[erlang-questions] Twoorl: an open source Twitter clone

Joe Armstrong <>
Fri May 30 16:18:11 CEST 2008

Hi Yariv

Well done - now a few questions:

    - what is Twitter? and why is it good (if it is good) - can you
explain in a couple of paragraphs what it does? It seemed to be some
kind of new way for interrupting people ...

      (this is from one who thinks that e-mail is intrusive and whose
mobile phone is usually
       turned off :-)

  - the reaction to your work seems to be (oh but it doesn't  scale -
so Erlang must be no good -
    despite the fact that I believe you expressly said it was a quick
hack and wasn't designed to

  - I might be nice to say "it doesn't scale YET" - and then sit back
and let us help
    you make it VERY scalable. I like a good challenge.

    Could you try to describe exactly what Twitter is (in an as
abstract way as possible) so that old
fogies like me can wrap our brains around the problem of making it scale -

   So what does it do? How many things must it scale to (give me
numbers here - what are
talking about - scaling is not some abstract quantity - it's number of
bytes of data delivered to end-users
per gram of CO2 - how many bytes/gm of CO2 are we aiming at?)

(aside) What does scalable mean? - I suppose the answer is some
constant cost per user.

A more literal answer would be "doesn't break when we add more users"
- but surely the cost
verses number of users curve must be more important.

In the context of Twitter what does the word "scalable mean" (how
about, we can handle
100,000 users per "box" - each box costs 500$ and consumes 25Watts -
this is constant up to
6x10^9 users)

So if anybody who knows about this stuff can chip in with a few
figures it would be helpful
- what are the desired costs for running twitter for a few million
people - how would you like
this to scale


/Joe Armstrong

On Thu, May 29, 2008 at 7:12 AM, Yariv Sadan <> wrote:
> Hi,
> I created an open source Twitter clone in Erlang called Twoorl. I
> wrote it on top of ErlyWeb/Yaws.  You can see it at http://twoorl.com.
> The code is at http://code.google.com/p/twoorl.
> I'll appreciate any feedback!
> Thanks,
> Yariv
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