Sunday, April 1, 2012

Devstack - Treading Lightly into the Openstack World

Devstack is a simple way to test drive Openstack before committing too much time to setting up a production-ready Openstack installation. It allows you to  setup a toy Openstack installation in as little as one single virtual machine running on your PC. Then you can start and stop virtual machines (nova-compute), assign storage (Nova swift), play with Openstack networking or run your own images (Glance), and monitor your personal cloud  via the nice graphical interface using Openstack Horizon in a web browser.

Devstack works by executing a bash script which sets up all the software dependencies and Openstack software to run Openstack. Its primary use case is for Openstack development - if you are interested in tweaking Openstack's software then Devstack flattens the steep learning curve of setting up the test environment. However, it is also an excellent "try before you dive in" option. Compared to the free Amazon AWS trial, you will gain first hand experience of the entire IaaS cloud ecosystem - from setting it up to provisioning cloud resources for your applications. 

Here are the steps to run Devstack:

  • Install VMware or another hypervisor of your choice (e.g. Virtualbox) on your computer; you probably need a powerful computer with lots of RAM because what we are going to do is run a virtual machine on this computer and then run the Openstack software inside this VM; which in turn will spawn virtual machines inside the outer virtual machine! I recommend at least a dual core processor with 4GB of RAM. 
  • Download the Ubuntu 11.10 ISO from here. You probably don't need the desktop version; the server version should be fine. Off course this is assuming that you will run the Openstack Horizon client in a web browser of the host operating system (otherwise you need to run the web browser in the VM, which means you need X). So make sure you have networking connectivity between the host and the guess Ubuntu 11.10 virtual machine.
  • Use the downloaded ISO to create the Ubuntu 11.10 server virtual machine using the hypervisor you selected. Make sure to assign it adequate resources. A good start would be 2.5 GB of RAM, 40 GB of disk space and two cores.
  • Next follow the straightforward instructions from the Devstack webpage
  • The main Devstack script ( spits out the url of the Openstack Horizon web server at the end of the run. If your virtual machine is (network) accessible from your host OS then you can now point your browser to the url, login (credentials: admin,password or demo,password) to play with your very own Openstack cloud!

Ok done! Now what? Well, spawn a VM or two using the Horizon GUI. If you are more enterprising go ahead and try the euca2ools command line tools (the same command line tools used to speak with AWS also work here because Openstack supports the EC2 API). Try to spawn a whole bunch of VMs until your cloud gives up (in this case, the VM running the cloud is giving up!). If you are interested in learning how Openstack is setup, then reading the Devstack script is a great introduction to Openstack's internals. You probably know that Openstack is opensource, and its written in accessible Python code. So you can get right into Openstack development  and contribute to the project if that is your kind of thing.

A word of caution - the cloud "starts clean"  every time its host system (in our case the Ubuntu 11.10 VM) is rebooted. This means that any old VMs, images, or other configuration is cleared (that is the logical thing to do for a developer relaunching the cloud every time she changes the code base). If this is problem for you then you can simply suspend the virtual machine instead of shutting it down. But again, this is another reason to not use Devstack for a production system.