MDEV-12009: Allow to force kill user threads/query which are flagged as high priority by Galera

As noted on kill_one_thread SUPER should be able to kill even
system threads i.e. threads/query flagged as high priority or
wsrep applier thread. Normal user, should not able to kill
threads/query flagged as high priority (BF) or wsrep applier
thread.

include/mysql/service_wsrep.h

@@ -112,6 +112,7 @@ extern struct wsrep_service_st {
   int                         (*wsrep_trx_order_before_func)(MYSQL_THD, MYSQL_THD);
   void                        (*wsrep_unlock_rollback_func)();
   void                        (*wsrep_set_data_home_dir_func)(const char *data_dir);
+  my_bool                     (*wsrep_thd_is_applier_func)(THD *thd);
 } *wsrep_service;
 
 #ifdef MYSQL_DYNAMIC_PLUGIN
@@ -155,6 +156,7 @@ extern struct wsrep_service_st {
 #define wsrep_trx_order_before(T1,T2) wsrep_service->wsrep_trx_order_before_func(T1,T2)
 #define wsrep_unlock_rollback() wsrep_service->wsrep_unlock_rollback_func()
 #define wsrep_set_data_home_dir(A) wsrep_service->wsrep_set_data_home_dir_func(A)
+#define wsrep_thd_is_applier(T) wsrep_service->wsrep_thd_is_applier_func(T)
 
 #define wsrep_debug get_wsrep_debug()
 #define wsrep_log_conflicts get_wsrep_log_conflicts()
@@ -214,6 +216,7 @@ void wsrep_thd_set_conflict_state(THD *thd, enum wsrep_conflict_state state);
 bool wsrep_thd_ignore_table(THD *thd);
 void wsrep_unlock_rollback();
 void wsrep_set_data_home_dir(const char *data_dir);
+my_bool wsrep_thd_is_applier(THD *thd);
 
 #endif
 

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

@@ -1,4 +1,8 @@
+CREATE USER foo@localhost;
+GRANT SELECT on test.* TO foo@localhost;
+# Open connection to the 1st node using 'test_user1' user.
 Got one of the listed errors
 Got one of the listed errors
 Got one of the listed errors
 Got one of the listed errors
+DROP USER foo@localhost;

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

@@ -0,0 +1,10 @@
+!include ../galera_2nodes.cnf
+
+[mysqld.1]
+wsrep_provider_options='base_port=@mysqld.1.#galera_port;pc.ignore_sb=true'
+auto_increment_offset=1
+
+[mysqld.2]
+wsrep_provider_options='base_port=@mysqld.2.#galera_port;pc.ignore_sb=true'
+auto_increment_offset=2
+

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

@@ -1,14 +1,25 @@
 #
 # This test checks that applier threads are immune to KILL QUERY and KILL STATEMENT
+# when USER is not SUPER
 #
 
 --source include/galera_cluster.inc
---source include/have_innodb.inc
 
 --connection node_1
 
+CREATE USER foo@localhost;
+GRANT SELECT on test.* TO foo@localhost;
+
 --let $applier_thread = `SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE != 'wsrep aborter idle' OR STATE IS NULL LIMIT 1`
 
+--let $aborter_thread = `SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep aborter idle' LIMIT 1`
+
+--echo # Open connection to the 1st node using 'test_user1' user.
+--let $port_1= \$NODE_MYPORT_1
+--connect(foo_node_1,localhost,foo,,test,$port_1,)
+
+--connection foo_node_1
+
 --disable_query_log
 --error ER_KILL_DENIED_ERROR,ER_KILL_DENIED_ERROR
 --eval KILL $applier_thread
@@ -16,11 +27,48 @@
 --error ER_KILL_DENIED_ERROR,ER_KILL_DENIED_ERROR
 --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`
-
 --error ER_KILL_DENIED_ERROR,ER_KILL_DENIED_ERROR
 --eval KILL $aborter_thread
 
