Crowbar modularized: latest changes that make clouds even easier to create, update, and maintain

In the last week, my team at Dell completed a major refactoring of Crowbar that significantly improves our ability to bring in community contributions and field customizations.  Today, we merged it into Crowbar’s public repo(s).

From the very first versions, our objective for Crowbar was to create the fastest and most reliable cloud deployments. Along the way, we realized Crowbar’s true potential lay in embracing DevOps as an operational model for maintaining clouds. That meant building up cloud deployments in layers from pieces that we call barclamps (extensions of Chef cookbooks). Our first version, centered on OpenStack Cactus, leveraged barclamps but was still created as a single system. This unified system was a huge step forward in cloud deployments, but did not live up to our CloudOps vision of continuous delivery.

In this version, each Crowbar barclamp is an independent delivery unit that can be integrated before, while or after installing Crowbar.

The core of the change is each barclamp, including the most core ones, are stored in independent code repositories. Putting the code into distinct repos means that each barclamp can have its own life cycle, its own maintainer site and its own dependency tree. This modularization allows customers to manage their Crowbar deployments with a very fine brush: they may choose to customize parts of the system, they could lock components to specific tag and they can bring in barclamps from other vendors.

While the core barclamps are automatically integrated into the Crowbar build using git submodules; other barclamps are installed into the system as needed. This allows you to pull in the suite of OpenStack barclamps at build time or to wait until your Crowbar system is running before installing. Once you install a barclamp, you are able to retrieve an updated barclamp and reapply it to the system.

This feature gives you the ability to 1) choose exactly what you want to include and 2) perform field updates to a live Crowbar system.

Let’s look at some examples:

  1. The Cloud Foundry barclamp can be sourced Cloud Foundry instead of bundled into the Crowbar repository. This allows the team working on the cloud application to take ownership for their own deployment. As a continuous delivery proponent, I believe strongly that the development team should be responsible for ensuring that their code is deployable (refer to my OpenStack “Deployer API” blue print attempting to codify this).
  2. DreamHost, maintainers of Ceph Storage, can maintain their own local barclamp repos for OpenStack that are cloned from our community Swift barclamp. This allows them to innovate and customize OpenStack deployments for their business and choose which updates to merge back to the community.
  3. Rackspace Cloud Builders can work on the most leading edge OpenStack features and maintaining workable deployments on branches. As the code stabilizes, they simply merge in their changes.
  4. Dell BIOS and RAID barclamps only support the PowerEdge C line today. When we offer PowerEdge R support, you will be able to install or update the barclamps to add that capability. If another hardware vendor creates a barclamp for their hardware then you can install that into your existing system.

I believe that these changes to Crowbar are a huge step forwards on our journey of creating a community supportable Open Operations framework. I hope that you are as excited as I am about these changes.

I encourage you to take the first step by trying out Crowbar and, ultimately, writing your own barclamps.

Post Scripts:

  • In addition to the modularization, the updated code includes RHEL as a deployment platform. At present, you must choose to be either RHEL or Ubuntu at build time.
  • We have enhanced the network barclamp to describe connections as more abstract connections, called conduits, between nodes. This is a powerful change, but requires some understanding before you start making changes.
  • We have only begun testing the change as of 9/12, we expect the system to be fully stabilized by 10/3. If you are not willing to deal with bugs then I recommend building the Crowbar “v1.0″ tag (or using the ISOs from our July launch).