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

Joe Armstrong <>
Thu May 29 16:19:40 CEST 2008


How about a using a 2-3 node ram replicated Mnesia as a front-end
cache with MySQL as a backend
store?

Add a time to live argument to all data and flush the cache to the
backend in idle time.

Adjust the time to live so as to keep the cache a reasonable size.

Best of both worlds.

/Joe


On Thu, May 29, 2008 at 8:39 AM, Yariv Sadan <> wrote:
> I've been using MySQL for Vimagi (http://vimagi.com) and haven't had
> any problems. ErlyDB makes working with MySQL very easy -- just as
> easy as Mnesia (if not easier in some cases) in terms of APIs. The
> main reasons I went with MySQL are that I didn't want to deal with
> fragmentation and dets repair times (yes, I know it wouldn't really
> affect an app such as Twoorl, but I've already gotten into the mindset
> of avoiding dets).
>
> I actually wouldn't mind offering Mnesia as an alternate data store if
> someone wants to implement it :)
>
> Yariv
>
> 2008/5/28 Rapsey <>:
>> Are the repair times really that much of a problem? It's not like servers or
>> erlang runtime crash that often.
>> I would think the advantages of using mnesia far outweight the
>> disadvantages. Mnesia is much easier to scale and work with than mysql.
>>
>>
>> Sergej
>>
>>
>> On Thu, May 29, 2008 at 7:38 AM, Yariv Sadan <> wrote:
>>>
>>> Facebook runs on MySQL -- that's pretty scalable :)
>>>
>>> The main reason I didn't go with Mnesia for storing most data is the
>>> dets issues discussed previously on this list (specifically, the long
>>> repair times and the need for fragmentation over 4gb). I use Mnesia
>>> for storing session data though.
>>>
>>> Yariv
>>>
>>> On Wed, May 28, 2008 at 10:26 PM, Nick Gerakines <>
>>> wrote:
>>> > MySQL? Seriously?
>>> >
>>> > I've heard from multiple sources database congestion is a major source
>>> > of scaling problems for websites. Why take MySQL over a fragmented
>>> > mnesia store or a set of hybrid services?
>>> >
>>> > # Nick Gerakines
>>> >
>>> > On Wed, May 28, 2008 at 10:12 PM, 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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>>> >>
>>> >
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