DBIAgent::Helper(3) User Contributed Perl Documentation DBIAgent::Helper(3)NAMEPOE::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.
perl v5.14.1 2004-09-17 DBIAgent::Helper(3)
