MDEV-19746: Galera test failures because of wsrep_slave_threads identification

Problem was that tests select INFORMATION_SCHEMA.PROCESSLIST processes
from user system user and empty state. Thus, there is not clear
state for slave threads.

Changes:
- Added new status variables that store current amount of applier threads
(wsrep_applier_thread_count) and rollbacker threads
(wsrep_rollbacker_thread_count). This will make clear how many slave threads
of certain type there is.
- Added THD state "wsrep applier idle" when applier slave thread is
waiting for work. This makes finding slave/applier threads easier.
- Added force-restart option for mtr to always restart servers between tests
to avoid race on start of the test
- Added wait_condition_with_debug to wait until the passed statement returns
true, or the operation times out. If operation times out, the additional error
statement will be executed

Changes to be committed:
	new file:   mysql-test/include/force_restart.inc
	new file:   mysql-test/include/wait_condition_with_debug.inc
	modified:   mysql-test/mysql-test-run.pl
	modified:   mysql-test/suite/galera/disabled.def
	modified:   mysql-test/suite/galera/r/MW-336.result
	modified:   mysql-test/suite/galera/r/galera_kill_applier.result
	modified:   mysql-test/suite/galera/r/galera_var_slave_threads.result
	new file:   mysql-test/suite/galera/t/MW-336.cnf
	modified:   mysql-test/suite/galera/t/MW-336.test
	modified:   mysql-test/suite/galera/t/galera_kill_applier.test
	modified:   mysql-test/suite/galera/t/galera_parallel_autoinc_largetrx.test
	modified:   mysql-test/suite/galera/t/galera_parallel_autoinc_manytrx.test
	modified:   mysql-test/suite/galera/t/galera_var_slave_threads.test
	modified:   mysql-test/suite/wsrep/disabled.def
	modified:   mysql-test/suite/wsrep/r/variables.result
	modified:   mysql-test/suite/wsrep/t/variables.test
	modified:   sql/mysqld.cc
	modified:   sql/wsrep_mysqld.cc
	modified:   sql/wsrep_mysqld.h
	modified:   sql/wsrep_thd.cc
	modified:   sql/wsrep_var.cc

21 files changed, 410 insertions, 171 deletions

diff --git a/mysql-test/include/force_restart.inc b/mysql-test/include/force_restart.inc
new file mode 100644
index 00000000000..88c9249bf99
--- /dev/null
+++ b/mysql-test/include/force_restart.inc
@@ -0,0 +1,14 @@
+# ==== Purpose ====
+#
+# Tell mtr that all servers must be restarted after the test has
+# finished.
+#
+# ==== Usage ====
+#
+# --source include/force_restart.inc
+#
+
+--let $_force_restart_datadir= `SELECT @@datadir`
+--append_file $_force_restart_datadir/mtr/force_restart
+1
+EOF
diff --git a/mysql-test/include/wait_condition_with_debug.inc b/mysql-test/include/wait_condition_with_debug.inc
new file mode 100644
index 00000000000..11af423670d
--- /dev/null
+++ b/mysql-test/include/wait_condition_with_debug.inc
@@ -0,0 +1,69 @@
+# include/wait_condition_with_debug.inc
+#
+# SUMMARY
+#
+#    Waits until the passed statement returns true, or the operation
+#    times out.  If the operation times out, the additional error
+#    statement will be executed.
+#
+# USAGE
+#
+#    let $wait_condition=
+#      SELECT c = 3 FROM t;
+#    let $wait_condition_on_error_output= select count(*) from t;
+#    [let $explicit_default_wait_timeout= N] # to override the default reset
+#    --source include/wait_condition_with_debug.inc
+#
+#   OR
+#
+#    let $wait_timeout= 60; # Override default 30 seconds with 60.
+#    let $wait_condition=
+#      SELECT c = 3 FROM t;
+#    let $wait_condition_on_error_output= select count(*) from t;
+#    --source include/wait_condition_with_debug.inc
+#    --echo Executed the test condition $wait_condition_reps times
+#
+#
+# EXAMPLE
+#    events_bugs.test, events_time_zone.test
+#
+
+let $wait_counter= 300;
+if ($wait_timeout)
+{
+  let $wait_counter= `SELECT $wait_timeout * 10`;
+}
+# Reset $wait_timeout so that its value won't be used on subsequent
+# calls, and default will be used instead.
+if ($explicit_default_wait_timeout)
+{
+  --let $wait_timeout= $explicit_default_wait_timeout
+}
+if (!$explicit_default_wait_timeout)
+{
+  --let $wait_timeout= 0
+}
+
+# Keep track of how many times the wait condition is tested
+# This is used by some tests (e.g., main.status)
+let $wait_condition_reps= 0;
+while ($wait_counter)
+{
+    --error 0,ER_NO_SUCH_TABLE,ER_LOCK_WAIT_TIMEOUT,ER_UNKNOWN_COM_ERROR,ER_LOCK_DEADLOCK
+    let $success= `$wait_condition`;
+    inc $wait_condition_reps;
+    if ($success)
+    {
+        let $wait_counter= 0;
+    }
+    if (!$success)
+    {
+        real_sleep 0.1;
+        dec $wait_counter;
+    }
+}
+if (!$success)
+{
+  echo Timeout in wait_condition.inc for $wait_condition;
+  --eval $wait_condition_on_error_output
+}
diff --git a/mysql-test/mysql-test-run.pl b/mysql-test/mysql-test-run.pl
index d88d99ce2f9..3095de2f819 100755
--- a/mysql-test/mysql-test-run.pl
+++ b/mysql-test/mysql-test-run.pl
@@ -842,6 +842,8 @@ sub run_test_server ($$$) {
 	    next if (defined $t->{reserved} and $t->{reserved} != $wid);
 	    if (! defined $t->{reserved})
 	    {
+	      # Force-restart not relevant when comparing *next* test
+	      $t->{criteria} =~ s/force-restart$/no-restart/;
 	      my $criteria= $t->{criteria};
 	      # Reserve similar tests for this worker, but not too many
 	      my $maxres= (@$tests - $i) / $opt_parallel + 1;
@@ -3699,6 +3701,25 @@ sub find_analyze_request
   return $analyze;
 }
 
