mysql, mariadb刪庫、恢復的完整模擬實現

模擬場景：

周日全備份 -- 周一10：00刪庫db1，-- 10：10發現某些頁面無法訪問，如何恢復數據？

注意：

由于庫不僅僅一個，因此db1刪除，用戶可能正常的訪問db2，但是多個數據庫之間往往是有關聯的，    
如商品數據庫和訂單數據庫，因此為了避免數據的不一致性，往往會導致邏輯上出現問題的；
此時應當停止服務；即暫停用戶的訪問，這是一個大的問題，這是需要慎重選擇的，是服務重要還是數據
更重要，最好向上級報告。

處理邏輯：

1、停止服務：斷開數據庫與遠程應用之間的網絡連接，這樣只有本地用戶可以管理；
2、邏輯梳理：
全備份恢復：周日的全備份；
周日至周1的10：00間的數據；刨除刪除的SQL命令；
周一10：00 - 10：10的數據；

如果業務數據不是十分的重要，那么就恢復周日的全備份，丟失全備份至周1 10：00的數據。

[root@centos7x ~]$mysqldump -A -F --master-data=2 --single-transaction > all_`date +%F_%T`.sql
[root@centos7x ~]$less all_2018-02-24_21\:46\:13.sql 
-- Position to start replication or point-in-time recovery from
--
-- CHANGE MASTER TO MASTER_LOG_FILE='mariadb-bin.000010', MASTER_LOG_POS=245;
--
-- Current Database: `hellodb`

那么對于測試環境，'mariadb-bin.000010', MASTER_LOG_POS=245之前的二進制日志數據都是可以刪除的； 
單機備份時，--master-data=1或者2都是可以的；但是如果是主動復制那么最好是1；

模擬故障：

模擬修改和刪除操作；
MariaDB [hellodb]> select * from students;
+-------+---------------+-----+--------+---------+-----------+
| StuID | Name | Age | Gender | ClassID | TeacherID |
+-------+---------------+-----+--------+---------+-----------+
| 1 | Shi Zhongyu | 22 | M | 2 | 3 |
| 2 | Shi Potian | 22 | M | 1 | 7 |
| 3 | Xie Yanke | 53 | M | 2 | 16 |
| 4 | Ding Dian | 32 | M | 4 | 4 |
| 5 | Yu Yutong | 26 | M | 3 | 1 |
| 6 | Shi Qing | 46 | M | 5 | NULL |
| 7 | Xi Ren | 19 | F | 3 | NULL |
| 8 | Lin Daiyu | 17 | F | 7 | NULL |
| 9 | Ren Yingying | 20 | F | 6 | NULL |
| 10 | Yue Lingshan | 19 | F | 3 | NULL |
| 11 | Yuan Chengzhi | 23 | M | 6 | NULL |
| 12 | Wen Qingqing | 19 | F | 1 | NULL |
| 13 | Tian Boguang | 33 | M | 2 | NULL |
| 14 | Lu Wushuang | 17 | F | 3 | NULL |
| 15 | Duan Yu | 19 | M | 4 | NULL |
| 16 | Xu Zhu | 21 | M | 1 | NULL |
| 17 | Lin Chong | 25 | M | 4 | NULL |
| 18 | Hua Rong | 23 | M | 7 | NULL |
| 19 | Xue Baochai | 18 | F | 6 | NULL |
| 20 | Diao Chan | 19 | F | 7 | NULL |
| 21 | Huang Yueying | 22 | F | 6 | NULL |
| 22 | Xiao Qiao | 20 | F | 1 | NULL |
| 23 | Ma Chao | 23 | M | 4 | NULL |
| 24 | Xu Xian | 27 | M | NULL | NULL |
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+
25 rows in set (0.00 sec)

    MariaDB [hellodb]> insert into students (name,age,gender) values('a','29','F');
    Query OK, 1 row affected (0.01 sec)

    MariaDB [hellodb]> select * from students;
    +-------+---------------+-----+--------+---------+-----------+
    | StuID | Name          | Age | Gender | ClassID | TeacherID |
    +-------+---------------+-----+--------+---------+-----------+
    |     1 | Shi Zhongyu   |  22 | M      |       2 |         3 |
    |     2 | Shi Potian    |  22 | M      |       1 |         7 |
    |     3 | Xie Yanke     |  53 | M      |       2 |        16 |
    |     4 | Ding Dian     |  32 | M      |       4 |         4 |
    |     5 | Yu Yutong     |  26 | M      |       3 |         1 |
    |     6 | Shi Qing      |  46 | M      |       5 |      NULL |
    |     7 | Xi Ren        |  19 | F      |       3 |      NULL |
    |     8 | Lin Daiyu     |  17 | F      |       7 |      NULL |
    |     9 | Ren Yingying  |  20 | F      |       6 |      NULL |
    |    10 | Yue Lingshan  |  19 | F      |       3 |      NULL |
    |    11 | Yuan Chengzhi |  23 | M      |       6 |      NULL |
    |    12 | Wen Qingqing  |  19 | F      |       1 |      NULL |
    |    13 | Tian Boguang  |  33 | M      |       2 |      NULL |
    |    14 | Lu Wushuang   |  17 | F      |       3 |      NULL |
    |    15 | Duan Yu       |  19 | M      |       4 |      NULL |
    |    16 | Xu Zhu        |  21 | M      |       1 |      NULL |
    |    17 | Lin Chong     |  25 | M      |       4 |      NULL |
    |    18 | Hua Rong      |  23 | M      |       7 |      NULL |
    |    19 | Xue Baochai   |  18 | F      |       6 |      NULL |
    |    20 | Diao Chan     |  19 | F      |       7 |      NULL |
    |    21 | Huang Yueying |  22 | F      |       6 |      NULL |
    |    22 | Xiao Qiao     |  20 | F      |       1 |      NULL |
    |    23 | Ma Chao       |  23 | M      |       4 |      NULL |
    |    24 | Xu Xian       |  27 | M      |    NULL |      NULL |
    |    25 | Sun Dasheng   | 100 | M      |    NULL |      NULL |
    |    26 | a             |  29 | F      |    NULL |      NULL |
    +-------+---------------+-----+--------+---------+-----------+
    26 rows in set (0.00 sec)

