Algorithms, Design, Code and more: Apache

Friday, May 3, 2013

Php Script To Display Process, Vmstat, Disk Usage, Syslog Of A Linux Server Via A Browser

A Php script that executes some standard shell programs for monitoring resource utilization & processes on a given Linux box. The script directs the output to a web-browser.

Apache web-server should be installed on the server. To run copy the script to the DocumentRoot (/var/www/html). Appropriate execute rights (-rw-x) need to be given to the apache user (which runs this script, but is not the owner) to execute this Php file & to be able to access /var/log/syslog.

Save this file as: showHealth.php in the /var/www/html folder:

<html>
<body>
<script type="text/javascript">

</script>
<div id="outermost">
<div id="mcdetails">
Showing stats from:

<?php
echo shell_exec("ip addr show | grep 'inet' | tail -1");
?>
<br/><br/>Server Date is:
<?php
echo shell_exec("date");
?>
<br/><br/>
</div>
<a href="#" onclick="toggle('vmstat');">-------Vmstat----------</a><br/><br/>
<div id="vmstat" style="display:none">
<?php
$output = shell_exec("vmstat| sed 's/$/<br\/>/g'| sed 's/ /./g'");
echo $output;
?>
</div>
<br/><a href="#" onclick="toggle('df');">-------df -m----------</a><br/><br/>
<div id="df" style="display:none">
<?php
$output = shell_exec("df -m | sed 's/$/<br\/>/g'| sed 's/ /./g'");
echo $output;
?>
</div>
<br/><a href="#" onclick="toggle('ps');">-------ps aux----------</a><br/><br/>
<div id="ps" style="display:none">
<?php
$output = shell_exec("ps aux | sed 's/$/<br\/><br\/>/g'| sed 's/ /./g'");
//$output = shell_exec('ls -l');
echo $output;
?>
</div>
<br/><a href="#" onclick="toggle('syslogdiv');">-------syslog----------</a><br/><br/>

<div id="syslogdiv" style="display:none">
<?php
$output = shell_exec("tail -200 /var/log/syslog | sed 's/$/<br\/>/g' ");
//$output = shell_exec('ls -l');
echo $output;
?>
</div>
</div>
</body>
</html>

Wednesday, February 6, 2013

Mocking AWS ELB Behaviour Locally For Testing

Once hosted out of Amazon, you make use of the AWS Elastic Load Balancer (ELB) for balancing load across your EC2's within or acroos Availability Zones (AZ). Since code gets developed and tested locally (outside of Amazon), at times you might want to test load balancer scenarios before deploying to production. Here's one way to mock up the load balancer behaviour for local testing.

Use Apache (you could very well use something like Nginx instead) in a reverse proxy, load balancer set up via mod_proxy & mod_proxy_balancer. Fairly simple for anyone with slight experience with configuring Apache. We used Apache as a load balancer front-end to IIS on local, exactly the way ELB would load balance in front of production IIS.

Additionally, since ELB was also an SSL end point for our production servers, we set up Apache to be the SSL end point (via mod_ssl) on local. Apache was configured to listen on port 443 (using a self-signed certificate), and would forward all traffic from port 443 to backend IIS on port 80.

Once we had that set-up going, we were quickly able to reproduce an issue with application generated Secure cookies not getting set properly across client request/ response. Once we had the fix on the local (which was to set the flag on the cookies in the request, not response) the same worked flawlessly on the AWS as well.