#!/usr/bin/perl -w

use strict;
use XML::Simple;
use DBI;

my $DESIREDDAYSTOEQUAL = 31;

my %servers;
my %counts;
my $totalcount = 0;
my %days;
my $totaldays = 0;

my $database = "campus";
my $table = "SmokepingData";

my $xml = new XML::Simple (KeyAttr=>[]);
my $confdata = $xml->XMLin("./servers.xml");

my $numhosts = 0;

foreach my $s (@{$confdata->{'server'}}) {

        my $db_handle = DBI->connect("dbi:".$s->{'dbengine'}.
                        ":host=".$s->{'hostname'}.
                        ";database=".$database.
                        ";user=".$s->{'user'}.
                        ";password=".$s->{'password'})
                or die("Couldn't connect to database: $DBI::errstr\n");

        my $statement = $db_handle->prepare("SELECT COUNT(*) AS count, DATEDIFF(NOW(),MAX(timestamp)) AS days FROM ".$table)
                or die("Couldn't prepare query: $DBI::errstr\n");
        $statement->execute()
                or die("Couldn't execute query: $DBI::errstr\n");
        my ($count,$days);
        $statement->bind_columns( \$count, \$days );
        $statement->fetch();

        $servers{$s->{'hostname'}} = $s;
        $counts{$s->{'hostname'}} = $count;
        $totalcount += $count;
	
	if ($days == 0) {
		$days++;
	}
	$days{$s->{'hostname'}} = $days;
	$totaldays += $days;
	$numhosts++;
}

print("Done getting information from db servers!\n");

my $averageinsertionrate = $totalcount/$totaldays;

my %weights;


my $insertsremaining = $DESIREDDAYSTOEQUAL * $averageinsertionrate;
my $minperhost = int(($insertsremaining / $numhosts) / 5);
my $insertamount = $minperhost/2;

for my $hostname (keys %servers ){
        #print($hostname."-".$counts{$hostname}."-".$days{$hostname}."\n");
	$weights{$hostname} = $minperhost;
	$insertsremaining -= $minperhost;
}


while ($insertsremaining > $insertamount) {
	#build a list of hosts with the smallest size
	#keep track of second smallest size
	my $minhostcount;
	my $secondminhostcount;
	my %minhosts;
	for my $hostname ( keys %servers ) {	
		if (!(defined($minhostcount))) {
			$minhostcount = $counts{$hostname};
			$minhosts{$hostname} = 1;
		} elsif ($minhostcount == $counts{$hostname}) {
			$minhosts{$hostname} = 1;
		} elsif ($minhostcount > $counts{$hostname}) {
			%minhosts = ();
			$secondminhostcount = $minhostcount;
			$minhostcount = $counts{$hostname};
			$minhosts{$hostname} = 1;
		}
	}
	#if second smallest size is empty
	if (!defined($secondminhostcount) {
		# divide up insertsremaining by numhosts and add to ech one
		for my $hostname ( keys %servers ) {
			$weights{$hostname} += ($insertsremaining/$numhosts)
		}
	} else {
		# put difference of smallest and second smallest into the smallest ones
		for my $hostname ( keys %minhosts ) {
			$insertsremaining -= ($secondminhostcount - $minhosts{$hostname});
			$weights{$hostname} += ($secondminhostcount - $minhosts{$hostname});
		}
		# if there is almost enough to do this, do this..
		if ($insertsremaining > ($numhosts/2 * $insertamount)) {
			# put insertamount into each host
			for my $hostname ( keys %servers ) {
				$insertsremaining -= $insertamount;
				$weights{$hostname} += $insertamount;
			}
		}
	}
}

# get the minimum weight of all the hosts
my $minweight;
for my $hostname ( keys %servers ) {
	if (!(defined($minweight) && ($minweight < $weights{$hostname}))) {
		$minweight = $weights{$hostname};
	}
}

# use the minweight to figure out the total weight for each host
for my $hostname ( keys %servers ) {
	$weights{$hostname} = int($weights{$hostname} / $minweight);
	print($hostname."-".$counts{$hostname}."-".$days{$hostname}."suggested weight: ".$weights{$hostname}."\n");
}