Udi Dahan   Udi Dahan – The Software Simplist
Enterprise Development Expert & SOA Specialist
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SOA Training Videos and Pricing

Posted in NServiceBus | SOA | Training

It looks like the SOA training videos will start coming in the next week or so.

So, I’ve started thinking what else should be included so that you get the most out of them.

Here’s what I’ve currently got in mind:

  • All the powerpoint presentations
  • Full source and samples of nServiceBus so you can run the code as I talk about it
  • 4 hours of online consultation so you can get up to speed quickly in applying these principles and practices to your project

If you have anything else in mind that you think will help, please drop me a comment below.

So far, 32 people have expressed interest in getting this and it looks like I should be able to handle up to about 40 in a timely manner with my current setup. I hadn’t originally thought about corporate licensing, but since there have been some requests (so that all employees can use the information freely, get copies of the DVD’s, etc), I’ll be doing that too. If you’ve already left a comment about your interest in the DVD’s, I’ll assume you want the personal option. If you want to change that to the corporate option, please leave a comment either here or on the previous post.


Ayende mentioned that the guys from Dot Net Rocks are selling Sharepoint training for about $700 per developer for a day of training. I really don’t know how much to charge for this – the guys in Australia paid quite a bit and I wouldn’t want them to feel – well, like you feel when you find out that the guy sitting next to you on the plane paid half what you did for his ticket; especially given that they’ve done so much of the production work on the DVD’s (Simon, Brad – you guys are my heroes. I really couldn’t do this without you).

So, I figure that I’ll hear what you guys think that the package is worth first. Leave me comment, or send me an email if you’d like more anonymity.

I’d also be interested in hearing what kind of domain you’re thinking about applying this stuff to – I might be able to put you in touch with people already applying SOA and nServiceBus in those areas so you can learn from each other as well.

Looking forward to hearing from you.

Posted on Monday, March 24th, 2008.

QCon London 2008 Recap

Well QCon was a blast.

NServiceBus Tutorial

I gave a full day tutorial on nServiceBus and we had a full house! The tutorial was about 90% how to think about distributed systems, and 10% mapping those concepts onto nServiceBus. I made an effort to cram about 3 days of a 5 day training course I give clients into one day, but I think I was only about 85% successful. People didn’t have the time needed to let things really sink in and ask questions, but the lively forums and skype conversations available will probably do the trick.

Jim Webber after looking at the unit testing features of nServiceBus had this to say:

“Oh my God – you’ve created testable middleware! It’ll never catch on. The vendors won’t have it.”

To which I replied that several vendors were already coming on board with their own implementations of transports and saga persistence. I have absolutely no intention, desire, or (quite frankly) the ability to write an enterprise-class middleware runtime. All I hope to do with nServiceBus is to make it so that developers use what’s out there in one, middleware-product-agnostic way that will make their code more robust and flexible.

MEST & Mark – REST & Stefan

It was also great finally meeting the head MESTian, Mark Little, who also happens to work for Redhat as SOA Technical Development Manager and Director of Standards in the JBoss division. It was interesting to see the difference between how I went about messaging in nServiceBus (full peer-to-peer including pub/sub) whereas most of the Java world has the messaging infrastructure handled by something database-like in a deployment/networking kind of perspective. If that’s the way things are done, then I can definitely appreciate the advantages of Space-Based Architectures.

And I even got to steal Stefan Tilkov’s RESTful ear for an hour or so before I had to jet back home. It looks like we MESTians and RESTians can be one big happy family. I’m guessing that our despise of WS connects us all at a deeper level :)

Core Design Principles

I also gave a talk about core design principles, “Intentions & Interfaces – making patterns concrete”, and it went over very well especially considering that that was the first time that I gave that talk. You can find the slides here. From the feedback I heard after the talk, I think many people were surprised how many different parts of a system can be designed this way, and how flexible it is without making the code any more complex. The message was this:

Make Roles Explicit

Despite its simplicity, that leads to IEntity, IValidator<T> where T : IEntity, (which I wrote about a year ago – generic validation) and with a bit of Service Locator capabilities, you can add a line of code to your infrastructure that will validate all entities before they’re sent from the client to the server.

It leads to IFetchingStrategy<T> for improved database loading performance (also a year old – better DDD implementation and the NHibernate implementation).

