OS:CentOS 7.4
DB:mysql 5.7.17
error.log日志里报错信息：
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
看到是max_open_files，难道是操作系统限制了？也没有啊
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？
果然是...把这个参数修改为65535后，重启mysql，问题消失了。
https://dev.mysql.com/doc/refman/5.7/en/using-systemd.html
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)
-
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
-
[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：https://blog.itpub.net/29734436/viewspace-2153280/ ，如需转载，请注明出处，否则将追究法律责任。
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