Re: [Haskell-cafe] Yet another Conduit question

Hmm, that's an interesting trick. I can't say that I ever thought bracketP would be used in that way. The only change I might recommend is using addCleanup[1] instead, which doesn't introduce the MonadResource constraint. Michael [1] http://haddocks.fpcomplete.com/fp/7.4.2/2012-12-11/conduit/Data-Conduit-Inte... On Mon, Feb 4, 2013 at 4:37 PM, Kevin Quick wrote:

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 wrote:

I think this is probably the right approach. However, there's something

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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

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wrote:

I guess you could use the Flush datatype [1] depending on how your

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data is generated.

Cheers,

[1] http://hackage.haskell.org/**packages/archive/conduit/0.5.** 4.1/doc/html/Data-Conduit.**html#t:Flushhttp://hackage.haskell.org/packages/archive/conduit/0.5.4.1/doc/html/Data-Co...

On Fri, Feb 1, 2013 at 6:28 AM, Simon Marechal wrote:

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On 01/02/2013 08:21, Michael Snoyman wrote:

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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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