MAGETWO-32726: Varnish: Catalog page is not updated after product returns to stock again

 - Added cache invalidation to stock indexer

Author: Andrey Konosov

app/code/Magento/CatalogInventory/Model/Indexer/Stock/AbstractAction.php

@@ -8,6 +8,8 @@
 
 namespace Magento\CatalogInventory\Model\Indexer\Stock;
 
+use Magento\Catalog\Model\Category;
+
 /**
  * Abstract action reindex class
  *
@@ -52,6 +54,17 @@ abstract class AbstractAction
      */
     protected $_isNeedUseIdxTable = false;
 
+    /**
+     * @var \Magento\Indexer\Model\CacheContext
+     */
+    private $cacheContext;
+
+    /**
+     * @var \Magento\Framework\Event\ManagerInterface
+     */
+    private $eventManager;
+
+
     /**
      * @param \Magento\Framework\App\Resource $resource
      * @param \Magento\CatalogInventory\Model\Resource\Indexer\StockFactory $indexerFactory
@@ -60,11 +73,16 @@ abstract class AbstractAction
     public function __construct(
         \Magento\Framework\App\Resource $resource,
         \Magento\CatalogInventory\Model\Resource\Indexer\StockFactory $indexerFactory,
-        \Magento\Catalog\Model\Product\Type $catalogProductType
+        \Magento\Catalog\Model\Product\Type $catalogProductType,
+        \Magento\Indexer\Model\CacheContext $cacheContext,
+        \Magento\Framework\Event\ManagerInterface $eventManager
+
     ) {
         $this->_resource = $resource;
         $this->_indexerFactory = $indexerFactory;
         $this->_catalogProductType = $catalogProductType;
+        $this->cacheContext = $cacheContext;
+        $this->eventManager = $eventManager;
     }
 
     /**
@@ -228,6 +246,16 @@ protected function _reindexRows($productIds = [])
             }
         }
 
+        $select = $adapter->select()
+            ->distinct(true)
+            ->from($this->_getTable('catalog_category_product'), [ 'category_id'])
+            ->where('product_id IN(?)', $processIds);
+
+        $affectedCategories = $adapter->fetchCol($select);
+        $this->cacheContext->registerEntities(Category::CACHE_TAG, $affectedCategories);
+
+        $this->eventManager->dispatch('clean_cache_by_tags', ['object' => $this->cacheContext]);
+
         return $this;
     }