+# The test can leave a file in var/tmp/ to signal
+# that all servers should be restarted
+sub restart_forced_by_test($)
+{
+  my $file = shift;
+  my $restart = 0;
+  foreach my $mysqld ( mysqlds() )
+  {
+    my $datadir = $mysqld->value('datadir');
+    my $force_restart_file = "$datadir/mtr/$file";
+    if ( -f $force_restart_file )
+    {
+      mtr_verbose("Restart of servers forced by test");
+      $restart = 1;
+      last;
+    }
+  }
+  return $restart;
+}
 
 # Return timezone value of tinfo or default value
 sub timezone {
@@ -4041,8 +4062,12 @@ sub run_testcase ($$) {
       if ( $res == 0 )
       {
         my $check_res;
-        if ( $opt_check_testcases and
-             $check_res= check_testcase($tinfo, "after"))
+	if ( restart_forced_by_test('force_restart') )
+        {
+          stop_all_servers($opt_shutdown_timeout);
+        }
+        elsif ( $opt_check_testcases and
+                $check_res= check_testcase($tinfo, "after"))
         {
           if ($check_res == 1) {
             # Test case had sideeffects, not fatal error, just continue
@@ -4077,7 +4102,8 @@ sub run_testcase ($$) {
         find_testcase_skipped_reason($tinfo);
         mtr_report_test_skipped($tinfo);
         # Restart if skipped due to missing perl, it may have had side effects
-        if ( $tinfo->{'comment'} =~ /^perl not found/ )
+	if ( restart_forced_by_test('force_restart_if_skipped') ||
+             $tinfo->{'comment'} =~ /^perl not found/ )
         {
           stop_all_servers($opt_shutdown_timeout);
         }
@@ -5227,6 +5253,11 @@ sub server_need_restart {
     return 0;
   }
 
