[Pgpool-general] saving state across pgpool restarts?

[Daniel.Crespo at l-3com.com]

Thanks for your reply, Jaume. Below are some comments.

> On Thu, Oct 29, 2009 at 6:21 PM,  <Daniel.Crespo at l-3com.com> wrote:
> 
> > It seems that there is not a good solution for this.
> > For example, let's say I have two backends: backend0 and backend1.
> >
> > 1. Network connection error happens on backend0.
> > 2. backend0 is denerated.
> > 3. New data incomes into pgpool->backend1.
> > 4. backend0 is now out of sync.
> > 5. Network connection is re-established on backend0.
> > 6. pgpool is restarted for some reason.
> > 7. pgpool connects to both backends.
> > 8. a client executes a query that causes to retrieve data from both
> > backends, but are mismatching.
> > 9. pgpool degenerate the one that is NOT the master -> backend1.
> > 10. DBA gets crazy because data was lost (in the backend1, when
> backend0
> > connection was down)
> 
> I think that you are going over the top by missing a few key points:
> 
> 2. After this event, pgsql in node 0 should be shut down by failover
> script configured in pgpool-II or any other mechanism.
> 
> 6. "For some reason" seems like kids playing around to me.

The reason was not relevant for the explanation.

> I can only see this happening if all of the following are true:

> a) No backup power available.
> b) Electricity goes down.
> c) No sysadmin receives an alert of what has happened

There you go!

> If you meant a software restart of the daemon, then you have a problem
> with humans, not with software.

Please, imagine a more suitable scenario.

Thanks,

Daniel