While on the subject of conduits and timing, I'm using the following conduit to add elapsed timing information:

timedConduit :: MonadResource m => forall l o u . Pipe l o o u m (u, NominalDiffTime)
timedConduit = bracketP getCurrentTime (\_ -> return ()) inner
    where inner st = do r <- awaitE
                        case r of
                          Right x -> yield x >> inner st
                          Left  r -> deltaTime st >>= \t -> return (r,t)
          deltaTime st = liftIO $ flip diffUTCTime st <$> getCurrentTime

I'm aware that this is primarily timing the downstream (and ultimately the Sink) more than the upstream, and I'm using the bracketP to attempt to delay the acquisition of the initial time (st) until the first downstream request for data.

I would appreciate any other insights regarding concerns, issues, or oddities that I might encounter with the above.

Thanks,
  Kevin

On Mon, 04 Feb 2013 02:25:11 -0700, Michael Snoyman <michael@snoyman.com> wrote:

I think this is probably the right approach. However, there's something
important to point out: flushing based on timing issues must be handled
*outside* of the conduit functionality, since by design conduit will not
allow you to (for example) run `await` for up to a certain amount of time.
You'll probably need to do this outside of your conduit chain, in the
initial Source. It might look something like this:

yourSource = do
    mx <- timeout somePeriod myAction
    yield $ maybe Flush Chunk mx
    yourSource


On Sun, Feb 3, 2013 at 5:06 PM, Felipe Almeida Lessa <felipe.lessa@gmail.com

wrote:

I guess you could use the Flush datatype [1] depending on how your
data is generated.

Cheers,

[1]
http://hackage.haskell.org/packages/archive/conduit/0.5.4.1/doc/html/Data-Conduit.html#t:Flush

On Fri, Feb 1, 2013 at 6:28 AM, Simon Marechal <simon@banquise.net> wrote:
> On 01/02/2013 08:21, Michael Snoyman wrote:
>> So you're saying you want to keep the same grouping that you had
>> originally? Or do you want to batch up a certain number of results?
>> There are lots of ways of approaching this problem, and the types don't
>> imply nearly enough to determine what you're hoping to achieve here.
>
> Sorry for not being clear. I would like to group them "as much as
> possible", that is up to a certain limit, and also within a "time
> threshold". I believe that the conduit code will be called only when
> something happens in the conduit, so an actual timer would be useless
> (unless I handle this at the source perhaps, and propagate "ticks").
>
> That is why in my first message I talked about stacking things into the
> list until the conduit has no more input available, or a maximum size is
> reached, but was not sure this even made sense.
>
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--
Felipe.

--
-KQ

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