MDEV-12008 : Change error code for Galera unkillable threads

Changed error code for Galera unkillable threads to
be ER_KILL_DENIED_HIGH_PRIORITY giving message

This is a high priority thread/query and cannot be killed
without the compromising consistency of the cluster

also a warning is produced
  Thread %lld is [wsrep applier|high priority] and cannot be killed
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>

mysql-test/suite/galera/r/galera_kill_applier.result

@@ -6,13 +6,13 @@ SELECT @@wsrep_slave_threads;
 1
 SET GLOBAL wsrep_slave_threads=2;
 KILL ID;
-Got one of the listed errors
+ERROR HY000: This is a high-priority thread/query and cannot be killed without compromising the consistency of the cluster
 KILL QUERY ID;
-Got one of the listed errors
+ERROR HY000: This is a high-priority thread/query and cannot be killed without compromising the consistency of the cluster
 KILL ID;
-Got one of the listed errors
+ERROR HY000: This is a high-priority thread/query and cannot be killed without compromising the consistency of the cluster
 KILL QUERY ID;
-Got one of the listed errors
+ERROR HY000: This is a high-priority thread/query and cannot be killed without compromising the consistency of the cluster
 SET GLOBAL wsrep_slave_threads=DEFAULT;
 connection node_1;
 create table t1(a int not null primary key) engine=innodb;

mysql-test/suite/galera/r/galera_kill_bf.result

+connection node_2;
+connection node_1;
+connect con1,127.0.0.1,root,,test,$NODE_MYPORT_1;
+call mtr.add_suppression("WSREP: ALTER TABLE isolation failure");
+CREATE TABLE t1(c1 INT PRIMARY KEY, c2 INT) ENGINE=InnoDB;
+INSERT into t1 values (1,1);
+SET DEBUG_SYNC = 'alter_table_after_open_tables SIGNAL bf_started WAIT_FOR bf_continue';
+ALTER TABLE t1 DROP COLUMN c2;;
+connection node_1;
+SET SESSION wsrep_sync_wait = 0;
+SET DEBUG_SYNC = 'now WAIT_FOR bf_started';
+KILL ID;
+ERROR HY000: This is a high-priority thread/query and cannot be killed without compromising the consistency of the cluster
+KILL QUERY ID;
+ERROR HY000: This is a high-priority thread/query and cannot be killed without compromising the consistency of the cluster
+connection node_1;
+SET DEBUG_SYNC = 'now SIGNAL bf_continue';
+connection con1;
+SET DEBUG_SYNC = 'RESET';
+SELECT * FROM t1;
+c1
+1
+connection node_1;
+DROP TABLE t1;
+disconnect con1;

mysql-test/suite/galera/t/galera_kill_applier.test

@@ -17,21 +17,21 @@ SET GLOBAL wsrep_slave_threads=2;
 --let $applier_thread = `SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep applier idle' LIMIT 1`
 
 --replace_result $applier_thread ID
---error ER_KILL_DENIED_ERROR,ER_KILL_DENIED_ERROR
+--error ER_KILL_DENIED_HIGH_PRIORITY
 --eval KILL $applier_thread
 
 --replace_result $applier_thread ID
---error ER_KILL_DENIED_ERROR,ER_KILL_DENIED_ERROR
+--error ER_KILL_DENIED_HIGH_PRIORITY
 --eval KILL QUERY $applier_thread
 
 --let $aborter_thread = `SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep aborter idle' LIMIT 1`
 
 --replace_result $aborter_thread ID
---error ER_KILL_DENIED_ERROR,ER_KILL_DENIED_ERROR
+--error ER_KILL_DENIED_HIGH_PRIORITY
 --eval KILL $aborter_thread
 
 --replace_result $aborter_thread ID
---error ER_KILL_DENIED_ERROR,ER_KILL_DENIED_ERROR
+--error ER_KILL_DENIED_HIGH_PRIORITY
 --eval KILL QUERY $aborter_thread
 
