jansipke.nl

Metering the meter cupboard

jansipke — Sun, 29 Aug 2010 19:44:48 +0000

In this article we will look at my meter cupboard and the meters inside it. In future articles we will see how I used a microcontroller and some sensors to meter the meters (at the time of writing the electricity meter works). From left to right, these are the electricity, gas and water meter:

Electricity

The electricity meter is a relatively new one with a digital display and a flashing LED. This LED flashes one thousand times for each kWh consumed, i.e. once per Wh.

Gas

The gas meter doesn’t have a flashing LED or something comparable. There is hope however, because there is a reflective area on the digit ’6′ at the far right of the display, just left of the ‘m2′. It also looks like there is some magnetic material in one of the last two digits, so there are actually two ways to go with this meter.

Water

The water meter doesn’t have a flashing LED or a reflective area anywhere. It also doesn’t have a colored dial, which most commercial water meter detectors use. There is a tiny bit of hope in the hole below ‘PR’. Using a magnetic sensor, I found some fluctuation in the values, but nothing consistent so far. The orientation of the sensor seems to be important, so I will fiddle a bit more with this one in the future.

Model View Controller (MVC) with JSP and JSTL

jansipke — Tue, 20 Jul 2010 07:28:32 +0000

In this article we will create a small web application that uses the Model View Controller (MVC) pattern with Java Server Pages (JSP) and JSP Standard Template Library (JSTL). A container like Tomcat is needed to run this combination.

Thanks go out to the author of the JSP – MVC Tutorial, who thought of the sample application that we will use here, the coffee advisor. The user is first presented with a choice in coffee taste she prefers. Pressing a button moves on to a page with advise about the type of coffee to drink based on that taste.

An MVC application has three parts:

Model. The model is the domain-specific representation of the data upon which the application operates. In our case this is implemented in the CoffeeExpert class.
View. The view renders the model into a form suitable for interaction, typically a user interface element. In our case this is implemented in a JSP file called coffee.jsp.
Controller. The controller receives input and initiates a response by making calls on model objects. In our case this is implemented in the CoffeeSelect class.

In addition to these three file we need a web.xml file that tells the container how to map a URL (e.g. /CoffeeSelect.do) into a class to run (e.g. com.example.web.CoffeeSelect). We also need a start page for the user input, which we will call coffee.html. In total this means we should create a .war file with the following structure:

coffee.html


    
        Coffee Advisor Input

CoffeeExpert.java

package com.example.model;

import java.util.*;

public class CoffeeExpert {
    public List getTypes(String taste) {
        List result = new ArrayList();
        if (taste.equals("milky")) {
            result.add("Latte");
            result.add("Cappuccino");
        } else if (taste.equals("froffy")) {
            result.add("Latte");
            result.add("Cappuccino");
            result.add("Frappuccino");
        } else if (taste.equals("icey")) {
            result.add("Frappuccino");
        } else if (taste.equals("strong")) {
            result.add("Espresso");
            result.add("Double espresso");
        } else {
            result.add("Vending machine");
        }
        return (result);
    }
}

CoffeeSelect.java

package com.example.web;

import java.io.IOException;
import java.util.List;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.example.model.CoffeeExpert;

public class CoffeeSelect extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
        List types = new CoffeeExpert().getTypes(request.getParameter("taste"));
        request.setAttribute("types", types);
        RequestDispatcher view = request.getRequestDispatcher("coffee.jsp");
        view.forward(request, response);
    }
}

coffee.jsp

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>


    
        Coffee Advisor Output

web.xml




    
        Coffee
        com.example.web.CoffeeSelect
    

    
        Coffee
        /CoffeeSelect.do

Changing CPU and memory settings on XenServer VMs

jansipke — Tue, 08 Jun 2010 15:33:18 +0000

You can change the CPU and memory settings of XenServer virtual machines using the API. XenServer allows you to set the priority of the virtual machine CPU (called weight), set a limit on the amount of CPU the virtual machine can use (called cap) and set the amount of memory the virtual machine gets.

CPU priority

You can set the weight parameter to a number between 1 and 65536. The default value is 256, meaning normal priority. A virtual machine with a weight of 512 will get twice as much CPU as a virtual machine with a weight of 256 on a contended XenServer host. The following code sets the weight to 128, meaning that it will get half as much CPU as a normal virtual machine.

Map vcpuParameters = new HashMap();
vcpuParameters.put("weight", "128");
vm.setVCPUsParams(connection, vcpuParameters);

CPU limit

You can set the cap parameter to a percentage number. The default value is 0, meaning there is no cap. The value 100 represents one virtual CPU, so half a virtual CPU can be set by using the value 50. The following code sets the cap to 35, meaning that it will not get more than 35 percent of one virtual CPU, even if the physical CPU is not used to its top.

Map vcpuParameters = new HashMap();
vcpuParameters.put("cap", "35");
vm.setVCPUsParams(connection, vcpuParameters);

Memory

You can set the amount of memory assigned to a virtual machine in bytes. The following code sets the amount of memory to 1 GB (1,073,741,824 bytes).

vm.setMemoryStaticMax(connection, new Long(1073741824));

Increasing the size of an LVM volume

jansipke — Thu, 03 Jun 2010 14:58:27 +0000

In a previous article we looked at LVM. This short article describes how to grow an existing volume by adding an extra disk to the system. Specifically, we use a XenServer guest VM with CentOS installed.

The first disk of a XenServer guest VM is called xvda, the second disk (the one we added) is called xvdb. We start with the creation of a Physical Volume (PV) on the extra disk.

pvcreate /dev/xvdb

Then we extend the existing Volume Group (VG) called VolGroup00.

vgextend VolGroup00 /dev/xvdb

Then we extend the Logical Volume (LV) by the size of the extra disk, in this case 8GB.

lvextend -L8G /dev/VolGroup00/LogVol00

Finally we resize the filesystem that uses this LV.

resize2fs /dev/VolGroup00/LogVol00

Installing XenServer Tools on Ubuntu 10.04

jansipke — Tue, 01 Jun 2010 10:03:00 +0000

XenServer supports a lot of Linux and Windows operating systems out of the box, but Ubuntu isn’t one of them. This means that running Ubuntu is slower, because it uses HVM (hardware-assisted virtualisation) instead of PV (paravirtualization). This article will explain how to create a paravirtualized Ubuntu 10.04 VM with the XenServer Tools installed. Many thanks go to the author of the article Ubuntu 10.04 LTS paravirtualised on Citrix XenServer.

We start with creating and installing a VM with HVM.

Create a VM from the Other install media template
Attach the Ubuntu 10.04 ISO to the DVD drive of the VM
Start the VM
At the disk partitioning stage make sure to replace Ext4 with Ext3, or create a specific boot partition with Ext3
Select at least the OpenSSH server package to be able to log in to the VM remotely
Finish installation and boot the VM

We now create a new console and edit the boot settings.

Connect to the VM using SSH
Create a new console for Xen

sudo cp /etc/init/tty1.conf /etc/init/hvc0.conf
sudo vi /etc/init/hvc0.conf

Replace all occurrences of tty1 with hvc0
Read /boot/grub/grub.cfg

sudo vi /boot/grub/grub.cfg

Copy the contents of menuentry near the bottom to a temporary text file, to be used as input for the makepv.sh script that we will use later on

menuentry 'Ubuntu, with Linux 2.6.32-21-server' --class ubuntu --class gnu-linux --class gnu --class os {
        recordfail
        insmod ext2
        set root='(hd0,1)'
        search --no-floppy --fs-uuid --set 02899ea9-1876-4e7b-8ef8-2b09b598cedb
        linux   /boot/vmlinuz-2.6.32-21-server root=UUID=02899ea9-1876-4e7b-8ef8-2b09b598cedb ro quiet
        initrd  /boot/initrd.img-2.6.32-21-server
}

Make special note of /boot/vmlinuz…, root=UUID=… and /boot/initrd.img…
Shutdown the VM

We now convert the VM to PV.

Connect to the XenServer host with SSH
Copy the makepv.sh script (download from here) to the XenServer host and make it executable

chmod +x makepv.sh

Run the makepv.sh script, replacing my-vm-name with the actual name of your VM

makepv.sh my-vm-name

Finally we install the XenServer tools.

