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: pool7.8htop
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
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