Bug#32989716: MISSING CORRECT CLOSE SESSION HANDLING DURING

              KEYRING MIGRATION

Description: Keyring migration server uses a mysql
connection to perform online migration. This mysql session
is not closed gracefully after the migration. This leads to
a 'Note' being printed on the online server error log:-
"[Note] Aborted connection x to db: 'xyz' user: 'abc' host:
'localhost' (Got an error reading communication packets)"

Analysis: After the online keyring migration, migration
server process is aborted before gracefully closing the
mysql session. This happens because the migration server
process exits before calling the destructor of
'Migrate_keyring', where the closing of the mysql session
is handled.

Fix: This issue is fixed in 8.0 as part of a code
refactoring done in this area by WL#13446. Back-porting the
relevant code changes to 5.7 to fix this bug and to make
the code consistent across versions.

RB#27186

Author: Arun Kuruvila

sql/mysqld.cc

@@ -4704,37 +4704,43 @@ int mysqld_main(int argc, char **argv)
       opt_keyring_migration_destination ||
       migrate_connect_options)
   {
-    Migrate_keyring mk;
-    if (mk.init(remaining_argc, remaining_argv,
-                opt_keyring_migration_source,
-                opt_keyring_migration_destination,
-                opt_keyring_migration_user,
-                opt_keyring_migration_host,
-                opt_keyring_migration_password,
-                opt_keyring_migration_socket,
-                opt_keyring_migration_port))
+    int exit_state = MYSQLD_ABORT_EXIT;
+    while (true)
     {
-      sql_print_error(ER_DEFAULT(ER_KEYRING_MIGRATION_STATUS),
-                      "failed");
-      log_error_dest= "stderr";
-      flush_error_log_messages();
-      unireg_abort(MYSQLD_ABORT_EXIT);
-    }
+      Migrate_keyring mk;
+      if (mk.init(remaining_argc, remaining_argv,
+                  opt_keyring_migration_source,
+                  opt_keyring_migration_destination,
+                  opt_keyring_migration_user,
+                  opt_keyring_migration_host,
+                  opt_keyring_migration_password,
+                  opt_keyring_migration_socket,
+                  opt_keyring_migration_port))
+      {
+        sql_print_error(ER_DEFAULT(ER_KEYRING_MIGRATION_STATUS),
+                        "failed");
+        log_error_dest= "stderr";
+        flush_error_log_messages();
+        break;
+      }
 
-    if (mk.execute())
-    {
-      sql_print_error(ER_DEFAULT(ER_KEYRING_MIGRATION_STATUS),
-                      "failed");
+      if (mk.execute())
+      {
+        sql_print_error(ER_DEFAULT(ER_KEYRING_MIGRATION_STATUS),
+                        "failed");
+        log_error_dest= "stderr";
+        flush_error_log_messages();
+        break;
+      }
+
+      sql_print_information(ER_DEFAULT(ER_KEYRING_MIGRATION_STATUS),
+                            "successful");
       log_error_dest= "stderr";
       flush_error_log_messages();
-      unireg_abort(MYSQLD_ABORT_EXIT);
+      exit_state = MYSQLD_SUCCESS_EXIT;
+      break;
     }
-
-    sql_print_information(ER_DEFAULT(ER_KEYRING_MIGRATION_STATUS),
-                          "successful");
-    log_error_dest= "stderr";
-    flush_error_log_messages();
-    unireg_abort(MYSQLD_SUCCESS_EXIT);
+    unireg_abort(exit_state);
   }
 
   /*