mysql生产环境常用命令

Posted 2020-10-28 Lazyball

唠唠mysql的连接数

1.查看mysql的当前连接数

[root@localhost ~]# mysqladmin -uroot -p123456 status
Uptime: 34070  Threads: 1  Questions: 8678  Slow queries: 0  Opens: 910  Flush tables: 43  Open tables: 4  Queries per second avg: 0.254
Therads 打开的连接数

mysql> show status like \'%Thread%\';
+------------------------------------------+-------+
| Variable_name                            | Value |
+------------------------------------------+-------+
| Delayed_insert_threads                   | 0     |
| Performance_schema_thread_classes_lost   | 0     |
| Performance_schema_thread_instances_lost | 0     |
| Slow_launch_threads                      | 0     |
| Threads_cached                           | 0     |
| Threads_connected                        | 1     |
| Threads_created                          | 4     |#创建的连接数
| Threads_running                          | 1     |#打开的连接数
+------------------------------------------+-------+
8 rows in set (0.00 sec

2.查看mysql允许的最大连接数

mysql> show variables like \'%max_connections%\'；
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_connections | 151   |
+-----------------+-------+
1 row in set (0.00 sec)

3.mysql连接数太多解决方案

http://www.cnblogs.com/lazyball/p/7424243.html

说说mysql的慢查询

慢查询产生的原因一般是因为select设计的条件比较多，比如子查询之类的，数据库一直在插卡在哪里，别的语句也无法运行造成阻塞。开发也不是万能的，也会写一些 吊炸天的sql语句，一眼望去看不到结尾。

1. 查看mysql里有哪些进程在运行

mysql> show processlist; #默认一般显示100行  加上full显示的多
+----+------+-----------+------+---------+------+-------+------------------+
| Id | User | Host      | db   | Command | Time | State | Info             |
+----+------+-----------+------+---------+------+-------+------------------+
|  4 | root | localhost | NULL | Sleep   |  882 |       | NULL             |
|  6 | root | localhost | NULL | Query   |    0 | NULL  | show processlist |
+----+------+-----------+------+---------+------+-------+------------------+
2 rows in set (0.00 sec)

mysql> show full processlist;
+----+------+-----------+------+---------+------+-------+-----------------------+
| Id | User | Host      | db   | Command | Time | State | Info                  |
+----+------+-----------+------+---------+------+-------+-----------------------+
|  4 | root | localhost | NULL | Sleep   |  894 |       | NULL                  |
|  6 | root | localhost | NULL | Query   |    0 | NULL  | show full processlist |
+----+------+-----------+------+---------+------+-------+-----------------------+
2 rows in set (0.00 sec)

[root@localhost ~]# mysqladmin -uroot -p processlist
Enter password: 
+----+------+-----------+----+---------+------+-------+------------------+
| Id | User | Host      | db | Command | Time | State | Info             |
+----+------+-----------+----+---------+------+-------+------------------+
| 4  | root | localhost |    | Sleep   | 1238 |       |                  |
| 7  | root | localhost |    | Query   | 0    |       | show processlist |
+----+------+-----------+----+---------+------+-------+------------------+

参数解释：
id       #ID标识，要kill一个语句的时候很有用
use      #当前连接用户
host     #显示这个连接从哪个ip的哪个端口上发出
db       #数据库名
command  #连接状态，一般是休眠（sleep），查询（query），连接（connect）
time     #连接持续时间，单位是秒
state    #显示当前sql语句的状态 
info     #显示这个sql语句

##慢查询发生的时候，state状态一般是 watting for table level lock 观察time 看是否运行的时间很久，紧急就杀死，不紧急找开发去，写的什么玩意（自己知道咋优化
的话，找开发炫耀去）

2. 紧急批量杀死mysql慢查询的脚本

 先说自己写的吧

#!/bin/bash
for id in `mysqladmin  -uxxx -h 192.168.1.1 -p\'xxxx\' processlist | grep Query | grep \'paigoushop\' | grep \'Sending data\'  |  awk \'{print $2}\'` 
        do 
                        mysqladmin  -uxxx -h 192.168.1.1 -p\'xxx\'  kill ${id} 
        done
#grep有点多  为了准确定位到自己想杀死的sql

下边这个是网上找的，我也没试过 放这里 万一以后自己用呢

#!/bin/bash
for i in `mysql -Bse \'show full processlist;\' | grep -i select |grep -i "Waiting for table level lock" | awk  \'{print $1}\'`
do
        mysql -Bse "kill  $i"
done

