[389-devel] Thought excersize: A different take on replication

[Soeren Malchow (MCon)]

Hi Gerrard,

Since you are already mentioning OSPF, how about grouping the Masterservers into "zones" and have only one of the hosts taking care of the communication to other "zones".

Changes could always only be replicated via the "communication master".

The main problem that arises here is the potential outage of one of those "communication masters", this could be solved by either an election process or by an explicit order.

I think this would be a good way to go because it is very close to real life scenarios form my point of view, I most likely have a view masters in geographically distributed locations, but not tens of servers in one location ( maybe already counting e.g. different buildings on a campus as locations )

Not sure if that is a way to go, but maybe it helps a little

Best Regards,

Soeren Malchow
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-----Original Message-----
From: 389-devel-bounces at lists.fedoraproject.org [mailto:389-devel-bounces at lists.fedoraproject.org] On Behalf Of Gerrard Geldenhuis
Sent: Friday, December 03, 2010 5:25 PM
To: '389-devel at lists.fedoraproject.org'
Subject: [389-devel] Thought excersize: A different take on replication

Hi
We were discussing different setups of replication agreements (multi master) between a large number of hosts and ways to minimize contention during updates with interconnected hosts. For example the same change might arrive on a host from two other hosts via different paths at the same time causing "errors" in the log because of exponential back off. If you have to many connections you get a replication storm, to little connections and replication takes to long.

The problem to us sounds very much like a network problem or maybe the effectiveness of the underlying database to lock the data more effectively. 

We dreamt up a couple of solutions/ideas and I am writing this email to illicit some more discussions and/or comments. One solution would be to change the underlying database to one that supports improved granular locking (firebird comes to mind ) .

Another idea we discussed was based on the following question:
What if you could only define the list of master servers and let the master servers figure out the details with regards to doing multi mastering and distributing the data and taking care of broken paths? There is similarities with OSPF...

Do you have any thoughts on this? Have you had similar ideas? Are we missing the point?

Regards

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