Problem w/ daemon threads

[Sean Devlin]

Hi all,
I'm trying to get a periodic daemon thread working. I've read some of
the stuff here:

http://groups.google.com/group/clojure/browse_thread/thread/4bc06d413fda157f/e953bb0c9286c5a7

With no luck. My code looks like this

(defn daemon
"Creates a new daemon thread and sets runnable to f"
[f]
(let [t (Thread. f)]
(do
(.setDaemon t true)
(.start t)
t)))

And I tried calling

user=>(daemon #(println "foo"))

I get the thread back, but it does not appear to execute. I've tried
this on OSX and XP. Does anyone know what I'm doing wrong?

Sean

[David Brown]

On Thu, Nov 12, 2009 at 07:50:31AM -0800, Sean Devlin wrote:

>(defn daemon
> "Creates a new daemon thread and sets runnable to f"
> [f]
> (let [t (Thread. f)]
> (do
> (.setDaemon t true)
> (.start t)
> t)))
>
>And I tried calling
>
>user=>(daemon #(println "foo"))
>
>I get the thread back, but it does not appear to execute. I've tried
>this on OSX and XP. Does anyone know what I'm doing wrong?

I tried this on Linux, and prints "foo" once, which is what I would
expect.

If you want it to be period, though, you'll need to use something like
Executors/newSingleThreadScheduledExecutor to create a scheduler for
it.

I tried writing a periodic scheduler using agents (and a ref to manage
state). Turns out that getting shutdown working robustly is actually
fairly tricky. I recommend just using the scheduler available in
Java.

David

[Sean Devlin]

Blargh!!! I've committed a good old-fashioned PEBCAK.

I should have been more specific. I executed this in SLIME/OSX and
enclojure/XP. The problem was that the output wasn't going to *out*
like I'd expect.

I tried a different example, and everything is cool.

user=>(def my-agent (agent 0))

user=>(daemon #(send my-agent inc))

user=>@my-agent
1

D'oh!
Sean