I had a solution for this (see below), but now realize it is flawed. In a set of modules that manage persistent objects stored in a SQL database, what is a good way to manage the database connections? Goals would be: (1) have a single place in the code where all connections are made so that it is easy to change connection parameters later; (2) have connections be persistent (Apache::DBI); (3) have one point in each module at which the connection is made for that module; (4) in a given process, share all connections (i.e. connection is a singleton or is managed by a singleton); (5) Have modules that require database access manage their own connection rather than require that a database handle be passed to them; (6) Minimize change from current solution.

The problem with my current solution is that

in a persistent environment (mod_perl) the class data ($dbh) gets initizalized only once, and potentially, the database connection referenced by $dbh can go away due to timeout or some other problem because the process can "live" for a long time. Apache::DBI is capable of checking for this, by "pinging" the database but it doesn't really get a chance to do this, because the connection is getting made only at BEGIN time, when the module is "use"-d.

Example of flawed code is below. MyProject::Dbh "isa" Apache::Singleton::Process that makes a connection using the correct DSN, user, and password using DBI. Apache::DBI is used as well to make the connections persistent, but that is beside the point. 

use MyProject::Dbh;
my $dbh = MyProject::Dbh->instance->dbh;

  sub method1 {
    $dbh->do("... query goes here ...");
  }

  sub method2 {
     my $sth = $dbh->prepare("... another query ...");
     $sth->prepare;
     #...
  }
}
1;

[download]
My question, then, what is a better way to manage the connection? Should it be in instance data rather than class data? Should it be set in each method that uses the database (ugly)? I am pleased almost all features of the current approach except for its flaw of never calling connect after initialization (which in Apache::DBI would take care of returning a good connection).

In reply to Problem managing persistent database connections in modules by mp

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.