Stream audit event on merge request approval

Stream audit events that relate to merge
approval actions performed within a project.

Changelog: added
EE: true

app/services/merge_requests/approval_service.rb

@@ -11,6 +11,7 @@ module MergeRequests
 
       reset_approvals_cache(merge_request)
       create_event(merge_request)
+      stream_audit_event(merge_request)
       create_approval_note(merge_request)
       mark_pending_todos_as_done(merge_request)
       execute_approval_hooks(merge_request, current_user)
@@ -52,6 +53,10 @@ module MergeRequests
     def create_event(merge_request)
       event_service.approve_mr(merge_request, current_user)
     end
+
+    def stream_audit_event(merge_request)
+      # Defined in EE
+    end
   end
 end
 

doc/administration/audit_event_streaming.md

@@ -259,3 +259,47 @@ Fetch:
   "target_id": 29
 }
 ```
+
+## Audit event streaming on merge request approval actions
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/271162) in GitLab 14.9.
+
+Stream audit events that relate to merge approval actions performed within a project.
+
+### Request headers
+
+Request headers are formatted as follows:
+
+```plaintext
+POST /logs HTTP/1.1
+Host: <DESTINATION_HOST>
+Content-Type: application/x-www-form-urlencoded
+X-Gitlab-Event-Streaming-Token: <DESTINATION_TOKEN>
+```
+
+### Example request body 
+
+```json
+{
+  "id": 1,
+  "author_id": 1,
+  "entity_id": 6,
+  "entity_type": "Project",
+  "details": {
+    "author_name": "example_username",
+    "target_id": 20,
+    "target_type": "MergeRequest",
+    "target_details": "merge request title",
+    "custom_message": "Approved merge request",
+    "ip_address": "127.0.0.1",
+    "entity_path": "example-group/example-project"
+  },
+  "ip_address": "127.0.0.1",
+  "author_name": "example_username",
+  "entity_path": "example-group/example-project",
+  "target_details": "merge request title",
+  "created_at": "2022-03-09T06:53:11.181Z",
+  "target_type": "MergeRequest",
+  "target_id": 20
+}
+```

ee/app/models/ee/merge_request.rb

@@ -302,6 +302,10 @@ module EE
       project.security_reports_up_to_date_for_ref?(target_branch)
     end
 
+    def audit_details
+      title
+    end
+
     private
 
     def has_approved_license_check?

ee/app/services/ee/merge_requests/approval_service.rb

@@ -46,6 +46,16 @@ module EE
         end
       end
 
+      override :stream_audit_event
+      def stream_audit_event(merge_request)
+        AuditEvents::BuildService.new(
+          author: current_user,
+          scope: merge_request.project,
+          target: merge_request,
+          message: 'Approved merge request'
+        ).execute.stream_to_external_destinations(use_json: true)
+      end
+
       def incorrect_approval_password?(merge_request)
         merge_request.project.require_password_to_approve? &&
           !::Gitlab::Auth.find_with_user_password(current_user.username, params[:approval_password])

ee/spec/models/merge_request_spec.rb

@@ -1362,4 +1362,12 @@ RSpec.describe MergeRequest do
       it { is_expected.to be false }
     end
   end
+
+  describe '#audit_details' do
+    it 'equals to the title' do
+      merge_request = create(:merge_request, title: 'I am a title')
+
+      expect(merge_request.audit_details).to eq(merge_request.title)
+    end
+  end
 end

ee/spec/services/merge_requests/approval_service_spec.rb

@@ -65,6 +65,14 @@ RSpec.describe MergeRequests::ApprovalService do
         service.execute(merge_request)
       end
 
+      it 'sends the audit streaming event' do
+        expect_next_instance_of(AuditEvent) do |instance|
+          expect(instance).to receive(:stream_to_external_destinations).with(use_json: true)
+        end
+
+        service.execute(merge_request)
+      end
+
       context 'with remaining approvals' do
         it 'fires an approval webhook' do
           expect(merge_request).to receive(:approvals_left).and_return(5)