Skip interim web processes from SUPERSEDED (CANCELED) deployments

When a deployment train is canceled, the latest interim web process is
scaled up. The introduction of a SUPERSEDED (CANCELED) state requires a
change to how this latest interim web process is determined.

Let's assume the following combination of actions:
  create + create + cancel + create + cancel

This would result in three deployments with the following states:
  SUPERSEDED (DEPLOYED) + SUPERSEDED (CANCELED) + CANCELING

And this should result in the web process from the SUPERSEDED (DEPLOYED)
deployment to be scaled up.

lib/cloud_controller/deployment_updater/updater.rb

@@ -44,9 +44,14 @@ def cancel_deployment
 
           deploying_web_process.lock!
 
-          prior_web_process = web_processes.
-                              reject { |p| p.guid == deploying_web_process.guid }.
-                              max_by(&:created_at)
+          # Find newest interim web process belonging to a SUPERSEDED (DEPLOYED) deployment.
+          interim_web_process = app.web_processes_dataset.qualify.
+                                join(:deployments, deploying_web_process_guid: :guid).
+                                where(deployments__state: DeploymentModel::DEPLOYED_STATE).
+                                where(deployments__status_reason: DeploymentModel::SUPERSEDED_STATUS_REASON).
+                                order(Sequel.desc(:created_at), Sequel.desc(:id)).
+                                first
+          prior_web_process = interim_web_process || app.oldest_web_process
           prior_web_process.lock!
 
           prior_web_process.update(instances: deployment.original_web_process_instance_count, type: ProcessTypes::WEB)
@@ -97,11 +102,7 @@ def deploying_web_process
       end
 
       def oldest_web_process_with_instances
-        @oldest_web_process_with_instances ||= app.processes.select { |process| process.web? && process.instances > 0 }.min_by(&:created_at)
-      end
-
-      def web_processes
-        app.processes.select(&:web?)
+        @oldest_web_process_with_instances ||= app.web_processes.select { |process| process.instances > 0 }.min_by(&:created_at)
       end
 
       def is_original_web_process?(process)
@@ -142,7 +143,7 @@ def promote_deploying_web_process
       end
 
       def cleanup_web_processes_except(protected_process)
-        web_processes.
+        app.web_processes.
           reject { |p| p.guid == protected_process.guid }.
           map(&:destroy)
       end

spec/unit/lib/cloud_controller/deployment_updater/updater_spec.rb

@@ -483,22 +483,28 @@ module VCAP::CloudController
       end
 
       context 'when there are interim deployments' do
-        let!(:interim_deploying_web_process) {
+        let!(:interim_deploying_web_process) do
           ProcessModel.make(
             app: app,
             created_at: an_hour_ago,
             type: ProcessTypes::WEB,
             instances: 1,
             guid: 'guid-interim'
           )
-        }
-
-        let!(:interim_route_mapping) {
+        end
+        let!(:interim_deployed_superseded_deployment) do
+          DeploymentModel.make(
+            deploying_web_process: interim_deploying_web_process,
+            state: 'DEPLOYED',
+            status_reason: 'SUPERSEDED'
+          )
+        end
+        let!(:interim_route_mapping) do
           RouteMappingModel.make(
             app: web_process.app,
             process_type: interim_deploying_web_process.type
           )
-        }
+        end
 
         it 'it scales up the most recent interim web process' do
           subject.cancel
@@ -510,6 +516,30 @@ module VCAP::CloudController
           subject.cancel
           expect(app.reload.processes.map(&:guid)).to eq([interim_deploying_web_process.guid])
         end
+
+        context 'when there is an interim deployment that has been SUPERSEDED (CANCELED)' do
+          let!(:interim_canceling_web_process) do
+            ProcessModel.make(
+              app: app,
+              created_at: an_hour_ago + 1,
+              type: ProcessTypes::WEB,
+              instances: 1,
+              guid: 'guid-canceling'
+            )
+          end
+          let!(:interim_canceled_superseded_deployment) do
+            DeploymentModel.make(
+              deploying_web_process: interim_canceling_web_process,
+              state: 'CANCELED',
+              status_reason: 'SUPERSEDED'
+            )
+          end
+
+          it 'sets the most recent interim web process belonging to a SUPERSEDED (DEPLOYED) deployment as the only web process' do
+            subject.cancel
+            expect(app.reload.processes.map(&:guid)).to eq([interim_deploying_web_process.guid])
+          end
+        end
       end
 
       context 'deployment got superseded' do