v3: Disallow ordering by updated_at for usage events

For app and service usage events, the underlying tables only keep track
of an `updated_at` timestamp. In the presented JSON, we do show an
`updated_at` field, but it's always derived from the `created_at` value
(since these events can't be updated).

When filtering lists of these events, our normal ordering queries won't
work for `order_by=updated_at`, since that column doesn't exist. Rather
than try to find a clever way to support this, we are just disallowing
ordering by `updated_at`. Ordering by `created_at` should be exactly
equivalent for these resources and is still supported.

[finishes #173185328]
[finishes #173185583]

Authored-by: Reid Mitchell <rmitchell@pivotal.io>

Author: reidmit

app/messages/app_usage_events_list_message.rb

@@ -16,6 +16,10 @@ class AppUsageEventsListMessage < ListMessage
 
     validates :guids, array: true, allow_nil: true
 
+    def valid_order_by_values
+      [:created_at]
+    end
+
     def self.from_params(params)
       super(params, %w(after_guid guids))
     end

app/messages/service_usage_events_list_message.rb

@@ -20,6 +20,10 @@ class ServiceUsageEventsListMessage < ListMessage
     validates :service_instance_types, array: true, allow_nil: true
     validates :service_offering_guids, array: true, allow_nil: true
 
+    def valid_order_by_values
+      [:created_at]
+    end
+
     def self.from_params(params)
       super(params, %w(after_guid guids service_instance_types service_offering_guids))
     end

docs/v3/source/includes/experimental_resources/app_usage_events/_list.md.erb

@@ -33,7 +33,7 @@ Name | Type | Description
 ---- | ---- | ------------
 **page** | _integer_ | Page to display. Valid values are integers >= 1.
 **per_page** | _integer_ | Number of results per page. <br>Valid values are 1 through 5000.
-**order_by** | _string_ | Value to sort by. Defaults to ascending. Prepend with `-` to sort descending. <br>Valid values are `created_at`, and `updated_at`.
+**order_by** | _string_ | Value to sort by. Defaults to ascending. Prepend with `-` to sort descending. <br>Valid value is `created_at`.
 **after_guid** | _string_ | Filters out events before and including the event with the given guid.
 **guids** | _list of strings_ | Comma-delimited list of usage event guids to filter by.
 

docs/v3/source/includes/experimental_resources/service_usage_events/_list.md.erb

@@ -33,7 +33,7 @@ Name | Type | Description
 ---- | ---- | ------------
 **page** | _integer_ | Page to display. Valid values are integers >= 1.
 **per_page** | _integer_ | Number of results per page. <br>Valid values are 1 through 5000.
-**order_by** | _string_ | Value to sort by. Defaults to ascending. Prepend with `-` to sort descending. <br>Valid values are `created_at`, and `updated_at`.
+**order_by** | _string_ | Value to sort by. Defaults to ascending. Prepend with `-` to sort descending. <br>Valid value is `created_at`.
 **after_guid** | _string_ | Filters out events before and including the event with the given guid.
 **guids** | _list of strings_ | Comma-delimited list of usage event guids to filter by.
 **service_instance_types** | _list of strings_ | Comma-delimited list of service instance types to filter by. Valid values are `managed_service_instance` and `user_provided_service_instance`.

spec/unit/messages/app_usage_events_list_message_spec.rb

@@ -77,6 +77,26 @@ module VCAP::CloudController
           expect(subject.guids).to eq(['some-guid'])
         end
       end
+
+      context 'when the order_by filter is provided' do
+        context 'and the value is invalid' do
+          let(:params) { { order_by: 'updated_at' } }
+
+          it 'validates and returns an error' do
+            expect(subject).not_to be_valid
+            expect(subject.errors[:order_by]).to include("can only be: 'created_at'")
+          end
+        end
+
+        context 'and the value is valid' do
+          let(:params) { { order_by: 'created_at' } }
+
+          it 'sets the message order_by to the provided value' do
+            expect(subject).to be_valid
+            expect(subject.order_by).to eq('created_at')
+          end
+        end
+      end
     end
   end
 end

spec/unit/messages/service_usage_events_list_message_spec.rb

@@ -114,6 +114,26 @@ module VCAP::CloudController
           expect(subject.service_instance_types).to eq(['managed_service_instance'])
         end
       end
+
+      context 'when the order_by filter is provided' do
+        context 'and the value is invalid' do
+          let(:params) { { order_by: 'updated_at' } }
+
+          it 'validates and returns an error' do
+            expect(subject).not_to be_valid
+            expect(subject.errors[:order_by]).to include("can only be: 'created_at'")
+          end
+        end
+
+        context 'and the value is valid' do
+          let(:params) { { order_by: 'created_at' } }
+
+          it 'sets the message order_by to the provided value' do
+            expect(subject).to be_valid
+            expect(subject.order_by).to eq('created_at')
+          end
+        end
+      end
     end
   end
 end