Question

I want to test performance (request per sec) of haskell warp http server. I don’t know anything about haskell. I want to do the same as in erlang code below:

1. load “page.txt” only once from disk (ascii file 100kB)
2. serve contents of that file on every request but without reloading it from disk

How to do this in haskell?

Erlang:

-module(test).
-export([start/0]).

start() ->
    {ok, Bin} = file:read_file("page.txt"), 
    misultin:start_link([{port, 3000}, {loop, fun(Req) -> Req:ok(Bin) end}]).

I came across this haskell example and i need to modified it to use contents loaded from a file.

Haskell:

{-# LANGUAGE OverloadedStrings #-}
import Network.Wai
import Network.Wai.Handler.Warp
import Blaze.ByteString.Builder (fromByteString)
import Network.HTTP.Types (status200)

main = run 3000 $ const $ return $ ResponseBuilder
    status200
    [("Content-Type", "text/plain"), ("Content-Length", "4")]
    $ fromByteString "TEST"

Please help! 🙂

Answer 1

Read the contents of the file as a strict ByteString using hGetContents from Data.ByteString, then pass it to Blaze’s fromByteString:

{-# LANGUAGE OverloadedStrings #-}
import Network.Wai
import Network.Wai.Handler.Warp
import Blaze.ByteString.Builder (fromByteString)
import Network.HTTP.Types (status200)
import System.IO (withBinaryFile, IOMode (..))
import Data.ByteString (hGetContents)

main = do
    contents <- withBinaryFile "full/path/to/page.txt" ReadMode hGetContents
    run 3000 $ const $ return $ ResponseBuilder
        status200
        [("Content-Type", "text/plain"), ("Content-Length", "4")]
        $ fromByteString contents

I didn’t get it to work with relative paths on Windows, but that might just be my lack of Haskell-fu.