Monthly Archives: November 2017

Poor man’s debugging high load on an Apache server

1 minute, 58 seconds

Hopefully you have a fancy solution to monitor your logs, but if you don’t, then I have a little treat for you. At work today I was trouble shooting why our web server would spike up to a load average of over 200 (I’d never actually seen a quad core server go much over 40 – neat!).  At first I stumbled around looking for non-obvious causes and then I just looked at the traffic.

I was pretty sure a single IP was slamming our server at midnight UTC.  To verify this I wrote a quick bash script to log the load averages, the count of the top process and it’s name, and finally, the count and IP of the top visitor over the prior minute.  It’s 13 lines of actual code and more than double that with comments.

By executing this in a crontab entry every minute, we get nice easy to read logs (and easy for a computer to parse):

* * * * * /root/ >> /var/log/httpd/apachetop.load.ps_log

The resulting log entry has the following handy fields:

  • LOAD_1 – load average for past 1 minute\
  • LOAD_5 – load average for past 5 minutes
  • LOAD_15 – load average for past 15 minutes
  • APACHE_CNT – Count of top IP in the last minute
  • APACHE_IP – Top IP in the last minute
  • APACHE_DIR – Top Directory being hit by IP
  • PROCESS_CNT – Count of top process
  • PROCESS – Process name for count

A sample log entry looks like this:

30/Nov/2017:07:24 LOAD_1="1.60" LOAD_5="1.50" LOAD_15="1.35" APACHE_CNT="5" APACHE_IP="" APACHE_DIR="/resources" PROCESS_CNT="25" PROCESS="/usr/sbin/httpd"

Otherwise, here’s the code from my gist, but please check it out on GitHub!

#!/usr/bin/env bash
date=`date --date='1 minutes ago' +%d/%b/%Y:%R`
apache=`grep $date /var/log/httpd/ssl_access_log |grep -v '::1'|cut -d' ' -f1,6,7|cut -d'/' -f 1,2|sort|uniq -c|sort -nr|head -n 1|tr '"' ' '|xargs`
apache_count=`echo $apache|cut -d' ' -f 1`
apache_IP=`echo $apache|cut -d' ' -f 2`
apache_dir=`echo $apache|cut -d' ' -f 4`
load1=`uptime|cut -d' ' -f14|tr ',' ' '|xargs`
load5=`uptime|cut -d' ' -f15|tr ',' ' '|xargs`
load15=`uptime|cut -d' ' -f16|tr ',' ' '|xargs`
process=`ps xa|cut -d':' -f 2|cut -d' ' -f 2|sort|uniq -c|sort -rn|head -n 1|tr '\n' ' '|xargs`
process_count=`echo $process|cut -d' ' -f 1`
process_name=`echo $process|cut -d' ' -f 2`
echo $date LOAD_1=\"$load1\" LOAD_5=\"$load5\" LOAD_15=\"$load15\" APACHE_CNT=\"$apache_count\" APACHE_IP=\"$apache_IP\" APACHE_DIR=\"$apache_dir\" PROCESS_CNT=\"$process_count\" PROCESS=\"$process_name\"