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#!/usr/bin/env perl
use bignum;
use warnings;
use strict;
use File::Compare;
use File::Copy;
use File::Temp;
use Sys::Hostname;
my $num_args = $#ARGV + 1;
if ($num_args < 2) {
print "\nUsage: $0 <user> <shared directory> [mode (0 for active/passive or 1 for active/active)] [cron spool directory]\n";
exit;
}
# We need a common directory for our nodes to write and read state from plus a couple of cronfiles
my ($user, $shareddir, $mode, $spooldir) = @ARGV;
# Set some defaults if we didn't get them
unless ($mode == 0) {
# mode 0 = active/passive, mode 1 = active/active
print "Mode not set on command line, going to active/active\n";
$mode = 1;
}
unless ($spooldir) {
$spooldir = "/var/spool/cron/crontabs";
}
my $sharedcrondir = "$shareddir/crontab";
my $cronfile = "$spooldir/$user";
my $activesharedcronfile = "$sharedcrondir/$user";
my $passivesharedcronfile = "$sharedcrondir/$user.passive";
my $oldactivesharedcronfile = "$sharedcrondir/$user.old";
my $oldpassivesharedcronfile = "$sharedcrondir/$user.passive.old";
my $electiondir = "$sharedcrondir/election";
my $hostname = hostname;
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my $failovertimeout = 40;
# Create directories
unless (-d $sharedcrondir) {
mkdir $sharedcrondir or die "Can not create shared directory: $!";
}
# Get the nodes in the cluster
sub get_nodes {
# Our data type is a hash with the following fields
# name, time, numeric
my @nodes = ();
my @files = <$electiondir/*>;
foreach my $filename (@files) {
chomp $filename;
my $nodename = $filename;
$nodename =~ s/^$electiondir\///;
# Don't add this host
unless ($nodename eq $hostname) {
my $node = {};
open(FILE, "<$filename") or die "Could not open file: $!";
$node->{'name'} = $nodename;
my $content = <FILE>;
chomp $content;
$node->{'time'} = $content;
$node->{'numeric'} = get_numeric($nodename);
close FILE;
push @nodes, $node;
}
}
return @nodes;
}
# Simply write a unix timestamp to a file with our name on it
sub write_timestamp {
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my $time = time;
open(FILE,"+>$electiondir/$hostname");
print FILE $time;
close FILE;
}
# Lets see if we are the active node
sub is_active {
my @nodes = @_;
# Assume you are active
my $state = 1;
# Loop all nodes
foreach my $node (@nodes) {
# If it has been active in the last 120 seconds it is eligable
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my $diff = time - $node->{'time'};
if( $diff < $failovertimeout ) {
print "Node: $node->{'name'} was active last $failovertimeout sec\n";
# Go to passive mode if the numeric of that host is less than that of this host
my $this = get_numeric($hostname);
my $that = $node->{'numeric'};
print "Numeric for $hostname is $this and for $node->{'name'} is $that\n";
if( $this > $that ) {
$state = 0 ;
print "I am not active\n";
} else {
print "I am active\n";
my $outfile = "$sharedcrondir/active";
open(OUTFILE,"+>$outfile");
print OUTFILE $hostname;
close OUTFILE;
}
} else {
print "Node: $node->{'name'} was not active last $failovertimeout sec\n";
}
}
return $state;
}
# Turn a hostname in to a decimal number used for comparison, lowest numer gets to be active if it is working
sub get_numeric {
my ($host) = @_;
my @ascii = unpack 'C*', $host;
my $numeric = '';
foreach my $val (@ascii) {
$numeric .= $val;
}
return $numeric + 0;
}
# But a # infront of any actime crontab entry
sub comment_out {
my ($infile, $outfile) = @_;
open(INFILE,"<$infile");
my $content = '';
while(my $line = <INFILE>) {
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$line =~ s/(^(?!#))/# $1/g;
$content .= $line;
}
close INFILE;
open(OUTFILE,"+>$outfile");
print OUTFILE $content;
close OUTFILE;
}
# Remove a # from any crontab entry
sub uncomment {
my ($infile, $outfile) = @_;
open(INFILE,"<$infile");
my $content = '';
while(my $line = <INFILE>) {
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$line =~ s/^(#\s?)([\d*])/ $2/g;
$content .= $line;
}
close INFILE;
open(OUTFILE,"+>$outfile");
print OUTFILE $content;
close OUTFILE;
}
sub cron_compare {
my ($one, $two, $three) = @_;
