Verify that rack attack logging does not perform additional queries

There is a user lookup in the rack attack logging code, but if there is
a user, we will have already looked up their details earlier in the
request cycle. That means that this will use the ActiveRecord cache and
not actually hit the database again.

This spec ensures we don't add more queries when logging than we do when
simply running normally.

spec/support/shared_examples/requests/rack_attack_shared_examples.rb

@@ -81,8 +81,15 @@ RSpec.shared_examples 'rate-limited token-authenticated requests' do
     end
 
     it 'logs RackAttack info into structured logs' do
-      requests_per_period.times do
-        make_request(request_args)
+      control_count = 0
+
+      requests_per_period.times do |i|
+        if i == 0
+          control_count = ActiveRecord::QueryRecorder.new { make_request(request_args) }.count
+        else
+          make_request(request_args)
+        end
+
         expect(response).not_to have_gitlab_http_status(:too_many_requests)
       end
 
@@ -99,7 +106,9 @@ RSpec.shared_examples 'rate-limited token-authenticated requests' do
 
       expect(Gitlab::AuthLogger).to receive(:error).with(arguments).once
 
-      expect_rejection { make_request(request_args) }
+      expect_rejection do
+        expect { make_request(request_args) }.not_to exceed_query_limit(control_count)
+      end
     end
   end
 
@@ -210,8 +219,15 @@ RSpec.shared_examples 'rate-limited web authenticated requests' do
     end
 
     it 'logs RackAttack info into structured logs' do
-      requests_per_period.times do
-        request_authenticated_web_url
+      control_count = 0
+
+      requests_per_period.times do |i|
+        if i == 0
+          control_count = ActiveRecord::QueryRecorder.new { request_authenticated_web_url }.count
+        else
+          request_authenticated_web_url
+        end
+
         expect(response).not_to have_gitlab_http_status(:too_many_requests)
       end
 
@@ -227,8 +243,7 @@ RSpec.shared_examples 'rate-limited web authenticated requests' do
       }
 
       expect(Gitlab::AuthLogger).to receive(:error).with(arguments).once
-
-      request_authenticated_web_url
+      expect { request_authenticated_web_url }.not_to exceed_query_limit(control_count)
     end
   end