Subject: Re: Logical replication and multimaster
To: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>
References: <565C7756.9070604@postgrespro.ru>
 <CANP8+jLmPXKxDsqXwf6RNSp9Q-6uc7UcZo=KNfCzH0PeehhE=w@mail.gmail.com>
 <CAMsr+YEfTEp35bQ5ia__nDwc2MwzYUQcuQ__vT_b=UNOHyooMA@mail.gmail.com>
 <CA+TgmoaqJJsPNb7JDAHTtGZbH7CSenuf=0trQ_j1+_scLE-c0w@mail.gmail.com>
 <CAMsr+YFf4hA=hLTe2hvPZ95-Fxf3bT80-_8CWwrDpDzva3LTOw@mail.gmail.com>
 <20151211101608.GN14789@awork2.anarazel.de>
 <CA+TgmobiQUpXpiJ0z+=PMjL4at5TteZ27A8JPMY+QQb_9NeyJA@mail.gmail.com>
Cc: Craig Ringer <craig@2ndquadrant.com>, Simon Riggs
 <simon@2ndquadrant.com>, Konstantin Knizhnik <k.knizhnik@postgrespro.ru>,
 pgsql-hackers <pgsql-hackers@postgresql.org>
From: Petr Jelinek <petr@2ndquadrant.com>
Message-ID: <566B27D6.8040709@2ndquadrant.com>
Date: Fri, 11 Dec 2015 20:45:26 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
 Thunderbird/38.4.0
MIME-Version: 1.0
In-Reply-To: 
 <CA+TgmobiQUpXpiJ0z+=PMjL4at5TteZ27A8JPMY+QQb_9NeyJA@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

On 2015-12-11 19:24, Robert Haas wrote:
> On Fri, Dec 11, 2015 at 5:16 AM, Andres Freund <andres@anarazel.de> wrote:
>> On 2015-12-11 18:12:55 +0800, Craig Ringer wrote:
>>> On 10 December 2015 at 03:19, Robert Haas <robertmhaas@gmail.com> wrote:
>>>> On Sun, Dec 6, 2015 at 10:24 PM, Craig Ringer <craig@2ndquadrant.com>
>>>> wrote:
>>>>> * A way to securely make a libpq connection from a bgworker without
>>>> messing
>>>>> with passwords etc. Generate one-time cookies, sometihng like that.
>>>>
>>>> Why would you have the bgworker connect to the database via TCP
>>>> instead of just doing whatever it wants to do directly?
>>
>>> pg_dump and pg_restore, mainly, for copying the initial database state.
>>
>> Well, you don't want to necessarily directly connect from the bgworker,
>> but from processes started from a bgworker. I guess that's where a good
>> bit of the Robert's confusion originated.
>
> That's part of it, yeah.  I'm a little scared of this design.  I mean,
> I understand now why Craig wants to do this (thanks for explaining,
> Craig!), but it seems like it's going to have a lot of the same
> reliability problems that pg_upgrade does.  I'm not saying there's a
> better way to get the functionality, but it's pretty obvious that
> depending on tools other than the server itself, and in particular
> pg_dump, vastly increases the failure surface area.
>

Well, it's better than trying to write completely new catalogs dump tool 
for this. As Craig said, it would be best if pg_dump functionality was 
moved to functions in a backend, but that's probably not gonna happen 
tomorrow.

-- 
  Petr Jelinek                  http://www.2ndQuadrant.com/
  PostgreSQL Development, 24x7 Support, Training & Services


-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers