Easy, Beautiful Charts with Flot

I’ve been looking for a free, open source chart library for a while and was struggling to find something that was good enough (and handled time series and missing data points well). For a long time I’ve been using Fusion Charts (FC) and Open Flash Chart (OFC) in any in-house work and those products are very good. But they’re Flash, a little slow and not supported by some popular mobile devices. I’ve also used pChart for some testing but it was fairly stale in development and being images, had no interaction.

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. Read more >>

Debug PHP Function Calls

Logging errors can be very helpful as your code base becomes huge. But sometime it’s still difficult to find out what’s calling the function that’s giving the error. Wouldn’t it be nice if there was a way to see how you’d got to that function?

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);

Using SQL Management Studio in Windows 7

If you happen to be using SQL Management Studio in Windows 7 and need to connect to a SQL 2005 instance not running on the standard port of 1433, you might be having some problems connecting. For some reason this mix seems to require the SQL port to be manually defined when connecting to any named instance.

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.

Beware the leading zero in Javascript parseInt()!

Exhibit A,

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

Using PHP exec() with IIS6

There are a few work arounds I’ve found since having to use PHP under IIS6 and Windows 2003. Every now and again I come across something that just doesn’t work the same way with this variation of web server, OS and PHP.

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.

Dashboards and Displaying Business Data

From Monolith Software blog, “even the best dashboards are somewhat myopic, and badly designed dashboards can lead to complacency, poor communication and eventually overlooked issues, degradations or outages.”

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.

Ignore Network Latency at Your Peril

We all know developers need to consider a few things outside their own backyard. Things like hardware and the network affect software even if there’s not much that can be done to control them (even if you’re Apple). This is especially true for the network if you develop software for mobile devices.

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.

Watching your Network Usage

I’m sure everyone else knows about the iftop tool, but it was new to me. I needed to confirm that traffic from DRBD was using a particular interface and iftop does the job by showing traffic sources, speed and culmulative data counts per interface.

The iftop tool shows you usage per interface

Missing Network Interfaces in Ubuntu Under VMware ESXi

Every now and again I clone a VM and add it to another host. ESXi prompts you for a new UID when you start the VM and I always remove the virtual network card(s) from the machine and re-add them later. I do this to make sure I don’t have two machines with the same MAC addresses on the network. But if you do this with Ubuntu, the new NIC(s) don’t get picked up by the OS. This is almost certainly not specific to VMware or their ESXi product, it’s just the environment I’m using.

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.

Installing VMware Server 2.0.2 in Ubuntu 10.04

After updating my trusty old server to Ubuntu Lucid Lynx 10.04 the installation of VMware Server 2.0.1 started giving problems. Resinstalling VMware didn’t help as I was repeatedly getting compilation problems in vmmon and vmnet modules. Luckily I stumbled across the following process from one of the VMware forum pages which pointed to a great work-around from the radu cotescu site.

So I take no credit for this but simply repeat it here so that the search gods may recognise it’s usefulness and +1 it’s importance.

Start by downloading VMware Server 2.0.2 from the official VMware site. If you haven’t already got a few licenses, get one now. (They’re free so you might as well get a few) I’m going to assume the downloaded file is in your home directory.

You also need to update the header files for your current kernel so that the configuration scripts from VMware can build the appropriate modules.

sudo apt-get install linux-headers-`uname -r` build-essential

Now just run the following commands.

cd /usr/local/src
sudo wget [http://codebin.cotescu.com/vmware/vmware-server-2.0.x-kernel-2.6.3x-install.sh]
sudo tar xvzf raducotescu-vmware-server-linux-2.6.3x-kernel-592e882.tar.gz
cd raducotescu-vmware-server-linux-2.6.3x-kernel-592e882/
sudo cp /home/<your_username>/VMware-server-2.0.2-203138.i386.tar.gz .
sudo tar xvzf VMware-server-2.0.2-203138.i386.tar.gz
sudo chmod +x vmware-server-2.0.x-kernel-2.6.3x-install.sh
./vmware-server-2.0.x-kernel-2.6.3x-install.sh

If you have a previous installation of VMware Server, you’ll be prompted that it’ll be removed as part of the install. Don’t worry, any guest VMs you had should still be there afterwards. The script will run through the usual prompts and you’ll see references to the patched files from Radu Cotescu. After a few minutes you should have a working install of VMware Server 2.0.2 on your Ubuntu 10.04 server.