+  if ( $tinfo->{'force_restart'} ) {
+    mtr_verbose_restart($server, "forced in .opt file");
+    return 1;
+  }
+
   if ( $opt_force_restart ) {
     mtr_verbose_restart($server, "forced restart turned on");
     return 1;
@@ -6209,6 +6240,7 @@ Misc options
                         servers to exit before finishing the process
   fast                  Run as fast as possible, don't wait for servers
                         to shutdown etc.
+  force-restart         Always restart servers between tests
   parallel=N            Run tests in N parallel threads (default 1)
                         Use parallel=auto for auto-setting of N
   repeat=N              Run each test N number of times
diff --git a/mysql-test/suite/galera/disabled.def b/mysql-test/suite/galera/disabled.def
index 79706631241..fcb4985ebc9 100644
--- a/mysql-test/suite/galera/disabled.def
+++ b/mysql-test/suite/galera/disabled.def
@@ -15,7 +15,6 @@ MW-328A : MDEV-17847 Galera test failure on MW-328[A|B|C]
 MW-328B : MDEV-17847 Galera test failure on MW-328[A|B|C]
 MW-328C : MDEV-17847 Galera test failure on MW-328[A|B|C]
 MW-329 : MDEV-19962 Galera test failure on MW-329
-MW-336 : MDEV-19746 Galera test failures because of wsrep_slave_threads identification
 MW-388: MDEV-19803 Long semaphore wait error on galera.MW-388	
 galera_account_management : MariaDB 10.0 does not support ALTER USER
 galera_as_master_gtid : Requires MySQL GTID
@@ -29,12 +28,8 @@ galera_flush :  MariaDB does not have global.thread_statistics
 galera_gcache_recover_manytrx : MDEV-18834 Galera test failure
 galera_ist_mariabackup : MDEV-18829 test leaves port open
 galera_ist_progress : MDEV-15236 fails when trying to read transfer status
-galera_kill_applier : MDEV-19746 Galera test failures because of wsrep_slave_threads identification
 galera_migrate : MariaDB does not support START SLAVE USER
-galera_parallel_autoinc_largetrx : MDEV-19746 Galera test failures because of wsrep_slave_threads identification
-galera_parallel_autoinc_manytrx : MDEV-19746 Galera test failures because of wsrep_slave_threads identification
 galera_ssl_upgrade : MDEV-19950 Galera test failure on galera_ssl_upgrade
 galera_sst_mariabackup_encrypt_with_key : MDEV-19926 Galera SST tests fail
-galera_var_slave_threads : MDEV-19746 Galera test failures because of wsrep_slave_threads identification
 galera_wan : MDEV-17259: Test failure on galera.galera_wan
 partition : MDEV-19958 Galera test failure on galera.partition
diff --git a/mysql-test/suite/galera/r/MW-336.result b/mysql-test/suite/galera/r/MW-336.result
index 191811680e0..ed2f0755f0d 100644
--- a/mysql-test/suite/galera/r/MW-336.result
+++ b/mysql-test/suite/galera/r/MW-336.result
@@ -1,39 +1,51 @@
-CREATE TABLE t1 (f1 INTEGER) Engine=InnoDB;
-INSERT INTO t1 values(0);
 connection node_1;
+CREATE TABLE t1 (f1 INTEGER) Engine=InnoDB;
 SET GLOBAL wsrep_slave_threads = 10;
+# Set slave threads to 10 step 1
 SET GLOBAL wsrep_slave_threads = 1;
-# Wait 10 slave threads to start 1
 connection node_2;
-SET SESSION wsrep_sync_wait=15;
-# Generate 100 replication events
+INSERT INTO t1 VALUES (1);
 connection node_1;
 SET SESSION wsrep_sync_wait=15;
 SELECT COUNT(*) FROM t1;
 COUNT(*)
-101
-# Wait 9 slave threads to exit 1
+1
 SET GLOBAL wsrep_slave_threads = 10;
-# Wait 10 slave threads to start 2
+# Set slave threads to 10 step 2
 SET GLOBAL wsrep_slave_threads = 20;
-# Wait 20 slave threads to start 3
+# Set slave threads to 20
 SET GLOBAL wsrep_slave_threads = 1;
 connection node_2;
-# Generate 100 replication events
+INSERT INTO t1 VALUES (1);
+INSERT INTO t1 VALUES (2);
+INSERT INTO t1 VALUES (3);
+INSERT INTO t1 VALUES (4);
+INSERT INTO t1 VALUES (5);
+INSERT INTO t1 VALUES (6);
+INSERT INTO t1 VALUES (7);
+INSERT INTO t1 VALUES (8);
+INSERT INTO t1 VALUES (9);
+INSERT INTO t1 VALUES (10);
 connection node_1;
+SET GLOBAL wsrep_slave_threads = 10;
 SELECT COUNT(*) FROM t1;
 COUNT(*)
-201
-# Wait 10 slave threads to exit 3
-SET GLOBAL wsrep_slave_threads = 10;
-SET GLOBAL wsrep_slave_threads = 1;
-# Wait 10 slave threads to start 3
+11
+# Set slave threads to 10 step 3
 connection node_2;
-# Generate 100 replication events
+INSERT INTO t1 VALUES (11);
+INSERT INTO t1 VALUES (12);
+INSERT INTO t1 VALUES (13);
+INSERT INTO t1 VALUES (14);
+INSERT INTO t1 VALUES (15);
+INSERT INTO t1 VALUES (16);
+INSERT INTO t1 VALUES (17);
+INSERT INTO t1 VALUES (18);
+INSERT INTO t1 VALUES (19);
+INSERT INTO t1 VALUES (20);
 connection node_1;
 SELECT COUNT(*) FROM t1;
 COUNT(*)
-301
-# Wait 10 slave threads to exit 4
-connection node_1;
+21
+SET GLOBAL wsrep_slave_threads = 1;
 DROP TABLE t1;
diff --git a/mysql-test/suite/galera/r/galera_kill_applier.result b/mysql-test/suite/galera/r/galera_kill_applier.result
index 6fa632c242f..075cbe6f702 100644
--- a/mysql-test/suite/galera/r/galera_kill_applier.result
+++ b/mysql-test/suite/galera/r/galera_kill_applier.result
@@ -1,5 +1,18 @@
-connection node_1;
+connection node_2;
+SET GLOBAL wsrep_slave_threads=2;
 Got one of the listed errors
 Got one of the listed errors
 Got one of the listed errors
 Got one of the listed errors
+SET GLOBAL wsrep_slave_threads=1;
+connection node_1;
+create table t1(a int not null primary key) engine=innodb;
+insert into t1 values (1);
+insert into t1 values (2);
+connection node_2;
+set global wsrep_sync_wait=15;
+select count(*) from t1;
+count(*)
+2
+connection node_1;
+drop table t1;
diff --git a/mysql-test/suite/galera/r/galera_var_slave_threads.result b/mysql-test/suite/galera/r/galera_var_slave_threads.result
index c28cc091ae9..d77a5a54cbf 100644
--- a/mysql-test/suite/galera/r/galera_var_slave_threads.result
+++ b/mysql-test/suite/galera/r/galera_var_slave_threads.result
@@ -16,22 +16,19 @@ SET GLOBAL wsrep_slave_threads = 1;
 SELECT COUNT(*) FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE LIKE '%wsrep aborter%';
 COUNT(*)
 1
-SET GLOBAL wsrep_slave_threads = 64;
 connection node_1;
 INSERT INTO t1 VALUES (1);
 connection node_2;
-SELECT COUNT(*) = 1 FROM t1;
-COUNT(*) = 1
+SELECT COUNT(*) FROM t1;
+COUNT(*)
 1
+SET GLOBAL wsrep_slave_threads = 64;
 SET GLOBAL wsrep_slave_threads = 1;
 connection node_1;
 connection node_2;
 SELECT COUNT(*) FROM t2;
 COUNT(*)
-64
-SELECT COUNT(*) FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE LIKE '%wsrep aborter%';
-COUNT(*)
-1
+70
 SET GLOBAL wsrep_slave_threads = 1;
 DROP TABLE t1;
 DROP TABLE t2;
@@ -47,11 +44,12 @@ connection node_1;
 INSERT INTO t1 VALUES (DEFAULT);
 INSERT INTO t1 VALUES (DEFAULT);
 INSERT INTO t1 VALUES (DEFAULT);
+INSERT INTO t1 VALUES (DEFAULT);
+INSERT INTO t1 VALUES (DEFAULT);
+INSERT INTO t1 VALUES (DEFAULT);
+INSERT INTO t1 VALUES (DEFAULT);
+INSERT INTO t1 VALUES (DEFAULT);
 DROP TABLE t1;
 connection node_2;
 SELECT NAME FROM INFORMATION_SCHEMA.INNODB_SYS_TABLES WHERE NAME LIKE 'test/t%';
 NAME
-SELECT COUNT(*) = 1 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE LIKE '%wsrep aborter%';
-COUNT(*) = 1
-1
-# End of tests
diff --git a/mysql-test/suite/galera/t/MW-336.cnf b/mysql-test/suite/galera/t/MW-336.cnf
new file mode 100644
index 00000000000..4f23644ca50
--- /dev/null
+++ b/mysql-test/suite/galera/t/MW-336.cnf
@@ -0,0 +1,8 @@
+!include ../galera_2nodes.cnf
+
+[mysqld.1]
+wsrep-debug=ON
+
+[mysqld.2]
+wsrep-debug=ON
+
diff --git a/mysql-test/suite/galera/t/MW-336.test b/mysql-test/suite/galera/t/MW-336.test
index 195418cff55..b6df78ac7a6 100644
--- a/mysql-test/suite/galera/t/MW-336.test
+++ b/mysql-test/suite/galera/t/MW-336.test
@@ -4,110 +4,77 @@
 
 --source include/galera_cluster.inc
 --source include/have_innodb.inc
-
-CREATE TABLE t1 (f1 INTEGER) Engine=InnoDB;
-INSERT INTO t1 values(0);
+--source include/force_restart.inc
 
 --connection node_1
+CREATE TABLE t1 (f1 INTEGER) Engine=InnoDB;
 
 SET GLOBAL wsrep_slave_threads = 10;
-SET GLOBAL wsrep_slave_threads = 1;
 
---echo # Wait 10 slave threads to start 1
---let $wait_timeout=600
---let $wait_condition = SELECT COUNT(*) = 11 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%');
---source include/wait_condition.inc
+# ensure that the threads have actually started running
+--echo # Set slave threads to 10 step 1
+--let $wait_condition = SELECT COUNT(*) = 10 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep applier idle';
+--let $wait_condition_on_error_output = SELECT COUNT(*), 10 as EXPECTED_VALUE FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep applier idle'; show processlist
+--source include/wait_condition_with_debug.inc
+
+SET GLOBAL wsrep_slave_threads = 1;
 
 --connection node_2
-SET SESSION wsrep_sync_wait=15;
-# Wait until inserts are replicated
---let $wait_condition = SELECT COUNT(*) = 1 FROM t1;
---source include/wait_condition.inc
---echo # Generate 100 replication events
---disable_query_log
---disable_result_log
---let $count = 100
-while ($count)
-{
-  INSERT INTO t1 VALUES (1);
-  --dec $count
-}
---enable_result_log
---enable_query_log
+INSERT INTO t1 VALUES (1);
 
