Thanks for your answer.

the connection id is already unique and during keep-alive it will be the same for the same visitor.
this is actually what i want, the only problem is that the restart of nginx resets the connection id
this makes log analysis complicated

having the start time of nginx would solve the problem.

manually setting a value for this on every reload is not a very good solution to me :)
i could probably write a startup script that includes a file where i increment a value, but asking for that variable could help a lot more :)

thanks
alex