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Registered VDA's unregister at session launch

Ross Faverty1709158252


We are running 2209 with MCS provisioned, non persistent VM's. We have 10+ machine catalogs. This morning, in one of those machine catalogs all the VDA's that were registered were going into an unregistered state during session launch which was producing the error "Cannot Start Desktop" to the users. In Director we were seeing a mixture of "Communication Error", "Other" or "Connection Timeout". Some of these users have access to other VDA's in different machine catalogs and they were able to log into those without issue so we proved it was Machine Catalog specific. 


This was replicable for internal and external users.

The last time this machine catalog was updated was a week ago. We have had no issues since the update or in the previous weeks during alpha and beta testing. That update included the 2209 VDA (from 2203) & Windows updates. These same updates have been applied to other machine catalogs (going back as far as early January) and we haven't yet seen a repeat of those issues.  


We put all the VDA's in MM, shut them down, brought them back up and they all came back registered but as soon as users started sessions on them they went into the unregistered state again. 


Checking the DC's (we have 2) we saw warning events ID #1039  on the Citrix Broker Service:


"The Citrix Broker Service failed to contact virtual machine 'vm-038.domain.com' (IP address xxx.xxx.xxx.xxx). 
Check that the virtual machine can be contacted from the controller and that any firewall on the virtual machine allows connections from the controller. See Citrix Knowledge Base article CTX126992. 
Error details: 
Exception 'The server was unable to process the request due to an internal error.  For more information about the error, either turn on IncludeExceptionDetailInFaults (either from ServiceBehaviorAttribute or from the <serviceDebug> configuration behavior) on the server in order to send the exception information back to the client, or turn on tracing as per the Microsoft .NET Framework SDK documentation and inspect the server trace logs.' of type 'System.ServiceModel.FaultException'."



I checked the master image and confirmed that both the DC's were listed in HKLM\Software\Citrix\VirtualDesktopAgent\ListofDDCs - they were. I was able to ping both DC's too and RDP to them from the master image. 



After checking the registry in the master image I shut it down, took a snapshot and then updated the machine catalog. After rebooting the VM's all users could start sessions. 


I'm stumped, any ideas or anyone else seen this behavior? 


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If I understood your thoughts and description of the problem, I´m glad the 


It seems like there was an issue with the communication between the Delivery Controller

and the Virtual Machines in that Catalog.
The warning event ID #1039 says that the Broker Service was unable to contact the Virtual Machine, possibly due to a firewall blocking the 
connection or some other communication issue.


The fact that shutting down the Virtual Machines and updating the Machine Catalog fixed the problem pointing to that there

may have been a configuration  issue or corruption in the previous setup. It's possible that the update to the VDA and Windows

updates may have worsen this issue?
Anyway, it seems like the problem was resolved by updating the Machine Catalog, which may have refreshed the configuration and fix it?

That's all I can think of.



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I had something similar happen on server VDAs with 1912. VDAs deregister upon launch. Saw something in the "fixed issues" for the next  documentation that could be it. I updated the VDA and that didn't solve it. 


The problem ended up being on the Delivery Controller itself. I updated all my ddcs to the latest CU level and that solved the issue. I spent a lot of time focusing on the VDA since that's what deregistered. You said you're at 2209. If you're on-prem consider updating the ddc.

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