Boot the VM and log in with SSH
In XenCenter, attach xs-tools.iso to the DVD drive of the VM
Mount xs-tools.iso, install the correct XenServer Tools package (replace amd64 with i386 if necessary) and unmount xs-tools.iso

sudo mount /dev/cdrom1 /mnt
sudo dpkg -i /mnt/Linux/xe-guest-utilities_5.5.0-466_amd64.deb
sudo umount /mnt

In XenCenter, detach xs-tools.iso from the DVD drive of the VM (this ensures that XenServer does not complain about too many bootable devices)
Reboot the VM and log in with SSH
Make sure the services run at boot time

sudo update-rc.d -f xe-linux-distribution remove
sudo update-rc.d xe-linux-distribution defaults

Reboot the VM for the last time
Restart XenCenter to be able to log in to the console of the VM

Installing Sun JDK 6 on Ubuntu 10.04

jansipke — Thu, 27 May 2010 13:21:32 +0000

The Sun JDK can be installed on Ubuntu by adding a repository and installing with apt-get. The following works with the latest versions of both at the time of writing:

sudo add-apt-repository "deb http://archive.canonical.com/ lucid partner"
sudo apt-get update
sudo apt-get install sun-java6-jdk

If the command add-apt-repository is missing, install it with the following command:

sudo apt-get install python-software-properties

With the alternatives system in place, the Java executable is automatically available:

/usr/bin/java -> /etc/alternatives/java
/etc/alternatives/java -> /usr/lib/jvm/java-6-sun/jre/bin/java

Setting up JAVA_HOME can now be done by editing /etc/profile and adding to the bottom:

export JAVA_HOME=/usr/lib/jvm/java-6-sun

Getting CPU, memory, disk and network metrics from XenServer

jansipke — Sat, 08 May 2010 18:56:20 +0000

In a previous article we looked at getting CPU and memory metrics from XenServer. As noted in that article, as of version 5.5 of XenServer, the preferred way of getting virtual machine metrics is through HTTP calls to get RRD XML files. We showed how to revert to the old way of doing things, but in this article we will look into the new, preferred way. This has the added benefit that disk and network metrics are also available, along with a history of metrics.

The first thing to note is that the metrics are not available through the XenServer API. The RRD XML files are stored on the physical machines that currently host the virtual machines. For example, if you have two physical machines (P1 and P2) with two virtual machines running on each of them (V1a, V1b, V2a and V2b), you need to query P1 for the metrics of V1a and V1b and query P2 for the metrics of V2a and V2b. If a virtual machine is not running at the moment, you can get the (old) metrics from the master in the pool.

Each physical machine has an HTTP interface at the following location:

http://machine_name_or_ip/rrd_updates?start=1234567890

The parameter start tells the server to only give metrics starting at this timestamp (seconds since January 1st 1970). The call requires a username and password, which will be asked if you connect through a webbrowser. The following code does this in Java:

Connection connection = new Connection(new URL(MASTER_HOST));
Session.loginWithPassword(connection, USERNAME, PASSWORD, APIVersion.latest().toString());

Map hostRecords = Host.getAllRecords(connection);
for (Host host : hostRecords.keySet()) {
    URL url = new URL("http://" + host.getAddress(connection) + "/rrd_updates?start=" + (System.currentTimeMillis() / 1000 - TIME_WINDOW));
    URLConnection urlConnection = url.openConnection();
    String encoding = new BASE64Encoder().encode((USERNAME + ":" + PASSWORD).getBytes());
    urlConnection.setRequestProperty ("Authorization", "Basic " + encoding);

    String rrdXportData = IOUtils.toString(urlConnection.getInputStream());
}

The code needs two libraries:

commons-io-1.4.jar. This package contains the code to get a string containing the data of an inputstream.
xenserver-5.5.0-1.jar. This package contains the code to connect to the XenServer pool.

The following constants are used in this piece of code and need to be filled in:

MASTER_HOST. This is the IP address or hostname of the master host in the pool.
TIME_WINDOW. XenServer will return RRD updates of the last TIME_WINDOW seconds.
USERNAME and PASSWORD. These are the credentials for connecting to the master host and the other physical hosts in the pool.

