Ⅰ、功能分析
1.1 多线程介绍
- mysqlpump是MySQL5.7的官方工具,用于取代mysqldump,其参数与mysqldump基本一样
- mysqlpump是多线程备份,但只能到表级别,单表备份还是单线程
- mysqldump备份时,有个默认队列（default）,队列下开N个线程去备份数据库/数据库中的表
- 支持开多个队列(对应不同库/表),然后每个队列设置不同线程,进行备份
1.2 优缺点
优点：
- 官方工具,听着牛逼
缺点：
- 只能并行到表级别,如果表特别大,开多线程和单线程是一样的,并行度不如mydumper
- 无法获取当前备份对应的binlog位置
- MySQL5.7.11之前的版本不要使用,并行导出和single-transaction是互斥的
1.3 重要参数
--default-parallelism 指定线程数,默认开2个线程进行并发备份
--parallel-schemas 指定哪些数据库进行并发备份
--set-gtid-purged=OFF 5.7.18后加入的参数,
Ⅱ、演示一手
[root@VM_0_5_centos ~]# mysqlpump --single-transaction --set-gtid-purged=OFF --parallel-schemas=2:employees --parallel-schemas=4:dbt3 -B employees dbt3 > /tmp/backup.sql
mysqlpump: [Warning] Using a password on the command line interface can be insecure.
Dump progress: 1/5 tables, 0/7559817 rows
Dump progress: 3/15 tables, 286750/12022332 rows
Dump progress: 3/15 tables, 686750/12022332 rows
Dump progress: 3/15 tables, 1042250/12022332 rows
...
Dump completed in 43732 milliseconds
新开一个会话看下情况
(root@172.16.0.10) [(none)]> show processlist;
+--------+------+------------------+------+---------+------+-------------------+------------------------------------------------------------------------------------------------------+
| Id | User | Host | db | Command | Time | State | Info |
+--------+------+------------------+------+---------+------+-------------------+------------------------------------------------------------------------------------------------------+
| 138199 | root | 172.16.0.5:39238 | NULL | Query | 0 | starting | show processlist |
| 138267 | root | 172.16.0.5:39776 | NULL | Sleep | 2 | | NULL |
| 138268 | root | 172.16.0.5:39778 | NULL | Query | 2 | Sending to client | SELECT SQL_NO_CACHE `emp_no`,`dept_no`,`from_date`,`to_date` FROM `employees`.`dept_emp` |
| 138269 | root | 172.16.0.5:39780 | NULL | Query | 2 | Sending to client | SELECT SQL_NO_CACHE `emp_no`,`birth_date`,`first_name`,`last_name`,`gender`,`hire_date` FROM `emplo |
| 138270 | root | 172.16.0.5:39782 | NULL | Query | 2 | Sending to client | SELECT SQL_NO_CACHE `o_orderkey`,`o_custkey`,`o_orderstatus`,`o_totalprice`,`o_orderDATE`,`o_orderpr |
| 138271 | root | 172.16.0.5:39784 | NULL | Query | 2 | Sending to client | SELECT SQL_NO_CACHE `p_partkey`,`p_name`,`p_mfgr`,`p_brand`,`p_type`,`p_size`,`p_container`,`p_retai |
| 138272 | root | 172.16.0.5:39786 | NULL | Query | 2 | Sending data | SELECT SQL_NO_CACHE `l_orderkey`,`l_partkey`,`l_suppkey`,`l_linenumber`,`l_quantity`,`l_extendedpric |
| 138273 | root | 172.16.0.5:39788 | NULL | Query | 2 | Sending to client | SELECT SQL_NO_CACHE `c_custkey`,`c_name`,`c_address`,`c_nationkey`,`c_phone`,`c_acctbal`,`c_mktsegme |
| 138274 | root | 172.16.0.5:39790 | NULL | Sleep | 2 | | NULL |
| 138275 | root | 172.16.0.5:39792 | NULL | Sleep | 1 | | NULL |
+--------+------+------------------+------+---------+------+-------------------+------------------------------------------------------------------------------------------------------+
10 rows in set (0.00 sec)
可以看到138268和138269在备份employees库,138270,138271,138272,138273在备份dbt3,这里没打印全,不过这是真的,不吹牛逼
Ⅲ、看下备份过程吧
session1:
(root@localhost) [(none)]> truncate mysql.general_log;
Query OK, 0 rows affected (0.10 sec)
(root@localhost) [(none)]> set global log_output = 'table';
Query OK, 0 rows affected (0.00 sec)
(root@localhost) [(none)]> set global general_log = 1;
Query OK, 0 rows affected (0.03 sec)
session2:
[root@VM_0_5_centos ~]# mysqlpump --single-transaction abc > /tmp/backup.sql
Dump completed in 592 milliseconds
(root@localhost) [(none)]> select thread_id,left(argument, 64) from mysql.general_log order by event_time;
省略部分输出：
+-----------+------------------------------------------------------------------+
| 7 | root@localhost on using Socket |
| 7 | FLUSH TABLES WITH READ LOCK |
| 7 | SHOW WARNINGS |
| 7 | SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ |
| 7 | SHOW WARNINGS |
| 7 | START TRANSACTION WITH CONSISTENT SNAPSHOT |
| 7 | SHOW WARNINGS |
| 8 | root@localhost on using Socket |
| 8 | SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ |
| 8 | SHOW WARNINGS |
| 8 | START TRANSACTION WITH CONSISTENT SNAPSHOT |
| 8 | SHOW WARNINGS |
| 9 | root@localhost on using Socket |
| 9 | SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ |
| 9 | SHOW WARNINGS |
| 9 | START TRANSACTION WITH CONSISTENT SNAPSHOT |
| 9 | SHOW WARNINGS |
| 7 | UNLOCK TABLES |
| 7 | SHOW WARNINGS |
| 9 | SET SQL_QUOTE_SHOW_CREATE= 1 |
| 9 | SHOW WARNINGS |
| 9 | SET TIME_ZONE='+00:00' |
| 8 | SET SQL_QUOTE_SHOW_CREATE= 1 |
| 8 | SHOW WARNINGS |
| 8 | SET TIME_ZONE='+00:00' |
| 3 | set global general_log = 0 |
+-----------+------------------------------------------------------------------+
1.线程7 进行 FLUSH TABLES WITH READ LOCK 。对表加一个读锁
2.线程7、8、9分别开启一个事务（RR隔离级别）去备份数据,由于之前锁表了,所以这三个线程备份出的数据是具有一致性的
3.线程7 解锁 UNLOCK TABLE
整个过程没有获取二进制位置点
Ⅳ、compress-output
mysqlpump支持压缩输出,支持LZ4和ZLIB（ZLIB压缩比相对较高,但是速度较慢）
[root@VM_0_5_centos tmp]# mysqlpump --single-transaction --compress-output=lz4 abc > /tmp/backup_abc.sql
Dump completed in 511 milliseconds
Ⅴ、备份恢复
未压缩的备份
mysql < backup.sql
压缩过的备份
先解压
zlib_decompress
lz4_decompress
lz4_decompress backup_abc.sql backup.sql
再导入
mysql < backup.sql
可以看出来,这个导入是单线程
tips：
mysqlpump备份的数据恢复时会先插入数据,再建索引,而mysqldump备份的数据恢复是在建立表的时候就把索引加上了,所以前者备份的数据恢复时速度要快一点
总结：后续关注,现在用不上