fix: Elasticsearch: Request Entity Too Large #28117 (#29062) (#29075)

Backport #29062 by @inferno-umar

Fix for gitea putting everything into one request without batching and
sending it to Elasticsearch for indexing as issued in #28117

This issue occured in large repositories while Gitea tries to
index the code using ElasticSearch.

Co-authored-by: dark-angel <70754989+inferno-umar@users.noreply.github.com>
(cherry picked from commit f0d34cd3b97dd2c9f29fc401ec58ea0661b7ca7d)

modules/indexer/code/elasticsearch/elasticsearch.go

@@ -180,11 +180,17 @@ func (b *Indexer) Index(ctx context.Context, repo *repo_model.Repository, sha st
 	}
 
 	if len(reqs) > 0 {
-		_, err := b.inner.Client.Bulk().
-			Index(b.inner.VersionedIndexName()).
-			Add(reqs...).
-			Do(ctx)
-		return err
+		esBatchSize := 50
+
+		for i := 0; i < len(reqs); i += esBatchSize {
+			_, err := b.inner.Client.Bulk().
+				Index(b.inner.VersionedIndexName()).
+				Add(reqs[i:min(i+esBatchSize, len(reqs))]...).
+				Do(ctx)
+			if err != nil {
+				return err
+			}
+		}
 	}
 	return nil
 }