If the objective is to have a second ZEO server available as a hot-backup,
how about the idea of having ZEO clients with the ability to write to two
separate ZEO servers (ideally running on separate hardware servers) with a
single 'write' command? We can accomplish this at the application level,
but it would be a nice option to have ZEO do it automatically.
Is this a reasonable extension to ZEO?
Jonathan
----- Original Message -----
From: "David Pratt" <[EMAIL PROTECTED]>
To: "Andreas Jung" <[EMAIL PROTECTED]>
Cc: "Tres Seaver" <[EMAIL PROTECTED]>; <zope@zope.org>
Sent: Tuesday, May 02, 2006 1:31 PM
Subject: Re: [Zope] Re: Zeo as a Zeo Client
Andreas Jung wrote:
repozo does not help you syncing multiple ZEO server..it just performs
an incremental backup of an existing Data.fs file. And I don't know of
any solution have multiple "master" ZEO servers. There can be only one.
-aj
For sure. I guess the best one could have would be replicated storage
clients that when offline could operate on their own data. When they go
online they would first attempt resolve their data with the (master)
server (synchronizing), and then append each new transaction to the local
replica as it was occuring (replicating) so that before you went offline
again, your storage is up to date.
I think this is all possible with a sync server, each client having an
independent asynchronous loop for synchronizing, and a synchronization
protocol for two way syncing. Zope has most of this now but it was never
designed to provide data to the local storage to keep it up to date (while
the zeo client is being used). This would be quite handy and I think there
are some possibilities to do this.
I guess in a general way, this is what the spread is doing for ZRS but the
mechanism and use case is different. I don't think you'd want any client
to be offline for long with this service with a replicated storage client.
I think the idea is more of a hot backup in case of failure of the main
storage but I know little of ZRS.
Regards
David
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