option to keep unknown/absent as unknown in addition to OK and Critical

resources/check_resmon_metric

@@ -90,6 +90,14 @@ the check information can be fetched, but the metric itself isn't listed in
 the XML output. If the check information cannot be fetched, then it is still a
 critical error.
 
+=item -k
+
+Specify that an absence should be treated as an UNKNOWN value. By default, if a
+metric is absent, it is treated as CRITICAL. A metric is considered absent if
+the check information can be fetched, but the metric itself isn't listed in
+the XML output. If the check information cannot be fetched, then it is still a
+critical error.
+
 =back
 
 =head1 THRESHOLDS
@@ -188,8 +196,8 @@ use utils qw($TIMEOUT %ERRORS &print_revision &support);
 delete @ENV{'PATH', 'IFS', 'CDPATH', 'ENV', 'BASH_ENV'};
 
 my ($port, $host, $module, $check, $age, $warning, $critical, $equals, $regex,
-    $metric, $url, $allow_absent) = (81, undef, undef, undef, 0, undef, undef,
-    undef, undef, 0);
+    $metric, $url, $allow_absent, $keep_unknown) = (81, undef, undef, undef, 0, undef, undef,
+    undef, undef, 0, 0);
 
 sub help {
     print "Usage: $0 [options]\n";
@@ -205,6 +213,7 @@ sub help {
     print " -e | --equals       metric must equal this value (numerical metrics only)\n";
     print " -r | --regex        regex match against the metric (string print metrics only)\n";
     print " -u | --url          specify an alternate URL to fetch\n";
+    print " -k | --keepunkown   Treat absences as UNKNOWN (default: critical)\n";
     print " -a | --allowabsent  Treat absences as OK (default: critical)\n";
     exit $ERRORS{'UNKNOWN'};
 }
@@ -294,6 +303,7 @@ GetOptions (
     "e|equals=i"   => \$equals,
     "r|regex=s"    => \$regex,
     "u|url=s"      => \$url,
+    "k|keepunknown" => \$keep_unknown,
     "a|allowabsent" => \$allow_absent);
 
 unless (defined $host && defined $module && defined $check) {
@@ -322,10 +332,10 @@ eval {
     my $res = $ua->request($t);
     my $now_after = Time::HiRes::time();
     die "could not fetch http://$host:$port$url - " . $res->status_line ."\n"
-        unless($res && $res->is_success);
+        unless($res && ( $res->is_success || $keep_unknown || $allow_absent) ) ;
     # Parse the xml
     eval { $ref = $xs->XMLin($res->content, ForceArray => 1); };
-    die "error parsing XML\n" if($@);
+    die "error parsing XML\n" unless (!($@) || $keep_unknown || $allow_absent);
 
     # Debugging
     # use Data::Dumper;
@@ -361,6 +371,8 @@ eval {
     if (!defined($metricval)) {
         if ($allow_absent) {
             $state = "OK";
+        } elsif ($keep_unknown) {
+            $state = "UNKNOWN";
         } else {
             $state = "CRITICAL";
         }