9 files changed, 76 insertions, 4 deletions

diff --git a/app/models/clusters/applications/cert_manager.rb b/app/models/clusters/applications/cert_manager.rb
index ac0e7eb03bc..d6a7d1d2bdd 100644
--- a/app/models/clusters/applications/cert_manager.rb
+++ b/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',
diff --git a/app/models/clusters/applications/helm.rb b/app/models/clusters/applications/helm.rb
index 71aff00077d..a83d06c4b00 100644
--- a/app/models/clusters/applications/helm.rb
+++ b/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,
diff --git a/app/models/clusters/applications/ingress.rb b/app/models/clusters/applications/ingress.rb
index 376d54aab2c..a1023f44049 100644
--- a/app/models/clusters/applications/ingress.rb
+++ b/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,
diff --git a/app/models/clusters/applications/jupyter.rb b/app/models/clusters/applications/jupyter.rb
index f86ff3551a1..987c057ad6d 100644
--- a/app/models/clusters/applications/jupyter.rb
+++ b/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,
diff --git a/app/models/clusters/applications/knative.rb b/app/models/clusters/applications/knative.rb
index 38cbc9ce8eb..9fbf5d8af04 100644
--- a/app/models/clusters/applications/knative.rb
+++ b/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,
diff --git a/app/models/clusters/applications/prometheus.rb b/app/models/clusters/applications/prometheus.rb
index 954c29da196..a6b7617b830 100644
--- a/app/models/clusters/applications/prometheus.rb
+++ b/app/models/clusters/applications/prometheus.rb
@@ -16,10 +16,12 @@ module Clusters
 
       default_value_for :version, VERSION
 
+      after_destroy :disable_prometheus_integration
+
       state_machine :status do
         after_transition any => [:installed] do |application|
           application.cluster.projects.each do |project|
-            project.find_or_initialize_service('prometheus').update(active: true)
+            project.find_or_initialize_service('prometheus').update!(active: true)
           end
         end
       end
@@ -47,6 +49,14 @@ module Clusters
         )
       end
 
+      def uninstall_command
+        Gitlab::Kubernetes::Helm::DeleteCommand.new(
+          name: name,
+          rbac: cluster.platform_kubernetes_rbac?,
+          files: files
+        )
+      end
+
       def upgrade_command(values)
         ::Gitlab::Kubernetes::Helm::InstallCommand.new(
           name: name,
@@ -82,6 +92,12 @@ module Clusters
 
       private
 
+      def disable_prometheus_integration
+        cluster.projects.each do |project|
+          project.prometheus_service&.update!(active: false)
+        end
+      end
+
       def kube_client
         cluster&.kubeclient&.core_client
       end
diff --git a/app/models/clusters/applications/runner.rb b/app/models/clusters/applications/runner.rb
index 3ebf7a5cfba..af648db3708 100644
--- a/app/models/clusters/applications/runner.rb
+++ b/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,
diff --git a/app/models/clusters/concerns/application_core.rb b/app/models/clusters/concerns/application_core.rb
index ee964fb7c93..4514498b84b 100644
--- a/app/models/clusters/concerns/application_core.rb
+++ b/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
diff --git a/app/models/clusters/concerns/application_status.rb b/app/models/clusters/concerns/application_status.rb
index 1273ed83abe..54a3dda6d75 100644
--- a/app/models/clusters/concerns/application_status.rb
+++ b/app/models/clusters/concerns/application_status.rb
@@ -25,9 +25,11 @@ module Clusters
           state :updating, value: 4
           state :updated, value: 5
           state :update_errored, value: 6
+          state :uninstalling, value: 7
+          state :uninstall_errored, value: 8
 
           event :make_scheduled do
-            transition [:installable, :errored, :installed, :updated, :update_errored] => :scheduled
+            transition [:installable, :errored, :installed, :updated, :update_errored, :uninstall_errored] => :scheduled
           end
 
           event :make_installing do
@@ -40,8 +42,9 @@ module Clusters
           end
 
           event :make_errored do
-            transition any - [:updating] => :errored
+            transition any - [:updating, :uninstalling] => :errored
             transition [:updating] => :update_errored
+            transition [:uninstalling] => :uninstall_errored
           end
 
           event :make_updating do
@@ -52,6 +55,10 @@ module Clusters
             transition any => :update_errored
           end
 
+          event :make_uninstalling do
+            transition [:scheduled] => :uninstalling
+          end
+
           before_transition any => [:scheduled] do |app_status, _|
             app_status.status_reason = nil
           end
@@ -65,7 +72,7 @@ module Clusters
             app_status.status_reason = nil
           end
 
-          before_transition any => [:update_errored] do |app_status, transition|
+          before_transition any => [:update_errored, :uninstall_errored] do |app_status, transition|
             status_reason = transition.args.first
             app_status.status_reason = status_reason if status_reason
           end