MySQL-负载很高排查思路

Love The Way You Lie 2024-02-18 22:30 33阅读 0赞

**思路：**  
1、确定高负载的类型 htop，dstat命令看负载高是CPU还是IO  
2、监控具体的sql语句，是insert update 还是 delete导致高负载  
3、检查mysql日志  
4、检查硬件问题

**dstat**

可以看到具体是哪个用户哪个进程占用了相关系统资源，当前CPU、内存谁在使用

![70][]

**htop**

htop是top的增强版，更直观

![70 1][]

**tcpdump**

抓取mysql包分析，一般抓3306端口的数据

[root@cc ~]# tcpdump -i eth0 -A -s 3000 port 3306 > ~/sql.log

然后使用awk,sort,wc 等命令进行分析

或者

[root@cc ~]# tcpdump -i eth0 -s 0 -l -w - dst port 3306 | strings | perl -e '
    while(<>) { chomp; next if /^[^ ]+[ ]*$/;
    if(/^(SELECT|UPDATE|DELETE|INSERT|SET|COMMIT|ROLLBACK|CREATE|DROP|ALTER)/i) {
        if (defined $q) { print "$qn"; }
        $q=$_;
        } else {
        $_ =~ s/^[ t]+//; $q.=" $_";
        }
    }'

就可以看出最繁忙的sql语句了

**strace**

查看系统调用是否有问题，进程是否堵塞，是否有Broken pipe

[root@cc ~]# strace -p 26578

**pt-query-digest**

分析mysql慢日志，查看哪些sql语句最耗时

[root@cc ~]#  pt-query-digest slow.logs
    
    # 390ms USER TIME, 10ms system TIME, 15.67M rss, 105.84M vsz  
    # CURRENT DATE: Thu DEC 29 13:22:42 2014  
    # Hostname: test   
    # Files: slow.log  
    # Overall: 776 total, 11 UNIQUE, 0.00 QPS, 0.00x concurrency _____________  
    # TIME range: 2011-09-10 04:03:19 TO 2011-12-29 05:02:51  
    # Attribute          total     MIN     MAX     avg     95%  stddev  median  
    # ============     ======= ======= ======= ======= ======= ======= =======  
    # EXEC TIME          5657s      2s     33s      7s     23s      6s      5s  
    # LOCK TIME            33s       0     19s    43ms    98us   715ms    38us  
    # ROWS sent        323.38k       0 107.36k  426.73    0.99   6.35k       0  
    # ROWS examine     323.39k       0 107.36k  426.74       0   6.35k       0  
    # Query SIZE       217.95k      38     562  287.61  420.77   81.78  284.79

**show processlist**

查看系统到底在干什么

**检查mysql配置参数是否有问题，引起大量的IO或者高CPU操作**

innodb\_flush\_log\_at\_trx\_commit 、innodb\_buffer\_pool\_size 、key\_buffer\_size 等重要参数

mysql> show variables like '%innodb%';
    +---------------------------------+----------------------------+
    | Variable_name                   | Value                      |
    +---------------------------------+----------------------------+
    | have_innodb                     | YES                        |
    | ignore_builtin_innodb           | ON                         |
    | innodb_adaptive_flushing        | ON                         |
    | innodb_adaptive_hash_index      | ON                         |
    | innodb_additional_mem_pool_size | 2097152                    |
    | innodb_autoextend_increment     | 8                          |
    | innodb_autoinc_lock_mode        | 1                          |
    | innodb_buffer_pool_size         | 2013265920                 |
    | innodb_change_buffering         | inserts                    |
    | innodb_checksums                | ON                         |

**通过show engine innodb status查看当前事务，内存使用**

mysql> show engine innodb status  \G
    
    LATEST DETECTED DEADLOCK
    ------------------------
    150731 10:36:50
    *** (1) TRANSACTION:
    TRANSACTION EBFBBEC, ACTIVE 0 sec, process no 20691, OS thread id 47345217033984 inserting
    mysql tables in use 1, locked 1
    LOCK WAIT 5 lock struct(s), heap size 1248, 4 row lock(s), undo log entries 2
    MySQL thread id 143249904, query id 1286731854 10.135.21.120 tybuser2014 update
    
    #此处具体sql省略
    
    ----------------------
    BUFFER POOL AND MEMORY
    ----------------------
    Total memory allocated 2058485760; in additional pool allocated 0
    Dictionary memory allocated 819282
    Buffer pool size   122879
    Free buffers       97599
    Database pages     24313
    Old database pages 8954
    Modified db pages  7
    Pending reads 0
    Pending writes: LRU 0, flush list 0, single page 0
    Pages made young 6, not young 0
    0.00 youngs/s, 0.00 non-youngs/s
    Pages read 1049, created 41853, written 30401604
    0.00 reads/s, 0.00 creates/s, 1.75 writes/s
    Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
    Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
    LRU len: 24313, unzip_LRU len: 0
    I/O sum[45]:cur[0], unzip sum[0]:cur[0]

最后通过zabbix或者cacti等监控来查看IO、CPU、MEMORY、磁盘等是否有异常

这样基本上就可以把问题找出来了

[70]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/c2d439191e764574a612c1595d421e4e.png
[70 1]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/71d58099139e4dc789bb17d15ce7d8fe.png