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

Ulf Wiger <>
Mon Mar 19 17:38:37 CET 2012

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.


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 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).

Ulf W

On 19 Mar 2012, at 17:19, Wojciech Knapik wrote:

> Hello everyone
> I have a question regarding mnesia that the books I have and the tutorials I found do not answer. 
> I tried IRC, but was refered here. I tried the Manning forum, but was refered here. And here I was completely ignored. Not even a "go away", nothing. I had to check the list archives to make sure my emails reached their destination.
> I know this isn't some paid support list and you have no obligation to help anyone, but with a community of this size, you decide about the language's popularity by answering (or not answering) people's questions.
> With any non-trivial project, there are situations where people have to depend on outside help - where the documentation available simply doesn't allow them to answer a question and they need the opinion of someone experienced with the language. And this is not C++, or Java - you can't just ask any coworker for help. If you don't get an answer on this list, you're likely not getting it anywhere. 
> I'm now part of a group of 9 developers undertaking a rather large project and Erlang is, in my opinion, the perfect fit for us. Most other members of the group are beginning to see this too. The only problem is that none of us know this language. Sure, we're reading the books (and they're excellent btw), but you know that books only go so far...
> I'd like nothing more than to stick to Erlang for this project, I've been a fan of functional languages for years, but we've only written a page of code and we've already run into a problem that noone seems to want, or be able to help us with.
> We all know a number of languages and make a living developing code in them, so the temptation to switch to something we're familiar with, where support will not be a problem, is pretty big. I'm guessing this is a very popular scenario when Erlang is being considered for a new project (once you get past the fact that everyone will have to learn a new language and, in most cases, a new programming paradigm).
> I could go on, but you get the idea. Perhaps these are the things to discuss in the next thread about Erlang's popularity, instead of ejabberd, Yaws and CouchDB... 
> br,
> WK
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