 --connection node_1
 SET SESSION wsrep_sync_wait=15;
-
 SELECT COUNT(*) FROM t1;
 
---echo # Wait 9 slave threads to exit 1
-# Wait until appliers exit
---let $wait_condition = SELECT COUNT(*) = 2 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%');
---source include/wait_condition.inc
-
 SET GLOBAL wsrep_slave_threads = 10;
 
---echo # Wait 10 slave threads to start 2
---let $wait_condition = SELECT COUNT(*) = 11 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%');
---source include/wait_condition.inc
+--echo # Set slave threads to 10 step 2
+--let $wait_condition = SELECT COUNT(*) = 10 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep applier idle';
+--let $wait_condition_on_error_output = SELECT COUNT(*), 10 as EXPECTED_VALUE FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep applier idle'; show processlist
+--source include/wait_condition_with_debug.inc
 
 SET GLOBAL wsrep_slave_threads = 20;
 
---echo # Wait 20 slave threads to start 3
---let $wait_condition = SELECT COUNT(*) = 21 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%');
---source include/wait_condition.inc
+--echo # Set slave threads to 20
+--let $wait_condition = SELECT COUNT(*) = 20 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep applier idle';
+--let $wait_condition_on_error_output = SELECT COUNT(*), 20 as EXPECTED_VALUE FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep applier idle'; show processlist
+--source include/wait_condition_with_debug.inc
 
 SET GLOBAL wsrep_slave_threads = 1;
 
 --connection node_2
---echo # Generate 100 replication events
---disable_query_log
---disable_result_log
---let $count = 100
-while ($count)
-{
-  INSERT INTO t1 VALUES (1);
-  --dec $count
-}
---enable_query_log
---enable_result_log
+INSERT INTO t1 VALUES (1);
+INSERT INTO t1 VALUES (2);
+INSERT INTO t1 VALUES (3);
+INSERT INTO t1 VALUES (4);
+INSERT INTO t1 VALUES (5);
+INSERT INTO t1 VALUES (6);
+INSERT INTO t1 VALUES (7);
+INSERT INTO t1 VALUES (8);
+INSERT INTO t1 VALUES (9);
+INSERT INTO t1 VALUES (10);
 
 --connection node_1
-SELECT COUNT(*) FROM t1;
-
---echo # Wait 10 slave threads to exit 3
-# Wait until appliers exit
---let $wait_condition = SELECT COUNT(*) = 2 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%');
---source include/wait_condition.inc
-
 SET GLOBAL wsrep_slave_threads = 10;
-SET GLOBAL wsrep_slave_threads = 1;
-
---echo # Wait 10 slave threads to start 3
---let $wait_timeout=600
---let $wait_condition = SELECT COUNT(*) = 11 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%');
---source include/wait_condition.inc
+SELECT COUNT(*) FROM t1;
+--echo # Set slave threads to 10 step 3
+--let $wait_condition = SELECT COUNT(*) = 10 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep applier idle';
+--let $wait_condition_on_error_output = SELECT COUNT(*), 10 as EXPECTED_VALUE FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep applier idle'; show processlist
+--source include/wait_condition_with_debug.inc
 
 --connection node_2
---echo # Generate 100 replication events
---disable_query_log
---disable_result_log
---let $count = 100
-while ($count)
-{
-  INSERT INTO t1 VALUES (1);
-  --dec $count
-}
---enable_result_log
---enable_query_log
+INSERT INTO t1 VALUES (11);
+INSERT INTO t1 VALUES (12);
+INSERT INTO t1 VALUES (13);
+INSERT INTO t1 VALUES (14);
+INSERT INTO t1 VALUES (15);
+INSERT INTO t1 VALUES (16);
+INSERT INTO t1 VALUES (17);
+INSERT INTO t1 VALUES (18);
+INSERT INTO t1 VALUES (19);
+INSERT INTO t1 VALUES (20);
 
 --connection node_1
 SELECT COUNT(*) FROM t1;
-
---echo # Wait 10 slave threads to exit 4
-# Wait until appliers exit
---let $wait_condition = SELECT COUNT(*) = 2 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%');
---source include/wait_condition.inc
-
---connection node_1
+SET GLOBAL wsrep_slave_threads = 1;
 DROP TABLE t1;
diff --git a/mysql-test/suite/galera/t/galera_kill_applier.test b/mysql-test/suite/galera/t/galera_kill_applier.test
index b66e0bcbbd0..4136bac5dc6 100644
--- a/mysql-test/suite/galera/t/galera_kill_applier.test
+++ b/mysql-test/suite/galera/t/galera_kill_applier.test
@@ -4,9 +4,16 @@
 
 --source include/galera_cluster.inc
 --source include/have_innodb.inc
+--source include/force_restart.inc
 
---connection node_1
---let $applier_thread = `SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE IS NULL LIMIT 1`
+--connection node_2
+SET GLOBAL wsrep_slave_threads=2;
+
+--let $wait_condition = SELECT COUNT(*) >= 1 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep applier idle';
+--let $wait_condition_on_error_output = SELECT COUNT(*), 2 as EXPECTED_VALUE FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep applier idle'; show processlist
+--source include/wait_condition_with_debug.inc
+
+--let $applier_thread = `SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep applier idle' LIMIT 1`
 
 --disable_query_log
 --error ER_KILL_DENIED_ERROR,ER_KILL_DENIED_ERROR
@@ -23,3 +30,17 @@
 --error ER_KILL_DENIED_ERROR,ER_KILL_DENIED_ERROR
 --eval KILL QUERY $aborter_thread
 --enable_query_log
+
+SET GLOBAL wsrep_slave_threads=1;
+
+--connection node_1
+create table t1(a int not null primary key) engine=innodb;
+insert into t1 values (1);
+insert into t1 values (2);
+
+--connection node_2
+set global wsrep_sync_wait=15;
+select count(*) from t1;
+
+--connection node_1
+drop table t1;
diff --git a/mysql-test/suite/galera/t/galera_parallel_autoinc_largetrx.test b/mysql-test/suite/galera/t/galera_parallel_autoinc_largetrx.test
index 34558283462..9e1f47b1ac4 100644
--- a/mysql-test/suite/galera/t/galera_parallel_autoinc_largetrx.test
+++ b/mysql-test/suite/galera/t/galera_parallel_autoinc_largetrx.test
@@ -5,6 +5,7 @@
 --source include/galera_cluster.inc
 --source include/have_innodb.inc
 --source include/big_test.inc
+--source include/force_restart.inc
 