    MariaDB [hellodb]> 

MariaDB [hellodb]> drop database hellodb ;
Query OK, 7 rows affected (0.01 sec)

MariaDB [(none)]> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
4 rows in set (0.00 sec)

MariaDB [(none)]> use test;
Database changed

MariaDB [test]> create table t1(id int);
Query OK, 0 rows affected (0.01 sec)

MariaDB [test]> select * from test;
ERROR 1146 (42S02): Table 'test.test' doesn''t exist
MariaDB [test]>
MariaDB [test]> show tables;
+----------------+
| Tables_in_test |
+----------------+
| t1 |
+----------------+
1 row in set (0.00 sec)

MariaDB [test]> flush tables with read lock;
Query OK, 0 rows affected (0.00 sec)

MariaDB [test]> select * from t1;
Empty set (0.00 sec)

MariaDB [test]> insert t1 values(1);
ERROR 1223 (HY000): Can''t execute the query because you have a conflicting read lock
MariaDB [test]>

數據恢復操作：

MariaDB [test]> show master logs;
+--------------------+-----------+
| Log_name | File_size |
+--------------------+-----------+
| mariadb-bin.000001 | 7700 |
| mariadb-bin.000002 | 290 |
| mariadb-bin.000003 | 290 |
| mariadb-bin.000004 | 290 |
| mariadb-bin.000005 | 290 |
| mariadb-bin.000006 | 290 |
| mariadb-bin.000007 | 290 |
| mariadb-bin.000008 | 290 |
| mariadb-bin.000009 | 290 |
| mariadb-bin.000010 | 669 |
+--------------------+-----------+
10 rows in set (0.00 sec)

刷新日志:
那么'mariadb-bin.000010', MASTER_LOG_POS=245之前的數據使用全備份恢復；
'mariadb-bin.000010', MASTER_LOG_POS=245與'mariadb-bin.000011', MASTER_LOG_POS=245
之間的數據使用二進制日志進行恢復；

MariaDB [test]> flush logs;
Query OK, 0 rows affected (0.01 sec)

MariaDB [test]> show master logs;
+--------------------+-----------+
| Log_name | File_size |
+--------------------+-----------+
| mariadb-bin.000001 | 7700 |
| mariadb-bin.000002 | 290 |
| mariadb-bin.000003 | 290 |
| mariadb-bin.000004 | 290 |
| mariadb-bin.000005 | 290 |
| mariadb-bin.000006 | 290 |
| mariadb-bin.000007 | 290 |
| mariadb-bin.000008 | 290 |
| mariadb-bin.000009 | 290 |
| mariadb-bin.000010 | 714 |
| mariadb-bin.000011 | 245 |
+--------------------+-----------+
11 rows in set (0.01 sec)

如果是全備份后的二進制日志有多個，那么需要都復制出來，并且合并；
[root@centos7x ~]$cp /var/lib/mysql/mariadb-bin.000010 .
[root@centos7x ~]$ls
all_2018-02-24_21:46:13.sql all.sql anaconda-ks.cfg hellodb_InnoDB.sql initial-setup-ks.cfg mariadb-bin.000010

[root@centos7x ~]$mysqlbinlog --start-position=245 mariadb-bin.000010

[root@centos7x ~]$mysqlbinlog --start-position=245 mariadb-bin.000010 > binlog.sql

刪除二進制日志中的刪除數據庫的SQL語句；
[root@centos7x ~]$vim binlog.sql
drop database hellodb

恢復數據之前還需要臨時將記錄二進制日志的功能暫時關掉；

MariaDB [test]> show variables like 'sql_log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_log_bin | ON |
+---------------+-------+
1 row in set (0.00 sec)

MariaDB [test]> set sql_log_bin=0;
Query OK, 0 rows affected (0.00 sec)

MariaDB [test]> show variables like 'sql_log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_log_bin | OFF |
+---------------+-------+
1 row in set (0.00 sec)

sql_log_bin和/etc/my.cnf中的log_bin選項，都是可以影響二進制記錄的選項，但是其中一個關閉，那么
二進制日志記錄功能就關閉了；其中log_bin在配置文件中，修改的話是需要重啟MySQL服務的；
而sql_log_bin是回話級別的，即時生效；

解鎖數據庫的讀鎖；
MariaDB [test]> unlock tables ;
Query OK, 0 rows affected (0.01 sec)

恢復全備份：
MariaDB [test]> source all_2018-02-24_21:46:13.sql

MariaDB [(none)]> select * from hellodb.students;

二進制日志恢復：
最后就是記錄二進制日志，恢復用戶的訪問；
MariaDB [(none)]> source binlog.sql
MariaDB [(none)]> select * from hellodb.students;
| 25 | Sun Dasheng | 100 | M | NULL | NULL |
| 26 | a | 29 | F | NULL | NULL |
+-------+---------------+-----+--------+---------+-----------+

MariaDB [test]> set sql_log_bin=1;
Query OK, 0 rows affected (0.00 sec)

MariaDB [test]> show variables like 'sql_log_bin';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_log_bin | ON |
+---------------+-------+
1 row in set (0.00 sec)