#!/usr/bin/perl -w
#
# Acknowledgements:
# - Sections of the code below were based on or, in some cases,
# taken from examples provided in one or more of the following
# places:
# - Christiansen, Tom, and Nathan Torkington. Perl Cookbook.
# 1st ed. O'Reilly and Associates, 1998.
# - Descartes, Alligator, and Tim Bunce. Programming the Perl
# DBI. O'Reilly and Associates, 2000.
# - Wall, Larry, Tom Christiansen, and Randal L. Schwartz.
# Programming Perl. 2nd ed. O'Reilly and Associates, 1996.
# - Szabo, Balazs. Documentation for
# Parallel::ForkManager-0.7.5.
+/Parallel-ForkManager-0.7.5/ForkManager.pm . 03 Jan 2003.
# Faults or incorrect implementations of code based upon code
# from the above sources should not be attributed to original
# source, but to my implementation.
# - My thanks to those individuals visiting the Perl Monks
# () "ChatterBox" between approximately
# 15:00 and 22:00 GMT on Friday, 03 Jan 2003, for answering
# questions, especially the user known as Tye for his assistance
# with questions while working out the child-to-parent messaging
# methodology.
# - If I have made an inappropriate attribution, or failed to
# make an attribution, it was not intentional. Please contact me,
# and I will be happy to attempt to correct the situation.
#
use DBI;
use Fcntl qw(:DEFAULT :flock);
use IO::Handle;
use Parallel::ForkManager;
use strict;
$| = 1;
my $table_name = "tablename";
my $cfg_data = "data.file";
my $db_type = "Oracle";
my $db_sid = "databasename";
my $username = "username";
my $password = "password";
#
# Process reads information for a database to determine items to
# handle, then handles each in a child process, as processing
# times can be lengthy.
#
my $dbh_parent =
DBI->connect( join ( ':', ( 'dbi', $db_type, $db_sid ) ),
$username, $password, { AutoCommit => 0 } )
or die (
join (
"\n",
(
'Database connection failed:',
'Error returned was:',
$DBI->errstr
)
)
. "\n"
);
$dbh_parent->{LongReadLen} = 64000;
my @targetlist = ();
{
#
# Get items to handle, and load into an array, so we do not need
# the parent db handle when we start creating child processes.
#
my ($item);
my $sql_statement = "SELECT UNIQUE items FROM " . $tablename;
my $statement_handle = $dbh_parent->prepare($sql_statement);
$statement_handle->execute
or die (
join (
"\n",
(
'Failure while executing SQL statement:',
$sql_statement,
'Error returned was:',
$DBI->errstr
)
)
. "\n"
);
my $result_handle =
$statement_handle->bind_columns( \$item );
#
# Because child processes inherit the environment of their
# parent when spawned, they will also inherit the DB handles
# of the parent-thus, we get the listing of hosts into an
# array, then no longer need that handle (and prevent
# spurtious errors regarding the parent DB handle not being
# closed when child exits.
#
while ( $statement_handle->fetch ) {
push ( @targetlist, $item );
}
}
#
# Loop is done,
# we no longer need the db connection from the parent process
#
$dbh_parent->disconnect;
#
# Code for returning a total count of modems handled at the end.
# The pipe created should allow the children to send a value back
# to the parent.
#
my $grandtotal = 0;
my $childcount = scalar(@targetlist);
pipe( READER, WRITER );
WRITER->autoflush(1);
my $MAX_PROCESSES = 7;
my $pm = new Parallel::ForkManager($MAX_PROCESSES);
foreach my $item (@targetlist) {
#
# Fork off the next child process using Parallel::ForkManager to
# keep the number of children to no more than $MAX_PROCESSES.
#
$pm->start and next;
# Close the read end of the pipe for the child processes.
close(READER);
#
# Each child needs its own handle to the database,
# as they do not play well with each other's
#
my $dbh =
DBI->connect( join ( ':', ( 'dbi', $db_type, $db_sid ) ),
$username, $password, { AutoCommit => 0 } )
or die (
join (
"\n",
(
'Database connection failed:',
'Error returned was:',
$DBI->errstr
)
)
. "\n"
);
$dbh->{LongReadLen} = 64000;
{
my ($loop);
#
# Child processing occurs herein, including count of whatever
# is being done (stored in $loop).
#
#
# ### CHILD PROCESS CODE HERE ####
#
#
# Child processes in original script had to occasionally
# append to a file, thus the routine below for handling
# file locking.
#
{
#
# Implemented using file locking to prevent data
# corruption.
#
open( OUTFILE, ">>" . $cfg_data );
{
flock( OUTFILE, LOCK_EX );
#
# ### CODE TO ADD APPROPRIATE DATA TO FILE HERE ###
#
}
close(OUTFILE);
}
#
# Child process clean-up:
# - send item and count to parent via pipe
# - close DB handle
# - close writing end of the pipe for the child
# - exit child process
#
print( WRITER join ( ' ', ( $item, $loop ) ), "\n" );
$dbh->disconnect;
}
close(WRITER);
$pm->finish;
}
#
# Close the writing end of the pipe for the parent,
# loop thru
# read a number of lines equal to the number of children
# expected, increment $grandtotal by the value read,
# then close the read end of the pipe
#
# Data on a line sent from child to parent is in the form:
# =
# - = [^\s]+
# = \s+
# =
#
{
close(WRITER);
for ( my $i = 0 ; $i < $childcount ; $i++ ) {
my $line = ;
chomp($line);
my @parts = split ( /\s+/, $line, 2 );
$grandtotal += $parts[1];
}
close(READER);
}
# Wait for any remaining children (should be none).
$pm->wait_all_children;
print <
Total items processed: $grandtotal
GRAND_TOTAL
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