Japh » Networking

Tracking memory usage

Japh — Fri, 06 Feb 2009 12:35:51 +0000

Recently I received a warning from my host that I was WAY over my memory limit. I had some long running processes going, and a few cron scripts that altogether were using about 220mb out of my 120mb of allowed memory usage… oops!

Anyway, there’s currently no way from my control panel to see how memory I’m currently using, I have to run a command from a terminal, and certainly no way to tell usage over time. So, after looking at a thread my hosting provider pointed me to, I decided to have a play with the Google Charts API!

This is a pretty rudimentary solution, but it’s working so far for me.

1. A very simple bash script

#!/bin/bash
ps -u username -o pid,rss,command | grep -e mpm -v | awk '{sum+=$2} END {print ",", sum}' >> /path/to/webroot/mem/memdata.csv

The script basically just outputs the current memory usage at the time of running and appends it to a CSV file.

2. Add the script to the crontab

By running the following command (or one similar), I edit my crontab:

crontab -e

I then insert this line:

0 * * * * /full/path/to/script/memlogger

So now that bash script will be run every hour, on the hour.

3. Writing a PHP script to display a Google Chart


// Settings
$max_mem = 120; // Your memory limit, in MB
$data_file = 'memdata.csv';
$chart_width = 550;
$chart_height = 400;
?>
DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Memory Usagetitle>
head>
 
<body>
<h2>Memory Usageh2>

$md = file_get_contents($data_file);
$md = preg_replace('/(\s+|\n)/', '', $md);
$md = explode(',', $md);
array_shift($md);
$max = 0;
$min = 0;
foreach ($md as $v) {
	if ($v > $max) {
		$max = $v;
	}
}
$base = 0;
if ($max > 0) {
	$base = ((($max_mem) * 1024) / $max) * 1;
	$base = round($base, 2);
}
?>
<p><img src="http://chart.apis.google.com/chart?cht=lc&chd=t:$md); ?>&chs=$chart_width; ?>x$chart_height; ?>&chxt=y,r&chxr=0,$min; ?>,$max; ?>|1,$min; ?>,$max; ?>&chds=$min; ?>,$max; ?>&chm=r,FF0000,0,$base; ?>,$base+0.005; ?>" />p>
body>
html>

This code basically just imports the data into an array, and then works a few things out for proper axis labelling, and away it goes! It’s pretty quick and dirty, and could probably have been done nicer… maybe I’ll come back and fix it up some time.

It also uses your memory limit amount to show a red line on the graph if you go over

Here’s the chart using some sample data:

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DIY Dynamic DNS

Japh — Wed, 08 Oct 2008 11:17:05 +0000

I’ve setup my home network with a domain and wanted to be able to access my home server, from my office, on a subdomain.

However, as is probably the case for most of you, I have a dynamic IP address assigned to my router when it connects to the Internet through my ISP. So I decided I’d have to setup my own dynamic DNS process!

First things first, it was necessary to create the subdomain I wanted and point it to my home router’s external IP address, and also to change the configuration on my router to forward all traffic on port 80 to my home server’s internal IP address.

Next I needed a small script, PHP in this case, on my web server that simply outputs a tiny bit of XML with the current IP address of the visitor.

'; ?>
]]>

Then I wrote a small Python script that retrieves the IP address from the PHP script, and calls WebFaction’s server API to update the DNS record. This script runs on a crontab every hour, so if my IP address changes, I only have to wait an hour at most for an update.

#!/usr/bin/env python
import urllib
from xml.dom import minidom
import xmlrpclib
dyndomain = 'homeserver.example.com'
ip_url = urllib.urlopen('http://www.example.com/ip.php')
ip_dom = minidom.parse(ip_url)
ip_string = ip_dom.toxml()
ip_address = ip_dom.getElementsByTagName("ip")[0].childNodes[0].data
print ip_address
server = xmlrpclib.ServerProxy('https://api.webfaction.com/')
session_id, account = server.login('username', 'password')
server.delete_dns_override(session_id, dyndomain)
server.create_dns_override(session_id, dyndomain, ip_address, '', '', '', '')

Next I may add logging, so I can see when my IP address changes, but that’s optional really.

Note: Also, if someone can recommend a really good code-highlighter plugin for WordPress, I’d be very grateful!

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Fun with wild-card domain names

Japh — Tue, 16 Sep 2008 00:25:59 +0000

After seeing quite a few websites with dynamic content based on the domain name, I wanted to give it a try to see how difficult it was to achieve.

Here’s what I came up with: DueABootin.com

As it turns out, it wasn’t very difficult at all! (Especially being hosted through WebFaction, they make it even easier!)

First, I added the domain to my control panel, an added a subdomain of “*”, as you can see in the screenshot below.

And that’s really the hardest part, because PHP provides a nice little pre-defined variable called $_SERVER['HTTP_HOST'] which then gives us “example.dueabootin.com”, which we can pull apart and do with what we like.

Update: I’ve had a bit of a look into how difficult it might be to achieve the same results with cPanel, and it’s not much more difficult.

Create a new sub-domain called “*” which does not re-direct, just points to public_html/, and you should be fine. If that alone doesn’t work, then you may need to add an A record to your DNS zone file something like:

*.example.com. 14400 IN A 192.168.1.101

(don’t forget the trailing “.” after “.com”)

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