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背景介绍
在我的项目选型中,在 KVM(16c 16G ssd160G) 的 Linux7.6 零碎上部署了 MYSQL MGR 集群 (GreatSQL 8.0.25)。
应用 sysbench 创立了 100 仓数据,且针对表创立为 partition 表,进行间断 12 小时的稳固下压测,来评估对应的架构的可能撑持的业务并发数,以及最高的 TPS/QPS 是多少。
在应用 256 并发,间断压测进行了 12 个小时之后,发现节点的 SSD 磁盘空间使用率达到 95% 以上,过后第一工夫去查看 log 目录,log 目录曾经达到 100G+,认为是 binlog 设置的工夫太长导致的 binlog 没有及时清理造成的,去清理 binlogbinlog 过期工夫设置的 1800s,理论 binlog 和 MGR 的 relay-group 空间占用在 11G 左右而 du -sh * 查看到的日志文件大小时,发现其中 undo 大小 1 个是 71G 另一个 4.1G,且 MGR 的 3 个节点的 undo 均是这个状况,急需开释空间。
然而 MySQL8.0 是否反对类型 oracle 的 undo 在线的替换来进行膨胀呢,答案是必定的,而且有些相似。
oracle/mysql undo 表空间设置主动扩大,如果业务上有跑批量或者大表的 DML 操作时,引起大事物,或针对多张大表关联更新工夫较长,可能短时间内会将 undo” 撑大 ”,oracle 咱们能够通过创立一个新的 undo,通过在线的替换的形式,将收缩的 undo 应用 drop 删除以开释空间。
mysql 8.0 同样能够应用这种形式来解决,因大事物或长事物引起的 undo 过大占用空间较多的状况。
办法如下
- 1、增加新的 undo 文件 undo003。mysql8.0 中默认 innodb_undo_tablespace 为 2 个,有余 2 个时,不容许设置为 inactive,且默认创立的 undo 受爱护,不容许删除。
- 2、将收缩的 undo 长期设置为 inactive,以及 innodb_undo_log_truncate=on,主动 truncate 开释收缩的 undo 空间。
- 3、从新将开释空间之后的 undo 设置为 active,可从新上线应用。
具体操作如下
[greatdb@mysql ~]$ mysql -ugreatsql -pgreatsql -h172.16.130.15 -P3307
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 74
Server version: 8.0.25-15 GreatSQL, Release 15, Revision c7feae175e0
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql[(none)]> show variables like '%undo%';
+--------------------------+-----------------------------+
| Variable_name | Value |
+--------------------------+-----------------------------+
| innodb_max_undo_log_size | 4294967296 |
| innodb_undo_directory | /app/dbdata/sqlnode3306/log |
| innodb_undo_log_encrypt | OFF |
| innodb_undo_log_truncate | ON |
| innodb_undo_tablespaces | 2 |
+--------------------------+-----------------------------+
5 rows in set (0.01 sec)
1、查看 undo 大小
mysql[(none)]> system du -sh /app/dbdata/datanode3307/log/undo*
4.1G /app/dbdata/datanode3307/log/undo_001
71G /app/dbdata/datanode3307/log/undo_002 -----12 小时间断稳定性压测,导致节点 undo 过大,达到 71G
2、增加新的 undo 表空间 undo003。零碎默认是 2 个 undo,大小设置 4G
mysql[(none)]>
mysql[(none)]> create undo tablespace undo003 add datafile '/app/dbdata/datanode3307/log/undo003.ibu';
Query OK, 0 rows affected (0.21 sec)
留神:创立增加新的 undo 必须以.ibu 结尾,否则触发如下谬误提醒
mysql[(none)]> create undo tablespace undo003 add datafile '/app/dbdata/datanode3307/log/undo_003.' ;
ERROR 3121 (HY000): The ADD DATAFILE filepath must end with '.ibu'.
