Category Archives: Software Development

Your ESB is going to kill you

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Recently I wrote about the fruitless plight of a schizophrenic service.  Now, I think that some of that schizophrenia exists in the ESB too (or is it rubbing off onto the ESB?).  I’ve always felt that the ESB was just another pattern that showed how to isolate things and deal with routing and transformations.  The most common implementation was a messaging gadget with some pluggable framework of sorts for the transformations, and some configurable framework for routing.
With such isolation of parts, it was convenient to not worry about what happened elsewhere when something was thrown to this gadget for processing.  And we started wondering about scalability things and decided that asynchronous was the way to go … disconnected, stateless, etc, all good, well-intentioned things and useful things.

Then the pattern became a product.  And on top of this product we had more products like business process orchestrators or workflow managers.  And below this product we had applications and databases and ftp locations and all sorts of things that catered for every imaginable protocol.  And around all of this we had some enterprise-ish sort of management thing to keep on eye on everything that was happening inside this very busy product.

Then, services moved from applications to the ESB product.  After all, it’s a service and that’s an enterprise service bus, right?  And when the services where moved over to their new home, all the dependencies had to come along too.  And then we started arguing about getting granularity right in the ESB.  I used to just think that the ESB had a proxy of sorts to the service that still was at the application.  Maybe I got it all wrong.

Now this ESB is starting to feel like an Application Server with a messaging gadget, workflow gadget, transformers, routers, protocol handlers.  And some ESB’s have a web server too, since they have browser based management consoles.

Some people also like the idea of a rules engine for their complex domain rules and embedded those in their applications.  Hold on, those content based routers in the ESB also used a rules engine.  Ok, let’s move our rules over to the ESB too.  Cool, my ESB is also a rules engine.

Now, I see people writing the most hellish XML that is meant to do everything from configure routing, define transformations, execute code, persist messages, fire off sets of rules and more.  It reminds me so much of those weird and wonderful stored procedures and cascading triggers that we wrote.  The other day I got a laugh out of a friend when I told him that ESB’s are now DB servers and everyone writes sprocs in XML.

And we tried to do everything in the database server – rules, custom types, defaults, constraints, sprocs, triggers, batch jobs … even jump into a shell and execute something else.  It did not work out very well then.

If I was an ESB, I’d be very confused.  I started life as a pattern with a reasonable implementation using messaging and transformation and routing.  Now all of this.  In fact, I’d be more stressed than confused.

Then again, maybe the ESB is not confused, and maybe the people that use the ESB that are confused.  In fact, if I was one of those people, I’d be stressed too.

Fast Track to Domain Driven Design

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I finally got out of neutral and pulled together the first public offering our Domain Driven Design courses in Cape Town, South Africa.  Normally we give these courses on-site with people on the same development team but I thought it may be fun and inspiring to open it up to everyone for a change.  Now I’m all excited again and really looking forward to a diverse mixture of people. Hopefully, I will see some old faces and lots of new people.
The one thing I can tell you is that the course is a very immersive experience.  I really hate lecturing but I enjoy probing conversations and that’s how I give the course. I don’t have answers to the practical work and concerns are addressed as we go along.  As a result, the day takes unexpected turns and routes.  But in the end I get you to the right destination.  Come along; you will leave exhausted, but inspired!

Take the Fast Track to Domain Driven Design

about the course /  course contents / should you attend? / register for the course

factor10 has expanded its services in South Africa to include our advanced and
expert level courses aimed for the software professional.  On September 8-9, 2009,
we will be offering a fast track to DDD for Architects at the BMW Pavilion in
Cape Town.

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Who should attend?

This course is for software professionals that want to take the right steps towards
advanced and expert levels in their careers.  Register for this course if you want to …

  • learn more than just another syntax and set of tools
  • write software for large, long living systems
  • increase the quality and maintainability of your design
  • design high quality models and use code to represent those models effectively
  • develop applications with a good APIs
  • add a design edge to your skill set

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Why should you learn DDD?

More and more developers and architects realise that learning every detail of a new
API just isn’t the way to deliver the best business value. It’s such a tough balancing
act; focus on the solving the business problem and focus on building working software
with your frameworks.

