On Fri, Feb 25, 2011 at 8:40 AM, Greg Smith <g...@2ndquadrant.com> wrote:
> I didn't get the Streaming Rep + Hot Standby features I wanted in 9.0 either. 
>  But committing what was reasonable to include in that version let me march 
> forward with very useful new code, doing another year of development on my 
> own projects and getting some new things get fixed in core.  And so far it 
> looks like 9.1 will sort out all of the kinks I was unhappy about.  The same 
> sort of thing will need to happen to get Sync Rep committed and then 
> appropriate for more use cases.  There isn't any margin left for discussions 
> of scope creep left here; really it's "is this subset useful for some 
> situations and stable enough to commit" now.

I mostly wanted to raise the issue to not be a blocker, but an attempt
to avoid boxing ourselves in for growing such a feature in 9.2.  if
9.1 ships with the syncrep patch as-conceived, it'll just mean that
it'll be hard/not possible to offer syncrep to users as well as at the
"infrastructure service provider" level...which is, actually, quite
fine -- most current users likely don't want to take the performance
hit of syncrep all the time, but to live with it during a switchover
is quite fine.  I just wanted to make a reasonable effort to ensure
its possibility in a 9.2-like timeframe.

>> 2. The unprivileged user can disable syncrep, in any situation. This
>> flexibility is *great*, but you don't really want people to do it when
>> one is performing the switchover.
> For the moment you may have to live with a situation where user connections 
> must be blocked during the brief moment of switchover to eliminate this 
> issue.  That's what I end up doing with 9.0 production systems to get a 
> really clean switchover, there's a second of hiccup even in the best case.  
> I'm not sure yet of the best way yet to build a UI to make that more 
> transparent in the sync rep case.  It's sure not a problem that's going to 
> get solved in this release though.

I'm totally okay killing all backends during the switchover between
9.1 and 9.2 releases, unless I get super clever with pgbouncer...which
I will have to do anyway.


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