Issue #3385294: AJAX HTTP error occurred when adding search server

src/Plugin/search_api/backend/SearchApiMeiliSearchBackend.php

@@ -792,4 +792,26 @@ class SearchApiMeiliSearchBackend extends BackendPluginBase implements Autocompl
     return $facets;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function __sleep(): array {
+    $properties = array_flip(parent::__sleep());
+    unset($properties['meiliService']);
+
+    return array_keys($properties);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __wakeup(): void {
+    parent::__wakeup();
+
+    $container = \Drupal::getContainer();
+    $this->meiliService = $container->get('search_api_meilisearch.api');
+    $this->meiliService->setUrl($this->configuration['meilisearch_host_address'] . ':' . $this->configuration['meilisearch_host_port']);
+    $this->meiliService->setMasterKey($this->configuration['meilisearch_master_key']);
+  }
+
 }