At the end of this piece of code we have the string rrdXportData containing the RRD XML data. Now we need to parse this data to get the metrics we want. The following listing contains the most important parts of this string (edited for clarity):


   
      1273342925
      5
      1273342980
      13
      31
      
         AVERAGE:vm:19ef51bd-2cbc-50d1-3fa2-ad8878699203:cpu0
         AVERAGE:vm:19ef51bd-2cbc-50d1-3fa2-ad8878699203:vif_4_tx
         ...
      
   
   
      
         1273342980
         0.0002
         0.0
         ...
      
      
         1273342975
         0.0003
         0.0
         ...
      
      ...

The following Java code will parse this RRD XML string and make it available in the four variables shown at the top. The variable metricsTimelines contains a hashmap of string to double[]. The string is the metric name (e.g. AVERAGE:vm:19ef51bd-2cbc-50d1-3fa2-ad8878699203:cpu0) and the double[] contains the values for this metric from startTime to endTime with a step size of step. Note that the value at endTime is at position 0 and the value at startTime is at the end of the array.

int endTime = 0;
HashMap metricsTimelines = null;
int startTime = 0;
int step = 0;

try {
   DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
   domFactory.setNamespaceAware(true);
   DocumentBuilder builder = domFactory.newDocumentBuilder();
   StringReader stringReader = new StringReader(rrdXportData);
   InputSource inputSource = new InputSource(stringReader);
   Document doc = builder.parse(inputSource);
   stringReader.close();

   ArrayList> dataRows = new ArrayList>();
   ArrayList legends = new ArrayList();
   NodeList xportChildNodes = doc.getDocumentElement().getChildNodes();
   for (int i = 0; i < xportChildNodes.getLength(); i++) {
      Node xportChildNode = xportChildNodes.item(i);
      if (xportChildNode.getNodeName().equals("meta")) {
         NodeList metaChildNodes = xportChildNode.getChildNodes();
         for (int j = 0; j < metaChildNodes.getLength(); j++) {
            Node metaChildNode = metaChildNodes.item(j);
            if (metaChildNode.getNodeName().equals("step")) {
               step = new Integer(metaChildNode.getTextContent()).intValue();
            } else if (metaChildNode.getNodeName().equals("start")) {
               startTime = new Integer(metaChildNode.getTextContent()).intValue();
            } else if (metaChildNode.getNodeName().equals("end")) {
               endTime = new Integer(metaChildNode.getTextContent()).intValue();
            } else if (metaChildNode.getNodeName().equals("legend")) {
               NodeList legendChildNodes = metaChildNode.getChildNodes();
               for (int k = 0; k < legendChildNodes.getLength(); k++) {
                  Node legendChildNode = legendChildNodes.item(k);
                  legends.add(k, legendChildNode.getTextContent());
               }
            }
         }
      } else if (xportChildNode.getNodeName().equals("data")) {
         NodeList dataChildNodes = xportChildNode.getChildNodes();
         for (int j = 0; j < dataChildNodes.getLength(); j++) {
            Node rowNode = dataChildNodes.item(j);
            NodeList rowChildNodes = rowNode.getChildNodes();
            ArrayList dataRow = new ArrayList();
            for (int k = 1; k < rowChildNodes.getLength(); k++) {
               Node rowChildNode = rowChildNodes.item(k);
               dataRow.add(k - 1, rowChildNode.getTextContent());
            }
            dataRows.add(dataRow);
         }
      }
   }

   int nrDataRows = dataRows.size();
   int nrLegends = legends.size();

   metricsTimelines = new HashMap();
   for (int i = 0; i < nrLegends; i++) {
      metricsTimelines.put(legends.get(i), new double[nrDataRows]);
   }
   for (int i = 0; i < nrLegends; i++) {
      for (int j = 0; j < nrDataRows; j++) {
         double[] values = metricsTimelines.get(legends.get(i));
         values[j] = new Double(dataRows.get(j).get(i)).doubleValue();
      }
   }
} catch (Exception e) {
   e.printStackTrace();
}

Using Google Visualization API with own data source

jansipke — Mon, 29 Mar 2010 18:18:18 +0000

The Google Visualization API allows you to create charts and maps based on data you provide. This data can be in a Google Spreadsheet or be something you provide yourself. The visualizations themselves are mostly written in Javascript, although there are some written in Flash.

In this article we will create an HTML page with multiple charts in it and a data source that is generated by a Python program. We start with the HTML page that has two named div’s in it (visualization1 and visualization2), including the Javascript code that loads the two charts into these div’s.



