Mike Meyer <[email protected]> writes:
> My simple web app
> (http://blog.mired.org/2010/11/x10-controller-in-clojure.html) has
> some stuff that needs to happen just once (in this case, opening the
> serial port). It's not clear how to get this to happen using ring. If
> I do it inside my ring handler, then it gets run on every request, and
> I have to check to make sure it's not run multiple times.
I would just open it lazily on the first request. That gives you a nice
place to gracefully retry on error as well, instead of being dead until
the entire servlet container is restarted. As a sysadmin I really hate
apps that can get stuck in a error state and need restarting. ;-)
For example you could be using a USB to Serial adapter, which somebody
might have temporarily removed and plugged in later. Similarly if
you're opening a database connection on startup and there's a network
dropout, or perhaps your app got started before the database server
did...
> If I run it outside the handler, then it gets run when I do "lein
> uberwar", which is simply wrong.
If you really want to do it at load time you can avoid executing
something at compile time by wrapping it in this:
(when-not *compile-files*
...)
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