MDEV-9312: storage engine not enforced during galera cluster replication

Perform a post initialization of plugin-related variables
of wsrep threads after their global counterparts have been
initialized.

4 files changed, 91 insertions, 26 deletions

diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index 8da8273083c..f69416c34ea 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -5077,6 +5077,12 @@ static int init_server_components()
   }
 
   /*
+    Since some wsrep threads (THDs) are create before plugins are
+    initialized, LOCK_plugin mutex needs to be initialized here.
+  */
+  plugin_mutex_init();
+
+  /*
     Wsrep initialization must happen at this point, because:
     - opt_bin_logname must be known when starting replication
       since SST may need it
@@ -5304,6 +5310,15 @@ static int init_server_components()
 #endif
 
 #ifdef WITH_WSREP
+  /*
+    Now is the right time to initialize members of wsrep startup threads
+    that rely on plugins and other related global system variables to be
+    initialized. This initialization was not possible before, as plugins
+    (and thus some global system variables) are initialized after wsrep
+    startup threads are created.
+  */
+  wsrep_plugins_post_init();
+
   if (WSREP_ON && !opt_bin_log)
   {
     wsrep_emulate_bin_log= 1;
diff --git a/sql/sql_plugin.cc b/sql/sql_plugin.cc
index e7286960599..d86876a973b 100644
--- a/sql/sql_plugin.cc
+++ b/sql/sql_plugin.cc
@@ -1548,9 +1548,6 @@ int plugin_init(int *argc, char **argv, int flags)
                    get_bookmark_hash_key, NULL, HASH_UNIQUE))
       goto err;
 
-
-  mysql_mutex_init(key_LOCK_plugin, &LOCK_plugin, MY_MUTEX_INIT_FAST);
-
   if (my_init_dynamic_array(&plugin_dl_array,
                             sizeof(struct st_plugin_dl *), 16, 16, MYF(0)) ||
       my_init_dynamic_array(&plugin_array,
@@ -3098,28 +3095,19 @@ void plugin_thdvar_init(THD *thd)
   thd->variables.dynamic_variables_size= 0;
   thd->variables.dynamic_variables_ptr= 0;
 
-  if (IF_WSREP((!WSREP(thd) || !thd->wsrep_applier),1))
-  {
-    mysql_mutex_lock(&LOCK_plugin);
-    thd->variables.table_plugin=
-        intern_plugin_lock(NULL, global_system_variables.table_plugin);
-    if (global_system_variables.tmp_table_plugin)
-      thd->variables.tmp_table_plugin=
-            intern_plugin_lock(NULL, global_system_variables.tmp_table_plugin);
-    if (global_system_variables.enforced_table_plugin)
-      thd->variables.enforced_table_plugin=
-            intern_plugin_lock(NULL, global_system_variables.enforced_table_plugin);
-    intern_plugin_unlock(NULL, old_table_plugin);
-    intern_plugin_unlock(NULL, old_tmp_table_plugin);
-    intern_plugin_unlock(NULL, old_enforced_table_plugin);
-    mysql_mutex_unlock(&LOCK_plugin);
-  }
-  else
-  {
-    thd->variables.table_plugin= NULL;
-    thd->variables.tmp_table_plugin= NULL;
-    thd->variables.enforced_table_plugin= NULL;
-  }
+  mysql_mutex_lock(&LOCK_plugin);
+  thd->variables.table_plugin=
+      intern_plugin_lock(NULL, global_system_variables.table_plugin);
+  if (global_system_variables.tmp_table_plugin)
+    thd->variables.tmp_table_plugin=
+          intern_plugin_lock(NULL, global_system_variables.tmp_table_plugin);
+  if (global_system_variables.enforced_table_plugin)
+    thd->variables.enforced_table_plugin=
+          intern_plugin_lock(NULL, global_system_variables.enforced_table_plugin);
+  intern_plugin_unlock(NULL, old_table_plugin);
+  intern_plugin_unlock(NULL, old_tmp_table_plugin);
+  intern_plugin_unlock(NULL, old_enforced_table_plugin);
+  mysql_mutex_unlock(&LOCK_plugin);
 
   DBUG_VOID_RETURN;
 }
@@ -4243,3 +4231,51 @@ int thd_setspecific(MYSQL_THD thd, MYSQL_THD_KEY_T key, void *value)
   return 0;
 }
 
