一、应急解决办法
在MySQL数据库连接数很多,而且大多属于活跃的状态时MySQL机器基本上负载很高,属于基本上快要死去的状态了. 这时怎么办呢?
有可能两个办法.
第一: 先限制Innodb的并发处理.如果innodb_thread_concurrency = 0 可以先改成 16或是64 看机器压力,如果 非常大,先改成16让机器的压力下来,然后慢慢增达,适应自已的业务. 处理方法:
set global innodb_thread_concurrency=16;
第二: 对于连接数已经超过600或是更多的情况,可以考虑适当的限制一下连接数,让前端报一下错,也别让DB挂了. DB在了,总是可以用来加载一下数据,当数据加载到了nosql里了,慢慢的DB压力也会降下来的. 限制单用户连接数在500以下. 如:
set global max_user_connections=500;
(MySQL随着连接数的增加性能会是下降的,这也是thread_pool出现的原因) 另外对于有的监控程序会读取information_schema下面的表的程序可以考虑关闭下面的参数 innodb_stats_on_metadata=0
set global innodb_stats_on_metadata=0;
这个参数主要防止对读取information_schema时造成大量读取磁盘进行信息统计(如果慢查询中出现关于information_schema中表时,也可以考虑禁用该参数)
二、问题分析
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
-
[root@cc ~]# dstat -l -m -r -c --top-io --top-mem --top-cpu -
--io/total- ------memory-usage----- --most-expensive- ----most-expensive---- -most-expensive- -
read writ| used buff cach free| memory process | i/o process | cpu process -
1.90 267 |3399M 178M 3892M 400M|php-fpm: poo 372M|init 1682k 647k|flush-202:0 0.1 -
0 72.0 |3399M 178M 3892M 400M|php-fpm: poo 372M|php-fpm: po 10k 143k|php-fpm: pool2.0 -
0 8.00 |3399M 178M 3892M 399M|php-fpm: poo 372M|nginx: work 228k 229k|php-fpm: pool0.5 -
0 88.0 |3399M 178M 3892M 399M|php-fpm: poo 372M|nginx: work 102k 166k|php-fpm: pool 11 -
0 38.0 |3399M 178M 3892M 399M|php-fpm: poo 372M|php-fpm: po 787k 650B|php-fpm: pool4.8 -
0 0 |3399M 178M 3892M 399M|php-fpm: poo 372M|php-fpm: po 788k 723B|php-fpm: pool1.8 -
0 140 |3400M 178M 3892M 399M|php-fpm: poo 372M|nginx: work 38k 154k|php-fpm: pool1.2 -
0 12.0 |3400M 178M 3892M 399M|php-fpm: poo 372M|nginx: work 178k 364k|php-fpm: pool1.5 -
0 0 |3400M 178M 3892M 399M|php-fpm: poo 372M|nginx: work 758k 639k|php-fpm: pool1.5 -
0 12.0 |3400M 178M 3892M 399M|php-fpm: poo 372M|nginx: work 773k 616k|php-fpm: pool2.0 -
6.00 0 |3401M 178M 3892M 398M|php-fpm: poo 372M|nginx: work 994k 688k|nginx: worker1.5 -
0 272 |3401M 178M 3892M 398M|php-fpm: poo 372M|nginx: work 388k 422k|php-fpm: pool1.5 -
0 0 |3400M 178M 3893M 398M|php-fpm: poo 372M|nginx: work 483k 548k|php-fpm: pool1.8 -
0 4.00 |3400M 178M 3893M 398M|php-fpm: poo 372M|php-fpm: po 787k 650B|php-fpm: pool1.5 -
0 12.0 |3400M 178M 3893M 398M|php-fpm: poo 372M|nginx: work 223k 323k|php-fpm: pool1.5 -
0 0 |3400M 178M 3893M 398M|php-fpm: poo 372M|nginx: work 371k 474k|php-fpm: pool7.8
htop
htop是top的增强版，更直观
-
[root@cc ~]# htop -
1 [||||||||||| 12.4%] -
2 [||||||||| 9.5%] -
3 [| 1.0%] -
4 [|| 1.9%] -
Mem[|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||3394/7869MB] -
Swp[|||||||||||||| 75/478MB] -
Tasks: 71, 12 thr; 2 running -
Load average: 0.39 0.39 0.31 -
Uptime: 526 days(!), 17:36:38 -
PID USER PRI NI VIRT RES SHR S CPU% MEM% TIME+ Command -
1 root 20 0 19232 396 248 S 0.0 0.0 0:01.86 /sbin/init -
30752 root 20 0 52532 72 56 S 0.0 0.0 0:00.16 ├─ /usr/sbin/vsftpd /etc/vsftpd/vsftpd.conf -
24301 root 20 0 193M 3268 1600 S 0.0 0.0 1:41.43 ├─ /usr/sbin/snmpd -LS0-6d -Lf /dev/null -p /var/run/snmpd.pid -
21361 root 20 0 902M 6500 1308 S 0.0 0.1 0:07.16 ├─ php-fpm: master process (/etc/php-fpm.conf) -
28627 www 20 0 962M 202M 138M S 0.0 2.6 0:34.46 │ ├─ php-fpm: pool www-c -
27537 www 20 0 965M 236M 171M R 1.4 3.0 1:19.64 │ ├─ php-fpm: pool www-c -
27449 www 20 0 961M 251M 189M S 0.0 3.2 1:35.54 │ ├─ php-fpm: pool www-a -
26442 www 20 0 962M 280M 217M S 0.0 3.6 2:29.71 │ ├─ php-fpm: pool www-a -
26310 www 20 0 917M 251M 234M S 1.9 3.2 2:46.45 │ ├─ php-fpm: pool www-a -
26162 www 20 0 962M 297M 233M S 0.0 3.8 2:37.50 │ ├─ php-fpm: pool www-b -
26147 www 20 0 924M 258M 233M S 0.0 3.3 2:38.37 │ ├─ php-fpm: pool www-c -
25717 www 20 0 965M 302M 238M S 0.0 3.8 2:54.50 │ ├─ php-fpm: pool www-c -
24585 www 20 0 964M 324M 260M S 0.0 4.1 4:15.20 │ ├─ php-fpm: pool www-b
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 或 pstack
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[root@cc ~]# pstack 26356pt-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
-
mysql> show full processlist; -
+-----------+---------------+---------------------+---------------------+---------+------+---------------+---------------------------+ -
| Id | User | Host | db | Command | Time | State | Info | -
+-----------+---------------+---------------------+---------------------+---------+------+---------------+---------------------------+ -
| 184498848 | testdb_rr1356 | 10.11.211.120:61343 | testdb_rr1356_db121 | Sleep | 1384 | | NULL | -
| 184508740 | testdb_rr1356 | 10.11.211.120:11809 | testdb_rr1356_db121 | Sleep | 87 | | NULL | -
| 184509415 | testdb_rr1356 | 10.11.211.120:12760 | testdb_rr1356_db121 | Query | 0 | NULL | show full processlist | -
| 184509451 | testdb_rr1356 | 10.11.211.120:12804 | testdb_rr1356_db121 | Sleep | 10 | | NULL | -
| 184509528 | testdb_rr1356 | 10.11.211.120:12919 | testdb_rr1356_db121 | Query | 0 | freeing items | DESCRIBE test_channel |
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