[reSIProcate] True uniqeness of Helper::computeCallID()

[Byron Campen]

	Hrm. Just some preliminary fiddling with the probabilities (alas, my  
installation of octave is hosed) makes it look _extremely_ likely  
that you would get repeats within a data set of 2 million (before the  
hash, we aren't talking about hash collisions here). Just throwing in  
a timestamp or a counter would make the pre-hash token effectively  
unique, or you could go with a longer string of random hex (16 should  
bring it down to a vanishingly small probability). Maybe we could  
have Helper::computeCallId() take an optional int parameter that  
would specify the length of random hex the caller wants to go in the  
hash?

Best regards,
Byron Campen

> Has anyone had issue with the true uniqueness of  
> Helper::computeCallID().
>
> I've used the value returned from this to push about two million  
> calls into cdr records....however I am discovering that some new  
> calls are attaching themselves to old cdr records.......
>
> The algorithm used in Helper.cxx is the base64 of md5 of hostname +  
> Random::getRandomHex(8)
>
> My guess is there is a good chance that you will get a random  
> number twice.
>
> Does anyone have an idea on how this can be improved or a quick  
> code snippet for me to create a truly unique callid?
>
> Thanks in advance,
>
> David
>
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