[v10.4.x] Alerting: Clamp Loki ASH range query to configured max_query_length (#84607)

Alerting: Clamp Loki ASH range query to configured max_query_length (#83986)

* Clamp range in loki http client to configured max_query_length

Defaults to 721h to match Loki default

(cherry picked from commit 97f37b2e6f)

Co-authored-by: William Wernert <william.wernert@grafana.com>

pkg/setting/setting_unified_alerting.go

@@ -61,6 +61,7 @@ const (
 	// DefaultRuleEvaluationInterval indicates a default interval of for how long a rule should be evaluated to change state from Pending to Alerting
 	DefaultRuleEvaluationInterval = SchedulerBaseInterval * 6 // == 60 seconds
 	stateHistoryDefaultEnabled    = true
+	lokiDefaultMaxQueryLength     = 721 * time.Hour // 30d1h, matches the default value in Loki
 )
 
 type UnifiedAlertingSettings struct {
@@ -136,6 +137,7 @@ type UnifiedAlertingStateHistorySettings struct {
 	// if one of them is set.
 	LokiBasicAuthPassword string
 	LokiBasicAuthUsername string
+	LokiMaxQueryLength    time.Duration
 	MultiPrimary          string
 	MultiSecondaries      []string
 	ExternalLabels        map[string]string
@@ -405,6 +407,7 @@ func (cfg *Cfg) ReadUnifiedAlertingSettings(iniFile *ini.File) error {
 		LokiTenantID:          stateHistory.Key("loki_tenant_id").MustString(""),
 		LokiBasicAuthUsername: stateHistory.Key("loki_basic_auth_username").MustString(""),
 		LokiBasicAuthPassword: stateHistory.Key("loki_basic_auth_password").MustString(""),
+		LokiMaxQueryLength:    stateHistory.Key("loki_max_query_length").MustDuration(lokiDefaultMaxQueryLength),
 		MultiPrimary:          stateHistory.Key("primary").MustString(""),
 		MultiSecondaries:      splitTrim(stateHistory.Key("secondaries").MustString(""), ","),
 		ExternalLabels:        stateHistoryLabels.KeysHash(),