Re: Ima::DBI and connections at Apache startup

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On Mon, 2004-10-04 at 10:03, Brad Bowman wrote:
> In short, combining Ima::DBI, Class::DBI::mysql and Apache opened 
> database connections at startup time and kept them across forking
> causing discomfort...

This won't happen if you use your own db_Main method, bypassing the
Ima::DBI connection stuff.  Apache::DBI is smart enough to avoid this. 
However you will get warnings about database handles (the ones opened at
startup) being destroyed.  I did an ugly workaround for this.  From our
startup.pl:

use Apache::DBI;
use DBI;
use DBD::mysql;
BEGIN{ $DBI::connect_via = 'connect_cached'; };
# The above line requires a little explanation.  We need to connect to
the
# database during startup to get table information for the Class::DBI
# objects.  Apache::DBI will skip the connection cache during startup to
# avoid forking problems, but this causes errors from Class::DBI about
# the database handle being DESTROY'd without an explicit disconnect.
# This is because Class::DBI expects the handles to be persistent.  To
fix
# this, we use a cheat to make DBI do a connect_cached during startup
# (as opposed to using Apache::DBI) and then explicitly disconnect that
# at the end of this fule and tell it to use Apache::DBI after that. 
Phew.

[... bunch of preload modules ...]

# Disconnect before fork and then switch to using Apache::DBI
My::ClassDBI::Base->db_Main()->disconnect();
$DBI::connect_via = 'Apache::DBI::connect';

Obviously we need to do better than this.

> This is one approach, make Ima::DBI mod_perl aware.
> 
> Another approach is to let DBI handle it and just call connect_cached.
> This'd be slower, I guess.

That was the main issue according to Schwern when I complained about the
closure thing before.

> But at least then Ima::DBI isn't duplicating
> Apache::DBI and DBI's functions.

Agreed, this would be highly desirable.  Maybe you could do some
benchmarking on how much of a difference the closure makes?

- Perrin