Posts Tagged ‘index page’

Auto restart Apache on High server load (bash shell script) – Fixing Apache server temporal overload issues

Saturday, March 24th, 2012

auto-restart-apache-on-high-load-bash-shell-script-fixing-apache-temporal-overload-issues

I've written a tiny script to check and restart, Apache if the server encounters, extremely high load avarage like for instance more than (>25). Below is an example of a server reaching a very high load avarage:;

server~:# uptime
13:46:59 up 2 days, 18:54, 1 user, load average: 58.09, 59.08, 60.05
load average: 0.09, 0.08, 0.08

Sometimes high load avarage is not a problem, as the server might have a very powerful hardware. A high load numbers is not always an indicator for a serious problems. Some 16 CPU dual core (2.18 Ghz) machine with 16GB of ram could probably work normally with a high load avarage like in the example. Anyhow as most servers are not so powerful having such a high load avarage, makes the machine hardly do its job routine.

In my specific, case one of our Debian Linux servers is periodically reaching to a very high load level numbers. When this happens the Apache webserver is often incapable to serve its incoming requests and starts lagging for clients. The only work-around is to stop the Apache server for a couple of seconds (10 or 20 seconds) and then start it again once the load avarage has dropped to less than "3".

If this temporary fix is not applied on time, the server load gets increased exponentially until all the server services (ssh, ftp … whatever) stop responding normally to requests and the server completely hangs …

Often this server overloads, are occuring at night time so I'm not logged in on the server and one such unexpected overload makes the server unreachable for hours.
To get around the sudden high periodic load avarage server increase, I've written a tiny bash script to monitor, the server load avarage and initiate an Apache server stop and start with a few seconds delay in between.

#!/bin/sh
# script to check server for extremely high load and restart Apache if the condition is matched
check=`cat /proc/loadavg | sed 's/\./ /' | awk '{print $1}'`
# define max load avarage when script is triggered
max_load='25'
# log file
high_load_log='/var/log/apache_high_load_restart.log';
# location of inidex.php to overwrite with temporary message
index_php_loc='/home/site/www/index.php';
# location to Apache init script
apache_init='/etc/init.d/apache2';
#
site_maintenance_msg="Site Maintenance in progress - We will be back online in a minute";
if [ $check -gt "$max_load" ]; then>
#25 is load average on 5 minutes
cp -rpf $index_php_loc $index_php_loc.bak_ap
echo "$site_maintenance_msg" > $index_php_loc
sleep 15;
if [ $check -gt "$max_load" ]; then
$apache_init stop
sleep 5;
$apache_init restart
echo "$(date) : Apache Restart due to excessive load | $check |" >> $high_load_log;
cp -rpf $index_php_loc.bak_ap $index_php_loc
fi
fi

The idea of the script is partially based on a forum thread – Auto Restart Apache on High Loadhttp://www.webhostingtalk.com/showthread.php?t=971304Here is a link to my restart_apache_on_high_load.sh script

The script is written in a way that it makes two "if" condition check ups, to assure 100% there is a constant high load avarage and not just a temporal 5 seconds load avarage jump. Once the first if is matched, the script first tries to reduce the server load by overwritting a the index.php, index.html script of the website with a one stating the server is ongoing a maintenance operations.
Temporary stopping the index page, often reduces the load in 10 seconds of time, so the second if case is not necessery at all. Sometimes, however this first "if" condition cannot decrease enough the load and the server load continues to stay too high, then the script second if comes to play and makes apache to be completely stopped via Apache init script do 2 secs delay and launch the apache server again.

The script also logs about, the load avarage encountered, while the server was overloaded and Apache webserver was restarted, so later I can check what time the server overload occured.
To make the script periodically run, I've scheduled the script to launch every 5 minutes as a cron job with the following cron:

# restart Apache if load is higher than 25
*/5 * * * * /usr/sbin/restart_apache_on_high_load.sh >/dev/null 2>&1

I have also another system which is running FreeBSD 7_2, which is having the same overload server problems as with the Linux host.
Copying the auto restart apache on high load script on FreeBSD didn't work out of the box. So I rewrote a little chunk of the script to make it running on the FreeBSD host. Hence, if you would like to auto restart Apache or any other service on FreeBSD server get /usr/sbin/restart_apache_on_high_load_freebsd.sh my script and set it on cron on your BSD.

