[erlang-questions] Use of uuidgen with a mnesia application
Fri Jun 6 17:29:43 CEST 2008
On Fri, Jun 6, 2008 at 9:43 AM, Alexander Lamb
> I need to generate ids to be used as mnesia keys which will be unique
> not only withing a cluster of Erlang nodes but also globally (e.g. may
> be read from a Java program).
> I initially thought of writing my own uuidgen function, but it seems
> like reading the mac address of network interfaces can be rather
> cumbersom depending on systems.
> So I decided to use uuidgen from the system and convert it to binary
> (for efficiency).
> Is this the correct way of doing things:
> verify_guuid(Value) ->
> A = lists:nth(9,Value),
> B = lists:nth(14,Value),
> C = lists:nth(19,Value),
> case [A,B,C] of
> "---" -> true;
> _ -> false
> make_guuid() ->
> First = os:cmd("uuidgen -t"),
> case verify_guuid(First) of
> true -> Result = First;
> false -> Second = os:cmd("uuidgen"),
> case verify_guuid(Second) of
> true -> Result = Second;
> false -> Result = "error",
> Now, the reason I have this cascade of case is because on Linux (our
> Ubuntu servers) it recognizes the -t option to generate the uuid and
> on MacOSX (our dev machines) it does not.
Wouldn't it be "nicer" to use os:type/0 and os:version/0 to detect
what system You are running on?
> Call me crazy, but I never feel confortable about using a totally
> random uuid to identity medical records that might be copied from
> system to system, exported, etc... even if the probability of
> collision is lower than that of a large asteroid hitting earth!
> What is your strategy for this (maybe this is a question to ask the
> couchdb developers, since they use guuids to identify the documents)?
> Alexander Lamb
> Founding Associate
> RODANOTECH Sàrl
> 4 ch. de la Tour de Champel
> 1206 Geneva
> Tel: 022 347 77 37
> Fax: 022 347 77 38
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