One way of taking a big leap in the right direction is to learn and apply domain driven
design. It is definitely not abstract and fluffy; it deals a lot with the code also. DDD
leads us to focus on understanding and to communicate that understanding very well;
in language, in design and in code. You will shift your focus away from designing for a
technology, and you will learn to design for the business domain; to the core of the
problems and solutions. Those are the most interesting parts and what your users
and customers really care about.

about the course /  course contents / should you attend? / register for the course

Pass the Parcel

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Fiona and I are planning Lia’s 5th birthday (27 July!) and a favourite kids’ party game is Pass the Parcel.  Kids sit in a circle, and there’s a surprise package with wads and wads of wrapping.  Music plays. Kids pass the parcel around. Music stops. Kid with parcel removes one layer of wrapping.  Music plays, pass it again.  And the last layer removed reveals the prize and that kid gets to keep it.  Do it once for each child, carefully timing the music and every kid is a winner 🙂
It reminded me of this business of tossing artifacts from once person to another in a development team.  In waterfall, it’s obvious who has what and what layer is peeled off when.  In fake agile(*), it’s not so obvious.  You know the music is playing when people ignore responsibility and toss it onwards or backwards.  The only difference, is that the party game everyone wins.  In the software game, everyone loses.

A few years back I sat in a class where Kent Beck explored XP with ten of us for a day.  For the first time, I realised that XP was less about coding practices and more about being decent people.  If I wanted to write quality software on time, on budget, etc. then I needed to have courage to accept responsibility for everything.  I don’t need to do everything, but I needed to feel responsible for everything.  No more passing the parcel, when it was convenient for me.  To do that, you need courage and respect.

Somehow, it feels like an Ubuntu coding thing again.  If you pass the parcel, make sure the receiver has good chance of winning the game.

(*) When the teams says they’re agile, practice agility mechanically, but don’t live by the value system which will make them agile in their heads.

Ubuntu Coding for your Friends

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Last week I gave a domain driven design course and one slide I put up was titled “Coding for Friends” with a single message “Avoid conceptual corruption”. In other words “Code so I can understand you and you don’t screw up my mind”.  I did not realise the significance until I started working through the practical exercises with the groups and kept on referring back to this simple idea.
So often we write code in isolation and the code reflects our personal interpretation of the problem and a personalised solution too.  We easily forget that other people will execute this code, modify it, and, at the very least, read it.  Coding is a social exercise first, then a technical exercise.  We have a responsibility towards increasing the probability of success for the next person or team that will work this code.

We can write code in isolation that is of high quality, focusing on self and metaphysics of quality, etc.  That’s a zen view and it is about you.  I like to think (believe?) that Ubuntu is zen for a group, not for an individual.

In Zulu, the Ubuntu philosophy is summed up as

Umuntu ngumuntu ngabantu

which roughly translates to

A person is a person through (other) persons

And in geek-speak it is

A developer is a developer through (other) developers

I get better because you make me better through your good actions.  And the opposite also holds true: You get worse at what you do when I am bad at what I do.

How do we write ubuntu code?  It’s not hard.  It’s based on “old” principles and wise words of many people.  It’s old material but worth revisiting with ubuntu glasses on: when you think about what the effect is on other developers and what the reciprocal effect will be, back onto yourself.

Reveal your intention, not your implementation. If you have designed a project management app with tasks and decided to implement it as a graph, call the class Task and give it a method called resolveCyclicDependencies().  Don’t create a class Node with a method called topologicalSort().

Avoid side effects. Let a method do one thing, and one thing only.  It’s frightening how many developers don’t do this.  For example, if you add a line item to an invoice, don’t update the total.  Have something else that calculates the total.  Basically, be boring and predictable.  I long time ago a SQL guru looked at my code and said “The optimizer does not like fancy code”.  Same thing.

Broken metaphors. Metaphors exist for conceptual understanding.  Once you get the conceptual break through, leave it.  It’s ok! Trying to build an economic model with a metaphoric model of fluid flows (or bears and bulls!) will just create havoc downstream.

Where am I? Figure out where you are in the bigger picture.  Are you upstream or downstream?  Is someone going call my code to create that Book object? Am I going to call someone else’s code to get the Customer object?  In other words, know what you supply and what you consume.

