[erlang-questions] Cowboy (Erlang) VS Haskell (Warp)

BM Kim bmktuwien@REDACTED
Tue Jun 25 13:51:03 CEST 2013

Hi folks,

First of all, I want to apologise for my poor english skills,
since english is not my first language, but I'll try my best
to formulate my quesions as clear as possible.

Second, I've just begun to learn erlang, so if I'm asking
obvious "noob" questions I apologise for that too in advance...

Anywho, now to my actual question:

I am planning to write a high-performance server application in erlang,
which will primarily handle HTTP requests. After some reseach with google,
I narrowed down my choices to cowboy, misultin and mochiweb and decided
to go with the cowboy library first...

Looking at some tutorials, I've quickly built a small server capable of
serving static files and was eager to see first benchmark-results...
I've also built a small Haskell server using Warp library to compare it
with erlang's cowboy...

But my first impression was, that my cowboy server is much much slower than
expected when serving static-files and after some research I found a presentation
of the cowboy's author claiming that cowboy shouldn't be used for serving
static-files. So I modified the server code, so that it replies to every
request with in-memory 4Kb binary blob and compared it with my haskell warp
server serving 4kb static file...

this is my simple cowboy's http handler:


blob() ->
    [<<0:8>> || _ <- lists:seq(1,4096)].

init({tcp, http}, Req, _Opts) ->
    {ok, Req, []}.

handle(Req, State) ->
    {ok, Req2} = cowboy_req:reply(200, [], blob(), Req),
    {ok, Req2, State}.

terminate(_Reason, _Req, _State) ->


I've tested both cowboy server and warp server with

weighttp -k -c200 -n10000 http://localhost:8888/4kblob.txt

on my i5-2540M thinkpad laptop running ubuntu 12.10.
Haskell code was compiled via GHC 7.6 and my erlang VM is R16B.


finished in 0 sec, 279 millisec and 52 microsec, 35835 req/s, 147331 kbyte/s


Cowboy (serving actually in-memory blob):

finished in 1 sec, 683 millisec and 264 microsec, 5940 req/s, 24447 kbyte/s

I've noticed, that when testing the cowboy-server the cpu usage is so much
higher than when testing the warp-server...
What do you guys think could be the problem here? Can't imagine that erlang
server is that much slower than haskell server...
I aplogise again, if the question is forumalted chaotic, if you need more
details just let me know...

I am trying to look into this on my own, but since I am still an erlang noob, some
helpful tips/advices from the experts will be much much appreciated!!!

Thanks in advance,


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