Add 'file-based-vcap-services' app feature functionality

Author: svkrieger

app/models/runtime/process_model.rb

@@ -178,6 +178,7 @@ def revisions_enabled?
     end
 
     delegate :service_binding_k8s_enabled, to: :app
+    delegate :file_based_vcap_services_enabled, to: :app
 
     def package_hash
       # this caches latest_package for performance reasons

app/presenters/system_environment/system_env_presenter.rb

@@ -4,12 +4,18 @@
 class SystemEnvPresenter
   def initialize(app_or_process)
     @service_binding_k8s_enabled = app_or_process.service_binding_k8s_enabled
+    @file_based_vcap_services_enabled = app_or_process.file_based_vcap_services_enabled
     @service_bindings = app_or_process.service_bindings
   end
 
   def system_env
     return { SERVICE_BINDING_ROOT: '/etc/cf-service-bindings' } if @service_binding_k8s_enabled
+    return { VCAP_SERVICES_FILE_PATH: '/etc/cf-service-bindings/vcap_services' } if @file_based_vcap_services_enabled
 
+    vcap_services
+  end
+
+  def vcap_services
     { VCAP_SERVICES: service_binding_env_variables }
   end
 

lib/cloud_controller/diego/service_binding_files_builder.rb

@@ -10,11 +10,24 @@ def self.build(app_or_process)
       end
 
       def initialize(app_or_process)
+        @app_or_process = app_or_process
         @service_binding_k8s_enabled = app_or_process.service_binding_k8s_enabled
+        @file_based_vcap_services = app_or_process.file_based_vcap_services_enabled
         @service_bindings = app_or_process.service_bindings
       end
 
       def build
+        if @service_binding_k8s_enabled
+          build_service_binding_k8s
+        elsif @file_based_vcap_services
+          vcap_services = SystemEnvPresenter.new(@app_or_process).vcap_services[:VCAP_SERVICES]
+          build_vcap_service_file(vcap_services)
+        end
+      end
+
+      private
+
+      def build_service_binding_k8s
         return nil unless @service_binding_k8s_enabled
 
         service_binding_files = {}
@@ -45,7 +58,15 @@ def build
         service_binding_files.values
       end
 
-      private
+      def build_vcap_service_file(vcap_services)
+        path = 'vcap_services'
+        vcap_services_string = Oj.dump(vcap_services, mode: :compat)
+        total_bytesize = vcap_services_string.bytesize + path.bytesize
+
+        raise IncompatibleBindings.new("Bindings exceed the maximum allowed bytesize of #{MAX_ALLOWED_BYTESIZE}: #{total_bytesize}") if total_bytesize > MAX_ALLOWED_BYTESIZE
+
+        [::Diego::Bbs::Models::File.new(path: path, content: vcap_services_string)]
+      end
 
       def binding_naming_convention
         /^[a-z0-9\-.]{1,253}$/

spec/request/apps_spec.rb

@@ -1615,6 +1615,20 @@
 
         it_behaves_like 'permissions for single object endpoint', ALL_PERMISSIONS
       end
+
+      context 'when file-based VCAP service bindings are enabled' do
+        let(:app_model_response_object) do
+          r = super()
+          r[:system_env_json] = { VCAP_SERVICES_FILE_PATH: '/etc/cf-service-bindings/vcap_services' }
+          r
+        end
+
+        before do
+          app_model.update(file_based_vcap_services_enabled: true)
+        end
+
+        it_behaves_like 'permissions for single object endpoint', ALL_PERMISSIONS
+      end
     end
 
     context 'when VCAP_SERVICES contains potentially sensitive information' do

spec/unit/lib/cloud_controller/diego/app_recipe_builder_spec.rb

@@ -67,7 +67,23 @@ module Diego
 
           it 'includes volume mounted files' do
             lrp = builder.build_app_lrp
-            expect(lrp.volume_mounted_files).not_to be_empty
+            expect(lrp.volume_mounted_files.size).to be > 1
+          end
+        end
+      end
+
+      shared_examples 'file-based VCAP service bindings' do
+        context 'when file-based VCAP service bindings are enabled' do
+          before do
+            app = process.app
+            app.update(file_based_vcap_services_enabled: true)
+            VCAP::CloudController::ServiceBinding.make(service_instance: ManagedServiceInstance.make(space: app.space), app: app)
+          end
+
+          it 'includes the vcap_services file' do
+            lrp = builder.build_app_lrp
+            expect(lrp.volume_mounted_files.size).to eq(1)
+            expect(lrp.volume_mounted_files[0].path).to eq('vcap_services')
           end
         end
       end
@@ -933,6 +949,7 @@ module Diego
           end
 
           include_examples 'k8s service bindings'
+          include_examples 'file-based VCAP service bindings'
         end
 
         context 'when the lifecycle_type is "cnb"' do
@@ -1026,6 +1043,7 @@ module Diego
           end
 
           include_examples 'k8s service bindings'
+          include_examples 'file-based VCAP service bindings'
         end
 
         context 'when the lifecycle_type is "docker"' do
@@ -1371,6 +1389,7 @@ module Diego
           end
 
           include_examples 'k8s service bindings'
+          include_examples 'file-based VCAP service bindings'
         end
       end