pkgs/apis/monitoring: support --max-samples flag in QuerySpec

Documentation/api.md

@@ -334,6 +334,7 @@ QuerySpec defines the query command line flags when starting Prometheus.
 | ----- | ----------- | ------ | -------- |
 | lookbackDelta | The delta difference allowed for retrieving metrics during expression evaluations. | *string | false |
 | maxConcurrency | Number of concurrent queries that can be run at once. | *int32 | false |
+| maxSamples | Maximum number of samples a single query can load into memory. Note that queries will fail if they would load more samples than this into memory, so this also limits the number of samples a query can return. | *int32 | false |
 | timeout | Maximum time a query may take before being aborted. | *string | false |
 
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example/prometheus-operator-crd/prometheus.crd.yaml

@@ -1898,6 +1898,10 @@ spec:
                   description: Number of concurrent queries that can be run at once.
                   format: int32
                   type: integer
+                maxSamples:
+                  description: Maximum number of samples a single query can load into memory. Note that queries will fail if they would load more samples than this into memory, so this also limits the number of samples a query can return.
+                  format: int32
+                  type: integer
                 timeout:
                   description: Maximum time a query may take before being aborted.
                   type: string

pkg/apis/monitoring/v1/types.go

@@ -298,6 +298,8 @@ type QuerySpec struct {
 	LookbackDelta *string `json:"lookbackDelta,omitempty"`
 	// Number of concurrent queries that can be run at once.
 	MaxConcurrency *int32 `json:"maxConcurrency,omitempty"`
+	// Maximum number of samples a single query can load into memory. Note that queries will fail if they would load more samples than this into memory, so this also limits the number of samples a query can return.
+	MaxSamples *int32 `json:"maxSamples,omitempty"`
 	// Maximum time a query may take before being aborted.
 	Timeout *string `json:"timeout,omitempty"`
 }

pkg/prometheus/statefulset.go

@@ -361,6 +361,14 @@ func makeStatefulSetSpec(p monitoringv1.Prometheus, c *Config, ruleConfigMapName
 				promArgs = append(promArgs, "-rules.alert.resend-delay="+p.Spec.Rules.Alert.ResendDelay)
 			}
 		}
+
+		if version.Minor >= 5 {
+			if p.Spec.Query != nil && p.Spec.Query.MaxSamples != nil {
+				promArgs = append(promArgs,
+					fmt.Sprintf("-query.max-samples=%d", *p.Spec.Query.MaxSamples),
+				)
+			}
+		}
 	default:
 		return nil, errors.Errorf("unsupported Prometheus major version %s", version)
 	}