This script is just a temporary work around, however as its obvious that the frequency of the high overload will be rising with time and we will need to buy new server hardware to solve permanently the issues, anyways, until this happens the script does a great job 🙂

I'm aware there is also alternative way to auto restart Apache webserver on high server loads through using monit utility for monitoring services on a Unix system. However as I didn't wanted to bother to run extra services in the background I decided to rather use the up presented script.

Interesting info to know is Apache module mod_overload exists – which can be used for checking load average. Using this module once load avarage is over a certain number apache can stop in its preforked processes current serving request, I've never tested it myself so I don't know how usable it is. As of time of writting it is in early stage version 0.2.2
If someone, have tried it and is happy with it on a busy hosting servers, please share with me if it is stable enough?

How to add sidebar to single.php (Single Posts) to your wordpress blog default theme

Tuesday, April 12th, 2011

Until recently, I have used a default wordpress theme which historically is a bit old and used to be a default theme to the older versions of wordpress.
Since however, I’ve went to many updates and on the other hand I do like and enjoy the template I have decided to continue use it for my blog until this very day.

However this nice theme’s default behaviour is a bit weird, since by default the Single opened posts are configured in a way that the usual index page sidebar is missing.
As in the sidebar there are plenty of navigation buttons and search in the blog button, at a certain moment I have realized it’s probably not a good idea that the single.php (single blog posts) open up with the right sidebar missing.

Thus I’ve decided to put back the missing sidebar in the single posts, with a hope that this will be helpful to my readers and hence have positive impact on the overall blog user experience.

Doing so prooved to be rather easy, here is how I added back the right sidebar to my wordpress single posts :

1. Edit blog/wp-content/themes/default/single.php

debian:~# vim /var/www/blog/wp-content/themes/default/single.php

2. In the single.php look up for the code:

<div id="content" class="widecolumn">

Substitute this html code with:

<div id="content" class="narrowcolumn">

3. Next find the code: <?php get_footer(); ?>

Right before the get_footer(); php function add in the function;

<?php get_sidebar(); ?>

Tadam! Refresh a single post in Firefox and you should see your blog index.php sidebar to show up.

How to add manually adsense code to your wordpress blog in blog index and single page posts

Thursday, April 7th, 2011

I’ve recently realized that the Easy Adsenser plugin which I used to place google adsense advertisements on my blog, is probably stealing some portion of my clicks.

There were some fraud reports on wordpress.org by people who have found out the author of Easy Adsenser rips clicks, by showing sometimes his own ad code even if the plugin is configured to not grant any clicks as a donation to the plugin author.
I don’t know how true this story is and I don’t have the time to observe the whole plugin code to say for sure if the rumors about clicks stealing are true.

However as I’m paying my internet access (that guarantees) by blog to stay online with some adsense advertisements and the adsense revenues are either equal to my internet tax or a bit higher (depending on the month), it’s quite unpleasent to hear someone is stealing from the ads clicks which still generate very low revenue.

Thus I took the time to read some blog posts online which gave me some hints on how can I directly place the google adsense advertisement code into the theme template files

My goal was to place one google adsense ad to appear right after the title of each article and one to appear as a vertical bar in the end of my sidebar.

In this article in short I’ll explain how I achieved this banner placement via the default wordpress template which obviously I use on my blog.

Let’s start:

1. Add adsense to the index page of the blog

Edit your blog/wp-content/themes/default/index.php file

Therein find the code:

<div id="content" class="narrowcolumn" role="main">

and right after this line put the following php code:

<?php
$postnum = 1;
$showadsense1 = 1;
?>

This code is necessery to assure the adsense code only appears on the first blog post from the blog index page

2. Find the code:

<small><?php the_time('F jS, Y') ?> <!-- by