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

Lev Walkin <>
Thu May 29 16:50:27 CEST 2008


Joe Armstrong wrote:
> 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.

This is the hardest part. It is easier to interface with memcached,
or several, at this point. You can even have more than 4g cached
in memory with several memcached and PAE on a single machine.

> 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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