On Tue, Apr 26, 2011 at 7:27 AM, Erik de Castro Lopo
Hi all,
I'm using Wai and http-enumerator to build a http proxy. The core of the code looks like this:
import qualified Network.HTTP.Enumerator as HE import qualified Network.Wai as Wai
serveRequest :: forall (m :: * -> *). (MonadControlIO m, Failure HE.HttpException m) => HE.Request m -> m Wai.Response serveRequest request = do HE.Response sc rh bs <- HE.withManager $ HE.httpLbsRedirect request return $ Wai.responseLBS (mkStatus sc) rh bs
This works but does not run in constant space as I would have hoped. The thing is, HE.httpLbsRedirect returns a lazy ByteString and Wai.responseLBS writes a lazy ByteString, so why isn't the whole thing lazy?
None of the "lbs" functions in http-enumerator can operate in constant space - they are all built on top of the utility function "lbsIter" which provides a warning:
Convert the HTTP response into a Response value.
Even though a Response contains a lazy bytestring, this function does not utilize lazy I/O, and therefore the entire response body will live in memory. If you want constant > memory usage, you'll need to write your own iteratee and use http or httpRedirect directly.
See: http://hackage.haskell.org/packages/archive/http-enumerator/0.6.0.2/doc/html... It might be good to have this warning on the functions that use "lbsIter", or have them use ByteStrings instead of Lazy ByteStrings. Antoine
I'd appreciate any clues.
Cheers, Erik -- ---------------------------------------------------------------------- Erik de Castro Lopo http://www.mega-nerd.com/
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