昨天线上应用反馈晚上 19：30-19：43以及 20：13到20：21两个时间段所有人包括我们自己建的教室都进不去，
classroom B套无法登陆，主页无法访问，已有超过10个老师和学生反馈进不去教室的问题
通过监控查看出现问题时数据库服务器的cpu使用率，负载，io，内存使用，swap剩余量等状况，发现数据库当时压力特别大，
数据库连接数：
数据库慢查询也出现很多
查看慢查询日志，发现一个SQL在慢查询日志中频繁出现切执行时间较长
# [email protected]: cms[cms] @ [172.17.43.24] # Query_time: 10.252490 Lock_time: 0.000052 Rows_sent: 1 Rows_examined: 2345869 SET timestamp=1522065887; select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_ .pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefin e9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from p articipant participan0_ where (participan0_.conferenceid=2680447 )and(participan0_.pin='1219' ); # [email protected]: cms[cms] @ [172.17.43.25] # Query_time: 10.297055 Lock_time: 0.000050 Rows_sent: 1 Rows_examined: 2345869 SET timestamp=1522065887; select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_ .pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefin e9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from p articipant participan0_ where (participan0_.conferenceid=2697493 )and(participan0_.pin='1492' ); # [email protected]: cms[cms] @ [172.17.43.25] # Query_time: 10.319839 Lock_time: 0.000048 Rows_sent: 1 Rows_examined: 2345869 SET timestamp=1522065887; select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_ .pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefin e9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from p articipant participan0_ where (participan0_.conferenceid=2680355 )and(participan0_.pin='9590' ); # [email protected]: cms[cms] @ [172.17.43.24] # Query_time: 10.163372 Lock_time: 0.000063 Rows_sent: 1 Rows_examined: 2345872 SET timestamp=1522065887; select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_ .pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefin e9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from p articipant participan0_ where (participan0_.conferenceid=2731041 )and(participan0_.pin='1506' ); # [email protected]: cms[cms] @ [172.17.43.24] # Query_time: 9.950549 Lock_time: 0.000073 Rows_sent: 1 Rows_examined: 2345881 SET timestamp=1522065887; select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_ .pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefin e9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from p articipant participan0_ where (participan0_.conferenceid=2682013 )and(participan0_.pin='6086' ); # [email protected]: cms[cms] @ [172.17.43.25] # Query_time: 9.992145 Lock_time: 0.000051 Rows_sent: 1 Rows_examined: 2345879 SET timestamp=1522065887; select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_ .pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefin e9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from p articipant participan0_ where (participan0_.conferenceid=2697493 )and(participan0_.pin='1103' );
查看该SQL的执行计划发现走了全表扫描，扫描了200多万行的数据；
mysql> explain select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_.pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefine9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from participant participan0_ where (participan0_.conferenceid=2724963 )and(participan0_.pin='5476' ); +----+-------------+--------------+------+---------------+------+---------+------+---------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+--------------+------+---------------+------+---------+------+---------+-------------+ | 1 | SIMPLE | participan0_ | ALL | NULL | NULL | NULL | NULL | 2042005 | Using where | +----+-------------+--------------+------+---------------+------+---------+------+---------+-------------+ 1 row in set (0.02 sec)
发现该表where条件的列上没有索引：
mysql> show index from participant; +-------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +-------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | participant | 0 | PRIMARY | 1 | id | A | 2384122 | NULL | NULL | | BTREE | | | +-------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ 1 row in set (0.00 sec)
和发开沟通后在该表上加上以下索引：
mysql> ALTER TABLE `participant` ADD INDEX index_conferenceid (`conferenceid`); Query OK, 0 rows affected (9.16 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> ALTER TABLE `participant` ADD INDEX index_pin (`pin`); Query OK, 0 rows affected (6.96 sec) Records: 0 Duplicates: 0 Warnings: 0
再次查看该SQL的执行计划：
mysql> explain select participan0_.id as id19_, participan0_.conferenceid as conferen2_19_, participan0_.name as name19_, participan0_.phone as phone19_, participan0_.pin as pin19_, participan0_.email as email19_, participan0_.mobile as mobile19_, participan0_.valid as valid19_, participan0_.userdefine1 as userdefine9_19_, participan0_.userdefine2 as userdefine10_19_, participan0_.userdefine3 as userdefine11_19_, participan0_.userdefine4 as userdefine12_19_ from participant participan0_ where (participan0_.conferenceid=2724963 )and(participan0_.pin='5476' ); +----+-------------+--------------+-------------+------------------------------+------------------------------+---------+------+------+------------------------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+--------------+-------------+------------------------------+------------------------------+---------+------+------+------------------------------------------------------------+ | 1 | SIMPLE | participan0_ | index_merge | index_conferenceid,index_pin | index_conferenceid,index_pin | 5,7 | NULL | 1 | Using intersect(index_conferenceid,index_pin); Using where | +----+-------------+--------------+-------------+------------------------------+------------------------------+---------+------+------+------------------------------------------------------------+ 1 row in set (0.01 sec)
-----------------------------我是分割线-----------------------
等到晚上约课较多的时间再次观察数据库的负载和慢查询日志
原文地址：http://blog.51cto.com/11784929/2091555
时间： 2024-08-04 22:22:36