[erlang-questions] [Q] Mnesia is overloaded

Ladislav Lenart lenartlad@REDACTED
Mon Sep 10 15:08:51 CEST 2007


we encountered the following mnesia warning report in our system log:

Mnesia is overloaded: {dump_log, write_threshold}

The log contains several such reports within one second and then
nothing for a while.

Our setup:
  * The core is one mnesia table of type disc_copies that contains
    persistent state of all entities (concurrent processes) in our
    system (one table row for one entity).
  * The system consists of 20 such entities.
  * Each entity is responsible for updating its state in the table
    whenever it changes.
  * We use mnesia:dirty_write/2, because we have no dependency
    among tables and each entity updates its state only.

In the worst case, there is 20 processes that want to write to the
table but each to a different row.

Our questions:
  * What precisely does the report mean?
  * Can we do something about it?
  * We plan to scale from units to thousands of entities. Will this
    be a problem? If so, how can we overcome it? If not, why not?

Thanks in advance,

Ladislav Lenart

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