Determine if our HDFS is in safemode for some reason.

check_hadoop_safemode.pl

#!/usr/bin/perl
#
# This script is managed by puppet.
#

use strict;
use warnings;
use File::stat;
use Getopt::Long;

if (not exists $ENV{SUDO_USER}) {
    if (scalar getpwuid($>) ne 'hdfs') {
        # re-exec this as hdfs user as a work around to being called from
        # nrpe.
        exec("/usr/bin/sudo -u hdfs $0 @ARGV");
    }
}

my $hadoop_bin = "/usr/bin/hadoop";

if ( not -x "/usr/bin/hadoop" ) {
        print "Could not find $hadoop_bin\n";
        exit 3;
}       

my $safemode = `$hadoop_bin dfsadmin -safemode get 2>&1`;

if ($safemode =~ /Safe mode is OFF/) {
        print "OK: safemode is off and hdfs is functioning correctly\n";
        exit;
} elsif ($safemode =~ /Safe mode is ON/) {
        print "CRITICAL: safemode is on - no writes to hdfs can occur!\n";
        exit 1;
} else {
        print "UNKNOWN: safemode status cannot be checked.  command returns '$safemode'\n";
        exit 3;
}