[Zope] Re: Zeo as a Zeo Client

[Jonathan]

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" <fairwinds at eastlink.ca>
To: "Andreas Jung" <lists at zopyx.com>
Cc: "Tres Seaver" <tseaver at palladion.com>; <zope at 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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