In this post I’ll talk about the optimising / configuring I did on Apache. So my site could live happily on its new home of AWS EC2 small instance ( running Amazon Linux ). The guide below covers sites that get maybe a few hundred page views per day (if you have bigger traffic you will probably need a bigger server).
I moved my site to AWS and it kept crashing Apache, I would restart it and it would be fine for while (maybe a few days or a week), then the same thing would happen again.
I looked in to the memory situation with Apache and found out it was launching a number of processes (too many, for the amount of RAM I had on my EC2 instance ). This is what I did to fix it. The command below can be handy to give you a quick view of whats currently being used (memory wise on your server).
free -m
Process
Check which MPM you running ( for small such as mine e.g. 1GB RAM , you want to be running prefork ):
httpd -V | grep MPM
If that doesn’t say prefork you need to alter Apache conf or one of the conf files ( I had to edit /etc/httpd/conf.modules.d/000-mpm.conf , but it can be different based on your distro, Amazon Linux seems to be quite similar to CentOS 7). Its good practice to always make a backup of any config you change. In your apache dir eg /etc/httpd in my case (grep might help you locate ).
grep -r “prefork”
I had to comment out the other (mpm event module ) and uncomment prefork so I had this loaded:
LoadModule mpm_prefork_module modules/mod_mpm_prefork.so
I then added this in the same file ( grep to check if you have some of this already):
<IfModule mpm_prefork_module>
StartServers 1
MinSpareServers 1
MaxSpareServers 1
MaxRequestWorkers 15
MaxConnectionsPerChild 0
</IfModule>
Because my memory was low. I needed to keep the Servers started low and MaxRequestWorkers also. This is how I calculated how to work out MaxRequestWorkers. First I grepped to see how many processes Apache had running:
ps -aux | grep apache
This showed me a bunch of php-fpm that I run this for to see the memory they were taking up:
ps -ylC php-fpm –sort:rss | awk ‘{sum+=$8; ++n} END {print “Tot=”sum”(“n”)”;print “Avg=”sum”/”n”=”sum/n/1024″MB”}’
This was telling me the memory the apache / php-fpm processes where taking up was about 60 MB per each , My MaxRequestWorkers was set to 256, so 256 * 60 MB = over 15GB of RAM required. Essentially Apache in the busier times was trying to simultaneously accept more connections that I had memory for on my EC2 instance ( I only had 600MB ish spare ). So needed to adjust this down ( 10 * 60MB = 600MB ).
MaxRequestWorkers is the amount of concurrent connections Apache will allow, I def need todo some optimising to get this figure up ( I only get maybe 200 page views per day so its ok for my site – and will be for many small sites / apps ).
Apache queues requests after MaxRequestWorkers reaches its max ( so new requests will wait to be serviced, this should be quick but depends, you may need a bigger EC2 instance if you have more traffic than you can handle ).
Other optimisations I did:
The main optimising the fixed my issues was the above, however I also added this to my apache conf file:
Timeout 60
KeepAlive on
MaxKeepAliveRequests 300
KeepAliveTimeout 2
I wont cover these but check out the liquid web link below (which covers these in detail).
Modules I removed:
Removing some Apache modules which would lower the MB used per Apache process ( so I could have more MaxRequestWorkers )
I grepped to find where modules where ( strewn about the place , but mostly in /etc/httpd/conf.modules.d/00-base.conf in my case):
grep -r LoadModule
Removed some modules, didn’t seem to make any difference so put them back in.
TODO: add what I did to my php-fpm config (www.conf)
References:
The video below is excellent:
https://www.linode.com/docs/guides/tuning-your-apache-server/
Disclaimer: All content on this site, is use at your own risk (Always backup before changing anything in your software/database/servers etc). Techs change, go out of date etc...I/we accept no liability if anything you use on this site adversely affects you.
Recent Comments