added ceph_reweight.pl - ceph reweighting script that helps to findoun and mass reweight near full osds.

ceph_reweight.pl

@@ -0,0 +1,65 @@
+#!/usr/bin/perl
+#
+# This script reweights osd by 0.02 if utilization overgrows 85%
+# it also reweight osd 80% full osds by 0.01 as a "bonus".
+# It assumes that ceph cluster is less than 75-77% packed with data. 
+
+use strict;
+use warnings "all";
+use Fcntl;
+
+use JSON::PP;
+use Data::Dumper;
+sub help();
+
+my $dry = 1;
+
+if (defined($ARGV[0]) and ($ARGV[0] eq '--do-it')) {
+	my $jstr = `ceph osd df --format=json-pretty`;
+	$jstr =~ s/\-nan/0/gi; # ceph tends to return broken json if custer is not in perfect shape
+	my $j = decode_json $jstr;
+
+	foreach my $osd (@{$j->{'nodes'}}) {
+# skip all unrelated objects
+		next unless (defined($osd->{'utilization'}));
+# skip all objects that are not 80% full
+		next if ($osd->{'utilization'} < 80.000001);
+		my $new_weight = 1;
+
+		if (($osd->{'utilization'} >= 80.000001) and ($osd->{'utilization'} < 85.000001)) {
+			$new_weight = $osd->{'reweight'} - 0.01;
+			printf ("osd.%s is %02.6f%% full, reweight it %01.6f -> %01.6f\n", $osd->{'id'}, $osd->{'utilization'}, $osd->{'reweight'}, $new_weight);
+		}
+
+		if ($osd->{'utilization'} >= 85.000001) {
+			$new_weight = $osd->{'reweight'} - 0.02;
+			printf ("osd.%s is %02.6f%% full, reweight it %01.6f -> %01.6f\n", $osd->{'id'}, $osd->{'utilization'}, $osd->{'reweight'}, $new_weight);
+		}
+
+		if (defined($ARGV[1])) {
+			help () if ($ARGV[1] ne '--dry');
+		} else {
+			system('ceph', 'osd', 'reweght', $osd->{'id'}, $new_weight);
+		}
+	}
+} else {
+	help();
+}
+
+sub help() {
+	print <<MSG;
+Usage: 
+$0			prints this help
+$0 --do-it		just reweghts osds
+$0 --do-it --dry	will print what should be done
+
+it reweghts 80% full osds by 0.01 and 85%+ full osds by 0.02
+
+Note: you should wait until rebalance ends in order to understand state of
+cluster utilization.
+MSG
+
+	return undef;
+}
+
+exit 0;