Re: Proposal: Implement failover on libpq connect level.

On Wed, Sep 2, 2015 at 4:52 AM, Shulgin, Oleksandr
<oleksandr(dot)shulgin(at)zalando(dot)de> wrote:
> On Tue, Sep 1, 2015 at 8:12 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>>
>> On 2015-09-01 14:07:19 -0400, Robert Haas wrote:
>> > But I think it's quite wrong to assume that the infrastructure for
>> > this is available and usable everywhere, because in my experience,
>> > that's far from the case.
>>
>> Especially when the alternative is a rather short patch implementing an
>> otherwise widely available feature.
>
> But that won't actually help in the case described by Robert: if the master
> server A failed, the client has no idea if B or C would become the new
> master.

Sure it does. You just need to ensure that whichever of those is the
new master accepts connections, and the other one doesn't. There are
lots of ways to do this; e.g. give the machine a second IP that
accepts connections only when the machine is the designated master,
and have read-write clients connect to that IP, and read-only clients
connect to the machine's main IP.

Andres's point is the same as mine: we ought to accept this feature,
in some form, because it's really quite useful.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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