3、查看零碎中的 undo 表空间信息,如下:
mysql[(none)]> select * from information_schema.INNODB_TABLESPACES where name like '%undo%';
+------------+-----------------+------+------------+-----------+---------------+------------+---------------+-------------+----------------+-----------------+----------------+---------------+------------+--------+
| SPACE | NAME | FLAG | ROW_FORMAT | PAGE_SIZE | ZIP_PAGE_SIZE | SPACE_TYPE | FS_BLOCK_SIZE | FILE_SIZE | ALLOCATED_SIZE | AUTOEXTEND_SIZE | SERVER_VERSION | SPACE_VERSION | ENCRYPTION | STATE |
+------------+-----------------+------+------------+-----------+---------------+------------+---------------+-------------+----------------+-----------------+----------------+---------------+------------+--------+
| 4294967279 | innodb_undo_001 | 0 | Undo | 16384 | 0 | Undo | 4096 | 4311744512 | 4311764992 | 0 | 8.0.25 | 1 | N | active |
| 4294967278 | innodb_undo_002 | 0 | Undo | 16384 | 0 | Undo | 4096 | 76067897344 | 76068229120 | 0 | 8.0.25 | 1 | N | active |
| 4294967277 | undo003 | 0 | Undo | 16384 | 0 | Undo | 4096 | 16777216 | 16777216 | 0 | 8.0.25 | 1 | N | active |
+------------+-----------------+------+------------+-----------+---------------+------------+---------------+-------------+----------------+-----------------+----------------+---------------+------------+--------+
3 rows in set (0.03 sec)
4、查看到上述视图中 innodb_undo_002 大小达到 76067897344(约 71G)其状态 state 为 active。手动将其设置为 inactive,使其主动触发 innodb_undo_log_truncate 回收。
mysql[(none)]> alter undo tablespace innodb_undo_002 set inactive;
Query OK, 0 rows affected (0.00 sec)
5、查看对应视图如下
mysql[(none)]> select * from information_schema.INNODB_TABLESPACES where name like '%undo%';
+------------+-----------------+------+------------+-----------+---------------+------------+---------------+------------+----------------+-----------------+----------------+---------------+------------+--------+
| SPACE | NAME | FLAG | ROW_FORMAT | PAGE_SIZE | ZIP_PAGE_SIZE | SPACE_TYPE | FS_BLOCK_SIZE | FILE_SIZE | ALLOCATED_SIZE | AUTOEXTEND_SIZE | SERVER_VERSION | SPACE_VERSION | ENCRYPTION | STATE |
+------------+-----------------+------+------------+-----------+---------------+------------+---------------+------------+----------------+-----------------+----------------+---------------+------------+--------+
| 4294967279 | innodb_undo_001 | 0 | Undo | 16384 | 0 | Undo | 4096 | 4311744512 | 4311764992 | 0 | 8.0.25 | 1 | N | active |
| 4294967151 | innodb_undo_002 | 0 | Undo | 16384 | 0 | Undo | 4096 | 16777216 | 2179072 | 0 | 8.0.25 | 1 | N | empty |
| 4294967277 | undo003 | 0 | Undo | 16384 | 0 | Undo | 4096 | 16777216 | 16777216 | 0 | 8.0.25 | 1 | N | active |
+------------+-----------------+------+------------+-----------+---------------+------------+---------------+------------+----------------+-----------------+----------------+---------------+------------+--------+
3 rows in set (0.01 sec)
此时能够查看对应操作系统目录中的 undo_002 大小,innodb_undo_002 FILE_SIZE 16777216 默认大小 2179072,STATE 为 empty
mysql[(none)]> system du -sh /app/dbdata/datanode3307/log/undo*
4.1G /app/dbdata/datanode3307/log/undo_001
2.1M /app/dbdata/datanode3307/log/undo_002
16M /app/dbdata/datanode3307/log/undo003.ibu
6、从新将其设置为 active 状态
mysql[(none)]> alter undo tablespace innodb_undo_002 set active;
Query OK, 0 rows affected (0.01 sec)
mysql[(none)]> select * from information_schema.INNODB_TABLESPACES where name like '%undo%';
+------------+-----------------+------+------------+-----------+---------------+------------+---------------+------------+----------------+-----------------+----------------+---------------+------------+--------+
| SPACE | NAME | FLAG | ROW_FORMAT | PAGE_SIZE | ZIP_PAGE_SIZE | SPACE_TYPE | FS_BLOCK_SIZE | FILE_SIZE | ALLOCATED_SIZE | AUTOEXTEND_SIZE | SERVER_VERSION | SPACE_VERSION | ENCRYPTION | STATE |
+------------+-----------------+------+------------+-----------+---------------+------------+---------------+------------+----------------+-----------------+----------------+---------------+------------+--------+
| 4294967279 | innodb_undo_001 | 0 | Undo | 16384 | 0 | Undo | 4096 | 4311744512 | 4311764992 | 0 | 8.0.25 | 1 | N | active |
| 4294967151 | innodb_undo_002 | 0 | Undo | 16384 | 0 | Undo | 4096 | 16777216 | 2195456 | 0 | 8.0.25 | 1 | N | active |
| 4294967277 | undo003 | 0 | Undo | 16384 | 0 | Undo | 4096 | 16777216 | 16777216 | 0 | 8.0.25 | 1 | N | active |
+------------+-----------------+------+------------+-----------+---------------+------------+---------------+------------+----------------+-----------------+----------------+---------------+------------+--------+
3 rows in set (0.01 sec)
7、有人说,为什么间接不能间接针对收缩的 undo 设置为 inactive,零碎默认创立的 undo 表空间默认 2 个,处于 active 小于 2 个时,会有如下提醒:
mysql[(none)]> mysql[(none)]> show variables like 'innodb_undo_tablespaces';
+--------------------------+-----------------------------+
| Variable_name | Value |
+--------------------------+-----------------------------+
| innodb_undo_tablespaces | 2 |
+--------------------------+-----------------------------+
5 rows in set (0.01 sec)
mysql[(none)]> alter undo tablespace innodb_undo_002 set inactive;
ERROR 3655 (HY000): Cannot set innodb_undo_002 inactive since there would be less than 2 undo tablespaces left active.
