About DNS irule TCL error

You should use catch function

try something like this

when DNS_RESPONSE 
{ 
	set timestamp [clock format [clock seconds] -format "%Y-%m-%d %H:%M:%S"] 
	# log local0. "Client IP : [IP::client_addr] / F5 answer : [DNS::answer]" 
	set kt_hsl [HSL::open -publisher /Common/kt_publisher] 
	
	if {[catch {HSL::send $kt_hsl "$timestamp DNS RESPONSE / Client IP : [IP::client_addr] / F5 answer : [DNS::answer]"}]} 
	{
        log local0. "ERROR: DNS RESPONSE FAILED"
    }
}