Download Submissions does not respect AWS load balancing constraints

@see https://docs.acquia.com/cloud-platform/manage/files/broken/

Exactly. Using the Gluster FS was the only thing that worked for us, and for #3118815: Files on submissions remain in directory _sid_, are therefore could be cleaned by cron and are inaccessible to users → . If this is to be worked around by the framework in some way I would consider that Drupal Core's responsibility, not Webform's.

(I updated the issue tags according to the guidelines.)

@jrockowitz: Should they use Elastic File System (Amazon EFS) as shared storage for the Drupal temporary directory?

Yes, I think you have to use the shared file storage as a temp directory.

I'm am a bit confused by the reference to how to solve problems with file uploads getting broken when this is for a file download. I take it that the file provided for downloading is saved to disk prior to the download, which makes the shared file system between AWS instances relevant. And the assumption is that the process of writing the file to a shared disk is all going to be properly handled without needing to deal with AWS stickiness?

We'll try something like EFS for the temp directory and report back here if that does not solve things.