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How to send FileInfo to a web service using Yesod and Http-Conduit?

I work with a standard Yesod scaffolding project.
I created a page that displays a simple form for uploading files.
(The form is likely to be created on the client using Javascript.)
For brevity, the form has one input file:

<form method="post" action=@{UploadR}>
   <input type="file" name="myfile">
   <button type="submit">

My task is to process the form data and then upload the file to the web service.
I have no problem processing the form; my problem is with the web service.
For example, given the following Yesod handler:

postUploadR :: Handler Html
postUploadR = do
    mgr <- fmap httpManager getYesod
    fi  <- runInputPost $ ireq fileField "myfile"
    let fSource = fileSource fi
        fName   = fileName fi
    req <- parseUrl "http://webservice/upload"
    let areq = req { method = methodPost
                   , requestBody = requestBodySourceChunked fSource
                   }
    res <- httpLbs areq mgr
    defaultLayout $ do
      setTitle "file uploaded"
      [whamlet|
       <h3> Success
       <p> You uploaded #{fName}.
      |]

Webservice returns an error: fail post content-lengthbut everything else works as expected. Perhaps the server does not support a piece of request?

+4
1

, . :

  • .
  • .
  • requestBodySource .

, (1) (2) sinkCacheLength. - :

(fSize, fSource) <- fileSource fi $$ sinkCacheLength
+2

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