Archive | December, 2011

PaaS Element Types

8 Dec

Please Note : This post builds directly on the previous post “A viable PaaS Model

What are PaaS Element Types?

PaaS Element Types are the constructs required to build a PaaS.  Each PaaS Element Type builds upon the previous, I’m not the first to come up with the overall concept of Types building upon one another, this was inspired by Data Types from Software Development.  It is important to understand that all PaaS Element Types end up being abstractions built upon one another.

Why are they important?

As we move to the new paradigm of application development, architecture, and management, applications will be the comprised of these new element types vs. the traditional patterns and designs we have all become used to.  By fully understanding PaaS Element Types, you will gain not only an understanding of how different PaaS solutions work, but what their capabilities, strengths, and weaknesses are and why they have these characteristics.

Compute, Networking, Storage, what about Memory?

You may have noticed that Memory is not listed as a column, why is that?  Storage is meant to encompass all forms of storage, which includes Memory (Memory is just a very fast form of volatile storage, just as an L1 Cache is even faster than standard memory it is all for storing bits and bytes – albeit briefly).  All of the PaaS Elements have the ability to leverage memory for whatever purpose they may need, but I see no reason to separate memory in the Element Types.

Primitives as defined in the previous blog post

Primitives are the Core Building Blocks of Resources.  What does this mean?  Primitives cannot be reasonably reduced to a more basic/granular bit of functionality.  You may be thinking that an Operating System could most certainly be reduced to a more simplistic bit of functionality and you would be correct if we were talking about us in a traditional Infrastructure, but not PaaS.  Part of the magic of PaaS is the prescriptive nature that PaaS brings, along with the obfuscation in most cases of components such as the Operating System.  In the case of the Operating System, it is also important to recognize that as a Primitive, the OS has not actually been instantiated (it isn’t a running OS).  One final note is that PaaS eliminates nearly all direct ties between code and the OS (There are still limits imposed by the runtimes, etc. which are difficult to avoid – e.g. Mono for .Net support on Linux)

Sophisticates : Composites / Combinations / Extensions of Building Blocks (Primitives)

Sophisticates are built from Primitives, meaning that a Sophisticate cannot exist unless it is backed by a Primitive with some addition, change, or a second PaaS Element Type such as a Primitive or Sophisticate.  A Sophisticate could be built from a combination of another Sophisticate and a Primitive!  Let’s take RDBMS as an example (note that this would just as easily apply to NoSQL solutions, etc).  RDBMS will likely leverage a RuntimeVM, an Operating System, Processes, an Interface, Block Store, Cache, and a File System.  While this may be complex it is hidden by the RDBMS Interfaces, which is part of the beauty of PaaS is exposing this combination as a Service or Extension that can be consumed by an API call or a DB connection.

Definitives : Instantiations (Running) of Primitives and Sophisticates either directly in use or wrapped in Services/APIs creating easily leverage abstractions.

These abstractions allow complex configurations of Primitives and Sophisticates coupled with Application Logic, Dynamic Configuration capabilities, and more.  Definitives are the live and fully implemented abstractions as they consume resources.  This could be a Schema in a RDBMS or a Collection with Documents in it in a Document Store.  Definitives are where all of the specificity occurs in PaaS and ultimately what differentiates applications from each other once they are running.

What can you do with all of this stuff?

If you use the prescriptive side (what a developer writing to a running PaaS offering would do) of PaaS and simply consume it, you can quickly and without a deep understand deploy applications within the limits of the PaaS App Space.  Alternatively you can design your own PaaS with whatever capabilities you require to support the behaviors and design patterns that you need for your App Space.  This is done by using the PaaS Element Types to make choices on the Control Space, which in turn creates the boundaries of the PaaS App Space.

Control Spaces share some characteristics of the App Spaces that they provide, this is because the Control Space operates on the same infrastructure that the App Space operates on.  This is true in the majority of PaaS cases that I have seen to date (it could at least in theory, change).  Control Space components are Definitives built from Primitives and Sophisticates to provide the prescriptive approach to the App Space that makes PaaS an attractive alternative to traditional software builds, configuration, deployments, etc.

The work in mapping Primitives, Sophisticate, and Definitives is not yet finished!

What I have provided is the beginning, not the end.  More work needs to be done in adding additional examples of PaaS Element Types, along with mapping all of the current PaaS offerings to both the PaaS Model and what Element Types are used/comprise each PaaS offering.  In future blog posts with help from different collaborators I hope to accurately map the major PaaSes to the PaaS Model and their PaaS Element Types.