3. 开启慢查询日志记录

总觉得上边的方法不太好，比较被动，对于一些不懂的人，又要骂运维了，我来学一下：“不，什么情况呀，小杨，你这数据库也太慢了吧，怎么搞得，赶紧给我查。”

说起来都是泪呀，那就不说了。用事实说话，把sql语句拿出来，让开发好好看看写的什么玩意。

3.11 查看是否开启慢查询记录

mysql> show  variables like \'%slow%\';
+---------------------+--------------------------------+
| Variable_name       | Value                          |
+---------------------+--------------------------------+
| log_slow_queries    | ON # 均为on                           |
| slow_launch_time    | 2  #超过两秒就是慢查询了                            |
| slow_query_log      | ON  #                           |
| slow_query_log_file | /data/mysql/localhost-slow.log |#慢查询文件路径
+---------------------+--------------------------------+
mysql> show  variables like \'%long%\';
+---------------------------------------------------+-----------+
| Variable_name                                     | Value     |
+---------------------------------------------------+-----------+
| long_query_time                                   | 2.000000  |#超过两秒就是慢查询了
| max_long_data_size                                | 314572800 |
| performance_schema_events_waits_history_long_size | 10000     |
+---------------------------------------------------+-----------+

3.12 命令行设置开启慢查询

mysql> set global slow_query_log=\'ON\';            //启用慢查询  
Query OK, 0 rows affected (0.28 sec)  

mysql> set global long_query_time=2;          //设置成2秒，加上global,下次进mysql已然生效  
Query OK, 0 rows affected (0.00 sec)  

3.13 在my.cnf里设置 需要重启mysql

修改mysql的配置文件my.cnf

在[mysqld]里面加上以下内容

long_query_time = 2  #设置超过2s的即为慢查询sql了

log-slow-queries = /usr/local/mysql/mysql-slow.log 

4.mysqldumpslow分析慢查询日志的工具

先大体看一下 效果

显示执行时间最长的前两个
[root@rac3 python]# mysqldumpslow  -s t -t 2 /opt/mysql/data/slowquery.log  
Reading mysql slow query log from /opt/mysql/data/slowquery.log
Count: 2  Time=412.54s (825s)  Lock=0.00s (0s)  Rows=1.0 (2), 
  select count(N) from sbtest ,t1 where t1.c=sbtest.c
Count: 1  Time=778.20s (778s)  Lock=0.00s (0s)  Rows=1.0 (1), 
  select count(N) from  sbtest where sbtest.id not in ( select id from t1 )

#显示次数最多的前两个 
[root@rac3 python]# mysqldumpslow  -s c -t 2 /opt/mysql/data/slowquery.log      
Reading mysql slow query log from /opt/mysql/data/slowquery.log
Count: 12  Time=0.00s (0s)  Lock=0.00s (0s)  Rows=1.0 (12), 
  select count(N) from tab_1
Count: 2  Time=412.54s (825s)  Lock=0.00s (0s)  Rows=1.0 (2),
  select count(N) from sbtest ,t1 where t1.c=sbtest.c

上述结果的解释：

主要功能是, 统计不同慢 sql 的

出现次数(Count),

执行最长时间(Time),

累计总耗费时间(Time()),

等待锁的时间(Lock),

发送给客户端的行总数(Rows),

扫描的行总数(Rows()）

mysqldumpslow常用参数

-s  排序ORDER     what to sort by (al, at, ar, c, l, r, t), \'at\' is default
                al: average lock time
                ar: average rows sent
                at: average query time
                 c: count  执行次数
                 l: lock time 锁定时间
                 r: rows sent 返回记录
                 t: query time  查询时间
-t  NUM       just show the top n queries
-g  PATTERN   grep: only consider stmts that include this string  就想grep一样 指定过滤的关键字
可根据具体需求具体分析，例如：
分析出使用频率最高的前50条慢sql：
mysqldumpslow -s c -t 50 slow.log

如只需分析处理速度最慢的10条sql：
mysqldumpslow –s t  -t 10 slow.log

[root@BlackGhost bin]# ./mysqldumpslow -s r -t 20 /usr/local/mysql/mysql-slow.log

[root@BlackGhost bin]# ./mysqldumpslow -s r -t 20 -g \'count\' /usr/local/mysql/mysql-slow.log

查看mysql的状态

show global status;
或者
mysqladmin -uroot -p extended-status

 

参数解释 看

https://blog.csdn.net/zhangjikuan/article/details/52263301#t120