Re: [bug fix] PG10: libpq doesn't connect to alternative hosts when some errors occur

On Thu, May 18, 2017 at 8:11 PM, Michael Paquier
<michael(dot)paquier(at)gmail(dot)com> wrote:
> On Thu, May 18, 2017 at 11:30 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> On Thu, May 18, 2017 at 7:06 AM, Michael Paquier
>> <michael(dot)paquier(at)gmail(dot)com> wrote:
>>> FWIW, I am of the opinion to not have an implementation based on any
>>> SQLSTATE codes, as well as not doing something similar to JDBC.
>>> Keeping things simple is one reason, a second is that the approach
>>> taken by libpq is correct at its root.
>>
>> Because why?
>
> Because it is critical to let the user know as well *why* an error
> happened. Imagine that this feature is used with multiple nodes, all
> primaries. If a DB admin busted the credentials in one of them then
> all the load would be redirected on the other nodes, without knowing
> what is actually causing the error. Then the node where the
> credentials have been changed would just run idle, and the application
> would be unaware of that.

The entire purpose of an application-level failover feature is to make
the application unaware of failures. That's like complaining that the
stove gets hot when you turn it on.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company