Extract prometheus_client out into shared concern

For later re-use, with Prometheus Cluster integration.
This also makes it much easier to delete
app/models/clusters/applications/prometheus.rb when the time comes

app/models/clusters/applications/prometheus.rb

@@ -3,7 +3,7 @@
 module Clusters
   module Applications
     class Prometheus < ApplicationRecord
-      include PrometheusAdapter
+      include ::Clusters::Concerns::PrometheusClient
 
       VERSION = '10.4.1'
 
@@ -58,14 +58,6 @@ module Clusters
         'https://gitlab-org.gitlab.io/cluster-integration/helm-stable-archive'
       end
 
-      def service_name
-        'prometheus-prometheus-server'
-      end
-
-      def service_port
-        80
-      end
-
       def install_command
         helm_command_module::InstallCommand.new(
           name: name,
@@ -106,29 +98,6 @@ module Clusters
         files.merge('values.yaml': replaced_values)
       end
 
-      def prometheus_client
-        return unless kube_client
-
-        proxy_url = kube_client.proxy_url('service', service_name, service_port, Gitlab::Kubernetes::Helm::NAMESPACE)
-
-        # ensures headers containing auth data are appended to original k8s client options
-        options = kube_client.rest_client.options
-          .merge(prometheus_client_default_options)
-          .merge(headers: kube_client.headers)
-        Gitlab::PrometheusClient.new(proxy_url, options)
-      rescue Kubeclient::HttpError, Errno::ECONNRESET, Errno::ECONNREFUSED, Errno::ENETUNREACH
-        # If users have mistakenly set parameters or removed the depended clusters,
-        # `proxy_url` could raise an exception because gitlab can not communicate with the cluster.
-        # Since `PrometheusAdapter#can_query?` is eargely loaded on environement pages in gitlab,
-        # we need to silence the exceptions
-      end
-
-      def configured?
-        kube_client.present? && available?
-      rescue Gitlab::UrlBlocker::BlockedUrlError
-        false
-      end
-
       def generate_alert_manager_token!
         unless alert_manager_token.present?
           update!(alert_manager_token: generate_token)
@@ -146,10 +115,6 @@ module Clusters
           .perform_async(cluster_id, ::PrometheusService.to_param) # rubocop:disable CodeReuse/ServiceClass
       end
 
-      def kube_client
-        cluster&.kubeclient&.core_client
-      end
-
       def install_knative_metrics
         return [] unless cluster.application_knative_available?
 

app/models/clusters/concerns/prometheus_client.rb

+# frozen_string_literal: true
+
+module Clusters
+  module Concerns
+    module PrometheusClient
+      extend ActiveSupport::Concern
+
+      included do
+        include PrometheusAdapter
+
+        def service_name
+          'prometheus-prometheus-server'
+        end
+
+        def service_port
+          80
+        end
+
+        def prometheus_client
+          return unless kube_client
+
+          proxy_url = kube_client.proxy_url('service', service_name, service_port, Gitlab::Kubernetes::Helm::NAMESPACE)
+
+          # ensures headers containing auth data are appended to original k8s client options
+          options = kube_client.rest_client.options
+            .merge(prometheus_client_default_options)
+            .merge(headers: kube_client.headers)
+          Gitlab::PrometheusClient.new(proxy_url, options)
+        rescue Kubeclient::HttpError, Errno::ECONNRESET, Errno::ECONNREFUSED, Errno::ENETUNREACH
+          # If users have mistakenly set parameters or removed the depended clusters,
+          # `proxy_url` could raise an exception because gitlab can not communicate with the cluster.
+          # Since `PrometheusAdapter#can_query?` is eargely loaded on environement pages in gitlab,
+          # we need to silence the exceptions
+        end
+
+        def configured?
+          kube_client.present? && available?
+        rescue Gitlab::UrlBlocker::BlockedUrlError
+          false
+        end
+
+        private
+
+        def kube_client
+          cluster&.kubeclient&.core_client
+        end
+      end
+    end
+  end
+end