mysql[(none)]>
8、新创建增加的能够失常设置为 inactive 之后,应用 drop 形式删除,如下:
mysql[(none)]> alter undo tablespace undo003 set inactive;
Query OK, 0 rows affected (0.00 sec)
mysql[(none)]> drop undo tablespace undo003;
Query OK, 0 rows affected (0.01 sec)
mysql[(none)]> select * from information_schema.INNODB_TABLESPACES where name like '%undo%';
+------------+-----------------+------+------------+-----------+---------------+------------+---------------+------------+----------------+-----------------+----------------+---------------+------------+--------+
| SPACE | NAME | FLAG | ROW_FORMAT | PAGE_SIZE | ZIP_PAGE_SIZE | SPACE_TYPE | FS_BLOCK_SIZE | FILE_SIZE | ALLOCATED_SIZE | AUTOEXTEND_SIZE | SERVER_VERSION | SPACE_VERSION | ENCRYPTION | STATE |
+------------+-----------------+------+------------+-----------+---------------+------------+---------------+------------+----------------+-----------------+----------------+---------------+------------+--------+
| 4294967279 | innodb_undo_001 | 0 | Undo | 16384 | 0 | Undo | 4096 | 4311744512 | 4311764992 | 0 | 8.0.25 | 1 | N | active |
| 4294967151 | innodb_undo_002 | 0 | Undo | 16384 | 0 | Undo | 4096 | 16777216 | 2244608 | 0 | 8.0.25 | 1 | N | active |
+------------+-----------------+------+------------+-----------+---------------+------------+---------------+------------+----------------+-----------------+----------------+---------------+------------+--------+
2 rows in set (0.01 sec)
总结
通过以上操作咱们就能够针对 unod 因遇到大事务,undo 持续增长的状况下,通过新增长期 undo,手动开释零碎默认的 2 个 undo 表空间 大小。
当然截断 UNDO 表空间文件对数据库性能是有肯定的影响的,尽量在绝对闲暇工夫进行。
当 UNDO 表空间被截断时,UNDO 表空间中的回滚段将被停用。其余 UNDO 表空间中的流动回滚段负责整个零碎负载,这可能会导致性能略有降落。性能受影响的水平取决于许多因素:
- 1、UNDO 表空间的数量
- 2、UNDO 记录日志的数据量
- 3、UNDO 表空间大小
- 4、磁盘 I / O 零碎的速度
- 5、现有长期运行的事务
那么防止潜在性能影响的最简略的办法:
- 1、就是通过 create undo tablespace undo_XXX add datafile ‘/path/undo_xxx.ibu’; 多增加几个 UNDO 表空间。
- 2、磁盘上如果条件容许采纳高性能的 SSD 来存储数据,存储 REDO,UNDO 等。
- 引起 UNDO 适度收缩的起因大多数是因为根底数据量大,业务并发高,表关联操作较频繁,呈现大且长的事物操作,导致 UNDO 始终处于 active 状态,不能及时开释回滚段等起因,大事物引起的问题由来已久,即便咱们能躲避 99% 的大事物,但理论业务遇到那 1% 的大事物刚性需要发过来时,这还要咱们的 MySQL 各种场景,各种架构和业务层好好磨合磨合。
Enjoy GreatSQL :)
文章举荐:
GreatSQL MGR FAQ
https://mp.weixin.qq.com/s/J6…
万答 #12,MGR 整个集群挂掉后,如何能力主动选主,不必手动干涉
https://mp.weixin.qq.com/s/07…
『2021 数据技术嘉年华·ON LINE』:《MySQL 高可用架构演进及实际》
https://mp.weixin.qq.com/s/u7…
一条 sql 语句慢在哪之抓包剖析
https://mp.weixin.qq.com/s/AY…
万答 #15,都有哪些状况可能导致 MGR 服务无奈启动
https://mp.weixin.qq.com/s/in…
技术分享 | 为什么 MGR 一致性模式不举荐 AFTER
https://mp.weixin.qq.com/s/rN…
对于 GreatSQL
GreatSQL 是由万里数据库保护的 MySQL 分支,专一于晋升 MGR 可靠性及性能,反对 InnoDB 并行查问个性,是实用于金融级利用的 MySQL 分支版本。
Gitee:
https://gitee.com/GreatSQL/Gr…
GitHub:
https://github.com/GreatSQL/G…
Bilibili:
https://space.bilibili.com/13…
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