Fix Elasticsearch reindexing count race condition

Ensure original and new index counts are captured at the same time after
indexing has paused. This prevents false positives when comparing document
counts caused by pending indexing operations.

EE: true

ee/app/services/search/elastic/cluster_reindexing_service.rb

@@ -133,10 +133,7 @@ def load_alias_info(klass:, name_suffix:)
 
       def launch_subtasks(items_to_reindex)
         items_to_reindex.each do |item|
-          # Record documents count
-          documents_count = elastic_helper.documents_count(index_name: item[:index_name_from], refresh: true)
-          # Create all subtasks
-          subtask = current_task.subtasks.create!(item.merge(documents_count: documents_count))
+          subtask = current_task.subtasks.create!(item)
 
           number_of_shards = elastic_helper.get_settings(index_name: item[:index_name_from])['number_of_shards'].to_i
           max_slice = number_of_shards * current_task.slice_multiplier
@@ -153,10 +150,10 @@ def launch_subtasks(items_to_reindex)
 
       def save_documents_count!(refresh:)
         current_task.subtasks.each do |subtask|
-          elastic_helper.refresh_index(index_name: subtask.index_name_to) if refresh
+          documents_count = elastic_helper.documents_count(index_name: subtask.index_name_from, refresh: refresh)
+          new_documents_count = elastic_helper.documents_count(index_name: subtask.index_name_to, refresh: refresh)
 
-          new_documents_count = elastic_helper.documents_count(index_name: subtask.index_name_to)
-          subtask.update!(documents_count_target: new_documents_count)
+          subtask.update!(documents_count: documents_count, documents_count_target: new_documents_count)
         end
       end
 

ee/spec/services/search/elastic/cluster_reindexing_service_spec.rb

@@ -218,15 +218,17 @@
           'response' => { 'total' => 20, 'created' => 20, 'updated' => 0, 'deleted' => 0 }
         }
       )
-      allow(helper).to receive(:refresh_index).and_return(true)
       allow(helper).to receive(:reindex).and_return('task_1', 'task_2', 'task_3', 'task_4', 'task_5', 'task_6')
     end
 
     context 'when errors are raised' do
       context 'when documents count does not match' do
         before do
-          allow(helper).to receive(:documents_count)
-            .with(index_name: anything).and_return(subtask.reload.documents_count * 2)
+          allow(helper).to receive(:documents_count).with(index_name: subtask.index_name_from, refresh: anything)
+            .and_return(subtask.reload.documents_count)
+          allow(helper).to receive(:documents_count).with(index_name: subtask.index_name_to, refresh: anything)
+            .and_return(subtask.reload.documents_count * 2)
+          allow(helper).to receive(:get_settings).with(index_name: subtask.index_name_from)
         end
 
         it 'changes task state to failure' do
@@ -398,7 +400,9 @@
 
       with_them do
         before do
-          allow(helper).to receive(:documents_count).with(index_name: subtask.index_name_to)
+          allow(helper).to receive(:documents_count).with(index_name: subtask.index_name_from, refresh: anything)
+            .and_return(subtask.reload.documents_count)
+          allow(helper).to receive(:documents_count).with(index_name: subtask.index_name_to, refresh: anything)
             .and_return(subtask.reload.documents_count)
           allow(helper).to receive(:get_settings).with(index_name: subtask.index_name_from)
             .and_return(current_settings.with_indifferent_access)