Avoid N+1 queries in PromethusService#available?

app/models/project_services/prometheus_service.rb

@@ -88,7 +88,9 @@ class PrometheusService < MonitoringService
     return false if template?
     return false unless project
 
-    project.all_clusters.enabled.any? { |cluster| cluster.application_prometheus_available? }
+    project.all_clusters.enabled.eager_load(:application_prometheus).any? do |cluster|
+      cluster.application_prometheus&.available?
+    end
   end
 
   def allow_local_api_url?

spec/models/project_services/prometheus_service_spec.rb

@@ -176,6 +176,15 @@ describe PrometheusService, :use_clean_rails_memory_store_caching do
         it 'returns true' do
           expect(service.prometheus_available?).to be(true)
         end
+
+        it 'avoids N+1 queries' do
+          service
+          5.times do |i|
+            other_cluster = create(:cluster_for_group, :with_installed_helm, groups: [group], environment_scope: i)
+            create(:clusters_applications_prometheus, :installing, cluster: other_cluster)
+          end
+          expect { service.prometheus_available? }.not_to exceed_query_limit(1)
+        end
       end
 
       context 'cluster belongs to gitlab instance' do