Apache2 需要每隔几个小时重新启动一次 - 速度很慢，并且没有过多的 RAM/CPU 使用率

Question

我最近部署了一台运行 Ubuntu 16.04 和 LAMP 的服务器（Ubuntu 16.04 默认使用 Apache 2.4.18）。在服务器投入生产之前，一切都很好，但现在 Apache2 每 2/3 小时就会变得非常慢（每个网站可能需要 2 分钟以上的时间才能加载）。sudo service apache2 restart不过，运行后，一切速度都会恢复。

我在其中一个时间段内检查了 RAM/CPU，但远未达到最大值。服务器有 2GB RAM 和 1 个 CPU 核心。这是top我在重新启动 Apache 之前的读数

%Cpu(s):  9.2 us,  3.1 sy,  0.0 ni, 86.1 id,  0.0 wa,  0.0 hi,  1.7 si,  0.0 st
KiB Mem :  2045252 total,   247516 free,   838924 used,   958812 buff/cache
KiB Swap:   524284 total,   523764 free,      520 used.  1047636 avail Mem 

其中唯一占用大量资源的进程mysqld平均使用 1-2% 的 CPU 和 8% 的 RAM。

唯一的错误来自/var/log/apache2/error.log于 12 小时前我mod_pagespeed在优化尝试期间添加的错误。

[Thu Nov 16 06:52:38.941504 2017] [pagespeed:warn] [pid 5794] [mod_pagespeed 1.12.34.2-0 @5794] RateController: drop deferred fetch of https://SERVERIP/images/banner.png

如下所示apache2.conf，所有设置均按照主机为 VPS 推荐的设置进行，但MaxClients我尝试稍微增加但没有变化。

# Global configuration
#

#
# ServerRoot: The top of the directory tree under which the server's
# configuration, error, and log files are kept.
#
# NOTE!  If you intend to place this on an NFS (or otherwise network)
# mounted filesystem then please read the Mutex documentation (available
# at <URL:http://httpd.apache.org/docs/2.4/mod/core.html#mutex>);
# you will save yourself a lot of trouble.
#
# Do NOT add a slash at the end of the directory path.
#
#ServerRoot "/etc/apache2"

#
# The accept serialization lock file MUST BE STORED ON A LOCAL DISK.
#
Mutex file:${APACHE_LOCK_DIR} default

#
# PidFile: The file in which the server should record its process
# identification number when it starts.
# This needs to be set in /etc/apache2/envvars
#
PidFile ${APACHE_PID_FILE}

#
# Timeout: The number of seconds before receives and sends time out.
#
Timeout 300

#
# KeepAlive: Whether or not to allow persistent connections (more than
# one request per connection). Set to "Off" to deactivate.
#
KeepAlive On

<IfModule mpm_prefork_module>
    StartServers 4
    MinSpareServers 20
    MaxSpareServers 40
    MaxClients 400
    MaxRequestsPerChild 4500
</IfModule>

#
# MaxKeepAliveRequests: The maximum number of requests to allow
# during a persistent connection. Set to 0 to allow an unlimited amount.
# We recommend you leave this number high, for maximum performance.
#
MaxKeepAliveRequests 100

#
# KeepAliveTimeout: Number of seconds to wait for the next request from the
# same client on the same connection.
#
KeepAliveTimeout 5


# These need to be set in /etc/apache2/envvars
User ${APACHE_RUN_USER}
Group ${APACHE_RUN_GROUP}

#
# HostnameLookups: Log the names of clients or just their IP addresses
# e.g., www.apache.org (on) or 204.62.129.132 (off).
# The default is off because it'd be overall better for the net if people
# had to knowingly turn this feature on, since enabling it means that
# each client request will result in AT LEAST one lookup request to the
# nameserver.
#
HostnameLookups Off

# ErrorLog: The location of the error log file.
# If you do not specify an ErrorLog directive within a <VirtualHost>
# container, error messages relating to that virtual host will be
# logged here.  If you *do* define an error logfile for a <VirtualHost>
# container, that host's errors will be logged there and not here.
#
ErrorLog ${APACHE_LOG_DIR}/error.log

#
# LogLevel: Control the severity of messages logged to the error_log.
# Available values: trace8, ..., trace1, debug, info, notice, warn,
# error, crit, alert, emerg.
# It is also possible to configure the log level for particular modules, e.g.
# "LogLevel info ssl:warn"
#
LogLevel warn

# Include module configuration:
IncludeOptional mods-enabled/*.load
IncludeOptional mods-enabled/*.conf

# Include list of ports to listen on
Include ports.conf


# Sets the default security model of the Apache2 HTTPD server. It does
# not allow access to the root filesystem outside of /usr/share and /var/www.
# The former is used by web applications packaged in Debian,
# the latter may be used for local directories served by the web server. If
# your system is serving content from a sub-directory in /srv you must allow
# access here, or in any related virtual host.
<Directory />
    Options FollowSymLinks
    AllowOverride None
    Require all denied
</Directory>

<Directory /usr/share>
    AllowOverride None
    Require all granted
</Directory>

<Directory /var/www/>
    Options Indexes FollowSymLinks
    AllowOverride None
    Require all granted
</Directory>

#<Directory /srv/>
#   Options Indexes FollowSymLinks
#   AllowOverride None
#   Require all granted
#</Directory>




# AccessFileName: The name of the file to look for in each directory
# for additional configuration directives.  See also the AllowOverride
# directive.
#
AccessFileName .htaccess

#
# The following lines prevent .htaccess and .htpasswd files from being
# viewed by Web clients.
#
<FilesMatch "^\.ht">
    Require all denied
</FilesMatch>


#
# The following directives define some format nicknames for use with
# a CustomLog directive.
#
# These deviate from the Common Log Format definitions in that they use %O
# (the actual bytes sent including headers) instead of %b (the size of the
# requested file), because the latter makes it impossible to detect partial
# requests.
#
# Note that the use of %{X-Forwarded-For}i instead of %h is not recommended.
# Use mod_remoteip instead.
#
LogFormat "%v:%p %h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" vhost_combined
LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %O" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent

# Include of directories ignores editors' and dpkg's backup files,
# see README.Debian for details.

# Include generic snippets of statements
IncludeOptional conf-enabled/*.conf

# Include the virtual host configurations:
IncludeOptional sites-enabled/*.conf

# vim: syntax=apache ts=4 sw=4 sts=4 sr noet
LoadModule rewrite_module modules/mod_rewrite.so

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