tokudb_tmp_dir导致的tokudb加载失败

安装TOKUDB数据库，安装完成后为了使配置生效，重启完数据库后，发现：

mysql> show engines;
+--------------------+---------+
| Engine             　| Support |
+--------------------+---------+
| InnoDB            　　| DEFAULT |
| CSV                　 | YES     |
| MRG_MYISAM      　　　 | YES     |
| BLACKHOLE         　　 | YES     |
| MEMORY             　　| YES     |
| PERFORMANCE_SCHEMA    | YES     |
| ARCHIVE             　 | YES     |
| MyISAM             　　 | YES     |
| FEDERATED          　　| NO      |
+--------------------+---------+
9 rows in set (0.06 sec)

无tokudb存储引擎，检查错误日志发现：

2016-06-15 20:08:18 5163 [Note] InnoDB:  Percona XtraDB (http://www.percona.com) 5.6.25-rel73.0 started; log sequence number 1626012
Couldn't start tokuft because some other tokuft process is using the same directory [/mysql/data/tmpdir] for [temp]
2016-06-15 20:08:18 5163 [ERROR] TokuDB unknown error 2
2016-06-15 20:08:18 5163 [ERROR] Plugin 'TokuDB' init function returned error.
2016-06-15 20:08:18 5163 [ERROR] Plugin 'TokuDB' registration as a STORAGE ENGINE failed.

原来是tokudb的配置参数tokudb_tmp_dir指定的目录不存在

解决方法：

mkdir /mysql/data/tmpdir
chown -R mysql.mysql /mysql/data/tmpdir

重启数据库：

mysql> show engines;
+--------------------+---------+-
| Engine             | Support |
+--------------------+---------+-
| InnoDB             | DEFAULT |
| CSV                | YES     |
| MRG_MYISAM         | YES     |
| BLACKHOLE          | YES     |
| MEMORY             | YES     |
| TokuDB             | YES     |
| PERFORMANCE_SCHEMA | YES     |
| ARCHIVE            | YES     |
| MyISAM             | YES     |
| FEDERATED          | NO      |
+--------------------+---------+-
10 rows in set (0.08 sec)

如上所示，tokudb已支持。