mnesia initialization

[I Gusti Ngurah Oka Prinarjaya]

Hi,

>> but it seems that my problem is connected to "Cannot get connection id
for node" when mnesia starts
How you start mnesia? It's so rare to happen. it looks like auto-connect
things.

>> I'm having a node at name@REDACTED could that be the issue??
That's strange, if you run node() in your erlang node shell you should get
nonode@REDACTED Except, if you run your erlang node with command: erl -sname
name@REDACTED

Try to start your erlang node with better node name such: erl -sname
node1@REDACTED where myhost mapped in `/etc/hosts` as 127.0.0.1

So then combined with your mnesia needs, you should run erl -sname
node1@REDACTED -mnesia dir "/home/yourusername/MY_MNESIA_PUT_HERE".

>> However half of the time it destroys old table returning {atomic, ok}
and another half it returns with already_exists.
I think it's because you set your mnesia's directory at `/tmp/*` then your
`/tmp/*` got auto-cleaned by the OS.



Pada tanggal Jum, 8 Nov 2019 pukul 22.29 Karlo Kuna <kuna.prime@REDACTED>
menulis:

> thank you all,
>
> but it seems that my problem is connected to "Cannot get connection id for
> node" when mnesia starts
> I'm having a node at name@REDACTED could that be the issue??
>
> On Fri, Nov 8, 2019 at 6:46 AM I Gusti Ngurah Oka Prinarjaya <
> okaprinarjaya@REDACTED> wrote:
>
>> Hi,
>>
>> Make sure to:
>>
>> 1. Start your erlang node with -mnesia dir
>> "/path/to/where/you/want/to/put/mnesia"
>> 2. Create the schema first
>> 3. start mnesia by using command mnesia:start()
>> 4. The create your tables
>>
>> >> I have a db_init function that initializes db so that if tables do not
>> exist they are created (ram with disc_copies)
>> If you want to do a table existence detection, you can do like the
>> following:
>>
>> case catch mnesia:table(your_table_name, version) of
>>   {{_, _}, []}
>>     -> table_exists;
>>
>>   Fail when Fail =:=
>> {'EXIT',{aborted,{no_exists,your_table_name,version}}}; Fail =:=
>> {aborted,{no_exists,your_table_name,version}}
>>     -> %% create your your_table_name table
>> end
>>
>> Also, as i stated above, you have to create your schema first then start
>> mnesia application. Example:
>>
>> case mnesia:create_schema([node()]) of
>>   {error,{_,{already_exists,_}}} ->
>>       io:format("Schema Already exists~n");
>>
>>     ok ->
>>       io:format("Schema Created~n")
>> end,
>>
>> application:ensure_started(mnesia),
>>
>> %% then init your tables here
>> %%
>> %%
>> .
>>
>> Please read http://erlang.org/doc/apps/mnesia/Mnesia_chap2.html
>>
>> >> However half of the time it destroys old table returning {atomic, ok}
>> and another half it returns with already_exists
>> I'm not sure with this. But maybe i think your schema location was not
>> consistent
>>
>> I suggest you to use rebar3 to manage your project.
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> Pada tanggal Jum, 8 Nov 2019 pukul 07.57 Karlo Kuna <kuna.prime@REDACTED>
>> menulis:
>>
>>> Hi,
>>>
>>> I have problem with mnesia initialization,
>>>
>>> I have a db_init function that initializes db so that if tables do not
>>> exist they are created (ram with disc_copies). For example:
>>>
>>> db_init() ->
>>>     mnesia:create_table(some_record,[{attributes, record_info(fields,
>>> some_record)},
>>>                                                                 {type,
>>> bag}, {disc_copies, [node()]}]).
>>>
>>> I'm running this function on the app start to make sure the table exists
>>> and is ready.
>>> However half of the time it destroys old table returning {atomic, ok}
>>> and another half it returns with already_exists. Also, this happens in the
>>> regular fashion, if I have n starts of application, even starts would
>>> destroy data and even wold keeps old data. I know that I am missing
>>> something probably obvious here but if anyone has any insights on why is
>>> this happening and how to fix it I would greatly appreciate it.
>>>
>>> Thank You,
>>> Karlo.
>>>
>>
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