Fail fast. Assert! It’s allowed in production code too.  I would rather fail quickly and dramatically than delay the effect until it is obscure.  More importantly, when I read an assert then I know that the particular condition is critical.  It is an invariant that must be honored.

Pairing. Programming in pairs is an active exercise, not a case of a second syntax checker.  I see many teams that pair mechanically and it does nothing for increasing code quality at all.  If you practice active pairing, you are closer to ubuntu coding.

There are other techniques which increase the collective responsibility of your design and code such as context maps in strategic design, values and attitudes such as responsibility and feedback.  I’ll deal with those on another day.

But for now, I think that

Code is code through (other) code!

Do you have any other ubuntu coding techniques? Attitudes?

One Hundreth Away from Fame

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I read an article on the strength of the Finnish schooling system yesterday.  It’s considered as the best in the world with a 4% variance between the best school and the worst school.  How did they achieve that?  They give a lot of focus on the bottom 99% of kids in the classroom and not the top 1%.
I have a fear that as a community we promote the top 1%.  I hear developers being labeled such as rock stars and ninjas.  It’s no different to junior developers and senior developers.  We find all sorts of measures to be in the top 1%:  Twitter follower-count, Facebook friends, LinkedIn connections.  I think such labels and measures create an air of exclusivity and elitism to the detriment of 99% of the people.  NINETY NINE PERCENT !!

My 1% rankings have always been nothing more than a fleeting moment.  Once I won a book prize at school and I got an award for some design in university and meal voucher or two for a job well done.  It was meaningfully great in that context, relative to the others in that context.  But it was perceived as such by a few at that moment in time.

Looking back, I feel sad.  Not because of the scarcity my top 1% ranking, but by the reflection that those fleeting moments did not have lasting value to those that were in that context with me.  I should have made it count more significantly.  These days, I want to do things that touch others meaningfully.  Is my my code worth reading and from which you can learn?  Did our conversation over coffee move us closer to understanding each other?  And I want to be affected similarly too, by 100% of the people, not just the 1%.

Sometimes you’re in the top 1% and sometimes you’re in the bottom 99%.  But you will always be part of the 100%.  I am nothing, yet I am everything.

Great Quotes for Domain Driven Design

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I am revisiting the material for the factor10 Domain Driven Design course as part of a “freshen up” for the when I give it to a development team on July 1, 2009.  So I started hunting for some quotes to liven it up a bit.
Here are some choice bites for ubiquitous language.

“They have been at a great feast of languages and stolen the scraps” — William Shakespear

and

“Thought is the blossom; language the bud; action the fruit behind it” — Ralph Waldo Emerson

And on the need for simplicity, I really liked this one.

“There is never any justification for things being complex when they could be simple” — Edward de Bono

Robert Bravery commented on an old blog post of mine and I re-discovered this one

“Don’t indulge in any unnecessary, sophisticated moves.  You’ll get clobbered if you do” — Bruce Lee

Lastly, and the one I’m definitely going to use to stress the importance of working directly with the domain expert.

“Never hold discussions with the monkey when the organ grinder is in the room” — Winston Churchill

What a diverse group of people but such collective value.  Do you have any classic quotes?  Obscure quotes?

Writing Specs is Writing Code is Designing

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A team that I am coaching has settled on using BDD stories and scenarios for describing their requirements and specifications.  They’ve also chosen cucumber as their acceptance testing tool.  All well and good, but they are making very slow progress and seem to be really struggling with the change in workstyle.  I think I’ve spotted the reason for this.
The feedback loop is missing.  They view the stories as a spec that has been handed down.  And they have not made the connection that spec writing is design work that is intended to clearly illustrates concepts in a domain.  It is a form of writing code.  But it’s just that this code is, maybe, non-executable.

Here’s my workflow and how I close the loop.

  • write story and scenario
  • Sketch a design if needed – helps when pairing to be on the same page.
  • Start writing test for scenario
  • ooops … test is getting complicated? stuck?
  • maybe the domain is not understood enough? Dig deeper, improve scenario, design (as needed) and continue writing test
  • or maybe the scenario was badly written? Ignore scenario structure, continue writing test.  Refactor scenario later.  We’re in deep discovery mode here.
  • get test to pass
  • refactor code
  • refactor scenario
  • … cycle the red-green-refactor until happy.

