The Flot JS library was something I’d seen a while back, but before I became comfortable with JS and jQuery. It does almost exactly what I want, is farily light-weight, extensible and easy to use. In a few hours last week I swapped out the FC code I had written for Overview and put in something almost half the size with Flot that created (in my view) a better product.

So I thought I might let others know what a nice, easy option Flot is with a little example. Beware this is not a fully working, copy and paste sort of example, it’s really just a chunk of generic code I pulled out.

The final output is a 24 hour chart of CPU usage for a server.

I call a PHP script called plot.php from the page that displays other server info. That plot.php script needs to know some info about what to draw, so it runs off to the database and fetches the last 24 hours of data about a particular data collector. Time is handled by Flot using the standard JS date object and displays in UTC. Any missing points are handled by joining the two points either side while the x-axis maintains spacing. NULL data points are not plotted to give a nice gap as expected.

So here’s a dump of plot.php, showing some of the Flot basics. If you download Flot, the API.txt file has pretty much all the info you will need.

Update: So the WordPress behaviour for pasting code is not the best, so have a look at this text file.

Anyone can schedule and show images, movies, messages, websites or RSS feeds to a group of computers. Rather than buy some sort of application that you must install on all your computers or a server, just get a low-powered machine and a web browser.

Features

DisplayPoint is being extended regularly and I’m open to requests for features which fit the general use of the product. Some of the current features are,

• completely browser-based
• centrally managed by anyone with a web browser
• content can be displayed for any duration
• show images like a slide show
• view movies from your own network or stream from YouTube
• post messages to inform others of meetings, news, etc
• import and cache RSS feeds from news sites
• display web pages that automatically scroll down to show all content
• set content to expire at a certain date and time
• add multiple display devices to content groups e.g. marketing sees one content group and the engineering teams see another

Use it to cycle through the photos from the company BBQ with messages about the next team meeting mixed in. You can even use it in public areas to highlight videos and show messages specific to that area.

Well of course there’s a way in PHP – debug_backtrace. Just add something similar in a suitable place in your code and you’ll be able to find what functions were called.

$trace=debug_backtrace();
$caller = $trace[1]['function'];
// or just dump all the info
var_dump($trace);

The fix is to specify the port in the server name used in the Connection prompt. So if your SQL instance was called SQL02 and running on port 3433, you’d use “MySql2005Server,3433 \SQL02″.

If you don’t know the port that SQL server is running on (maybe you have an external vendor supporting SQL), you can connect to the server from a Windows XP machine and run,

netstat -a | find /i "mysqlserver"

This will show you the network connection from your machine to the SQL server and the port being used.

parseInt('01'); //equals 1
parseInt('02'); //equals 2
parseInt('03'); //equals 3
parseInt('04'); //equals 4
parseInt('05'); //equals 5
parseInt('06'); //equals 6
parseInt('07'); //equals 7
parseInt('08'); //equals 0 !!
parseInt('09'); //equals 0 !!

When Javascript encounters a leading zero it assumes an octal number. So when it sees 08 or 09 then there are problems.

The fix is to add the radix to the function call,

myInt = parseInt('08',10); //equals 8

I needed to double-check the DNS hostname being reported from users on an internal website. Our DNS is a little scratchy when it comes to scavenging and keeping itself tidy, so often a DNS lookup of the client IP will give an incorrect name. This happens especially for laptops that hop off and on wireless APs.

So to compare against DNS (and because it’s an internal site) I thought to query the machines NetBIOS name with,

exec("nbtstat.exe -A 123.123.123.123",$r);

and that quickly fails with an error about “failing to fork”. Essentially this means, PHP can’t do what you want.

It boils down to file permissions. you need to run cmd.exe and nbtstat.exe with that single command. Both those files are secured against non-system users – probably rightly so too.

To resolve, just allow your IUSR_SERVER user to have read and execute permissions on both those files. Your exec() command should now be working.

REMEMBER: You are responsible for the security of your server. If you really don’t need to let programs run on your web server, then don’t.

This is something that comes up repeatedly when displaying data from one area to those from the wider business. Data in any form needs to come with the required info or education to provide clarity. The most basic chart can be mis-interpreted by those who make assumptions on the colours, format, numbers, etc before them. Admittedly, providing clear, functional, beautiful dashboards of a business’s data is difficult – and that’s one of the key reasons I enjoy doing it.

So to help us all understand why the nuances of any network are important to all of us, Nic Wise has a good little blog post about what to keep in mind. It’s written in people language and not TCP layers, so we can all benefit from this one.

This problem seems to be caused by a lack of automatic hardware probing at boot, probably for a good reason but I’m no Linux kernel guru so won’t make a judgement there. The root of the issue is located in the file /etc/udev/rules.d/70-persistent-net.rules where you’ll see the old interfaces still listed alongside the new ones. Simply remove the old NIC(s) and ensure the new ones have the MAC addresses you expect and the correct ethx labels. Give the system a reboot and you should be happy.

Steps to resolve a missing network interface in Ubuntu 10.04 Lucid Lynx (and possibly earlier):

1. sudo nano /etc/udev/rules.d/70-persistent-net.rules
2. Delete the lines with the old interfaces after comparing with your VMs newly assigned MAC addresses.
3. Confirm the interface names are what you expect at the end of each line.
4. Ctrl-X to save and exit.
5. sudo shutdown -r now
6. Run ifconfig to confirm the interfaces are up with the correct IPs.
7. If the interfaces are up, check your /etc/network/interfaces config to adjust IP settings as required.