[erlang-questions] Support for newcomers and the popularity of Erlang

Jesse Gumm <>
Mon Mar 19 18:08:07 CET 2012

Have you looked into riak for distributed, master-less data replication?

Jesse Gumm
Owner, Sigma Star Systems
On Mar 19, 2012 11:59 AM, "Wojciech Knapik" <> wrote:

> On Mon, Mar 19, 2012 at 5:38 PM, Ulf Wiger <> wrote:
>> I, for one, don't recall what your question was. I can assure you that I
>> didn't actively choose to ignore it.
>> If you are part of a group doing commercial work in Erlang, you might
>> want to contact Erlang Solutions. There, you can actually pay for the
>> privilige of a guaranteed response, something you cannot do here. They also
>> sell training and commercial support for Erlang - even have an office in
>> Krakow.
>> http://www.erlang-solutions.com/section/13/support
> Thanks for the hint. The project will be open source (BSD/MIT), but we're
> considering a separate license for commercial use.
>> As far as your question goes, a google search indicates you posted it
>> once, 4 days ago. I'd say 4 days is a bit short before lecturing the
>> community on their lack of responsiveness. It might be a suitable length of
>> time before reposting the question, though. ;-)
> I wasn't expecting a reply after that time, considering the pretty healthy
> activity in other threads, but perhaps you're right ;]
>> I much prefer to have a slightly more strict setup, where you e.g.
>> designate one or two "master" machines that keep a persistent copy of the
>> database. The other machines can start up with the env variable:
>> extra_db_nodes : MasterNodes, and access the database without even having
>> their own copy.
>> Why does the data need to be fully replicated? Nodes starting with
>> extra_db_nodes as above enjoy full distribution transparency. If very rapid
>> read response is required, you can add a ram-based replica on the fly with
>> the function mnesia:add_table_copy_type(Table, Node, CopyType).
>> Update cost will increase noticeably with every replica you add, so in
>> many cases, it may be counter-productive to use full replication. For fault
>> tolerance, having two persistent copies of the data goes a long way.
>> Nodes can also start with extra_db_nodes, receive a ram copy of the
>> schema, and then change their schema to a persistent copy using
>> mnesia:change_table_copy_type(schema, node(), disc_copies).
> Ok, that's a lot to process for someone new to mnesia, so let me answer
> this fully, once I'm back home from work.
> For now a quick answer - we're aiming for a fully distributed setup, where
> every node is equal. We'd like the system to be able to function as long as
> at least a single node is up. We're just starting to work on the code, so
> we might change the approach to achieving this, but the goal will likely
> remain in place. There won't be much data stored in mnesia. For the larger
> sets of data, there will be a regular SQL database.
> Like I said - we're all new to Erlang, so our implementations might be far
> from optimal - that's why I was so looking forward to hearing your input.
> Thanks for the answers, I'll write more in a few hours.
> br,
> WK
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