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From Ian Boston <...@tfd.co.uk>
Subject Re: [jr3] Store journal as nodes
Date Thu, 25 Mar 2010 10:01:32 GMT

On 15 Mar 2010, at 15:04, Thomas Müller wrote:

> Hi,
> 
>> wasn't the journal added to be separate from the persistence manager
>> implementation and allow for a "fast" exchange of master/slave node
>> information and latest revisions? Or is this separation not useful?
> 
> I'm not sure what the reasons for the current implementation were.

IIRC The Journal was introduced to support cluster wide replication of state changes (and
that alone). If you have append only persistence with versions of a master root node, then
you effectively have a journal.

For cluster wide replication of state changes, something based on transmission before persistence
should, IMHO be used that would allow each node in a cluster to maintain a journal for the
entire cluster alongside the append only storage.

I did a prototype of this for the 1.x APIs a while back based on JGroups with master election
which looked reasonable and performed at about the IO speed of disk, but I haven't tried it
for real.

Ian
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