Hello

I've been experiencing some consistent booting issues with this version of Umbraco on Azure where the instances seem to get stuck in boot cycles and fail to fully start.

No errors are being thrown in the log file, but picking out the section of logging on each boot cycle, the reboot appears to happen after a new application url (localhost) is discovered:

{
    "@t": "2021-04-16T08:56:47.3319049Z",
    "@mt": "Starting initialize async background thread.",
    "SourceContext": "Umbraco.Web.Search.BackgroundIndexRebuilder",
    "ProcessId": 13256,
    "ProcessName": "w3wp",
    "ThreadId": 1,
    "AppDomainId": 2,
    "AppDomainAppId": "LMW3SVC132432012ROOT",
    "MachineName": "RD0050F2BCFF91",
    "Log4NetLevel": "INFO ",
    "HttpRequestNumber": 1,
    "HttpRequestId": "0dc55980-db72-4460-9fad-20b1ea14a174"
}{
    "@t": "2021-04-16T08:56:47.3319049Z",
    "@mt": "{EndMessage} ({Duration}ms) [Timing {TimingId}]",
    "EndMessage": "Booted.",
    "Duration": 44160,
    "TimingId": "6ba65c3",
    "SourceContext": "Umbraco.Core.Runtime.CoreRuntime",
    "ProcessId": 13256,
    "ProcessName": "w3wp",
    "ThreadId": 1,
    "AppDomainId": 2,
    "AppDomainAppId": "LMW3SVC132432012ROOT",
    "MachineName": "RD0050F2BCFF91",
    "Log4NetLevel": "INFO ",
    "HttpRequestNumber": 1,
    "HttpRequestId": "0dc55980-db72-4460-9fad-20b1ea14a174"
}{
    "@t": "2021-04-16T08:56:47.6444158Z",
    "@mt": "New url {Url} detected, re-discovering application url.",
    "Url": "http://localhost:80/umbraco",
    "SourceContext": "Umbraco.Core.Sync.ApplicationUrlHelper",
    "ProcessId": 13256,
    "ProcessName": "w3wp",
    "ThreadId": 9,
    "AppDomainId": 2,
    "AppDomainAppId": "LMW3SVC132432012ROOT",
    "MachineName": "RD0050F2BCFF91",
    "Log4NetLevel": "INFO ",
    "HttpRequestNumber": 2,
    "HttpRequestId": "e02a985d-29ec-41cf-82ff-cc9c94892bbf"
}{
    "@t": "2021-04-16T08:56:47.6444158Z",
    "@mt": "ApplicationUrl: {UmbracoAppUrl} (UmbracoModule request)",
    "UmbracoAppUrl": "http://localhost:80/umbraco",
    "SourceContext": "Umbraco.Core.Sync.ApplicationUrlHelper",
    "ProcessId": 13256,
    "ProcessName": "w3wp",
    "ThreadId": 9,
    "AppDomainId": 2,
    "AppDomainAppId": "LMW3SVC132432012ROOT",
    "MachineName": "RD0050F2BCFF91",
    "Log4NetLevel": "INFO ",
    "HttpRequestNumber": 2,
    "HttpRequestId": "e02a985d-29ec-41cf-82ff-cc9c94892bbf"
}{
    "@t": "2021-04-16T08:56:54.1601772Z",
    "@mt": "{StartMessage} [Timing {TimingId}]",
    "StartMessage": "Booting Umbraco 8.12.2.",
    "TimingId": "c9ea859",
    "SourceContext": "Umbraco.Core.Runtime.CoreRuntime",
    "ProcessId": 6324,
    "ProcessName": "w3wp",
    "ThreadId": 1,
    "AppDomainId": 2,
    "AppDomainAppId": "LMW3SVC132432012ROOT",
    "MachineName": "RD0050F2BCFF91",
    "Log4NetLevel": "INFO ",
    "HttpRequestNumber": 1,
    "HttpRequestId": "b63e0add-686f-4b86-a327-03902de62a2e"
}

The Web App in question failed to boot for around 8 hours then in the middle of the night did successfully boot itself, so is currently 'up', but next code deployment will likely bring it down again.

We have quite a number of other Umbraco instances running on Azure (all as single instances) with the same configuration/setup (all following the recommended configuration documentation post on Our Umbraco) including a very recent 8.11.1 instance, and none of these have shown this issue so wonder if it is releated to 8.12 specifically.

This particular instance actually started life as a 8.12.0 install which was then upgraded to 8.12.2 and I noticed that after the upgrade was pushed to the App Service the intsaller wizard failed to run, so did have to trigger it manually. This is something I've never come across before. 8.12 contained unattended upgrades but I've not yet enabled this. This could be unrelated to the original issue though.

I should also say this issue doesn't occur when running locally.

Has anyone else experienced this issue or have any ideas what might be happening? Any insights or help would be greatly appreciated.

Many thanks

Lewis