# Current cronfile and shared cronfile is not same
if(compare($one, $two) != 0) {
print "$one and $two is not the same\n";
# This means that the other node has changed the cron file
if(compare($one, $three) == 0) {
print "Some other node has changed the file\n";
return 1;
# This means that my node has changed the cron file
} else {
print "This node has changed the cron file\n";
return 2;
}
}
return 0;
}
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sub run {
print "Host: $hostname started run at: " . time . "\n";
print "Mode: $mode, user: $user, shareddir: $shareddir and spooldir: $spooldir\n";
if(-e $activesharedcronfile) {
unless(-e $oldactivesharedcronfile) {
copy($activesharedcronfile, $oldactivesharedcronfile);
}
}
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unless (-d $electiondir) {
mkdir $electiondir;
}
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# If we are running in active/passive mode
if($mode == 0) {
if(-e $passivesharedcronfile) {
unless(-e $oldpassivesharedcronfile) {
copy($passivesharedcronfile, $oldpassivesharedcronfile);
}
}
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# Update timestamp
write_timestamp;
# If we have an active shared cronfile, we should also have an old shared
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# See if I am the one
if (is_active(get_nodes) ){
if(compare($cronfile, $passivesharedcronfile)) == 0) {
print "There has been a failover, switching to active cronfile\n";
copy($activesharedcronfile, $cronfile);
}
my $tempfile = tmpnam();
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my $compare = cron_compare($cronfile, $activesharedcronfile, $oldactivesharedcronfile );
# The other node has changed the file
# This would mean that we are in some kind of multi master mode which is not invented yet, should not happen
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if($compare == 1) {
copy($activesharedcronfile, $cronfile);
copy($activesharedcronfile, $oldactivesharedcronfile);
# This node has changed the file
} elsif ($compare == 2) {
copy($cronfile, $activesharedcronfile);
# Since we are the only master we need to update the old one as well
copy($activesharedcronfile, $oldactivesharedcronfile);
comment_out($cronfile, $passivesharedcronfile);
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}
comment_out($cronfile, $tempfile);
$compare = cron_compare($tempfile, $passivesharedcronfile, $oldpassivesharedcronfile);
# The other node has changed the file
if($compare == 1) {
uncomment($passivesharedcronfile, $cronfile);
copy($passivesharedcronfile, $oldpassivesharedcronfile);
copy($cronfile, $activesharedcronfile);
copy($activesharedcronfile, $oldactivesharedcronfile);
# This node has changed the file
} elsif ($compare == 2) {
copy($cronfile, $activesharedcronfile);
comment_out($cronfile, $passivesharedcronfile);
}
unlink $tempfile;
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# We are passive node
} else {
my $compare = cron_compare($cronfile, $passivesharedcronfile, $oldpassivesharedcronfile );
# The other node has changed the file
if($compare == 1) {
copy($passivesharedcronfile, $cronfile);
copy($passivesharedcronfile, $oldpassivesharedcronfile);
# We have changed stuff
} elsif ($compare == 2) {
comment_out($cronfile, $passivesharedcronfile);
copy($passivesharedcronfile, $cronfile);
}
}
}
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# If we are running in active/active mode
else {
my $compare = cron_compare($cronfile, $activesharedcronfile, $oldactivesharedcronfile );
# The other node has changed the file
if($compare == 1) {
copy($activesharedcronfile, $cronfile);
copy($activesharedcronfile, $oldactivesharedcronfile);
# We have changed things
} elsif ($compare == 2) {
copy($cronfile, $activesharedcronfile);
}
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}
print "Host: $hostname finished run at: " . time . "\n\n\n";
}
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for (my $i = 0; $i < 6; $i++) {
my $start = time;
$| = 1;
run;
if ((my $remaining = 10 - (time - $start)) > 0) {
sleep $remaining;
}
}
exit;