Hi,
I was thinking about building a cluster control program that would automate
> the cluster rebuild without any human intervention.
>
That would be great of course!
Yes, I know, in many cases you would not want such an automatism because
> there is so much that can go wrong...
>
Well, if 99.999% of all risks can be eliminated, then automating this would
be great :-)
However, I need to deal with customers that don't want to control
> their database manually (in fact they don't want to care about these
> 'details').
>
That's understandable.
> In the case I have described, that system could end up in a situation
> where one client (that was connected when cluster frgamentation occured)
> works on only one database while another client (that did connect
> when network connectivity was up again) works on both of them ...
> with nobody even noticing that they are running into more
> and more inconsistent databases.
>
I think there is a mechanism that ensures this can't happen. If this
mechanism doesn't work, then it's a bug.
But first let's define what you mean with "cluster fragmentation", because
this is a term I never heard. Do you mean one of the cluster nodes
(instances) was killed?
Well ... I was hoping you would answer that there already is a
> mechanism in place that would help the clients to safely detect
> the inconsistent situation and force them to reconnect.
>
Yes, there is such a mechanism in the "CreateCluster" tool: it sets the
exclusive mode and kills other connections ("SET EXCLUSIVE 2"). The other
connections need to use the auto-reconnect feature. This is documented.
If it doesn't work for you please tell me - even better please post a simple
test case.
Regards,
Thomas
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