 Comment here on the blog or ping me on Twitter (@mccrory) with your thoughts and ideas.

A viable PaaS Model

7 Dec

What makes a PaaS a PaaS?

I’ve seen many discussions on blogs and twitter around this topic, so much so that many people are tired of talking about it because it always leads to cyclical discussions.  I for one haven’t been satisfied with any of the answers that I have seen.  Some people try to define PaaS with requirements such as it must be on demand, while others say that an API and services need to be exposed.  I disagree with these requirements/constraints on describing PaaS.  I think there is a model should be applied to define what is PaaS, to make this model credible there is a necessity that it can be mapped to most (if not all) current and future offerings defined as PaaS (Which will be a follow-on series to this post).

The PaaS Model

The PaaS Model is made up of two different constructs, which are called Spaces.  These two Spaces serve different purposes, but are composed of the same PaaS Element Types (elements will be explained in detail, in an App Space deep-dive follow-on post).  The Control Space and App Space are show in the diagram below, notice that the App Space is fully wrapped/contained within the Control Space.

Control Space:

The Control Space performs all of the automation, management, provisioning that is required by the PaaS.  Interaction with other lower level components such as an Orchestrator is achieved through API abstractions if/when necessary. The Control Space and its implementation also determine what elements are allowed/exposed to the App Space. Further, the Control Space is responsible for maintaining App Space coherency and dependencies.  While the Control Space is comprised of several separate functions, they may be combined in different manners depending on the specific PaaS implementation.  All of this will also commonly be exposed through one or more API interfaces (this however, isn’t necessarily a requirement in the model presently).

App Space:

The App Space is where end-user/customer applications are deployed, updated, and run.  The App Space is controlled (and commonly coordinated) by the Control Space.  The exposure of PaaS Element types by the Control Space to the App Space is one of the key differentiating factors between different PaaS implementations.  App Space characteristics are controlled by how the Control Space is built/designed along with what PaaS Elements were used to build the Control Space.

  • App Network: The path which applications communicate with app each other and services/resources exposed to apps.  The App Network exposes Network connectivity to the App Space.
  • Executor: The application bootstrapping mechanism for apps being or currently deployed.  The executor provides compute/memory resources to the App Space.
  • Code Processor: Examines code, libraries, and dependencies before sending to the Engine and/or Executor.  This can also be thought of as a code inspector or post/pre-processor.
  • Coordination Network: Where the Control Space components communicate/coordinate with each other.  Think of this as a management network that is in most cases out-of-band from the App Network.  The Coordination and App Networks could be combined, however in a production system this would introduce too large of a security risk.
  • Engine: Coordinates the distribution and provisioning of code, services, and their dependencies (most frequently in the Control Space).  The Engine decides the where and how of what happens in the App Space.  Also, the Engine may be capable of coordinating with an Orchestration Layer or other automation tools outside of the Control Space to provide new/additional resources to either/both the Control Space and the App Space.
  • Monitor: Looks at the state of the App Space and the Control Space, signaling other Control Space components to resolve conflicts.  The component most likely to resolve conflicts would be the Engine or a specialized component designed purely for conflict resolution.
  •  Notes: These components/functions may be grouped differently based on the specific PaaS implementation.  Also, some of the functionality or components could be put into an API, split into sub-components, or even externalized through/in a Client or Client side API.

PaaS Elements:

PaaS Elements are abstractions on top of different layers of resources.  Most PaaS Element abstractions are done through Service based or Service centric abstractions.  This is not the only way of creating/doing an abstraction, but it is one of the most flexible ways.  PaaS Elements are broken up into three primary types which are defined below:

Please note there will be an in-depth post on PaaS Elements following this blog post.

  • Primitives : The Core Building Blocks of Resources
  • Sophisticates : Composites / Combinations / Extensions of Building Blocks (Primitives)
  • Definitives : Instantiations of Primitives and Sophisticates either directly in use or wrapped in Services/APIs

All PaaS Elements have the ability to provide or interact through a pass-through interface or abstraction to any other PaaS Element type all provided by the Control Space.  Elements are combined to create an Application (App) in the App Space.  The most interesting twist to the model is that the Control Space is made up entirely of PaaS Elements as well.  There is a great deal more to be covered on this topic both here on this blog and out in the community.  Please provide feedback and questions in the comments section of this post or live on Twitter (@mccrory)

I would like to give a special thanks to Shlomo Swidler (@shlomoswidler) and Derek Collison (@derekcollison) for providing valuable feedback in several draft iterations of this post.