On versions 15.0.0-15.0.1.1 14.1.0-14.1.2 14.0.0-14.0.1 13.1.0-13.1.3.1 12.1.0-12.1.5 and 11.5.2-11.6.5.1 the BIG-IP APM system logs the client-session-id when a per-session policy is attached to the virtual server with debug logging enabled.