 # Create a second connection to node1 so that we can run transactions concurrently
 --let $galera_connection_name = node_1a
@@ -20,11 +21,11 @@ CREATE TABLE t1 (f1 INTEGER AUTO_INCREMENT PRIMARY KEY, f2 INTEGER) Engine=InnoD
 --connection node_2
 set session wsrep_sync_wait=15;
 --let $wsrep_slave_threads_orig = `SELECT @@wsrep_slave_threads`
+
 SET GLOBAL wsrep_slave_threads = 4;
---let $wait_condition = SELECT COUNT(*) = @@wsrep_slave_threads + 1 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%');
+--let $wait_condition = SELECT VARIABLE_VALUE = 4 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_applier_thread_count';
 --source include/wait_condition.inc
 
-
 --connection node_1
 --send INSERT INTO t1 (f2) SELECT 1 FROM ten AS a1, ten AS a2, ten AS a3, ten AS a4;
 
diff --git a/mysql-test/suite/galera/t/galera_parallel_autoinc_manytrx.test b/mysql-test/suite/galera/t/galera_parallel_autoinc_manytrx.test
index d04603891db..b82a160657d 100644
--- a/mysql-test/suite/galera/t/galera_parallel_autoinc_manytrx.test
+++ b/mysql-test/suite/galera/t/galera_parallel_autoinc_manytrx.test
@@ -5,6 +5,7 @@
 --source include/galera_cluster.inc
 --source include/have_innodb.inc
 --source include/big_test.inc
+--source include/force_restart.inc
 
 --connection node_1
 CREATE TABLE ten (f1 INTEGER) Engine=InnoDB;
@@ -24,8 +25,9 @@ CREATE TABLE t1 (f1 INTEGER AUTO_INCREMENT PRIMARY KEY, f2 INTEGER) Engine=InnoD
 --connection node_2
 set session wsrep_sync_wait=15;
 --let $wsrep_slave_threads_orig = `SELECT @@wsrep_slave_threads`
+
 SET GLOBAL wsrep_slave_threads = 4;
---let $wait_condition = SELECT COUNT(*) = @@wsrep_slave_threads + 1 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%');
+--let $wait_condition = SELECT VARIABLE_VALUE = 4 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_applier_thread_count';
 --source include/wait_condition.inc
 
 --connection node_1
diff --git a/mysql-test/suite/galera/t/galera_var_slave_threads.test b/mysql-test/suite/galera/t/galera_var_slave_threads.test
index 80edcb2aff9..87e9f6de0ce 100644
--- a/mysql-test/suite/galera/t/galera_var_slave_threads.test
+++ b/mysql-test/suite/galera/t/galera_var_slave_threads.test
@@ -6,9 +6,10 @@
 
 --source include/galera_cluster.inc
 --source include/have_innodb.inc
---let $wsrep_slave_threads_orig = `SELECT @@wsrep_slave_threads`
+--source include/force_restart.inc
 
 --connection node_1
+--let $wsrep_slave_threads_orig = `SELECT @@wsrep_slave_threads`
 CREATE TABLE t1 (f1 INT PRIMARY KEY) Engine=InnoDB;
 CREATE TABLE t2 (f1 INT AUTO_INCREMENT PRIMARY KEY) Engine=InnoDB;
 
@@ -23,23 +24,23 @@ SET GLOBAL wsrep_slave_threads = 1;
 # There is a separate wsrep_aborter thread at all times
 SELECT COUNT(*) FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE LIKE '%wsrep aborter%';
 
-#
-# Increase the number of slave threads. The change takes effect immediately
-#
-
-SET GLOBAL wsrep_slave_threads = 64;
-
 --connection node_1
 INSERT INTO t1 VALUES (1);
 
 --connection node_2
+
 --let $wait_timeout=600
 --let $wait_condition = SELECT COUNT(*) = 1 FROM t1;
 --source include/wait_condition.inc
 
-SELECT COUNT(*) = 1 FROM t1;
+SELECT COUNT(*) FROM t1;
+
+#
+# Increase the number of slave threads. The change takes effect immediately
+#
+SET GLOBAL wsrep_slave_threads = 64;
 
---let $wait_condition = SELECT COUNT(*) = @@wsrep_slave_threads + 1 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%');
+--let $wait_condition = SELECT VARIABLE_VALUE = 64 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_applier_thread_count';
 --source include/wait_condition.inc
 
 #
@@ -52,8 +53,8 @@ SET GLOBAL wsrep_slave_threads = 1;
 
 --disable_result_log
 --disable_query_log
-# Generate 64 replication events
---let $count = 64
+# Generate 70 replication events
+--let $count = 70
 while ($count)
 {
   INSERT INTO t2 VALUES (DEFAULT);
@@ -65,10 +66,8 @@ while ($count)
 --connection node_2
 SELECT COUNT(*) FROM t2;
 
---let $wait_condition = SELECT COUNT(*) = @@wsrep_slave_threads + 1 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%')
+--let $wait_condition = SELECT VARIABLE_VALUE = 1 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_applier_thread_count';
 --source include/wait_condition.inc
-SELECT COUNT(*) FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE LIKE '%wsrep aborter%';
-
 
 --eval SET GLOBAL wsrep_slave_threads = $wsrep_slave_threads_orig
 
@@ -84,7 +83,7 @@ CREATE TABLE t1 (i INT AUTO_INCREMENT PRIMARY KEY) ENGINE=INNODB;
 
 --connection node_2
 SET GLOBAL wsrep_slave_threads = 4;
---let $wait_condition = SELECT COUNT(*) = @@wsrep_slave_threads + 1 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%')
+--let $wait_condition = SELECT VARIABLE_VALUE = 4 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_applier_thread_count';
 --source include/wait_condition.inc
 
 SET GLOBAL wsrep_slave_threads = 1;
@@ -93,21 +92,20 @@ SET GLOBAL wsrep_slave_threads = 1;
 INSERT INTO t1 VALUES (DEFAULT);
 INSERT INTO t1 VALUES (DEFAULT);
 INSERT INTO t1 VALUES (DEFAULT);
+INSERT INTO t1 VALUES (DEFAULT);
+INSERT INTO t1 VALUES (DEFAULT);
+INSERT INTO t1 VALUES (DEFAULT);
+INSERT INTO t1 VALUES (DEFAULT);
+INSERT INTO t1 VALUES (DEFAULT);
 DROP TABLE t1;
 