spec/models/clusters/applications/prometheus_spec.rb

@@ -74,85 +74,8 @@ RSpec.describe Clusters::Applications::Prometheus do
   end
 
   describe '#prometheus_client' do
-    shared_examples 'exception caught for prometheus client' do
-      before do
-        allow(kube_client).to receive(:proxy_url).and_raise(exception)
-      end
-
-      it 'returns nil' do
-        expect(subject.prometheus_client).to be_nil
-      end
-    end
-
-    context 'cluster is nil' do
-      it 'returns nil' do
-        expect(subject.cluster).to be_nil
-        expect(subject.prometheus_client).to be_nil
-      end
-    end
-
-    context "cluster doesn't have kubeclient" do
-      let(:cluster) { create(:cluster) }
-
-      subject { create(:clusters_applications_prometheus, cluster: cluster) }
-
-      it 'returns nil' do
-        expect(subject.prometheus_client).to be_nil
-      end
-    end
-
-    context 'cluster has kubeclient' do
-      let(:cluster) { create(:cluster, :project, :provided_by_gcp) }
-      let(:kubernetes_url) { subject.cluster.platform_kubernetes.api_url }
-      let(:kube_client) { subject.cluster.kubeclient.core_client }
-
-      subject { create(:clusters_applications_prometheus, cluster: cluster) }
-
-      before do
-        subject.cluster.platform_kubernetes.namespace = 'a-namespace'
-        stub_kubeclient_discover(cluster.platform_kubernetes.api_url)
-
-        create(:cluster_kubernetes_namespace,
-               cluster: cluster,
-               cluster_project: cluster.cluster_project,
-               project: cluster.cluster_project.project)
-      end
-
-      it 'creates proxy prometheus_client' do
-        expect(subject.prometheus_client).to be_instance_of(Gitlab::PrometheusClient)
-      end
-
-      it 'merges proxy_url, options and headers from kube client with prometheus_client options' do
-        expect(Gitlab::PrometheusClient)
-          .to(receive(:new))
-          .with(a_valid_url, kube_client.rest_client.options.merge({
-            headers: kube_client.headers,
-            timeout: PrometheusAdapter::DEFAULT_PROMETHEUS_REQUEST_TIMEOUT_SEC
-          }))
-        subject.prometheus_client
-      end
-
-      context 'when cluster is not reachable' do
-        it_behaves_like 'exception caught for prometheus client' do
-          let(:exception) { Kubeclient::HttpError.new(401, 'Unauthorized', nil) }
-        end
-      end
-
-      context 'when there is a socket error while contacting cluster' do
-        it_behaves_like 'exception caught for prometheus client' do
-          let(:exception) { Errno::ECONNREFUSED }
-        end
-
-        it_behaves_like 'exception caught for prometheus client' do
-          let(:exception) { Errno::ECONNRESET }
-        end
-      end
-
-      context 'when the network is unreachable' do
-        it_behaves_like 'exception caught for prometheus client' do
-          let(:exception) { Errno::ENETUNREACH }
-        end
-      end
+    include_examples '#prometheus_client shared' do
+      let(:factory) { :clusters_applications_prometheus }
     end
   end
 

spec/support/shared_examples/models/clusters/prometheus_client_shared.rb

+# frozen_string_literal: true
+
+# Input
+#  - factory: [:clusters_applications_prometheus, :clusters_integrations_prometheus]
+RSpec.shared_examples '#prometheus_client shared' do
+  shared_examples 'exception caught for prometheus client' do
+    before do
+      allow(kube_client).to receive(:proxy_url).and_raise(exception)
+    end
+
+    it 'returns nil' do
+      expect(subject.prometheus_client).to be_nil
+    end
+  end
+
+  context 'cluster is nil' do
+    it 'returns nil' do
+      expect(subject.cluster).to be_nil
+      expect(subject.prometheus_client).to be_nil
+    end
+  end
+
+  context "cluster doesn't have kubeclient" do
+    let(:cluster) { create(:cluster) }
+
+    subject { create(factory, cluster: cluster) }
+
+    it 'returns nil' do
+      expect(subject.prometheus_client).to be_nil
+    end
+  end
+
+  context 'cluster has kubeclient' do
+    let(:cluster) { create(:cluster, :project, :provided_by_gcp) }
+    let(:kubernetes_url) { subject.cluster.platform_kubernetes.api_url }
+    let(:kube_client) { subject.cluster.kubeclient.core_client }
+
+    subject { create(factory, cluster: cluster) }
+
+    before do
+      subject.cluster.platform_kubernetes.namespace = 'a-namespace'
+      stub_kubeclient_discover(cluster.platform_kubernetes.api_url)
+
+      create(:cluster_kubernetes_namespace,
+             cluster: cluster,
+             cluster_project: cluster.cluster_project,
+             project: cluster.cluster_project.project)
+    end
+
+    it 'creates proxy prometheus_client' do
+      expect(subject.prometheus_client).to be_instance_of(Gitlab::PrometheusClient)
+    end
+
+    it 'merges proxy_url, options and headers from kube client with prometheus_client options' do
+      expect(Gitlab::PrometheusClient)
+        .to(receive(:new))
+        .with(a_valid_url, kube_client.rest_client.options.merge({
+        headers: kube_client.headers,
+        timeout: PrometheusAdapter::DEFAULT_PROMETHEUS_REQUEST_TIMEOUT_SEC
+      }))
+      subject.prometheus_client
+    end
+
+    context 'when cluster is not reachable' do
+      it_behaves_like 'exception caught for prometheus client' do
+        let(:exception) { Kubeclient::HttpError.new(401, 'Unauthorized', nil) }
+      end
+    end
+
+    context 'when there is a socket error while contacting cluster' do
+      it_behaves_like 'exception caught for prometheus client' do
+        let(:exception) { Errno::ECONNREFUSED }
+      end
+
+      it_behaves_like 'exception caught for prometheus client' do
+        let(:exception) { Errno::ECONNRESET }
+      end
+    end
+
+    context 'when the network is unreachable' do
+      it_behaves_like 'exception caught for prometheus client' do
+        let(:exception) { Errno::ENETUNREACH }
+      end
+    end
+  end
+end