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On Sun, 2 Aug 1998, Patrick Michael Kane wrote:

Date: Sun, 2 Aug 1998 11:38:39 -0700
From: Patrick Michael Kane <modus@pr.es.to>
Reply-To: modperl@apache.org
To: modperl@apache.org
Subject: Re: How to rid off persistent database connection ?

On Sun, Aug 02, 1998 at 08:32:22PM +0200, Edmund Mergl wrote:

Oleg Bartunov wrote:

Currently we have about 150 000 queries (selects only) to postgres in day and
our server ( DUAL PPRO, 256 Mb RAM, SCSI UW) seems works ok.
Will see what happens when I switch to mod_perl enhanced apache with
Apache::DBI authorization.

But what I'm really worry about is how to gently interrupt alive database
connection, for example to do some administrative job (backup, update ...)

Regards,

Oleg

[snip]

For backups there should be no need to interrupt the database
connection,
at least for read-only access.

For updates I would keep the database connections and just redirect
any access to a page which tells the user, that the database is
currently
not accessible.

Edmund's suggestion has the additional benefit of working even if you
shutdown the database and bring it back up, assuming your DBD has a ping()
method. Apache::DBI will notice that the database handle is no longer valid
and bring a new one online, without any intervention on your part.

Just tried to shutdown database (PostgreSQL) by killing postmaster
and keeping established connections (backends) alive. This works fine -
I still can access database using these connections
(through mod_perl cgi, of course, only)
But new connection couldn't established because of absent of postmaster
and I can't restart it because it can't bind port:

mira:~$ runpostgres
FATAL: StreamServerPort: bind() failed: errno=98
Is another postmaster already running on that port?
If not, wait a few seconds and retry.
/usr/local/pgsql/bin/postmaster: cannot create INET stream port

There are no postmaster I already killed him.
I don't know if this postgreSQL problem, though.
After killing all backends I restarted postmaster and noticed in error_log
messages from Apache::DBI
Database handle destroyed without explicit disconnect ....
and this I understand. Is it possible accurately close all connections
using Apache::DBI and then do all admin. jobs (redirect requests to
another page, shutdown database etc..)

Regards,

Oleg

--
Patrick Michael Kane
<modus@pr.es.to>

_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83