From: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> |
---|---|
To: | Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com> |
Cc: | Jing Wang <jingwangian(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> |
Subject: | Re: Libpq support to connect to standby server as priority |
Date: | 2018-07-16 14:42:23 |
Message-ID: | 1531752143.2534.60.camel@cybertec.at |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Haribabu Kommi wrote:
> > On Wed, Jul 4, 2018 at 11:14 PM Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> wrote:
> > > Haribabu Kommi wrote:
> > >
> > > - I think the construction with "read_write_host_index" makes the code even more
> > > complicated than it already is.
> > >
> > > What about keeping the first successful connection open and storing it in a
> > > variable if we are in "prefer-read" mode.
> > > If we get the read-only connection we desire, close that cached connection,
> > > otherwise use it.
> >
> > Even if we add a variable to cache the connection, I don't think the logic of checking
> > the next host for the read-only host logic may not change, but the extra connection
> > request to the read-write host again will be removed.
>
> I evaluated your suggestion of caching the connection and reuse it when there is no
> read only server doesn't find, but I am thinking that it will add more complexity and also
> the connection to the other servers delays, the cached connection may be closed by
> the server also because of timeout.
>
> I feel the extra time during connection may be fine, if user is preferring the prefer-read
> mode, instead of adding more complexity in handling the cached connection?
>
> comments?
I tested the new patch, and it works as expected.
I don't think that time-out of the cached session is a valid concern, because that
would have to be a really short timeout.
On the other hand, establishing the connection twice (first to check if it is read-only,
then again because no read-only connection is found) can be quite costly.
But that is a matter of debate, as is the readability of the code.
Since I don't think I can contribute more to this patch, I'll mark it as
ready for committer.
Yours,
Laurenz Albe
From | Date | Subject | |
---|---|---|---|
Next Message | Robert Haas | 2018-07-16 14:58:58 | Re: GiST VACUUM |
Previous Message | Tom Lane | 2018-07-16 14:39:26 | Re: ENOSPC FailedAssertion("!(RefCountErrors == 0)" |