How can I filter nodes by author name? I'm trying to make page with nodes filtered by author name. My context filter is comming from url. 

My path looks like domain.xx/drupal/authors/johny

If i set validation by user ID, and send user ID in path, all works properly.

You can see contextual filter setup in attachment.
On editing view, click the advanced settings then click relationships area, click Add.

There are many tables you can join to the content listing. In this case, search for "author" options, and select Content: Content author. Click Apply. Now add field 'user' in view also set filter criteria as needed.