Hi,
what do you mean with session ID? Do you want to print the server-side session ID to the logfile? I don't think, that this is not easily possible, as it is not provided as variable in the logger (see the OSGI console for the list of supported data for logging. You likely need to extend the code, but note: AEM 5.6.1 still uses slf4j, while AEM 6.x uses logback as backend.
kind regards,
Jörg