iRule to log HTTP request as Apache combined standard format

Hello,

I discover that we loose some logs using the log local0. command. it seems due to the UDP protocol. I need to send log to syslog by TCP. I update my irule by using the HSL command. Can i specify the source IP from which the syslog receives the logs? What is the default source IP when nothing is precised?

when HTTP_REQUEST { set host [HTTP::host]
    set username [HTTP::username]
    set client_IP [IP::client_addr]
    set request "\"[HTTP::method] [HTTP::uri] HTTP/[HTTP::version]\""
    set request_time [clock clicks -milliseconds]
    set referer [HTTP::header "Referer"]
    set ua [HTTP::header "User-Agent"]
    set xff [HTTP::header "X-Forwarded-For"]
}
when HTTP_RESPONSE {
    set response_time [expr [clock clicks -milliseconds] - $request_time]
    set now [clock format [clock seconds] -format "%d/%b/%Y:%H:%M:%S %z"]
    set contentlength [HTTP::header "Content-Length"]
    set status [HTTP::status]

    HSL::send [HSL::open -proto TCP -pool /CLI01_COPR/POOL_SYSLOG] "$host $client_IP $username $now $request $status $contentlength \"$referer\" \"$ua\" \"$xff\" $response_time" 
}

This irule is used by the VS whith the address 172.19.143.2%201:81. POOL_SYSLOG has one member, the node: 10.100.100.13:514.

Please help!