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POE::Component::DBIAgent::Helper.3pm

NAME

POE::Component::DBIAgent::Helper - DBI Query Helper for DBIAgent

SYNOPSYS

  use Socket qw/:crlf/;
  use POE qw/Filter::Line Wheel::Run Component::DBIAgent::Helper/;
 
  sub _start {
      my $helper = POE::Wheel::Run ->new(
              Program     => sub {
                  POE::Component::DBIAgent::Helper->run($self->{dsn},
                                                        $self->{queries}
                                                       );
              },
              StdoutEvent => 'db_reply',
              StderrEvent => 'remote_stderr',
              ErrorEvent  => 'error',
              StdinFilter => POE::Filter::Line->new(),
              StdoutFilter => POE::Filter::Line->new( Literal => CRLF),
              StderrFilter => POE::Filter::Line->new(),
             )
       or carp "Can't create new DBIAgent::Helper: $!\n";
 
  }
 
  sub query {
       my ($self, $query, $package, $state, @rest) = @_;
 
       $self->{helper}->put(join '|', $query, $package, $state, @rest);
  }
 
  sub db_reply {
     my ($kernel, $self, $heap, $input) = @_[KERNEL, OBJECT, HEAP, ARG0];
 
     # $input is either the string 'EOF' or a Storable object.
 
  }
 
 

DESCRIPTION

This is our helper routine for DBIAgent. It accepts queries on STDIN, and returns the results on STDOUT. Queries are returned on a row-by-row basis, followed by a row consisting of the string 'EOF'.

Each row is the return value of $sth->fetch, which is an arrayref. This row is then passed to Storable for transport, and printed to STDOUT. HOWEVER, Storable uses newlines (``\n'') in its serialized strings, so the Helper is designed to use the ``network newline'' pair CR LF as the line terminator for STDOUT.

When fetch() returns undef, one final row is returned to the calling state: the string 'EOF'. Sessions should test for this value FIRST when being invoked with input from a query.

Initialization

The Helper has one public subroutine, called "run()", and is invoked with two parameters:

The DSN

An arrayref of parameters to pass to DBI->connect (usually a dsn, username, and password).

The Queries.

A hashref of the form Query_Name => ``$SQL''. See POE::Component::DBIAgent for details.

BUGS

I have NO idea what to do about handling signals intelligently. Specifically, under some circumstances, Oracle will refuse to acknowledge SIGTERM (presumably since its libraries are non-reentrant) so sometimes SIGKILL is required to terminate a Helper process.

AUTHOR

This module has been fine-tuned and packaged by Rob Bloodgood <robb@empire2.com>. However, most of the code came directly from Fletch <fletch@phydeaux.org>, either directly (Po:Co:DBIAgent:Queue) or via his ideas. Thank you, Fletch!

However, I own all of the bugs.

This module is free software; you may redistribute it and/or modify it under the same terms as Perl itself.