ID 476984 - Import/From Photoshop: Panels will sometimes be stuck on Processing following a completed import during heavy traffic on the server(s)

Problem summary
Panels can stay indefinitely be stuck on "Processing" when on a multi-server setup experiencing heavy traffic. When this happen, users have to save and reload the Client, which rarely resolves the issue straight away as panels will appear white; the panels only show correctly when the cache is cleared and the Client is reloaded once more.

Customer reported version
Flix 6.3.5

Customer reported platform

macOS

Steps to reproduce

Note: this issue is more likely to happen when the Flix Server is very busy, and with larger batches of panels being imported; the following steps give a somewhat consistent method of reproduction, though this is an intermittent issue.

1) Have at least 12 users on 5 servers with ~4 vCPUs each. 

2) Have: 

• one user publish a medium sized sequence of all unpublished panels to Avid (~400 panels)
• one user exporting a QuickTime for a medium sized sequence (~400 panels)
• one user publish back from Avid
• 3 users import at least 100 panels (from PS or manually, it doesn't matter)

At least one of the users importing panels will hit this problem.

Expected behaviour
All imported panels should show successfully in the Panel Browser, and only panels for which the thumbnail is genuienly still processing should show as 'Processing'.

Actual behaviour
Some panels will appear with a Processing state in the Panel Browser, even though processing for all panels seem to have been completed on the Server. No helpful errors/warnings found in the Server, Transfer-Util nor Client logs.

Workaround
Reload the Client. If blank panels appear, clear your Local Asset Cache, then reload the Client once more.

Reproduced by support

This bug has been reproduced in:
6.3.6-3 - macOS Client - CentOS 7 Server

Due to the complexity of the reproduction steps, this bug has not been fully regression tested.