ensure proper closure of resp.Body in error handling and empty response cases in datasource.go to prevent resource leak (#537)

Author: arturminchukov

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## tip
 
+* BUGFIX: fix closing connections in the datasource backend to prevent resource leak. See [pr #537](https://github.com/VictoriaMetrics/victorialogs-datasource/pull/537).
+
 ## v0.23.4
 
 * BUGFIX: update dependencies to fix security issues with react-router. See [pr #534](https://github.com/VictoriaMetrics/victorialogs-datasource/pull/534).

pkg/plugin/datasource.go

@@ -413,6 +413,8 @@ func (di *DatasourceInstance) datasourceQuery(ctx context.Context, q *Query, isS
 	}
 
 	if resp.StatusCode != http.StatusOK {
+		defer resp.Body.Close()
+
 		switch resp.StatusCode {
 		case http.StatusUnprocessableEntity:
 			return nil, parseErrorResponse(resp.Body)
@@ -426,6 +428,7 @@ func (di *DatasourceInstance) datasourceQuery(ctx context.Context, q *Query, isS
 	// This is to handle cases where VictoriaLogs returns no data
 	// and avoid json decoding errors
 	if resp.ContentLength == 0 {
+		resp.Body.Close()
 		return nil, nil
 	}