BUG#26042764: BACKPORT BUG#25642343 AND BUG#24311527 TO 5.7

BUG#24311527: PLUGIN-LOAD FAILS AFTER MYSQLD --INITIALIZE
BUG#25642343: THE SERVER SHOULD HAVE A DEFAULT USER FOR THE SERVER SESION SERVICE

There were two leaks after the above patch was introduced:
  1) There was a possible memory leak on method
     Session_plugin_thread::terminate_session_thread(), on which the
     terminate event could be queued after the thread handler being
     already terminated. This would cause the terminate event memory
     not to be released.
     In order to prevent that, the
     Session_plugin_thread::terminate_session_thread ensures that
     when it ends all queued events are released.

  2) When the Group Replication was not able to contact the server
     core through the SQL API, some memory structures were not being
     released.
     Now that memory structures are properly released.

Author: nacarvalho

rapid/plugin/group_replication/src/delayed_plugin_initialization.cc

@@ -148,6 +148,18 @@ int Delayed_initialization_thread::initialization_thread_handler()
     DBUG_ASSERT(server_engine_initialized());
     wait_on_engine_initialization= false;
 
+    //Avoid unnecessary operations
+    bool enabled_super_read_only= false;
+
+    char *hostname, *uuid;
+    uint port;
+    unsigned int server_version;
+    st_server_ssl_variables server_ssl_variables=
+      {false,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL};
+
+    get_server_parameters(&hostname, &port, &uuid, &server_version,
+                          &server_ssl_variables);
+
     sql_command_interface= new Sql_service_command_interface();
     if (sql_command_interface->
             establish_session_connection(PSESSION_INIT_THREAD,
@@ -158,22 +170,11 @@ int Delayed_initialization_thread::initialization_thread_handler()
       log_message(MY_ERROR_LEVEL,
                   "It was not possible to establish a connection to "
                     "server SQL service");
-      goto end;
+      error= 1;
+      goto err;
       /* purecov: end */
     }
 
-    //Avoid unnecessary operations
-    bool enabled_super_read_only= false;
-
-    char *hostname, *uuid;
-    uint port;
-    unsigned int server_version;
-    st_server_ssl_variables server_ssl_variables=
-      {false,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL};
-
-    get_server_parameters(&hostname, &port, &uuid, &server_version,
-                          &server_ssl_variables);
-
     if ((error= configure_group_communication(&server_ssl_variables)))
       goto err; /* purecov: inspected */
 

rapid/plugin/group_replication/src/sql_service/sql_service_command.cc

@@ -640,6 +640,13 @@ Session_plugin_thread::terminate_session_thread()
 
   DBUG_ASSERT(!m_session_thread_running);
 
+  while (!this->incoming_methods->empty())
+  {
+    st_session_method *method= NULL;
+    this->incoming_methods->pop(&method);
+    my_free(method);
+  }
+
   mysql_mutex_unlock(&m_run_lock);
 
   DBUG_RETURN(0);