mysql报错Changed limits: max_open_files: 5000

OS:CentOS 7.4
DB:mysql 5.7.17
error.log日志里报错信息：

 2018-04-08T09:52:52.641263Z 0 [Warning] Changed limits: max_open_files: 5000 (requested 50000)
 2018-04-08T09:52:52.641467Z 0 [Warning] Changed limits: max_connections: 4190 (requested 10000)
 2018-04-08T09:52:52.641476Z 0 [Warning] Changed limits: table_open_cache: 400 (requested 2000)

看到这个错误第一反应是去数据库查查当前的参数都是多少，和日志里提示的是一样的

 mysql> show variables like '%files%';
 +---------------------------+--------+
 | Variable_name | Value |
 +---------------------------+--------+
 | character_set_filesystem | binary |
 | innodb_log_files_in_group | 2 |
 | innodb_open_files | 400 |
 | keep_files_on_create | OFF |
 | large_files_support | ON |
 | open_files_limit | 5000 |
 +---------------------------+--------+
 6 rows in set (0.00 sec)

 mysql> show variables like '%connections%';
 +----------------------+-------+
 | Variable_name | Value |
 +----------------------+-------+
 | max_connections | 4190 |
 | max_user_connections | 0 |
 +----------------------+-------+
 2 rows in set (0.00 sec)


 mysql> show variables like '%table_open_cache%';
 +----------------------------+-------+
 | Variable_name | Value |
 +----------------------------+-------+
 | table_open_cache | 400 |
 | table_open_cache_instances | 16 |
 +----------------------------+-------+
 2 rows in set (0.01 sec)

看到是 max_open_files，难道是操作系统限制了？也没有啊

 [root@iz2ze6jo3o3bqbcongnypoz mysql]# ulimit -n
 65535

my.cnf文件里也没有对这些参数做修改，因为是用mysqld.service启动的，难道是这个文件的问题吗？

 [root@iz2ze6jo3o3bqbcongnypoz system]# more /usr/lib/systemd/system/mysqld.service
 # Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation; version 2 of the License.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 #
 # systemd service file for MySQL forking server
 #

 [Unit]
 Description=MySQL Server
 Documentation=man:mysqld(8)
 Documentation=http://dev.mysql.com/doc/refman/en/using-systemd.html
 After=network.target
 After=syslog.target

 [Install]
 WantedBy=multi-user.target

 [Service]
 User=mysql
 Group=mysql

 Type=forking

 PIDFile=/var/run/mysqld/mysqld.pid

 # Disable service start and stop timeout logic of systemd for mysqld service.
 TimeoutSec=0

 # Execute pre and post scripts as root
 PermissionsStartOnly=true

 # Needed to create system tables
 ExecStartPre=/usr/bin/mysqld_pre_systemd

 # Start main service
 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid $MYSQLD_OPTS

 # Use this to switch malloc implementation
 EnvironmentFile=-/etc/sysconfig/mysql

 # Sets open_files_limit
 LimitNOFILE = 5000

果然是...把这个参数修改为65535后，重启mysql，问题消失了。

 LimitNOFILE = 5000 这个值默认就是5000，下面这篇文档说清楚这个事了：

https://dev.mysql.com/doc/refman/5.7/en/using-systemd.html

来自 “ ITPUB博客 ” ，链接：http://blog.itpub.net/20893244/viewspace-2152685/，如需转载，请注明出处，否则将追究法律责任。

转载于:http://blog.itpub.net/20893244/viewspace-2152685/