I've been seeing this weird looping behavior with some go loops over the
last few days. An exception is being thrown from a function within the loop
and rather than logging and looping back around to a waiting take, the loop
seems to just hop back to the line before the function call. It's been
driving me crazy, because it's, well, crazy :)
I think i've managed to boil it down to the following:
(def s (chan))
(def single
(go-loop []
(try
(prn "Awaiting single")
(<! s)
(prn "Single")
(throw (new Throwable))
(catch Throwable t
(prn t)))
(recur)))
(def d (chan))
(def double
(go-loop []
(try
(prn "Awaiting double")
(<! d)
(prn "Double")
(throw (new Throwable))
(catch Exception re
(prn re))
(catch Throwable t
(prn t)))
(recur)))
Now if you (>!! s :a), you'll see the throwable printed out and the loop go
back to waiting on the s channel. However, (>!! d :a) and you'll get to
enjoy an infinite stream of 'Double'. In actual fact you can remove the
-loop from double and get the same result.
Not sure what's going on here at all. In the macro expanded version of
double '(prn t)' doesn't appear at all (it does in single's expansion), so
it looks like it's not surviving the move into the state machine and
instead is routing back to (prn "Double") or the take isn't really
completing somehow, leaving the :a on the chan. Either way it doesn't seem
right!
I'd love for someone to shed some light on this behavior and/or point me at
something that would explain it.
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