   
      
      
         Google Visualization API

There are two things that you really need to do before this works correctly:

Make sure that the parent node of the div that holds your chart, is not also the parent of one of the other div’s that holds a chart. In the HTML page above we surrounded the chart div with another div to accomplish this.
The chart is updated with new data every 5 seconds. It is a known bug of the Google Visualization API that the data needs to be fetched from another server then the one that is hosting the HTML page for the refresh to actually work. In the HTML page above the data source chart-data.py is therefore fetched from jansipke.nl and the HTML is fetched from www.jansipke.nl.

We will create our own data source in Python. There is a description of how you should do this on the Writing Your Own Data Source page from Google. One of the most common mistakes in writing these data sources is the need for the program to read the request identifier (reqId) and return this value in the response. The API needs this to distinguish between responses for different charts on the same page.

import cgi, random

def index(req):
   reqId = None
   if (req.args):
      for arg in req.args.split("&"):
         (key, value) = arg.split("=")
         if (key == "tqx"):
            for parameter in value.split(";"):
               if (parameter.find("%3A") > 0):
                  (par_key, par_value) = parameter.split("%3A")
               if (par_key == "reqId"):
                  reqId = par_value

   a = str(random.randint(1, 3))
   b = str(random.randint(1, 3))
   c = str(random.randint(1, 3))
   d = str(random.randint(1, 3))

   s = ""
   s += "google.visualization.Query.setResponse(\n"
   s += "{\n"
   if (reqId != None):
      s += "   reqId:'" + reqId + "',\n"
   s += "   status:'ok',\n"
   s += "   table:\n"
   s += "   {\n"
   s += "      cols:\n"
   s += "      [\n"
   s += "         {id:'Col1',label:'',type:'string'},\n"
   s += "         {id:'Col2',label:'Label1',type:'number'},\n"
   s += "         {id:'Col3',label:'Label2',type:'number'},\n"
   s += "         {id:'Col4',label:'Label3',type:'number'}\n"
   s += "      ],\n"
   s += "      rows:\n"
   s += "      [\n"
   s += "         {c:[{v:'a',f:'a'},{v:1.0,f:'1'},{v:1.0,f:'1'},{v:" + a + ",f:'1'}]},\n"
   s += "         {c:[{v:'b',f:'b'},{v:2.0,f:'2'},{v:1.5,f:'1'},{v:" + b + ",f:'1'}]},\n"
   s += "         {c:[{v:'c',f:'c'},{v:3.0,f:'3'},{v:2.5,f:'1'},{v:" + c + ",f:'1'}]},\n"
   s += "         {c:[{v:'d',f:'d'},{v:4.0,f:'1'},{v:2.0,f:'1'},{v:" + d + ",f:'1'}]}\n"
   s += "      ]\n"
   s += "   }\n"
   s += "});"

   return s

We can test this data source by following the link without parameters and following the link with the reqId parameter present:

http://jansipke.nl/res/visualization/chart-data.py

http://jansipke.nl/res/visualization/chart-data.py?tqx=reqId%3A0

Notice that the first one does not have reqId present in the response, but the second one does.

Update: it seems that the refreshing of data only happens correctly in Firefox and Opera. IE doesn’t refresh at all and Chrome only refreshes once. Oh joy!

Using XenServer in a routed IP network

jansipke — Sun, 28 Mar 2010 11:19:10 +0000

Hetzner is a hosting company in Germany where you can rent dedicated root servers per month. Using their KVM-over-IP setup, it is possible to install operating systems that are not available by default, such as XenServer by Citrix. With the machine, you get four public IP addresses. One of these addresses is given to you when the machine is assigned to you, the other three are assigned to you on request.

There is a problem with the public IP addresses Hetzner gives you. Within the Hetzner network, there is a hard connection between the MAC address of your machine and the IP addresses you have been given. This is a problem for virtual machines that are bridged onto the network by the host machine. These virtual machines have their own MAC address and the Hetzner network will drop packets from these unknown MAC addresses.

