Create lib/Safeguards.pm to implement new --disk-bytes-free and --disk-pct-free in pt-agent.

bin/pt-agent

@@ -7746,7 +7746,7 @@ Once the previous step are complete, run:
 
    $ pt-agent --daemonize
 
-The tool daemonizes and continues running in the background.
+The agent daemonizes and continues running in the background.
 
 =item 5. Configure the agent at L<https://pws.percona.com>
 
@@ -7812,7 +7812,7 @@ See the L<"--help"> output for a list of default config files.
 
 =item --daemonize
 
-Daemonize the tool.  This causes the tool to fork into the background and
+Daemonize the agent.  This causes the agent to fork into the background and
 L<"--log"> all output.
 
 Fork to the background and detach from the shell.  POSIX operating systems only.
@@ -7824,9 +7824,30 @@ short form: -F; type: string
 Only read MySQL options from the given file.  You must give an absolute
 pathname.
 
+=item --disk-bytes-free
+
+type: size; default: 100M
+
+Stop all services if the disk has less than this much free space.
+This prevents the agent from filling up the disk with service data.
+
+Valid size value suffixes are k, M, G, and T.
+
+=item --disk-pct-free
+
+type: int; default: 5
+
+Stop all services if the disk has less than this percent free space.
+This prevents the agent from filling up the disk with service data.
+
+This option works similarly to L<"--disk-bytes-free"> but specifies a
+percentage margin of safety instead of a bytes margin of safety.
+The agent honors both options, and will not collect any data unless both
+margins are satisfied.
+
 =item --help
 
-Print the tool's help and exit.
+Print the agent's help and exit.
 
 =item --host
 
@@ -7911,7 +7932,7 @@ type: Array
 
 Set the MySQL variables in this comma-separated list of C<variable=value> pairs.
 
-By default, the tool sets:
+By default, the agent sets:
 
 =for comment ignore-pt-internal-value
 MAGIC_set_vars
@@ -7922,7 +7943,7 @@ Variables specified on the command line override these defaults.  For
 example, specifying C<--set-vars wait_timeout=500> overrides the default
 value of C<10000>.
 
-The tool prints a warning and continues if a variable cannot be set.
+The agent prints a warning and continues if a variable cannot be set.
 
 =item --socket
 
@@ -7956,7 +7977,7 @@ MySQL user, if not the current system user.
 
 =item --version
 
-Print the tool's version and exit.
+Print the agent's version and exit.
 
