IE 11 webcache.dat file lock with Teams Optimization Enabled

[pbastiaans]

Really, really, REALLY Odd.

It appears that when we enable Teams Optimization, the file webcache.dat file becomes locked and importing fails(no cookies).

Teams Optimization Setting:

FlexEngine Log error:

Disabling the GPO, and everything works again. Enabling the setting, causes the issue.

Have tried:

• Different ref images
• New DEM config with just this GPO and slimmed down IE config
• No app stacks
• Appears to work on 'vanilla' W10, hard to tell, have to make other tweaks to get it to work in our secure environment
• Working with VMware and sent many logs, procmon, etc.
• Works in Edge (I know, I know...IE 11 goes EOL, until then I have to support 🙂 )

1. Anyone else dealt with this or something similar (file lock on DEM import)?
2. Troubleshooting suggestions?

[Pim_van_de_Vis]

The filelock seems to appear on 1 of the .log files. In my testing these .log files where not needed to roam the cookies and other IE settings. Just the WebCacheV01.dat file was enough.

Could you test only roaming that file with DEM to see if that works and still saves all users personal IE settings?

[pbastiaans]

Thanks Pim.

Roaming just the webcachev01.dat file exhibits the same behavior.

Enabling the computer environment GPO for teams optimization in DEM, the issue occurs. Disabling the GPO, no issues. The issue also occurs if the registry key is set manually.

There is a theory that something is locking the file before DEM import, I do not understand this theory as the file isn't there until DEM import.

[DEMdev · Accepted solution]

Hi @pbastiaans,

You probably already saw the update from my support colleague on your ticket, but to provide an intermediate summary for the forum audience: analysis of the latest ProcMon boot log shows that if Teams optimization is enabled, Horizon configures a proxy setting early during logon, and announces that to other processes by calling a WinInet API. (WinInet is a Windows component that deals with HTTP connections, caches, cookies, ...)

That API call triggers the launch of a DllHost process that creates/loads the WebCache-related files, and prevents DEM from overwriting some of them during logon.

[pbastiaans]

Yes, shout out to Dylan and his team for working with us, initial testing is promising.

The suggestion is to add this key to default user:

\Software\Microsoft\Windows\CurrentVersion\Internet Settings@ProxyOverride to "view-localhost"

For the Initial testing, I loaded the default user registry hive (ntuser.dat) and added the key AND I added to the key to HKEY_USERS\.DEFAULT, not sure at this time which one of these is the true location for the fix.

Will update with correct answer.

[DEMdev]

Hi @pbastiaans,

Ummm yeah, I guess I'm "Dylan's team" on this SR 🙂

Registry changes for the default user profile must be done via ntuser.dat, as HKU\.DEFAULT is SYSTEM's registry, confusingly.

[pbastiaans]

Yes, shout out to DEMdev and team for working with us 😉

This has resolved the file lock issue, we have it in our DEV environment to understand collateral damage that may/may not occur. (will post if we notice any negative impact)

Awesome work Team VMware! Thank you!