Expose can_uninstall in cluster_status.json

Only prometheus can be uninstalled atm, the rest will be dealt with
later.

Presumption is that new application types will have uninstallation
implmemented at the same time.

app/models/clusters/applications/cert_manager.rb

@@ -24,6 +24,12 @@ module Clusters
         'stable/cert-manager'
       end
+      # We will implement this in future MRs.
+      # Need to reverse postinstall step
+      def allowed_to_uninstall?
+        false
+      end
+
       def install_command
         Gitlab::Kubernetes::Helm::InstallCommand.new(
           name: 'certmanager',

app/models/clusters/applications/helm.rb

@@ -29,6 +29,13 @@ module Clusters
         self.status = 'installable' if cluster&.platform_kubernetes_active?
       end
+      # We will implement this in future MRs.
+      # Basically we need to check all other applications are not installed
+      # first.
+      def allowed_to_uninstall?
+        false
+      end
+
       def install_command
         Gitlab::Kubernetes::Helm::InitCommand.new(
           name: name,

app/models/clusters/applications/ingress.rb

@@ -35,6 +35,13 @@ module Clusters
         'stable/nginx-ingress'
       end
+      # We will implement this in future MRs.
+      # Basically we need to check all dependent applications are not installed
+      # first.
+      def allowed_to_uninstall?
+        false
+      end
+
       def install_command
         Gitlab::Kubernetes::Helm::InstallCommand.new(
           name: name,

app/models/clusters/applications/jupyter.rb

@@ -38,6 +38,12 @@ module Clusters
         content_values.to_yaml
       end
+      # Will be addressed in future MRs
+      # We need to investigate and document what will be permenantly deleted.
+      def allowed_to_uninstall?
+        false
+      end
+
       def install_command
         Gitlab::Kubernetes::Helm::InstallCommand.new(
           name: name,

app/models/clusters/applications/knative.rb

@@ -51,6 +51,12 @@ module Clusters
         { "domain" => hostname }.to_yaml
       end
+      # Handled in a new issue:
+      # https://gitlab.com/gitlab-org/gitlab-ce/issues/59369
+      def allowed_to_uninstall?
+        false
+      end
+
       def install_command
         Gitlab::Kubernetes::Helm::InstallCommand.new(
           name: name,

app/models/clusters/applications/runner.rb

@@ -29,6 +29,13 @@ module Clusters
         content_values.to_yaml
       end
+      # Need to investigate if pipelines run by this runner will stop upon the
+      # executor pod stopping
+      # I.e.run a pipeline, and uninstall runner while pipeline is running
+      def allowed_to_uninstall?
+        false
+      end
+
       def install_command
         Gitlab::Kubernetes::Helm::InstallCommand.new(
           name: name,

app/models/clusters/concerns/application_core.rb

@@ -18,6 +18,16 @@ module Clusters
           self.status = 'installable' if cluster&.application_helm_available?
         end
+        def can_uninstall?
+          allowed_to_uninstall?
+        end
+
+        # All new applications should uninstall by default
+        # Override if there's dependencies that needs to be uninstalled first
+        def allowed_to_uninstall?
+          true
+        end
+
         def self.application_name
           self.to_s.demodulize.underscore
         end

app/serializers/cluster_application_entity.rb

@@ -10,4 +10,5 @@ class ClusterApplicationEntity < Grape::Entity
   expose :hostname, if: -> (e, _) { e.respond_to?(:hostname) }
   expose :email, if: -> (e, _) { e.respond_to?(:email) }
   expose :update_available?, as: :update_available, if: -> (e, _) { e.respond_to?(:update_available?) }
+  expose :can_uninstall?, as: :can_uninstall
 end

spec/fixtures/api/schemas/cluster_status.json

@@ -36,7 +36,8 @@
         "external_hostname": { "type": ["string", "null"] },
         "hostname": { "type": ["string", "null"] },
         "email": { "type": ["string", "null"] },
-        "update_available": { "type": ["boolean", "null"] }
+        "update_available": { "type": ["boolean", "null"] },
+        "can_uninstall": { "type": "boolean" }
       },
       "required" : [ "name", "status" ]
     }

spec/models/clusters/applications/cert_manager_spec.rb

@@ -10,6 +10,12 @@ describe Clusters::Applications::CertManager do
   include_examples 'cluster application version specs', :clusters_applications_cert_managers
   include_examples 'cluster application initial status specs'
+  describe '#can_uninstall?' do
+    subject { cert_manager.can_uninstall? }
+
+    it { is_expected.to be_falsey }
+  end
+
   describe '#install_command' do
     let(:cert_email) { 'admin@example.com' }