There is a solution to this problem: have the host machine route IP packets from the virtual machines to the network and vice versa. We will use the following addresses in the example below:

IP addresses	188.40.109.204 (host), 188.40.109.250 (VM)
Netmask	255.255.255.192
Gateway	188.40.109.193 (host)
DNS	213.133.100.100

We start with the configuration of the host machine (running XenServer). The first file is the configuration file of eth0: /etc/sysconfig/network-scripts/ifcfg-eth0

XEMANAGED=yes
DEVICE=eth0
ONBOOT=no
TYPE=Ethernet
HWADDR=40:61:86:be:ce:88 (replace with MAC address of host)
BRIDGE=xenbr0

Notice that this file does not contain any IP configuration. The second file is the configuration file of xenbr0: /etc/sysconfig/network-scripts/ifcfg-xenbr0

XEMANAGED=yes
DEVICE=xenbr0
ONBOOT=no
TYPE=Bridge
DELAY=0
STP=off
PIFDEV=eth0
BOOTPROTO=none
IPADDR=188.40.109.204 (replace with IP address of host)
NETMASK=255.255.255.192
GATEWAY=188.40.109.193 (replace with gateway of host)
DNS1=213.133.100.100
DNS2=213.133.99.99
DNS3=213.133.98.98

Now we need to enable IP forwarding on the host machine. We start with the sysctl configuration file: /etc/sysctl.conf

net.ipv4.ip_forward=1
net.ipv4.conf.all.send_redirects=0
net.ipv4.conf.default.send_redirects=0
net.ipv4.conf.lo.send_redirects=0
net.ipv4.conf.xenbr0.send_redirects=0

The first line tells the machine to perform IP forwarding. The four lines after that tell the machine to disable sending ICMP redirects. The last file we need to edit is the firewall configuration file: /etc/sysconfig/iptables. Add this text below the line -A RH-Firewall-1-INPUT -i lo -j ACCEPT:

-A RH-Firewall-1-INPUT -i xenbr0 -o xenbr0 -j ACCEPT

Now reboot the machine and continue with the IP configuration of the virtual machine running on XenServer. There is only one file we need to edit here, which is the configuration file of eth0: /etc/sysconfig/network-scripts/ifcfg-eth0

DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
HWADDR=8e:35:1e:3b:12:aa (replace with MAC address of VM)
IPADDR=188.40.109.250 (replace with IP address of VM)
NETMASK=255.255.255.192
GATEWAY=188.40.109.204 (replace with IP address of host)

The gateway in this configuration is crucial: it needs to be the IP address of the host itself, not the gateway of the host.

Creating web charts using Open Flash Chart

jansipke — Wed, 24 Mar 2010 19:32:06 +0000

Open Flash Chart gives you the possibility to have Flash based charts on your website without the need to know Flash. All it takes is a JSON file that describes the chart. This JSON file can be a static file that you created yourself with a text editor or dynamically created by a program, e.g. written in Java or Python.

There are several different types of charts that can be displayed. Some of them are shown here:

We start by creating an HTML page that will contain the chart:

Then we create a JSON file called chart1.data that describes how the chart should look:

{
  "title":{
    "text":  "Bar Glass Chart",
    "style": "{font-size: 20px; color:#0000ff; font-family: Verdana; text-align: center;}"
  },

  "bg_colour": "#FFFFFF",

  "x_axis":
  {
    "stroke":      1,
    "tick_height": 10,
    "colour":      "#CCCCCC",
    "grid_colour": "#00ff00",
    "labels":
    {
      "labels": ["Server 1", "Server 2", "Server 3"]
    }
  },

  "y_axis":
  {
    "steps":       20,
    "tick_length": 100,
    "colour":      "#CCCCCC",
    "grid_colour": "#00FF00",
    "offset":      0,
    "max":         100
  },

  "elements":
  [
    {
      "type":      "bar_glass",
      "alpha":     0.5,
      "colour":    "#9933CC",
      "text":      "CPU load",
      "font-size": 10,
      "values" :   [90, 60, 70]
    },
    {
      "type":      "bar_glass",
      "alpha":     0.5,
      "colour":    "#CC9933",
      "text":      "Memory usage",
      "font-size": 10,
      "values" :   [60, 70, 90]
    }
  ]
}

Copy the HTML file, the JSON file and the open-flash-chart.swf and swfobject.js files from the Open Flash Chart website to your own webserver and point your webbrowser to the HTML file. The result should look like the chart on this page.