NuCache.Content.db locked when app starts after inactivity on Azure

Sometimes when our web app in Azure turns off due to inactivity, whenever someone tries to go to the website the websites throws the following exception:

-> Umbraco.Core.Exceptions.BootFailedException: Boot failed.

-> System.IO.IOException: The process cannot access the file 'D:\home\site\wwwroot\App_Data\TEMP\NuCache\NuCache.Content.db' because it is being used by another process.

FullException.txt UmbracoTraceLog.RD0003FF744804.20190910.zip

This seems to only happen when the site goes offline due to inactivity, and a restart causes the file to be unlocked and everything to work properly again.

We do not use deployments slots or application insights currently. And the settings as described in Issue 5035 have also been configured properly. I am currently trying out the “fix” to ignore the localDb file but obviously I hope for a more appropriate solution. If there are any more logs needed please do tell.

Reproduction

• Release an Umbraco site to Azure
• Wait until it goed offline due to inactivity
• Try to go to a page

Umbraco version: 8.1.3

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This item has been added to our backlog AB#3407

[claushingebjerg]

experienced this in vanilla 8.6 as well on normal hosting, not Azure

[vladicaivanovski]

The process cannot access the file ‘D:\local\Temp\UmbracoData\8c88e448981650d162c7b798b5f3e3de\NuCache\NuCache.Content.db’ because it is being used by another process.

Happening a lot in our Umbraco Azure website v8.18.4. We have deployment slots and proper settings as suggested for Azure websites, but still we see this frustrating error very often which crashes the whole site and requires restart in order to get up and running.

Please help