On Wed, Jan 21, 2009 at 11:36 PM, Belka <[email protected]> wrote:
>
> Hi!
>
> Could somebody please share some experience on how to implement daemon
> start
> and stop directives. In theory I need something like this:
> 1. "my_daemon start" - starts my app with an infinite loop of serving
> inside.
> 2. "my_daemon stop" - puts in some TVar a value signalizing, that stop is
> given - infinite loop brakes.
You can abstract this pattern:
-- runs its argument in an infinite loop, and returns an action that stops
the loop
daemon :: IO () -> IO (IO ())
daemon action = do
stopvar <- atomically $ newTVar False
let run = do
stop <- atomically $ readTVar stopvar
if stop then return () else (action >> run)
forkIO run
return (atomically $ writeTVar stopvar True)
TVars are overkill here, actually, an IORef would be just fine, I think.
Luke
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