PT-196 pt-onine-schema-change is pausing because {some_status_variable}=0

Description here

bin/pt-online-schema-change

@@ -5238,7 +5238,7 @@ sub wait {
             die "$var=$val exceeds its critical threshold "
                . "$self->{critical_val_for}->{$var}\n";
          }
-         if ( !$val || $val >= $self->{max_val_for}->{$var} ) {
+         if ( $val >= $self->{max_val_for}->{$var} ) {
             $vals_too_high{$var} = $val;
          }
          else {

bin/pt-table-checksum

@@ -8683,7 +8683,7 @@ sub wait {
             die "$var=$val exceeds its critical threshold "
                . "$self->{critical_val_for}->{$var}\n";
          }
-         if ( !$val || $val >= $self->{max_val_for}->{$var} ) {
+         if ( $val >= $self->{max_val_for}->{$var} ) {
             $vals_too_high{$var} = $val;
          }
          else {

lib/MySQLStatusWaiter.pm

@@ -175,7 +175,7 @@ sub wait {
             die "$var=$val exceeds its critical threshold "
                . "$self->{critical_val_for}->{$var}\n";
          }
-         if ( !$val || $val >= $self->{max_val_for}->{$var} ) {
+         if ( $val >= $self->{max_val_for}->{$var} ) {
             $vals_too_high{$var} = $val;
          }
          else {

t/pt-online-schema-change/pt-196.t

@@ -0,0 +1,67 @@
+#!/usr/bin/env 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 threads;
+
+use English qw(-no_match_vars);
+use Test::More;
+
+use Data::Dumper;
+use PerconaTest;
+use Sandbox;
+use SqlModes;
+use File::Temp qw/ tempdir /;
+
+plan tests => 2;
+
+require "$trunk/bin/pt-online-schema-change";
+
+my $dp = new DSNParser(opts=>$dsn_opts);
+my $sb = new Sandbox(basedir => '/tmp', DSNParser => $dp);
+my $master_dbh = $sb->get_dbh_for('master');
+my $master_dsn = 'h=127.1,P=12345,u=msandbox,p=msandbox';
+
+if ( !$master_dbh ) {
+   plan skip_all => 'Cannot connect to sandbox master';
+}
+
+# The sandbox servers run with lock_wait_timeout=3 and it's not dynamic
+# so we need to specify --set-vars innodb_lock_wait_timeout=3 else the
+# tool will die.
+my @args       = (qw(--set-vars innodb_lock_wait_timeout=3));
+my $output;
+my $exit_status;
+my $sample  = "t/pt-online-schema-change/samples/";
+
+$sb->load_file('master', "$sample/pt-196.sql");
+
+
+($output, $exit_status) = full_output(
+   sub { pt_online_schema_change::main(@args, "$master_dsn,D=test,t=test",
+         '--execute', '--alter', 'DROP COLUMN test', '--max-load', 
+         'THREADPOOL_IDLE_THREADS=1'
+         ),
+      },
+);
+
+is(
+      $exit_status,
+      0,
+      "--alter rename columns with uppercase names -> exit status 0",
+);
+
+$master_dbh->do("DROP DATABASE IF EXISTS test");
+
+# #############################################################################
+# Done.
+# #############################################################################
+$sb->wipe_clean($master_dbh);
+ok($sb->ok(), "Sandbox servers") or BAIL_OUT(__FILE__ . " broke the sandbox");
+done_testing;

t/pt-online-schema-change/samples/pt-196.sql

@@ -0,0 +1,10 @@
+DROP SCHEMA IF EXISTS test;
+CREATE SCHEMA test;
+USE test;
+
+CREATE TABLE test(
+    id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, 
+    test INT
+);
+
+INSERT INTO test (test) VALUES(1),(2),(3);

t/pt-table-checksum/samples/default-results-5.7.txt

@@ -4,12 +4,13 @@ ERRORS DIFFS ROWS SKIPPED TABLE
 0 0 2 0 mysql.engine_cost
 0 0 0 0 mysql.event
 0 0 0 0 mysql.func
-0 0 0 0 mysql.gtid_executed
 0 0 40 0 mysql.help_category
 0 0 682 0 mysql.help_keyword
 0 0 1340 0 mysql.help_relation
 0 0 637 0 mysql.help_topic
 0 0 0 0 mysql.ndb_binlog_index
+0 0 0 0 mysql.plugin
+0 0 0 0 mysql.proc
 0 0 0 0 mysql.procs_priv
 0 0 0 0 mysql.proxies_priv
 0 0 6 0 mysql.server_cost
@@ -40,3 +41,4 @@ ERRORS DIFFS ROWS SKIPPED TABLE
 0 0 16044 0 sakila.rental
 0 0 2 0 sakila.staff
 0 0 2 0 sakila.store
+0 0 6 0 sys.sys_config

t/pt-table-checksum/samples/static-chunk-size-results-5.7.txt

@@ -4,12 +4,13 @@ ERRORS DIFFS ROWS CHUNKS SKIPPED TABLE
 0 0 2 1 0 mysql.engine_cost
 0 0 0 1 0 mysql.event
 0 0 0 1 0 mysql.func
-0 0 0 1 0 mysql.gtid_executed
 0 0 40 1 0 mysql.help_category
 0 0 682 1 0 mysql.help_keyword
 0 0 1340 1 0 mysql.help_relation
 0 0 637 1 0 mysql.help_topic
 0 0 0 1 0 mysql.ndb_binlog_index
+0 0 0 1 0 mysql.plugin
+0 0 0 1 0 mysql.proc
 0 0 0 1 0 mysql.procs_priv
 0 0 0 1 0 mysql.proxies_priv
 0 0 6 1 0 mysql.server_cost
@@ -40,3 +41,4 @@ ERRORS DIFFS ROWS CHUNKS SKIPPED TABLE
 0 0 16044 19 0 sakila.rental
 0 0 2 1 0 sakila.staff
 0 0 2 1 0 sakila.store
+0 0 6 1 0 sys.sys_config