req.xid semantics?

[Niall O'Higgins]

Hi all,

I am looking for some sort of VCL identifier which I can use to
disambiguate requests which occur within the same second, but in
different threads.

I *think* that req.xid will work here, but I'm unable to determine
exactly what its semantics are, since there doesn't seem to be any
documentation for it.

It appears from my tests to increase monotonically with each request.

Is this indeed the case?

Thanks!

-- 
Niall O'Higgins
Software Engineer
Metaweb Technologies, Inc.