins(Rule): Fix query for long rule evaluations.
+- [#6121](https://github.com/thanos-io/thanos/pull/6121) Receive: Deduplicate metamonitoring queries.
 
 ### Changed
 

pkg/receive/head_series_limiter.go

@@ -106,7 +106,7 @@ func NewHeadSeriesLimit(w WriteLimitsConfig, registerer prometheus.Registerer, l
 func (h *headSeriesLimit) QueryMetaMonitoring(ctx context.Context) error {
 	c := promclient.NewWithTracingClient(h.logger, h.metaMonitoringClient, httpconfig.ThanosUserAgent)
 
-	vectorRes, _, err := c.QueryInstant(ctx, h.metaMonitoringURL, h.metaMonitoringQuery, time.Now(), promclient.QueryOptions{})
+	vectorRes, _, err := c.QueryInstant(ctx, h.metaMonitoringURL, h.metaMonitoringQuery, time.Now(), promclient.QueryOptions{Deduplicate: true})
 	if err != nil {
 		h.metaMonitoringErr.Inc()
 		return err