 --connection node_2
 
 # Wait until above DDL is replicated
---let $wait_condition = SELECT COUNT(*) = 0 FROM INFORMATION_SCHEMA.INNODB_SYS_TABLES WHERE NAME LIKE 'test/t%';
---source include/wait_condition.inc
-
-SELECT NAME FROM INFORMATION_SCHEMA.INNODB_SYS_TABLES WHERE NAME LIKE 'test/t%';
-
 #
 # make sure that we are left with exactly one applier thread before we leaving the test
 #
---let $wait_condition = SELECT COUNT(*) = 2 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%')
+--let $wait_condition = SELECT VARIABLE_VALUE = 1 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_applier_thread_count';
 --source include/wait_condition.inc
-SELECT COUNT(*) = 1 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE LIKE '%wsrep aborter%';
 
---echo # End of tests
+SELECT NAME FROM INFORMATION_SCHEMA.INNODB_SYS_TABLES WHERE NAME LIKE 'test/t%';
diff --git a/mysql-test/suite/wsrep/disabled.def b/mysql-test/suite/wsrep/disabled.def
index bcaebf7ff4d..fcaf38a3d7b 100644
--- a/mysql-test/suite/wsrep/disabled.def
+++ b/mysql-test/suite/wsrep/disabled.def
@@ -9,5 +9,3 @@
 #  Do not use any TAB characters for whitespace.
 #
 ##############################################################################
-
-variables : MDEV-19746 Galera test failures because of wsrep_slave_threads identification
diff --git a/mysql-test/suite/wsrep/r/variables.result b/mysql-test/suite/wsrep/r/variables.result
index a5f95971367..99e30788488 100644
--- a/mysql-test/suite/wsrep/r/variables.result
+++ b/mysql-test/suite/wsrep/r/variables.result
@@ -22,6 +22,7 @@ CALL mtr.add_suppression("WSREP: Could not open saved state file for reading.*")
 # wsrep
 SHOW GLOBAL STATUS LIKE 'wsrep%';
 Variable_name	Value
+wsrep_applier_thread_count	#
 wsrep_apply_oooe	#
 wsrep_apply_oool	#
 wsrep_apply_window	#
@@ -75,6 +76,7 @@ wsrep_repl_keys_bytes	#
 wsrep_repl_other_bytes	#
 wsrep_replicated	#
 wsrep_replicated_bytes	#
+wsrep_rollbacker_thread_count	#
 wsrep_thread_count	#
 SHOW GLOBAL STATUS LIKE 'wsrep_local_state_comment';
 Variable_name	Value
@@ -132,7 +134,16 @@ wsrep_thread_count	0
 # Setting wsrep_cluster_address triggers the creation of
 # applier/rollbacker threads.
 SET GLOBAL wsrep_cluster_address= 'gcomm://';
-# Wait for applier threads to get created.
+# Wait for applier thread to get created 1.
+SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_applier_thread_count';
+VARIABLE_VALUE
+1
+SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_rollbacker_thread_count';
+VARIABLE_VALUE
+1
+SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_thread_count';
+VARIABLE_VALUE
+2
 SELECT @@global.wsrep_provider;
 @@global.wsrep_provider
 libgalera_smm.so
@@ -148,13 +159,19 @@ wsrep_thread_count	2
 
 SET @wsrep_slave_threads_saved= @@global.wsrep_slave_threads;
 SET GLOBAL wsrep_slave_threads= 10;
-# Wait for applier threads to get created.
+# Wait for 9 applier threads to get created.
+SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_applier_thread_count';
+VARIABLE_VALUE
+10
+SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_rollbacker_thread_count';
+VARIABLE_VALUE
+1
+SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_thread_count';
+VARIABLE_VALUE
+11
 SHOW STATUS LIKE 'threads_connected';
 Variable_name	Value
 Threads_connected	1
-SHOW STATUS LIKE 'wsrep_thread_count';
-Variable_name	Value
-wsrep_thread_count	11
 set wsrep_on=0;
 set wsrep_on=1;
 create user test@localhost;
diff --git a/mysql-test/suite/wsrep/t/variables.test b/mysql-test/suite/wsrep/t/variables.test
index 1a2ab2579a5..e01ba3e3a8b 100644
--- a/mysql-test/suite/wsrep/t/variables.test
+++ b/mysql-test/suite/wsrep/t/variables.test
@@ -1,4 +1,5 @@
 --source include/have_wsrep.inc
+--source include/force_restart.inc
 
 SET @wsrep_provider_options_saved= @@global.wsrep_provider_options;
 SET @wsrep_cluster_address_saved= @@global.wsrep_cluster_address;
@@ -102,11 +103,15 @@ SHOW STATUS LIKE 'wsrep_thread_count';
 --echo # applier/rollbacker threads.
 SET GLOBAL wsrep_cluster_address= 'gcomm://';
 
---echo # Wait for applier threads to get created.
+--echo # Wait for applier thread to get created 1.
 --let $wait_timeout=600
---let $wait_condition = SELECT COUNT(*) = 2 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%');
+--let $wait_condition = SELECT VARIABLE_VALUE = 1 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_applier_thread_count';
 --source include/wait_condition.inc
 
+SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_applier_thread_count';
+SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_rollbacker_thread_count';
+SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_thread_count';
+
 --replace_regex /.*libgalera_smm.*/libgalera_smm.so/
 SELECT @@global.wsrep_provider;
 SELECT @@global.wsrep_cluster_address;
@@ -117,12 +122,15 @@ SHOW STATUS LIKE 'wsrep_thread_count';
 SET @wsrep_slave_threads_saved= @@global.wsrep_slave_threads;
 SET GLOBAL wsrep_slave_threads= 10;
 
---echo # Wait for applier threads to get created.
---let $wait_condition = SELECT COUNT(*) = 11 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND (STATE IS NULL OR STATE NOT LIKE 'InnoDB%');
+--echo # Wait for 9 applier threads to get created.
+--let $wait_condition = SELECT VARIABLE_VALUE = 10 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_applier_thread_count';
 --source include/wait_condition.inc
 
+SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_applier_thread_count';
+SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_rollbacker_thread_count';
+SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_thread_count';
+
 SHOW STATUS LIKE 'threads_connected';
-SHOW STATUS LIKE 'wsrep_thread_count';
 
