resynchronizing mnesia nodes

Chandrashekhar Mullaparthi Chandrashekhar.Mullaparthi@REDACTED
Fri Apr 12 10:23:27 CEST 2002

I think when such a thing happens, you can set the master nodes for each
table so that when the nodes resync, one of the tables is considered the
"correct" one. But I don't think it is possible to merge tables - I'm not
sure that it is even desirable. But if it is - then mnesia could invoke a
user defined merge fun which would take in as parameters each conflict entry
and return a result such as {ok, NewEntry} or discard. For large tables -
this can mean that mnesia will take a long time to resync.


-----Original Message-----
From: Hal Snyder [mailto:hal@REDACTED]
Sent: 10 April 2002 15:06
To: erlang-questions@REDACTED
Subject: resynchronizing mnesia nodes

We are looking at various policies for recovering from communication
failure with mnesia, and studying Chapter 6 of the Mnesia User's
Guide, Version 4.0.

Suppose you have several nodes running mnesia, replicating content.
They become partitioned long enough to record mutual mnesia_down
entries, and continue to receive updates.
In some special cases - for example, when updates to a table consist
only of adding a positive increment to a counter, or of inserting a
record with a globally unique key - it should be possible to
resynchronize automatically without fear of inconsistencies.
Is this sort of thing readily feasible with mnesia?
Is anyone doing it?

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