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

David Mitchell <>
Sun Jun 1 10:41:05 CEST 2008


This is a REALLY interesting discussion, but at this point it's
becoming obvious that I don't know enough about Twitter...

Are you suggesting that Twoorl should be architected as follows:
- when they register, every user gets assigned their own RabbitMQ
incoming and outgoing queues
- user adds a message via Web/Yaws interface (I know, this could be
SMS or something else later...)
- message goes to that user's RabbitMQ incoming queue
- a backend reads messages from the user's incoming queue, looks up in
e.g. a Mnesia table to see who should be receiving messages from that
user and whether they're connected or not.  If "yes" to both, RabbitMQ
then forwards the message to each of those users' outgoing queues
- either the receiving users poll their outgoing queue for the
forwarded message, or a COMET-type Yaws app springs to life and
forwards the message to their browser (again, ignoring SMS)

This seems like a reasonable approach; I'm just curious if that's what
you're suggesting, or whether you've got something else in mind.

Great thread, and thanks Yariv for getting this discussion going with Twoorl

Regards

Dave M.

2008/6/1 Steve <>:
>
> On May 31, 5:04 pm, "Yariv Sadan" <> wrote:
>> ...but it's the only way you can scale this kind of service when N is
>> big.
>
> Hmmm, Yariv, aren't you still thinking about this in the way that Dave
> Smith pointed to as the heart of the issue? i.e.
> Dave said: "My understanding is that the reason they have such poor
> uptime is due to the fact that they modeled the problem as a web-app
> instead of a messaging system."
>
> I'm aware that you are likely a good way away from hitting any
> scalability problems, but some kind of tiering would seem to be
> appropriate if twoorl is to be "twitter done right". Yaws at the front
> end, definitely - but rather /RabbitMQ/ at the back end. I believe
> that you'd then have the flexibility to distribute/cluster as
> necessary to scale to the required level (whatever that may be).
>
> For sure, Twoorl is a great demo of what can be done with Erlang in an
> incredibly short time. I'm a relative noob to Erlang, and have learned
> a great deal from your blog/code/examples.
>
> Steve
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