 #
 # privileges for wsrep_on
diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index bafc92696c4..33e15b1db07 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -6036,6 +6036,8 @@ int mysqld_main(int argc, char **argv)
         wsrep_init_startup (false);
       }
 
+      WSREP_DEBUG("Startup creating %ld applier threads running %lu",
+	      wsrep_slave_threads - 1, wsrep_running_applier_threads);
       wsrep_create_appliers(wsrep_slave_threads - 1);
     }
   }
diff --git a/sql/wsrep_mysqld.cc b/sql/wsrep_mysqld.cc
index 88ea6faf1c6..8c3be114c19 100644
--- a/sql/wsrep_mysqld.cc
+++ b/sql/wsrep_mysqld.cc
@@ -39,6 +39,7 @@
 #include "log_event.h"
 #include <slave.h>
 #include "sql_plugin.h"                         /* wsrep_plugins_pre_init() */
+#include <vector>
 
 wsrep_t *wsrep                  = NULL;
 /*
@@ -135,7 +136,11 @@ mysql_mutex_t LOCK_wsrep_desync;
 mysql_mutex_t LOCK_wsrep_config_state;
 
 int wsrep_replaying= 0;
-ulong  wsrep_running_threads = 0; // # of currently running wsrep threads
+ulong  wsrep_running_threads = 0; // # of currently running wsrep
+				  // # threads
+ulong  wsrep_running_applier_threads = 0; // # of running applier threads
+ulong  wsrep_running_rollbacker_threads = 0; // # of running
+					     // # rollbacker threads
 ulong  my_bind_addr;
 
 #ifdef HAVE_PSI_INTERFACE
@@ -2021,7 +2026,8 @@ bool wsrep_grant_mdl_exception(MDL_context *requestor_ctx,
 pthread_handler_t start_wsrep_THD(void *arg)
 {
   THD *thd;
-  wsrep_thd_processor_fun processor= (wsrep_thd_processor_fun)arg;
+  wsrep_thread_args* args= (wsrep_thread_args*)arg;
+  wsrep_thd_processor_fun processor= args->processor;
 
   if (my_thread_init() || (!(thd= new THD(next_thread_id(), true))))
   {
@@ -2099,6 +2105,19 @@ pthread_handler_t start_wsrep_THD(void *arg)
 
   mysql_mutex_lock(&LOCK_thread_count);
   wsrep_running_threads++;
+
+  switch (args->thread_type) {
+    case WSREP_APPLIER_THREAD:
+      wsrep_running_applier_threads++;
+      break;
+    case WSREP_ROLLBACKER_THREAD:
+      wsrep_running_rollbacker_threads++;
+      break;
+    default:
+      WSREP_ERROR("Incorrect wsrep thread type: %d", args->thread_type);
+      break;
+  }
+
   mysql_cond_broadcast(&COND_thread_count);
   mysql_mutex_unlock(&LOCK_thread_count);
 
@@ -2107,7 +2126,25 @@ pthread_handler_t start_wsrep_THD(void *arg)
   close_connection(thd, 0);
 
   mysql_mutex_lock(&LOCK_thread_count);
+  DBUG_ASSERT(wsrep_running_threads > 0);
   wsrep_running_threads--;
+
+  switch (args->thread_type) {
+    case WSREP_APPLIER_THREAD:
+      DBUG_ASSERT(wsrep_running_applier_threads > 0);
+      wsrep_running_applier_threads--;
+      break;
+    case WSREP_ROLLBACKER_THREAD:
+      DBUG_ASSERT(wsrep_running_rollbacker_threads > 0);
+      wsrep_running_rollbacker_threads--;
+      break;
+    default:
+      WSREP_ERROR("Incorrect wsrep thread type: %d", args->thread_type);
+      break;
+  }
+
+  my_free(args);
+
   WSREP_DEBUG("wsrep running threads now: %lu", wsrep_running_threads);
   mysql_cond_broadcast(&COND_thread_count);
   mysql_mutex_unlock(&LOCK_thread_count);
@@ -2141,6 +2178,8 @@ pthread_handler_t start_wsrep_THD(void *arg)
 error:
   WSREP_ERROR("Failed to create/initialize system thread");
 
+  my_free(args);
+
   /* Abort if its the first applier/rollbacker thread. */
   if (!mysqld_server_initialized)
     unireg_abort(1);
diff --git a/sql/wsrep_mysqld.h b/sql/wsrep_mysqld.h
index 4640766404b..718e188cdc4 100644
--- a/sql/wsrep_mysqld.h
+++ b/sql/wsrep_mysqld.h
@@ -31,6 +31,7 @@ typedef struct st_mysql_show_var SHOW_VAR;
 #include "mysqld.h"
 #include "sql_table.h"
 #include "wsrep_mysqld_c.h"
+#include <vector>
 
 #define WSREP_UNDEFINED_TRX_ID ULONGLONG_MAX
 
@@ -89,6 +90,8 @@ extern my_bool     wsrep_restart_slave_activated;
 extern my_bool     wsrep_slave_FK_checks;
 extern my_bool     wsrep_slave_UK_checks;
 extern ulong       wsrep_running_threads;
+extern ulong       wsrep_running_applier_threads;
+extern ulong       wsrep_running_rollbacker_threads;
 extern bool        wsrep_new_cluster;
 extern bool        wsrep_gtid_mode;
 extern uint32      wsrep_gtid_domain_id;
@@ -310,7 +313,21 @@ void thd_binlog_flush_pending_rows_event(THD *thd, bool stmt_end);
 void thd_binlog_rollback_stmt(THD * thd);
 void thd_binlog_trx_reset(THD * thd);
 
+enum wsrep_thread_type {
+  WSREP_APPLIER_THREAD=1,
+  WSREP_ROLLBACKER_THREAD=2
+};
+
 typedef void (*wsrep_thd_processor_fun)(THD *);
+
+typedef struct {
+	pthread_t thread_id;
+	wsrep_thd_processor_fun processor;
+	enum wsrep_thread_type thread_type;
+} wsrep_thread_args;
+
+extern std::vector<wsrep_thread_args*> wsrep_thread_arg;
+
 pthread_handler_t start_wsrep_THD(void *arg);
 int wsrep_wait_committing_connections_close(int wait_time);
 extern void wsrep_close_client_connections(my_bool wait_to_end,
diff --git a/sql/wsrep_thd.cc b/sql/wsrep_thd.cc
index 1d00a64c972..31b6622d30c 100644
--- a/sql/wsrep_thd.cc
+++ b/sql/wsrep_thd.cc
@@ -360,6 +360,7 @@ static void wsrep_replication_process(THD *thd)
   thd->variables.option_bits|= OPTION_BEGIN;
   thd->server_status|= SERVER_STATUS_IN_TRANS;
 
