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A Vision for OpenStack

One of the great things about forcing yourself to write down your thoughts is that it occasionally produces one of those lightbulb moments of clarity, where the jigsaw pieces you have been mentally turning over suddenly all fit together. I had one of those this week while preparing my platform for the OpenStack Technical Committee election.

I want to talk a little about Keystone, the identity management component of OpenStack. Although Keystone supports a database back-end for managing users, the most common way to deploy it in a private cloud is with a read-only LDAP connection to the organisation’s existing identity management system. As a consequence, a ‘user’ in Keystone parlance typically refers to a living, breathing human user with an LDAP entry and an HR file and a 401(k) account.

That should be surprising, because once you have gone to the trouble of building a completely automated system for allocating resources with a well-defined API the very least interesting thing you can do next is to pay a bunch of highly-evolved primates to press its buttons. That is to say, the transformative aspect of a ‘cloud’ is the ability for the applications running in it to interact with and control their own infrastructure. (Autoscaling is the obvious example here, but it is just the tip of an unusually dense iceberg.) I think that deserves to stand alongside multi-tenancy as one of the pillars of cloud computing.

Now when I think back to all the people who have told me they think OpenStack should provide “infrastructure only” I still do not understand their choice of terminology, but I think I finally understand what they mean. I think they mean that applications should not talk back. Like in the good old days.

I think the history of Linux in the server market is instructive here. Today, Linux is the preferred target platform for server applications, but imagine for a moment that this had never come to pass: cast your mind back 15 years to when Steve Ballmer was railing about communists and imagine that .NET had gone on to win the API wars. What would that world look like for Linux? Certainly not a disaster. A great many legacy applications would still have been migrated to Linux from the many proprietary UNIX platforms that proliferated in the 1990s. (Remember AIX? HP/UX? Me neither.) When hardware vendors stopped maintaining their own entire operating systems to focus on adding hardware support to a common open source kernel, everybody benefited (they scaled back an unprofitable line of business, their customers stopped bleeding money, platform vendors still made a healthy profit and the technology advances accrued to the community at large). Arguably, that transition may have funded a lot of the development of Linux over the past 15 years. Yet if that is all that had happened, we could not call it fully successful either.

Real success for open source platforms means applications written against open implementations of open APIs. Moving existing applications over is important, and may provide the bridge funding to accelerate development, but new applications are written every day. Each one written for a proprietary platform instead of an open one represents a cost to society. Linux has come to dominate the server platform, but applications are bigger than a single server now. They need to talk back to the cloud and if OpenStack is to succeed—really succeed—in the long term then it needs to be able to listen.

MicroSoft understands this very well, by the way. The subject of Marxist theory and its similarities to the open source movement usually does not even come up when you launch a Linux VM on their cloud—the goal now is to lock you in to Azure, not .NET. Of course the other proprietary clouds (Amazon, Google) are doing exactly the same.

I am passionate about OpenStack because I think it is our fastest route to making an open source platform the preferred option for the applications of the (near) future. I hope you will join me. We can get started right now.

Having an application interact with the OpenStack APIs is really hard to do at the moment, because there is no way I am going to put the unhashed password that authenticates me to my corporate overlords on an application server connected to the Internet. The first step to fixing this actually already exists: Keystone now supports multiple domains, each with its own backend, so that application ‘user’ accounts in a database can co-exist with real meatspace-based user accounts in LDAP. The Heat project has cobbled together some workarounds that make use of this but they rely on Heat’s privileged position as one of the services deployed by the operator, and other projects do not automatically get the benefit either.

The next obstacle is that the authorisation functionality provided by Keystone is too simplistic: all rules must be predefined by the operator; by default a user does not need any particular role in a tenant to be granted permission for most operations; and, incidentally, user interfaces have no way of determining which operations should be exposed to any given user. We need to put authorisation under user control by allowing users to decide which operations are authorised for an account, including filtering on tenant-specific data. To get this to work properly, every OpenStack service will need to co-operate at least to some extent.

That gets us a long way toward applications talking back to the cloud, but when the cloud itself talks it must do so asynchronously, without sacrificing reliability. Fortunately, the Zaqar team has already developed a reliable, asynchronous, multi-tenant messaging service for OpenStack. We now need to start the work of adopting it.

These are the first critical building blocks on which we can construct a consistent user experience for application developers across projects like Zaqar, Heat, Mistral, Ceilometer, Murano, Congress, and probably others I am forgetting. There is no need to take anything away from other projects or make them harder to deploy. What we will need is consensus on what we are trying to achieve.