Set the Fetch Tag Limit in config instead of hardcoded constant.

Author: wigman

src/Model/TagRepository.php

@@ -5,6 +5,7 @@
 
 use Magento\Framework\App\ResourceConnection;
 use IntegerNet\AsyncVarnish\Model\ResourceModel\Tag as TagResource;
+use Magento\Framework\App\Config\ScopeConfigInterface;
 
 class TagRepository
 {
@@ -16,7 +17,7 @@ class TagRepository
     /**
      * Limits the amount of tags being fetched from database
      */
-    const TAG_LIMIT = 1000000;
+    const FETCH_TAG_LIMIT_CONFIG_PATH = 'system/full_page_cache/async_varnish/varnish_fetch_tag_limit';
 
     private $lastUsedId;
 
@@ -35,16 +36,25 @@ class TagRepository
      */
     private $tagResource;
 
+    private $scopeConfig;
+
     /**
      * @param \Magento\Framework\App\ResourceConnection $resource
      */
     public function __construct(
         ResourceConnection $resource,
-        TagResource $tagResource
+        TagResource $tagResource,
+        ScopeConfigInterface $scopeConfig
     ) {
         $this->connection = $resource->getConnection();
         $this->resource = $resource;
         $this->tagResource = $tagResource;
+        $this->scopeConfig = $scopeConfig;
+    }
+
+    private function getTagFetchLimit()
+    {
+        return $this->scopeConfig->getValue(self::FETCH_TAG_LIMIT_CONFIG_PATH);
     }
 
     /**
@@ -102,8 +112,9 @@ public function getAll()
         $tags = [];
 
         $tagResource = $this->tagResource;
+        $tagFetchLimit = $this->getTagFetchLimit();
 
-        $maxIdResult = $tagResource->getMaxTagId(self::TAG_LIMIT);
+        $maxIdResult = $tagResource->getMaxTagId($tagFetchLimit);
 
         if (empty($maxIdResult)) {
             return $tags;

src/etc/adminhtml/system.xml

@@ -16,6 +16,17 @@
                             <field id="caching_application">1</field>
                         </depends>
                     </field>
+                    <field id="varnish_fetch_tag_limit" type="text" translate="label comment" sortOrder="110"
+                           showInDefault="1" showInWebsite="0" showInStore="0" canRestore="1">
+                        <label>Varnish fetch tag limit.</label>
+                        <backend_model>IntegerNet\AsyncVarnish\Model\System\Config\Backend\HeaderLength</backend_model>
+                        <comment>The maximum amount of tags that are fetched in 1 purge request. This can be
+                            set to a fairly high number (1 million by default), unless you run into resource
+                            limits/timeouts.</comment>
+                        <depends>
+                            <field id="caching_application">1</field>
+                        </depends>
+                    </field>
                 </group>
             </group>
         </section>

src/etc/config.xml

@@ -10,6 +10,7 @@
             <full_page_cache>
                 <async_varnish>
                     <varnish_max_header_length>8000</varnish_max_header_length>
+                    <varnish_fetch_tag_limit>1000000</varnish_fetch_tag_limit>
                 </async_varnish>
             </full_page_cache>
         </system>