 =back
 

lib/Safeguards.pm

@@ -0,0 +1,94 @@
+# This program is copyright 2013 Percona Ireland Ltd.
+# Feedback and improvements are welcome.
+#
+# THIS PROGRAM IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
+# WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+# MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation, version 2; OR the Perl Artistic License.  On UNIX and similar
+# systems, you can issue `man perlgpl' or `man perlartistic' to read these
+# licenses.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+# Place, Suite 330, Boston, MA  02111-1307  USA.
+# ###########################################################################
+# Safeguards package
+# ###########################################################################
+package Safeguards;
+
+use strict;
+use warnings FATAL => 'all';
+use English qw(-no_match_vars);
+
+use constant PTDEBUG => $ENV{PTDEBUG} || 0;
+
+sub new {
+   my ($class, %args) = @_;
+   my $self = {
+      disk_bytes_free => $args{disk_bytes_free} || 104857600,  # 100 MiB
+      disk_pct_free   => $args{disk_pct_free}   || 5,
+   };
+   return bless $self, $class;
+}
+
+sub get_disk_space {
+   my ($self, %args) = @_;
+   my $filesystem = $args{filesystem} || $ENV{PWD};
+
+   # Filesystem   1024-blocks     Used Available Capacity  Mounted on
+   # /dev/disk0s2   118153176 94409664  23487512    81%    /
+   my $disk_space = `df -P -k "$filesystem"`;
+   chop($disk_space) if $disk_space;
+   PTDEBUG && _d('Disk space on', $filesystem, $disk_space);
+
+   return $disk_space;
+}
+
+sub check_disk_space() {
+   my ($self, %args) = @_;
+   my $disk_space = $args{disk_space};
+   PTDEBUG && _d("Checking disk space:\n", $disk_space);
+
+   # There may be other info, so extract just the partition line,
+   # i.e. the first line starting with /, as in:
+   #   Filesystem   1024-blocks     Used Available Capacity  Mounted on
+   #   /dev/disk0s2   118153176 94409664  23487512    81%    /
+   my ($partition) = $disk_space =~ m/^\s*(\/.+)/m;
+   PTDEBUG && _d('Partition:', $partition);
+   die "Failed to parse partition from disk space:\n$disk_space"
+      unless $partition;
+
+   # Parse the partition line.
+   my (undef, undef, $bytes_used, $bytes_free, $pct_used, undef)
+      = $partition =~ m/(\S+)/g;
+   PTDEBUG && _d('Bytes used:', $bytes_used, 'free:', $bytes_free,
+      'Percentage used:', $pct_used);
+
+   # Convert 1024-blocks blocks to bytes.
+   $bytes_used = ($bytes_used || 0) * 1024;
+   $bytes_free = ($bytes_free || 0) * 1024;
+
+   # Convert pct used to free.
+   $pct_used =~ s/%//;
+   my $pct_free = 100 - ($pct_used || 0);
+
+   # Return true if both thresholds are ok.
+   return $bytes_free >= $self->{disk_bytes_free}
+       && $pct_free   >= $self->{disk_pct_free};
+}
+
+sub _d {
+   my ($package, undef, $line) = caller 0;
+   @_ = map { (my $temp = $_) =~ s/\n/\n# /g; $temp; }
+        map { defined $_ ? $_ : 'undef' }
+        @_;
+   print STDERR "# $package:$line $PID ", join(' ', @_), "\n";
+}
+
+1;
+# ###########################################################################
+# End Safeguards package
+# ###########################################################################

t/lib/Safeguards.t

@@ -0,0 +1,69 @@
+#!/usr/bin/perl
+
+BEGIN {
+   die "The PERCONA_TOOLKIT_BRANCH environment variable is not set.\n"
+      unless $ENV{PERCONA_TOOLKIT_BRANCH} && -d $ENV{PERCONA_TOOLKIT_BRANCH};
+   unshift @INC, "$ENV{PERCONA_TOOLKIT_BRANCH}/lib";
+};
+
+use strict;
+use warnings FATAL => 'all';
+use English qw(-no_match_vars);
+use Test::More;
+
+use Safeguards;
+use Percona::Test;
+
+use Data::Dumper;
+$Data::Dumper::Indent    = 1;
+$Data::Dumper::Sortkeys  = 1;
+$Data::Dumper::Quotekeys = 0;
+
+my $sample = "t/lib/samples/bash/";
+
+my $safeguards = Safeguards->new(
+   disk_bytes_free => 104857600,
+   disk_pct_free   => 10,
+);
+
+# Filesystem   1024-blocks     Used Available Capacity  Mounted on
+# /dev/disk0s2   118153176 94409664  23487512    81%    /
+#
+# Those values are in Kb, so:
+#   used     = 94409664 (94.4G) = 96_675_495_936 bytes
+#   free     = 23487512 (23.4G) = 24_051_212_288 bytes
+#   pct free = 100 - 81         = 19 %
+my $df = slurp_file("$trunk/$sample/diskspace001.txt");
+
+ok(
+   $safeguards->check_disk_space(
+      disk_space => $df,
+   ),
+   "diskspace001: Enough bytes and pct free"
+);
+
+$safeguards = Safeguards->new(
+   disk_bytes_free => 104857600,
+   disk_pct_free   => 20,
+);
+
+ok(
+   !$safeguards->check_disk_space(
+      disk_space => $df,
+   ),
+   "diskspace001: Not enough pct free"
+);
+
+$safeguards = Safeguards->new(
+   disk_bytes_free => 24_051_212_289,
+   disk_pct_free   => 5,
+);
+
+ok(
+   !$safeguards->check_disk_space(
+      disk_space => $df,
+   ),
+   "diskspace001: Not enough bytes free"
+);
+
+done_testing;