+void plugin_mutex_init()
+{
+  mysql_mutex_init(key_LOCK_plugin, &LOCK_plugin, MY_MUTEX_INIT_FAST);
+}
+
+#ifdef WITH_WSREP
+
+/*
+  Placeholder for global_system_variables.table_plugin required during
+  initialization of startup wsrep threads.
+*/
+static st_plugin_int wsrep_dummy_plugin;
+static st_plugin_int *wsrep_dummy_plugin_ptr;
+
+/*
+  Initialize wsrep_dummy_plugin and assign it to
+  global_system_variables.table_plugin.
+*/
+void wsrep_plugins_pre_init()
+{
+  wsrep_dummy_plugin_ptr= &wsrep_dummy_plugin;
+  wsrep_dummy_plugin.state= PLUGIN_IS_DISABLED;
+  global_system_variables.table_plugin=
+    plugin_int_to_ref(wsrep_dummy_plugin_ptr);
+}
+
+/*
+  This function is intended to be called after the plugins and related
+  global system variables are initialized. It re-initializes some data
+  members of wsrep startup threads with correct values, as these value
+  were not available at the time these threads were created.
+*/
+void wsrep_plugins_post_init()
+{
+  THD *thd;
+  I_List_iterator<THD> it(threads);
+
+  while ((thd= it++))
+  {
+    if (IF_WSREP(thd->wsrep_applier,1))
+    {
+      plugin_thdvar_init(thd);
+    }
+  }
+
+  return;
+}
+#endif /* WITH_WSREP */
diff --git a/sql/sql_plugin.h b/sql/sql_plugin.h
index 77ec24bbe9c..d11c449962a 100644
--- a/sql/sql_plugin.h
+++ b/sql/sql_plugin.h
@@ -180,6 +180,7 @@ sys_var *find_plugin_sysvar(st_plugin_int *plugin, st_mysql_sys_var *var);
 void plugin_opt_set_limits(struct my_option *, const struct st_mysql_sys_var *);
 extern SHOW_COMP_OPTION plugin_status(const char *name, size_t len, int type);
 extern bool check_valid_path(const char *path, size_t length);
+extern void plugin_mutex_init();
 
 typedef my_bool (plugin_foreach_func)(THD *thd,
                                       plugin_ref plugin,
@@ -194,3 +195,9 @@ extern bool plugin_dl_foreach(THD *thd, const LEX_STRING *dl,
 
 extern void sync_dynamic_session_variables(THD* thd, bool global_lock);
 #endif
+
+#ifdef WITH_WSREP
+extern void wsrep_plugins_pre_init();
+extern void wsrep_plugins_post_init();
+#endif /* WITH_WSREP */
+
diff --git a/sql/wsrep_mysqld.cc b/sql/wsrep_mysqld.cc
index 776bf4a3ab2..5f25ea1ef38 100644
--- a/sql/wsrep_mysqld.cc
+++ b/sql/wsrep_mysqld.cc
@@ -36,6 +36,7 @@
 #include <cstdlib>
 #include "log_event.h"
 #include <slave.h>
+#include "sql_plugin.h"                         /* wsrep_plugins_pre_init() */
 
 wsrep_t *wsrep                  = NULL;
 /*
@@ -771,7 +772,6 @@ void wsrep_thr_init()
   mysql_mutex_init(key_LOCK_wsrep_config_state, &LOCK_wsrep_config_state, MY_MUTEX_INIT_FAST);
 }
 
-
 void wsrep_init_startup (bool first)
 {
   if (wsrep_init()) unireg_abort(1);
@@ -782,6 +782,13 @@ void wsrep_init_startup (bool first)
      wsrep_debug, wsrep_convert_LOCK_to_trx,
      (wsrep_on_fun)wsrep_on);
 
+  /*
+    Pre-initialize global_system_variables.table_plugin with a dummy engine
+    (placeholder) required during the initialization of wsrep threads (THDs).
+    (see: plugin_thdvar_init())
+  */
+  wsrep_plugins_pre_init();
+
   /* Skip replication start if dummy wsrep provider is loaded */
   if (!strcmp(wsrep_provider, WSREP_NONE)) return;