+  thd_proc_info(thd, "wsrep applier idle");
   rcode = wsrep->recv(wsrep, (void *)thd);
   DBUG_PRINT("wsrep",("wsrep_repl returned: %d", rcode));
 
@@ -415,13 +416,12 @@ static void wsrep_replication_process(THD *thd)
   DBUG_VOID_RETURN;
 }
 
-static bool create_wsrep_THD(wsrep_thd_processor_fun processor)
+static bool create_wsrep_THD(wsrep_thread_args* args)
 {
   ulong old_wsrep_running_threads= wsrep_running_threads;
-  pthread_t unused;
   mysql_mutex_lock(&LOCK_thread_count);
-  bool res= pthread_create(&unused, &connection_attrib, start_wsrep_THD,
-                           (void*)processor);
+  bool res= pthread_create(&args->thread_id, &connection_attrib, start_wsrep_THD,
+                           (void*)args);
   /*
     if starting a thread on server startup, wait until the this thread's THD
     is fully initialized (otherwise a THD initialization code might
@@ -451,8 +451,20 @@ void wsrep_create_appliers(long threads)
 
   long wsrep_threads=0;
   while (wsrep_threads++ < threads) {
-    if (create_wsrep_THD(wsrep_replication_process))
+    wsrep_thread_args* arg;
+    if((arg = (wsrep_thread_args*)my_malloc(sizeof(wsrep_thread_args), MYF(0))) == NULL) {
+      WSREP_ERROR("Can't allocate memory for wsrep replication thread %ld\n", wsrep_threads);
+      assert(0);
+    }
+
+    arg->thread_type = WSREP_APPLIER_THREAD;
+    arg->processor = wsrep_replication_process;
+
+    if (create_wsrep_THD(arg)) {
       WSREP_WARN("Can't create thread to manage wsrep replication");
+      my_free(arg);
+      return;
+    }
   }
 }
 
@@ -539,9 +551,21 @@ void wsrep_create_rollbacker()
 {
   if (wsrep_provider && strcasecmp(wsrep_provider, "none"))
   {
+    wsrep_thread_args* arg;
+    if((arg = (wsrep_thread_args*)my_malloc(sizeof(wsrep_thread_args), MYF(0))) == NULL) {
+      WSREP_ERROR("Can't allocate memory for wsrep rollbacker thread\n");
+      assert(0);
+    }
+
+    arg->thread_type = WSREP_ROLLBACKER_THREAD;
+    arg->processor = wsrep_rollback_process;
+
     /* create rollbacker */
-    if (create_wsrep_THD(wsrep_rollback_process))
+    if (create_wsrep_THD(arg)) {
       WSREP_WARN("Can't create thread to manage wsrep rollback");
+      my_free(arg);
+      return;
+    }
   }
 }
 
diff --git a/sql/wsrep_var.cc b/sql/wsrep_var.cc
index 78269c56733..0f7f7ef2acf 100644
--- a/sql/wsrep_var.cc
+++ b/sql/wsrep_var.cc
@@ -28,8 +28,6 @@
 
 ulong   wsrep_reject_queries;
 
-static long wsrep_prev_slave_threads = wsrep_slave_threads;
-
 int wsrep_init_vars()
 {
   wsrep_provider        = my_strdup(WSREP_NONE, MYF(MY_WME));
@@ -502,6 +500,8 @@ bool wsrep_cluster_address_update (sys_var *self, THD* thd, enum_var_type type)
   if (wsrep_start_replication())
   {
     wsrep_create_rollbacker();
+    WSREP_DEBUG("Cluster address update creating %ld applier threads running %lu",
+	    wsrep_slave_threads, wsrep_running_applier_threads);
     wsrep_create_appliers(wsrep_slave_threads);
   }
 
@@ -595,18 +595,20 @@ void wsrep_node_address_init (const char* value)
 
 static void wsrep_slave_count_change_update ()
 {
-  wsrep_slave_count_change = (wsrep_slave_threads - wsrep_prev_slave_threads);
-  WSREP_DEBUG("Change on slave threads: New %lu old %lu difference %d",
-	  wsrep_slave_threads, wsrep_prev_slave_threads, wsrep_slave_count_change);
-  wsrep_prev_slave_threads = wsrep_slave_threads;
+  wsrep_slave_count_change = (wsrep_slave_threads - wsrep_running_applier_threads);
+  WSREP_DEBUG("Change on slave threads: New %ld old %lu difference %d",
+	  wsrep_slave_threads, wsrep_running_applier_threads, wsrep_slave_count_change);
 }
 
 bool wsrep_slave_threads_update (sys_var *self, THD* thd, enum_var_type type)
 {
   wsrep_slave_count_change_update();
+
   if (wsrep_slave_count_change > 0)
   {
+    WSREP_DEBUG("Creating %d applier threads, total %ld", wsrep_slave_count_change, wsrep_slave_threads);
     wsrep_create_appliers(wsrep_slave_count_change);
+    WSREP_DEBUG("Running %lu applier threads", wsrep_running_applier_threads);
     wsrep_slave_count_change = 0;
   }
   return false;
@@ -708,7 +710,9 @@ static SHOW_VAR wsrep_status_vars[]=
   {"provider_name",     (char*) &wsrep_provider_name,     SHOW_CHAR_PTR},
   {"provider_version",  (char*) &wsrep_provider_version,  SHOW_CHAR_PTR},
   {"provider_vendor",   (char*) &wsrep_provider_vendor,   SHOW_CHAR_PTR},
-  {"thread_count",      (char*) &wsrep_running_threads,   SHOW_LONG_NOFLUSH}
+  {"thread_count",      (char*) &wsrep_running_threads,   SHOW_LONG_NOFLUSH},
+  {"applier_thread_count", (char*)&wsrep_running_applier_threads, SHOW_LONG_NOFLUSH},
+  {"rollbacker_thread_count", (char *)&wsrep_running_rollbacker_threads, SHOW_LONG_NOFLUSH},
 };
 
 static int show_var_cmp(const void *var1, const void *var2)