[Dancer-users] Using persistent DB connections in Dancer::Tutorial

[Puneet Kishor]

On Saturday, January 8, 2011 at 12:31 PM, Gurunandan Bhat wrote:

> 
> 
> On Sat, Jan 8, 2011 at 8:26 PM, Puneet Kishor <punk.kish at gmail.com> wrote:
> 
> > 
> > 
> >  Gurunandan Bhat wrote:
> > 
> > >  If I rewrite connect_db as:
> > > 
> > >  my $dbh;
> > >  sub connect_db {
> > > 
> > >  if (! defined $dbh) {
> > >  $dbh = DBI->connect("dbi:SQLite:dbname=".setting('database')) or
> > >  die $DBI::errstr;
> > > 
> > >  }
> > >  return $dbh;
> > >  }
> > > 
> > >  will the application use a single connection for all connections under
> > >  all perl webservers (in-built, mod_perl, Starman, Twiggy etc.).
> > > 
> > > 
> > 
> > 
> > 
> >  I am interested in a definitive and clear answer as well. I tried the above method a while back, and kept on getting errors on transactions (I am using SQLite).
> > 
> > 
> > 
> 
> Admittedly, this (using a common database handle for all connections) might not neccesarily be a Good Thing precisely because of transaction issues (and consequently slowdowns because of locks) that it leads to.
> 
> However one way to handle transaction issues could be to have a per-session database handle. Requestor passes a session id to connect_db, which sees if the session has been allocated a handle and generates a new handle if not. If the session is an old one, it merely picks up the correct previously allocated  handle and returns it. If per-session persistence is possible, then you should not have transaction issues. 
> 
> Is that possible?
> 
> 
> 
> 
> 
> 


heh heh! I have no idea, although, the logic that you describe seems very, well, logical. Should work. I just don't know how to do it.


If someone who is first-hand experienced in this, and especially with different web servers, would do a little write-up, that would be tremendous.


-- 
Puneet Kishor
Sent with Sparrow


> 
> 
> >  Since I am using Apache, I added `PerlModule Apache::DBI` to my httpd.conf, and went back to a simple $dbh creation instead of checking for `defined $dbh`
> > 
> >  Knowing the correct way to implement this, perhaps even the way*s* for different servers (I am assuming different web servers might have different ways of implementing persistent connections) would be tremendously helpful.
> > 
> > 
> > >  If that is true, a line to that effect in an appropriate place in the
> > >  tutorial would emphasize the persistent features of the solution.
> > > 
> > >  Also, are any hooks run when the application instance is destroyed? If
> > >  there are, implementing a graceful closing of open DB connection(s)
> > >  might provide a valuable lesson in the Tutorial.
> > > 
> > >  Thank you.
> > > 
> > > 
> > > 
> > > 
> > 
> > 
> 
> 
> 
> 




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