KB43754 - Warnings from rule "Application Firewall Enforcer": Use of connection.close is deprecated for HTTP virtual servers. Use http.sendResponse with http.disableClientKeepalive instead

This article describes an issue where upgrading the Traffic Manager version and restoring the WAF configuration will produce a warning from rule 'Application Firewall Enforcer'.

The following warning appears after upgrading the Traffic Manager version and restoring the WAF configuration:

Warnings from rule 'Application Firewall Enforcer':

Use of connection.close is deprecated for HTTP virtual servers. 
Use http.sendResponse with http.disableClientKeepalive instead.  
This error was reported by all traffic manager machines.

This error is caused by restoring a configuration backup of the Application Firewall  that predates version 4.9-37341.  The WAF code was changed to deprecate the connection.close() function in version 10.2 and higher but in the event that an earlier version of WAF is restored, this may cause AFM to drop the whole connection instead of the stream.

Upgrading to a supported version of the Traffic Manager will update the version of the Application Firewall and resolve this error. 

In the event that the vTM is upgraded but an older version of AFM is restored, then updating the Application Firewall via the WAF interface to the current version will resolve this error: AFM  web UI > Administration > Cluster Management > Updater.