Re: Proposal: Implement failover on libpq connect level.

Robert Haas wrote:
> On Wed, Aug 19, 2015 at 9:41 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > That sort-of ties into what seems to me the main objection to this
> > proposal, namely that there is already a way to do this sort of thing:
> > DNS-based load balancing.  All the clients think they connect to
> > db.mycompany.com, but which server they actually get is determined by
> > what IP address the DNS server tells them to use.
> 
> But that kinda sucks.  I mean, suppose I have three servers, A, B, and
> C.  I point db.mycompany.com to A, which is the master; then A dies.
> Under your proposal, whatever script I use to control failover now has
> to change the DNS records to repoint db.mycompany.com to B, my new,
> and newly-promoted, new master.   It's quite possible that some
> machines on the network, or some processes, will have the old IP
> address cached, and it may be several minutes before those caches time
> out.  In the meantime, I'm down: even if I bounce the application
> servers, they may just try to reconnect to A.

The solution to this part seems to be to lower the TTL, which seems
easy enough.

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
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