spec/models/clusters/applications/helm_spec.rb

@@ -18,6 +18,14 @@ describe Clusters::Applications::Helm do
     it { is_expected.to contain_exactly(installed_cluster, updated_cluster) }
   end
+  describe '#can_uninstall?' do
+    let(:helm) { create(:clusters_applications_helm) }
+
+    subject { helm.can_uninstall? }
+
+    it { is_expected.to be_falsey }
+  end
+
   describe '#issue_client_cert' do
     let(:application) { create(:clusters_applications_helm) }
     subject { application.issue_client_cert }

spec/models/clusters/applications/ingress_spec.rb

@@ -18,6 +18,12 @@ describe Clusters::Applications::Ingress do
     allow(ClusterWaitForIngressIpAddressWorker).to receive(:perform_async)
   end
+  describe '#can_uninstall?' do
+    subject { ingress.can_uninstall? }
+
+    it { is_expected.to be_falsey }
+  end
+
   describe '#make_installed!' do
     before do
       application.make_installed!

spec/models/clusters/applications/jupyter_spec.rb

@@ -10,6 +10,15 @@ describe Clusters::Applications::Jupyter do
   it { is_expected.to belong_to(:oauth_application) }
+  describe '#can_uninstall?' do
+    let(:ingress) { create(:clusters_applications_ingress, :installed, external_hostname: 'localhost.localdomain') }
+    let(:jupyter) { create(:clusters_applications_jupyter, cluster: ingress.cluster) }
+
+    subject { jupyter.can_uninstall? }
+
+    it { is_expected.to be_falsey }
+  end
+
   describe '#set_initial_status' do
     before do
       jupyter.set_initial_status

spec/models/clusters/applications/knative_spec.rb

@@ -39,6 +39,12 @@ describe Clusters::Applications::Knative do
     end
   end
+  describe '#can_uninstall?' do
+    subject { knative.can_uninstall? }
+
+    it { is_expected.to be_falsey }
+  end
+
   describe '#schedule_status_update with external_ip' do
     let(:application) { create(:clusters_applications_knative, :installed) }

spec/models/clusters/applications/prometheus_spec.rb

@@ -29,6 +29,14 @@ describe Clusters::Applications::Prometheus do
     end
   end
+  describe '#can_uninstall?' do
+    let(:prometheus) { create(:clusters_applications_prometheus) }
+
+    subject { prometheus.can_uninstall? }
+
+    it { is_expected.to be_truthy }
+  end
+
   describe '#prometheus_client' do
     context 'cluster is nil' do
       it 'returns nil' do

spec/models/clusters/applications/runner_spec.rb

@@ -13,6 +13,14 @@ describe Clusters::Applications::Runner do
   it { is_expected.to belong_to(:runner) }
+  describe '#can_uninstall?' do
+    let(:gitlab_runner) { create(:clusters_applications_runner, runner: ci_runner) }
+
+    subject { gitlab_runner.can_uninstall? }
+
+    it { is_expected.to be_falsey }
+  end
+
   describe '#install_command' do
     let(:kubeclient) { double('kubernetes client') }
     let(:gitlab_runner) { create(:clusters_applications_runner, runner: ci_runner) }

spec/serializers/cluster_application_entity_spec.rb

@@ -21,6 +21,10 @@ describe ClusterApplicationEntity do
       expect(subject[:status_reason]).to be_nil
     end
+    it 'has can_uninstall' do
+      expect(subject[:can_uninstall]).to be_falsey
+    end
+
     context 'non-helm application' do
       let(:application) { build(:clusters_applications_runner, version: '0.0.0') }

spec/support/shared_examples/models/cluster_application_core_shared_examples.rb

@@ -2,6 +2,14 @@ shared_examples 'cluster application core specs' do |application_name|
   it { is_expected.to belong_to(:cluster) }
   it { is_expected.to validate_presence_of(:cluster) }
+  describe '#can_uninstall?' do
+    it 'calls allowed_to_uninstall?' do
+      expect(subject).to receive(:allowed_to_uninstall?).and_return(true)
+
+      expect(subject.can_uninstall?).to be_truthy
+    end
+  end
+
   describe '#name' do
     it 'is .application_name' do
       expect(subject.name).to eq(described_class.application_name)