 SET GLOBAL wsrep_slave_threads=DEFAULT;

mysql-test/suite/galera/t/galera_kill_bf.test

+--source include/galera_cluster.inc
+--source include/have_debug_sync.inc
+--source include/have_debug.inc
+
+--connect con1,127.0.0.1,root,,test,$NODE_MYPORT_1
+
+call mtr.add_suppression("WSREP: ALTER TABLE isolation failure");
+
+CREATE TABLE t1(c1 INT PRIMARY KEY, c2 INT) ENGINE=InnoDB;
+INSERT into t1 values (1,1);
+
+SET DEBUG_SYNC = 'alter_table_after_open_tables SIGNAL bf_started WAIT_FOR bf_continue';
+--send ALTER TABLE t1 DROP COLUMN c2;
+
+--connection node_1
+SET SESSION wsrep_sync_wait = 0;
+SET DEBUG_SYNC = 'now WAIT_FOR bf_started';
+--let $wait_condition = SELECT COUNT(*) = 1 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE STATE = 'debug sync point: alter_table_after_open_tables'
+--source include/wait_condition.inc
+
+--let $applier_thread = `SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST WHERE STATE LIKE 'debug sync point:%' LIMIT 1`
+
+--replace_result $applier_thread ID
+--error ER_KILL_DENIED_HIGH_PRIORITY
+--eval KILL $applier_thread
+
+--replace_result $applier_thread ID
+--error ER_KILL_DENIED_HIGH_PRIORITY
+--eval KILL QUERY $applier_thread
+
+--connection node_1
+SET DEBUG_SYNC = 'now SIGNAL bf_continue';
+
+--connection con1
+--reap
+SET DEBUG_SYNC = 'RESET';
+SELECT * FROM t1;
+
+--connection node_1
+DROP TABLE t1;
+--disconnect con1

sql/share/errmsg-utf8.txt

@@ -9111,3 +9111,5 @@ ER_NOT_ALLOWED_IN_THIS_CONTEXT
         eng "'%-.128s' is not allowed in this context"
 ER_DATA_WAS_COMMITED_UNDER_ROLLBACK
         eng "Engine %s does not support rollback. Changes were committed during rollback call"
+ER_KILL_DENIED_HIGH_PRIORITY
+        eng "This is a high-priority thread/query and cannot be killed without compromising the consistency of the cluster"

sql/sql_parse.cc

@@ -9415,17 +9415,21 @@ kill_one_thread(THD *thd, my_thread_id id, killed_state kill_signal, killed_type
 
     mysql_mutex_lock(&tmp->LOCK_thd_data); // Lock from concurrent usage
 
-#ifdef WITH_WSREP
-    if (((thd->security_ctx->master_access & PRIV_KILL_OTHER_USER_PROCESS) ||
-        thd->security_ctx->user_matches(tmp->security_ctx)) &&
-        !wsrep_thd_is_BF(tmp, false) && !tmp->wsrep_applier)
-#else
     if ((thd->security_ctx->master_access & PRIV_KILL_OTHER_USER_PROCESS) ||
         thd->security_ctx->user_matches(tmp->security_ctx))
-#endif /* WITH_WSREP */
-    {
     {
 #ifdef WITH_WSREP
+      if (wsrep_thd_is_BF(tmp, false) || tmp->wsrep_applier)
+      {
+        error= ER_KILL_DENIED_HIGH_PRIORITY;
+        push_warning_printf(thd, Sql_condition::WARN_LEVEL_NOTE,
+                            ER_KILL_DENIED_HIGH_PRIORITY,
+                            "Thread %lld is %s and cannot be killed",
+                            tmp->thread_id,
+                           (tmp->wsrep_applier ? "wsrep applier" : "high priority"));
+      }
+      else
+      {
         if (WSREP(tmp))
         {
           /* Object tmp is not guaranteed to exist after wsrep_kill_thd()
@@ -9435,7 +9439,9 @@ kill_one_thread(THD *thd, my_thread_id id, killed_state kill_signal, killed_type
 #endif /* WITH_WSREP */
         tmp->awake_no_mutex(kill_signal);
         error= 0;
+#ifdef WITH_WSREP
       }
+#endif /* WITH_WSREP */
     }
     else
       error= (type == KILL_TYPE_QUERY ? ER_KILL_QUERY_DENIED_ERROR :
@@ -9565,7 +9571,9 @@ void sql_kill(THD *thd, my_thread_id id, killed_state state, killed_type type)
       thd->send_kill_message();
   }
   else
+  {
     my_error(error, MYF(0), id);
+  }
 }