Thursday, November 13, 2014

Micro Services - Conway Law and Application Integration teams

"Micro Services" is a new buzzword in world of IT architects. As it talks about application components communicating over a network and contains "services", it probably has something to do with SOA and integration. So I had to look into it.

Let's bulletize the description from the article by Martin Fowler and James Lewis:
  • The Microservices architectural style is an approach to
  • developing a single application < application architecture
  • as a suite of small services, < componentization, no libraries
  • each (service) running in its own process
  • and communicating with lightweight mechanisms, < over the network
  • often an HTTP resource API. < REST, message bus
  • These services are built around business capabilities < Domain Driven Design
  • and independently deployable by fully automated deployment machinery.
  • There is a bare minimum of centralized management of these services, 
  • which may be written in different programming languages and
  • use different data storage technologies < eventual consistency
Microservices are an architecture used by very large, modern IT systems such as LinkedIn, Netflix, Amazon and eBay. There's all sorts of interesting aspects to Micro Services, e.g. the GUI part, security, transactional integrity, versioning etc.

Conway law - Integration Competence Center
But there was one aspect that triggered me in particular when learning about Microservices: Conway Law: "any organization that designs a system (defined broadly) will produce a design whose structure is a copy of the organization's communication structure".

So this law states that an application architecture will reflect the way an IT department is organized. Microservices advocates refer a lot to it.

Service boundaries reinforced by team boundaries (picture from article by Martin Fowler)

For Microservices to focus and align with business functionality, the teams developing (and maintaining) the Microservices should therefore be cross-functional, including the full range of skills required for the development: user-experience, database, and project management.

Orthogonal to the view of the Microservices architects, that Conway Law confirms my personal view and opinion that any IT organization that wishes to leverage a central integration platform to a great extent, requires a separate team developing on and managing that integration platform.

How did I learn about MicroServices?

PS: when searching for the term "micro service", I found the term also in the book "Java Web Services Architecture" back from 2003!

Saturday, November 8, 2014

ESB = Erroneous Spaghetti Box?

While re-reading the Microservices article by Martin Fowler, I was triggered by the following footnote #7: We can't resist mentioning Jim Webber's statement that ESB stands for "Egregious Spaghetti Box"I viewed the presentation - from 2008 - in which Jim Webber and Martin Fowler bash the Enterprise Service Bus and translate the acronym ESB into Erroneous Spaghetti Box.

I do agree that often, the integration platform simply contains a spaghetti of point-2-point integrations. But that's good! Way better than all that integration logic dispersed over many systems. With a wide variety of integration techniques, protocols and message formats. And spaghetti in a box is exactly what I tell when explaining what an integration platform is. Only by taking the next step of careful service and message design, one can arrive at a true Service Oriented Architecture.

Let's sum up the main advantages of an integration platform:
  • A standardized way to have applications talk to one another
  • No coding in a 3GL such as Java or C# but configuration in an application specifically built for the task of integrating systems
  • Support for applications of different kinds and ages, including packaged applications
  • Strongly reduced diversity in the tools and techniques used to integrate applications
  • Support for reliable, asynchronous communication using queuing and message persistence (which Fowler doesn't seem to like either)
  • Trivial connectivity through adapters
  • Central place to monitor and manage the communication between systems, in particular the reliable message exchange
  • Help turn packaged or older applications into services if desired (not everything is developed in-house)
With the disadvantages:
  • That it is a central, separate platform,
  • Requiring some specific skills (XML)
  • The cost of the integration development and support becoming truly visible.
Where Webber and Fowler do have a point, is that middleware vendors come with a whole slew of products. Obviously one should only pick the parts that are useful. And the ESB will definitely not create the Service Oriented Architecture for you.