Ensure CheckIngressIpAddressService obtains exclusive lease per ingress controller (#42643)

app/services/clusters/applications/check_ingress_ip_address_service.rb

 module Clusters
   module Applications
     class CheckIngressIpAddressService < BaseHelmService
+      LEASE_TIMEOUT = 3.seconds.to_i
+
       def execute(retries_remaining)
         return if app.external_ip
+        return unless try_obtain_lease
 
         service = get_service
 
@@ -18,6 +21,12 @@ module Clusters
 
       private
 
+      def try_obtain_lease
+        Gitlab::ExclusiveLease
+          .new("check_ingress_ip_address_service:#{app.id}", timeout: LEASE_TIMEOUT)
+          .try_obtain
+      end
+
       def resolve_external_ip(service)
         app.update!( external_ip: service.status.loadBalancer.ingress[0].ip)
       end

spec/services/clusters/applications/check_ingress_ip_address_service_spec.rb

@@ -16,9 +16,14 @@ describe Clusters::Applications::CheckIngressIpAddressService do
   end
   let(:kubeclient) { double(::Kubeclient::Client, get_service: kube_service) }
   let(:ingress) { [{ ip: '111.222.111.222' }] }
+  let(:exclusive_lease) { instance_double(Gitlab::ExclusiveLease, try_obtain: true) }
 
   before do
     allow(application.cluster).to receive(:kubeclient).and_return(kubeclient)
+    allow(Gitlab::ExclusiveLease)
+      .to receive(:new)
+      .with("check_ingress_ip_address_service:#{application.id}", timeout: 3.seconds.to_i)
+      .and_return(exclusive_lease)
   end
 
   describe '#execute' do
@@ -52,6 +57,20 @@ describe Clusters::Applications::CheckIngressIpAddressService do
       end
     end
 
+    context 'when the exclusive lease cannot be obtained' do
+      before do
+        allow(exclusive_lease)
+          .to receive(:try_obtain)
+          .and_return(false)
+      end
+
+      it 'does not call kubeclient' do
+        expect(kubeclient).not_to receive(:get_service)
+
+        service.execute(1)
+      end
+    end
+
     context 'when there is already an external_ip' do
       let(:application) { create(:clusters_applications_ingress, :installed, external_ip: '001.111.002.111') }