Fallback to NATs if staging over http isn't there

lib/cloud_controller/dea/app_stager_task.rb

@@ -63,7 +63,8 @@ def handle_http_response(response)
       private
 
       def stage_with_http(url, msg)
-        Dea::Client.stage(url, msg)
+        success = Dea::Client.stage(url, msg)
+        stage_with_nats(msg) unless success
       rescue => e
         @app.mark_as_failed_to_stage('StagingError')
         logger.error e.message

lib/cloud_controller/dea/client.rb

@@ -44,12 +44,17 @@ def enabled?
         def stage(url, msg)
           raise ApiError.new_from_details('StagerError', 'Client not HTTP enabled') unless enabled?
 
+          status = 999
           begin
             response = @http_client.post("#{url}/v1/stage", header: { 'Content-Type' => 'application/json' }, body: MultiJson.dump(msg))
+            status = response.status
+            return true if status == 202
+            return false if status == 404
           rescue => e
             raise ApiError.new_from_details('StagerError', "url: #{url}/v1/stage, error: #{e.message}")
           end
-          raise ApiError.new_from_details('StagerError', "received #{response.status} from #{url}/v1/stage") unless response.status == 202
+
+          raise ApiError.new_from_details('StagerError', "received #{status} from #{url}/v1/stage")
         end
 
         def start(app, options={})

spec/unit/lib/cloud_controller/dea/app_stager_task_spec.rb

@@ -61,6 +61,16 @@ module VCAP::CloudController
       }
     end
 
+    def stage(&blk)
+      stub_schedule_sync do
+        @before_staging_completion.call if @before_staging_completion
+        message_bus.respond_to_request("staging.#{stager_id}.start", first_reply_json)
+      end
+
+      response = staging_task.stage(&blk)
+      response
+    end
+
     before do
       expect(app.staged?).to be false
 
@@ -85,10 +95,21 @@ module VCAP::CloudController
           expect(app).to receive(:update).with({ package_state: 'PENDING', staging_task_id: staging_task.task_id })
           expect(message_bus).to receive(:publish).with('staging.stop', { app_id: app.guid })
           expect(dea_pool).to receive(:reserve_app_memory).with(stager_id, app.memory)
-          expect(Dea::Client).to receive(:stage).with(dea_advertisement.url, staging_message)
+          expect(Dea::Client).to receive(:stage).with(dea_advertisement.url, staging_message).and_return(true)
+          expect(message_bus).not_to receive(:publish).with('staging.my_stager.start', staging_task.staging_request)
           staging_task.stage
         end
 
+        context 'when staging is not supported' do
+          it 'failsover to NATs' do
+            expect(message_bus).to receive(:publish).with('staging.stop', { app_id: app.guid })
+            expect(Dea::Client).to receive(:stage).with(dea_advertisement.url, staging_message).and_return(false)
+            expect(message_bus).to receive(:publish).with('staging.my_stager.start', staging_task.staging_request)
+
+            stage
+          end
+        end
+
         context 'when an error occurs' do
           let(:logger) { double(Steno) }
 
@@ -441,16 +462,6 @@ module VCAP::CloudController
 
     describe 'staging' do
       describe 'receiving the first response from the stager (the staging setup completion message)' do
-        def stage(&blk)
-          stub_schedule_sync do
-            @before_staging_completion.call if @before_staging_completion
-            message_bus.respond_to_request("staging.#{stager_id}.start", first_reply_json)
-          end
-
-          response = staging_task.stage(&blk)
-          response
-        end
-
         context 'it sets up the app' do
           before do
             allow(app).to receive(:update).and_call_original

spec/unit/lib/cloud_controller/dea/client_spec.rb

@@ -224,11 +224,18 @@ def create_ad(id, url=nil)
 
       it 'sends a stage message to the dea' do
         stub_request(:post, post_url).with(body: /#{staging_msg}/, headers: { 'Content-Type' => 'application/json' }).to_return(status: [202, 'Accepted'])
-        expect { Dea::Client.stage(stager_url, staging_msg) }.not_to raise_error
+        expect(Dea::Client.stage(stager_url, staging_msg)).to be_truthy
       end
 
       context 'when an error occurs' do
-        context 'when we get a status other than 202' do
+        context 'when we get a status of 404' do
+          it 'returns false' do
+            stub_request(:post, post_url).with(body: /#{staging_msg}/, headers: { 'Content-Type' => 'application/json' }).to_return(status: [404, 'Not Found'])
+            expect(Dea::Client.stage(stager_url, staging_msg)).to be_falsey
+          end
+        end
+
+        context 'when we get a status other than 202 or 404' do
           it 'raises an error' do
             stub_request(:post, post_url).with(body: /#{staging_msg}/, headers: { 'Content-Type' => 'application/json' }).to_return(status: [500, 'Internal Server Error'])
             expect { Dea::Client.stage(stager_url, staging_msg) }.to raise_error CloudController::Errors::ApiError, /received 500 from #{post_url}/