I had to handle high traffic loads in my career and I fought with down-time, not used memory and a lot of trouble in my past. In this article I want to give a step-by-step guide to apache2 performance settings, which is a concentrated result of a lot of reading and trying.
My environment
- AWS EC2 (m4.xlarge): 4 *2,4GHz | 16GB RAM
- Ubuntu 16.04
- Apache 2.4 using mpm_event (See what’s best for you, How to switch)
- PHP FPM (5.6, 7.1)
Precalculation of average memory usage and maxclients/max-children
1. Calculate process size
You need to know how many processes can run on your machine. So calculate the process size of your main CPU/memory drivers is necessary.
There are several calculation methods out there. Personally I prefer this python script as it takes shared memory into account and will give insights into real memory usage.
cd ~
wget https://raw.githubusercontent.com/pixelb/ps_mem/master/ps_mem.py
chmod a+x ps_mem.py
sudo python ps_mem.pyps_mem.py will produce output like this:
Here you can see that there are 30 apache2 processes, consuming a total of 352 MiB, so each Apache process is using roughly 12MiB of RAM. The php-fpm5.6 process will use about 50MiB.
2. Calculate apache MaxRequestWorkers
To be safe though, I’ll reserve 15% of memory for all other processes (in my case ~1,2GiB) and round up apache process size to 15MiB.
MaxRequestWorkers= (Total RAM - Memory used for Linux, DB, etc.) / process sizeMaxRequestWorkers= (8192MB - 1200MB) / 15MB = 466
3. Calculate php-fpm max-children
To be safe though, I’ll reserve 1 GiB for all other processes and round up php process size to 55MiB.
maxclients = (Total RAM - Memory used for Linux, DB, etc.) / process size
maxclients = (8048MB - 1024MB) / 55MB = 128My colleague Thomas prepared this Excel Sheet for the calculation: https://s3.buckpesch.io/downloads/apache_performance.xlsx
Detailed Setup
In the /etc/apache2/mods-enabled/mpm-event.conf or /etc/apache2/mods-enabled/mpm-worker.conf file:
<IfModule mpm_*_module>MaxRequestWorkers
ServerLimit (Total RAM - Memory used for Linux, DB, etc.) / process size
StartServers (Number of Cores)
MinSpareThreads 25
MaxSpareThreads 75
ThreadsLimit 64
ThreadsPerChild 25
(Total RAM - Memory used for Linux, DB, etc.) / process size
MaxConnectionsPerChild 1000
</IfModule>
Note that the default settings did not contain the “ServerLimit”, so I added it here.
In the /etc/php/7.1/fpm/pool.d/www.conf change the following settings:
pm = dynamic
pm.max_children (total RAM - (DB etc) / process size)
pm.start_servers (cpu cores * 4)
pm.min_spare_servers (cpu cores * 2)
pm.max_spare_servers (cpu cores * 4)
pm.max_requests 1000To learn about all php-fpm settings I recommend watching the video on that page: https://serversforhackers.com/c/php-fpm-process-management
My final settings
My server has 16GB RAM and 4 CPUs à 2,4GHz. My avarage apache process has 15MB, an average PHP process takes 55MB.
/etc/apache2/mods-available/mpm_event.conf
# Optimized settings for avg. apache process 15MB and AWS EC2 m4.xlarge Server
<IfModule mpm_event_module>
ServerLimit 925
StartServers 4
MinSpareThreads 25
MaxSpareThreads 75
ThreadLimit 64
ThreadsPerChild 25
MaxRequestWorkers 925
MaxConnectionsPerChild 1000
</IfModule>
/etc/php/7.1/fpm/pool.d/www.conf
; Optimized for php-fpm request size of 55MB on AWS EC2 m4.xlarge (4CPU cores, 16GB RAM)
pm = dynamic
pm.max_children = 200
pm.start_servers = 20
pm.min_spare_servers = 10
pm.max_spare_servers = 20
pm.max_requests = 1000
Save your settings and restart your apache and php-fpm processes
sudo service apache2 restart
sudo service php7.1-fpm restart
Test you settings
To test your server settings you can run Apache Bench tests and see how your server behaves in htop .
Open 2 terminals and the following command to test 5000 requests with a concurrency of 100 parallel requests:
ab -n 5000 -c 100
I hope this helps. Drop me a line, when you have other experience or think I might can improve my formular/calculation. As well I might create a simple web-interface to calculate the settings… But now I have to go back to work ;-)
References
- http://drupalwxt.github.io/performance/apache-fpm/
- http://www.gk-root.com/GK-Blog/optimize-mysql-apache-on-cpanelwhm-server/
- https://fuscata.com/kb/set-maxclients-apache-prefork
- https://serverfault.com/a/383634/424932
- https://askubuntu.com/a/525035/409738
- https://serversforhackers.com/c/php-fpm-process-management
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