 --error ER_KILL_DENIED_ERROR,ER_KILL_DENIED_ERROR
 --eval KILL QUERY $aborter_thread
 --enable_query_log
+
+#
+# SUPER can kill applier threads
+#
+--connection node_2
+
+--let $applier_thread = `SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE != 'wsrep aborter idle' OR STATE IS NULL LIMIT 1`
+
+--disable_query_log
+--eval KILL $applier_thread
+--enable_query_log
+
+--let $aborter_thread = `SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep aborter idle' LIMIT 1`
+
+--disable_query_log
+--eval KILL $aborter_thread
+--enable_query_log
+
+--source include/restart_mysqld.inc
+
+--connection node_2
+--let $applier_thread = `SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE != 'wsrep aborter idle' OR STATE IS NULL LIMIT 1`
+
+--disable_query_log
+--eval KILL QUERY $applier_thread
+--enable_query_log
+
+--let $aborter_thread = `SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST WHERE USER = 'system user' AND STATE = 'wsrep aborter idle' LIMIT 1`
+
+--disable_query_log
+--eval KILL QUERY $aborter_thread
+--enable_query_log
+
+--source include/restart_mysqld.inc
+
+--connection node_1
+--disconnect foo_node_1
+DROP USER foo@localhost;
+

sql/sql_parse.cc

@@ -8292,11 +8292,19 @@ kill_one_thread(THD *thd, longlong id, killed_state kill_signal, killed_type typ
       It's ok to also kill DELAYED threads with KILL_CONNECTION instead of
       KILL_SYSTEM_THREAD; The difference is that KILL_CONNECTION may be
       faster and do a harder kill than KILL_SYSTEM_THREAD;
+
+      Note that if thread is wsrep Brute Force or applier thread we
+      allow killing it only when we're SUPER.
     */
 
-    if (((thd->security_ctx->master_access & SUPER_ACL) ||
-        thd->security_ctx->user_matches(tmp->security_ctx)) &&
-	!wsrep_thd_is_BF(tmp, false))
+    if ((thd->security_ctx->master_access & SUPER_ACL) ||
+	(thd->security_ctx->user_matches(tmp->security_ctx)
+#ifdef WITH_WSREP
+	 &&
+	 !tmp->wsrep_applier &&
+	 !wsrep_thd_is_BF(tmp, false)
+#endif
+	))
     {
       tmp->awake(kill_signal);
       error=0;

sql/sql_plugin_services.ic

@@ -181,7 +181,8 @@ static struct wsrep_service_st wsrep_handler = {
   wsrep_trx_is_aborting,
   wsrep_trx_order_before,
   wsrep_unlock_rollback,
-  wsrep_set_data_home_dir
+  wsrep_set_data_home_dir,
+  wsrep_thd_is_applier,
 };
 
 static struct thd_specifics_service_st thd_specifics_handler=

sql/wsrep_dummy.cc

@@ -20,6 +20,9 @@
 my_bool wsrep_thd_is_BF(THD *, my_bool)
 { return 0; }
 
+my_bool wsrep_thd_is_applier(THD *)
+{ return 0; }
+
 int wsrep_trx_order_before(THD *, THD *)
 { return 0; }
 

sql/wsrep_mysqld.cc

@@ -2470,7 +2470,6 @@ extern "C" void wsrep_thd_set_exec_mode(THD *thd, enum wsrep_exec_mode mode)
   thd->wsrep_exec_mode= mode;
 }
 
-
 extern "C" void wsrep_thd_set_query_state(
 	THD *thd, enum wsrep_query_state state)
 {

sql/wsrep_thd.cc

@@ -596,6 +596,15 @@ my_bool wsrep_thd_is_BF(THD *thd, my_bool sync)
   return status;
 }
 
+my_bool wsrep_thd_is_applier(THD *thd)
+{
+  my_bool ret = FALSE;
+  if (thd) {
+      ret = thd->wsrep_applier;
+  }
+  return ret;
+}
+
 extern "C"
 my_bool wsrep_thd_is_BF_or_commit(void *thd_ptr, my_bool sync)
 {

sql/wsrep_thd.h

@@ -37,6 +37,7 @@ int  wsrep_abort_thd(void *bf_thd_ptr, void *victim_thd_ptr,
 */
 extern void  wsrep_thd_set_PA_safe(void *thd_ptr, my_bool safe);
 extern my_bool  wsrep_thd_is_BF(THD *thd, my_bool sync);
+extern my_bool wsrep_thd_is_applier(THD *thd);
 extern my_bool wsrep_thd_is_wsrep(void *thd_ptr);
 
 enum wsrep_conflict_state wsrep_thd_conflict_state(void *thd_ptr, my_bool sync);
@@ -47,6 +48,7 @@ extern "C" int  wsrep_thd_in_locking_session(void *thd_ptr);
 #else /* WITH_WSREP */
 
 #define wsrep_thd_is_BF(T, S) (0)
+#define wsrep_thd_is_applier(T) (0)
 #define wsrep_abort_thd(X,Y,Z) do { } while(0)
 #define wsrep_create_appliers(T) do { } while(0)