I'm recently deployed an server running Ubuntu 16.04 and LAMP (Apache 2.4.18 as default with Ubuntu 16.04). Everything was fine in before the server went into production, however now Apache2 slows to a crawl (potentially 2+ minutes per for site to load) every 2/3 hours. Running sudo service apache2 restart speeds everything back up again though.

I've checked RAM/CPU during one of these periods and there are nowhere near maxing out. The server is 2GB RAM and 1 CPU core. This is thetop readout just before I restart apache

%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 

The only process using significant resources in mysqld which is using 1 - 2% CPU and 8% RAM average.

The only errors in /var/log/apache2/error.log are from 12+ hours ago when I added mod_pagespeed to during optimisation attempts.

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

The apache2.conf is as follows, everything all the settings are as the host recommended for the VPS except MaxClients which I tried increasing slightly but with no change.

# 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

# 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

# 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

# HostnameLookups: Log the names of clients or just their IP addresses
# e.g., www.apache.org (on) or (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 /usr/share>
    AllowOverride None
    Require all granted

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

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

# 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

# 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

The site makes fairly heavy use of AJAX and get about 30 active users at off peak times and 100 - 150 at peak times.

  • Do the mqsql logs show something unusual? Can mysql cope with the number of concurrent request on connection level? – Nils Nov 16 '17 at 19:59
  • @Nils The logs don't show anything strange. The only weird thing I've now noticed is that the apache logs show MaxRequestWorkers reached when the server is launched, which seems weird. – Flatlyn Nov 17 '17 at 12:20

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