[erlang-questions] auto-syncing mnesia after a network split

mats cronqvist <>
Mon Dec 8 15:47:30 CET 2008


Chandru <> writes:

> 2008/12/8 mats cronqvist <>:
>> Claes Wikström <> writes:
>>
>>> mats cronqvist wrote:
>>>> "Felix Hamilton" <> writes:
>>>>
>>>>> I have used NTP (the Network Time Protocol) quite effectively to sync
>>>>> timestamps in widely distributed systems with a fairly high degree of
>>>>> accuracy.
>>>>
>>>>   i personally would not bet a dirty sock on ordering events by time
>>>>   stamps (in a distributed system). and for once Leslie Lamport seems
>>>>   to agreewith me.
>>>>
>>>
>>> I think I would. In retrospect I think the worst part of mnesia (apart
>>> from the sucky dets module I once wrote) is how we chose to deal with
>>> partitioned networks.
>>>
>>> We should have chosen to rely on the system clock. For example if
>>> all nodes make a persistent note of when they lost contact with other
>>> nodes. Once they reunite they could compare timestamps, and also compare
>>> timestamps on the last committed transaction.
>>> In a vast majority of cases it would be possible to automatically chose
>>> a winner.
>>
>>  and what would happen in the small minority of cases?
>
> I presume it would be whatever happens today -- nothing.

  that would be nice.

  but i was kind of assuming that everyone would reach the same
  conclusion as I; we pick the wrong winner.



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