QlikView server becomes unresponsive - "Fiber loop" errors might appear in the logs

When opening certain apps the QlikView Server (QVS) may become unresponsive for unexplained reason.

• resources are well within parameters
• the pagefile is correcty sized
• some fiber loop errors appear in the logs (not necessarily connected with the issue)

Possible symptoms:

• impossible to connect to the server
• when connected, objects will not render properly, stay in hourglass icon, or similar.

Environment:

• QlikView 12.20 SR3 to SR9

• QV-15294

Fixed Version:

• QlikView November 2018 (12.30 IR)

Workaround:
Try the following on every QVS node:

• stop all QlikView Server services
• edit the C:\ProgramData\QlikTech\QlikViewServer\settings.ini files to add "DisableCacheQueue=1" to their [Settings 7] section (before the [Authentication] one)
• restart the services

The action should revert to a behavior that was different in the early versions of 12.20, and that does not present the problem.

If the actions above solves the problem, we are for sure in the scenario of bug QV-15294. A permanent fix is included in QlikView November 2018 (12.30 IR)

If it doesn't, an upgrade is still recommended because of improvements around this area.