apache运行过程中报MaxClients setting错误问题处理

apache在运行的过程中，错误日志中出现如下一段报错信息

[error] server reached MaxClients setting, consider raising the MaxClients setting

检查apache的版本

[root@ logs]# httpd -v
Server version: Apache/2.2.31 (Unix)
Server built:   May 26 2016 01:33:18

查看apache工作模型，可以看以prefork.c

[root@ logs]# apachectl -l
Compiled in modules:
core.c
mod_authn_file.c
mod_authn_dbm.c
mod_authn_anon.c
mod_authn_dbd.c
mod_authn_default.c
mod_authz_host.c
mod_authz_groupfile.c
mod_authz_user.c
mod_authz_dbm.c
mod_authz_owner.c
mod_authz_default.c
mod_auth_basic.c
mod_auth_digest.c
mod_dbd.c
mod_dumpio.c
mod_reqtimeout.c
mod_ext_filter.c
mod_include.c
mod_filter.c
mod_substitute.c
mod_deflate.c
mod_log_config.c
mod_logio.c
mod_env.c
mod_expires.c
mod_headers.c
mod_ident.c
mod_setenvif.c
mod_version.c
prefork.c
http_core.c
mod_mime.c
mod_dav.c
mod_status.c
mod_autoindex.c
mod_asis.c
mod_info.c
mod_cgi.c
mod_dav_fs.c
mod_vhost_alias.c
mod_negotiation.c
mod_dir.c
mod_imagemap.c
mod_actions.c
mod_speling.c
mod_userdir.c
mod_alias.c
mod_rewrite.c
mod_so.c

apache中MaxClient设置是在apache工作目录下的conf/extra/httpd-mpm.conf
prefork模型的默认设置如下，最在连接数只 150，远远无法满足生产需求

<IfModule mpm_prefork_module>
StartServers          5
MinSpareServers       5
MaxSpareServers      10
MaxClients          150
MaxRequestsPerChild   0
</IfModule>

StartServers：初始启动进程数
MinSpareServers:最小闲置进程数
MaxSpareServers：最大闲置进程数
MaxClients:最大客户端连接数
MaxRequestsPerChild：每个子进程可处理的请求数，0为不限制
修改为如下：

<IfModule mpm_prefork_module>
StartServers          10
MinSpareServers       10
MaxSpareServers      15
ServerLimit         2000
MaxClients          1000
MaxRequestsPerChild   10000
</IfModule>

如果是worker模型，初始设置为：

<IfModule mpm_worker_module>
StartServers          2
MaxClients          150
MinSpareThreads      25
MaxSpareThreads      75
ThreadsPerChild      25
MaxRequestsPerChild   0
</IfModule>

可修改为如下：

<IfModule mpm_worker_module>
ThreadLimit        200
ServerLimit        25
StartServers        3
MaxClients         2000
MinSpareThreads      50
MaxSpareThreads      200
ThreadsPerChild      100
MaxRequestsPerChild     0
</IfModule>

MaxClients必须是ThreadsPerChild的整数倍，ThreadsPerChild*ServerLimit必须大于MaxClients
修改完成后重启apache服务