Acknowledging when you’re in discovery mode and knowing that you are allowed to refactor requirements is the trick.  Nothing is cast in concrete.  That’s why I like frequent feedback loops with tight turning circles.

No feedback loop, no progress.

BTW, I really don’t like explaining such things as flow-charts and sequences.  You got to find your own style.  It’s not a recipe or rules thing.  The above is something that is about as close to what I do but it changes when the need arises.  That’s also another key feature of being agile – adapt or die in the waterfall.

Domain Specific Reference Architectures

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Many big vendors have invested a lot on blue print or reference architectures.  I came across another in recent months.  I witnessed a vendor team moving from client to client implementing this reference architecture as part of their SOA solution.
What were they actually doing? They were mapping the client’s domain to the reference architecture domain and thereby identified reference architecture services that supported the client’s needs.  This most probably works for some people.   But I feel uncomfortable with it because…

  • It means translating from one domain to another and back again.  It’s like having one massive bounded context around the reference architecture with a gigantic set of adaptors and transformers.
  • There is a very real possibility of semantic impedance on the boundary of the two domains.
  • There is likely to be two domain vocabularies or one large polluted vocabulary with synonyms, etc.

There are other reasons but these few are just old problems and habits coming back again.  Things that we accepted as dangerous and limits success in creating good software.

So, are reference architectures bad? Yes and no.  Maybe you should consider adopting its domain vocabulary as a first step.  A reference architecture with a rich metamodel is more likely to be more valuable than one without a metamodel.

And the moment you start thinking at a meta level, then you’re moving into a higher level of abstraction.  In this higher level, you will have a greater opportunity to describe your intentions agnostic of the reference architecture and the vendor’s technology stack.

The way I see it, services are defined at a meta level.  They describe your intentions and are independent of a reference architecture.  However, if you chose a reference architecture up front, then describe your intentions in the vocabulary of the reference architecture.

Does this make sense?  Because I’m just hypothesising here.

Wanted: Muse. No experience needed.

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Artists have muses.  Muses are their creative inspiration.  The Greeks also called it a daemon – that mythical thing that gave magical creativity.  It’s actually their genius spirit that helps them when they’re stuck in a metaphorical tight corner.  Same thing, I think.  So when did we stop having geniuses and became geniuses?
I think I am actually searching for a muse.  Something that will be my creative genius.  I gave up trying to be a genius a long time ago.  Now I just want to learn from those that are better than me, whatever the context.  Maybe my muse is the sum of every engagement with the genius in each person with whom I work and live.

Searching for miracles

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I never liked the words pilot nor proof of concept.   I have been through many pilot projects and proof of concept as projects or in projects.  Although the intention is well understood by everyone at the very beginning, by the time we reached the end, there almost always seems to be confusion about the purpose and next step.  Now I don’t even seem to know the differences and intentions anymore.  Even though everyone seems to know that they are different, they receive the same miracle software expectation.  It’s an execution confusion issue.
But I think the main reason for pilots and proof of concepts is to get feedback.  Spikes do the same thing too.  You know you’re seeking enlightenment when you start saying “I don’t know … enough…” or “It depends…” or “What if.” Whenever we work with a new domain or a tricky part of an application, we are searching for feedback, not miracles.  If you practice TDD and do exploratory testing of concepts that are not 100% clear in design and even understanding, then you know what I mean.  Perhaps we must just drop the grand classification labels and our response should be something like “Well, let’s explore this tiny bit and see what happens” or “Why don’t we try out this idea by doing …”.

So we do proof of concepts and pilots all the time.  It’s just that I hate searching for miracles but I like feedback which helps me change the probabilities of certain of things happening.  And I like it to be part of my workflow.  Exploration gives me feedback and increased understanding that leads to more exploration.  I hate it being a milestone on a Gantt chart and when that milestone is a common point in critical execution paths for the project, then I know, for sure, someone was actually looking for a miracle.

If you are somewhere on the agile adoption curve, then drop the Gantt chart.  Now you’ve just removed the shrine for miracle worship.  There are no shortcuts to enlightenment, just feedback with every step.  Success depends on how you absorb and react to that feedback.