[erlang-questions] my mnesia is lazy

Steve Kirsch <>
Fri May 8 18:25:01 CEST 2009


well, this is really a common problem that really should be fixed.

i ran into the same thing.

you start mnesia and then you put your laptop to sleeep or do nothing.

you come back the next day, open your laptop and you find mnesia
complains about being overloaded.

It basically is because you didn't do any transactions for a day.

It has nothing to do with being overloaded and mnesia should
differentiate this case.

when i was a newbie to erlang, this is one of the first things i tried
and i was appalled that this highly touted reliable erlang system with
this really cool rock solid database called mnesia could be overloaded
when no transactions were sent. 

Gosh, I thought, if it's overloaded with no transactions, i wonder how
it performs when asked to do real work?

It did cause me to think twice at the time about using erlang for
anything serious.

Of course, now that i understand the history (and the fact that only 1/2
a person works on maintaining mnesia), this makes more sense.

still, this is a very misleading error message that should be fixed to
say: warning, no transactions in the last 24 hours, if anything at all.

-----Original Message-----
From: Ulf Wiger [mailto:] 
Sent: Friday, May 08, 2009 1:50 AM
To: Larry White
Cc: 
Subject: Re: [erlang-questions] my mnesia is lazy

Mnesia sends that report when a log dump starts before the previous log
dump has finished. It doesn't have to be a problem, but is an indication
that Mnesia is, at least temporarily, a bit backlogged.

Things to look at to improve the situation is to use a thread pool (if
you aren't already), and perhaps tune the values of
dump_log_time_threshold and dump_log_write_threshold.

BR,
Ulf W

Larry White wrote:
> I just started working with mnesia and it seems to be working fine, 
> but I keep getting streams of these error messages when it isn't doing

> anything at all in terms of handling requests:
> 
> =ERROR REPORT==== 7-May-2009::14:37:29 ===
> Mnesia(): ** WARNING ** Mnesia is overloaded: {dump_log,
>                                                             
> time_threshold}
> 
> It happens a few times every day.  Is this normal behavior?



--
Ulf Wiger
CTO, Erlang Training & Consulting Ltd
http://www.erlang-consulting.com
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