While working on upgrading a Windows 2012 R2 ADFS Farm to Window Server 2016 I noticed the worried looks of the systems administrators while looking at a warning in the ADFS event log, which they wanted to trouble shoot. I knew they had a hardware load balancer in place which made me 99.999% sure it wasn’t a real issue. You see, early documentation on configuring load balancing for and ADFS farm was often configured with a health check for the following url: /FederationMetadata/2007-06/FederationMetadata.xml. This leads you to an XML file that should be available on a working ADFS node.

This works fine. The Kemp Loadmaster knows the ADFS nodes are functional or not and can do it’s job. There’s a nagging issue however. The ADFS log on the ADFS farm node keep logging every health check with a warning

Event ID 143 AD FS

The Federation Service was unable to create the federation metadata document as a result of an error.Document Path: /FederationMetadata/2007-06/FederationMetadata.xml

Additional Data
Exception details:
System.Net.HttpListenerException (0x80004005): The specified network name is no longer available at System.Net.HttpResponseStream.Write(Byte[] buffer, Int32 offset, Int32 size) at Microsoft.IdentityServer.Service.FederationMetadata.SamlMetadataListener.OnGetContext(IAsyncResult result)

As you cans see it just fills the logs every 9 seconds (the frequency of the health check).

This leads to hunting for a “ghost” issue that’s actually only an artefact of checking for .

Kemp has updated their documentation with 2 other values for the health check url to use. The good news is these don’t cause the above artefact of logging warning to the ADFS event log. These 2 options are:

• /adfs/services/trust/mex

This leads to an XML file as well but it doesn’t cause the warning to be logged.

• /adfs/ls/idpInitiatedSignon.aspx.

This leads to the ADFS login page which also doesn’t cause a warning to be logged.

So by changing your health check to any of the  above you get a functional health check for your nodes and you don’t have the phantom warning entries in the ADFS event log. That’s a lot better and at least doesn’t cause any unneeded concerns by the initiated accidental ADFS administrator.