It’s also how nServiceBus does message handling – IMessage, IMessageHandler<T> where T: IMessage, ISaga<T> where T : IMessage.

San Francisco?

Just a quick shout to my readers in the San Francisco area, if you’d be interested in hearing these talks/tutorials, give the organizers of QCon a shout and they’ll bring me out. That’s actually what got me to London – one of the attendees of a talk I gave at Oredev in Sweden last November missed my tutorial there so he put in a request and that did it. (Thanks Jan, I appreciate it!)

If you’re in a different part of the world and you’d like to have me give one of these talks, or other ones (I have a fair amount of material on Domain Models/DDD and Occasionally Connected Smart Clients), I’d be happy to make the trip and see you there as well.

Comments [3]
Posted on Thursday, March 20th, 2008.

Sundblad Mistaken on Services

The brilliant guys at 2xSundbland have launched their architect academy and it looks quite promising. I haven’t yet taken the trial lesson, but its in the queue. I have taken a look at the articles they have on the site as well, and they’re quite good. I especially like the Software Architecture vs. Software Engineering one. There is one topic in that article where I beg to differ, and it’s around services. The article (on page 7) describes the following scenario:

Typically, in such an environment [SOA], services tend to be parts of multiple systems. For example, consider a Products service! It might start its life as part of a sales system. Later it might be involved in a purchasing system, a product development system, a marketing system, a warehousing system, and perhaps in several other systems too. This process may take years, and it really never ends. The service is the same, but its responsibilities and its external exposure are increased with each system it’s enrolled in.

One of the core tenets of SOA that all vendors and analysts agree upon is that there should be loose coupling between services. If you were to design such a product service, it’s clear that changing part of its interface could break almost every system in the enterprise. That doesn’t sound like loose coupling to me.

If there’s one place that is the source of loose coupling – it’s the business. Warehousing is viewed by the business as being fairly independent of Marketing. While Sales might make use of data created in Product Development, business wouldn’t want any problems in IT related to Product Development to inhibit Sales ability to accept orders. That is another kind of loose coupling – the ability of one service to make use of “not-accurate-up-to-the-millisecond” data created by another service. That’s known as loose “temporal” coupling, as in loose coupling in the dimension of time.

Loosely-Coupled Services

So, in the example described we’d see the following services:

  • Sales
  • Purchasing
  • Product Development
  • Marketing
  • Warehousing / Inventory

Product data would flow between the services but each would have a very different internal view of it.

  • Product Development would be more interested in managing the schedule and risk around a product’s development.
  • Marketing would probably be more focused on its relation to competing products and pricing.
  • Purchasing would be maintaining data as to which suppliers are being used to supply raw materials for the production of the product.
  • Sales would be looking at actually accepting orders and giving discounts.
  • Warehousing would be focused on the storage and transportation aspects of the product.

As you can see, there is very little overlap in the data between these services even on something similar like product data. The logic of each service around the management of its data would be even more different. This leads to services with a high level of autonomy.

There Be Dragons…

Without starting at this business-level loose coupling, I doubt that any technical effort will succeed. That is to say every time I’ve seen this style implemented it has failed, but that’s no proof. Conversely, every time that we did start our SOA efforts by identifying the clear business fracture lines, we were able to maintain loose coupling all the way down. That is not to say that it always will succeed, but the logic is sound.

I suppose that the difference between my view on SOA and Sundblad’s stems from the fact that they put systems at a higher level of abstraction than services, and I put services on top. Regardless, I do agree with their views about architecture and engineering and consider them quite valuable.

Comments [1]
Posted on Sunday, March 16th, 2008.

[Podcast] REST + Messaging = Enterprise Solutions

In this podcast we revisit the topic of REST and how to make it work for process-centric enterprise systems. After describing the basic advantages and pitfalls of plain resource thinking, we’ll look at how mapping messaging concepts to resources provides solutions for transactional, multi-resource processing.



Download via the Dr. Dobb’s site

Or download directly here.

Additional References

Want more?

Check out the “Ask Udi” archives.

Got a question?

Send Udi your question to answer on the show.

Comments [10]
Posted on Sunday, March 16th, 2008.

How to create fully encapsulated Domain Models

image Update: The new and improved solution is now available: Domain Events, Take 2.

Most people getting started with DDD and the Domain Model pattern get stuck on this. For a while I tried answering this on the discussion groups, but here we have a nice example that I can point to next time.

The underlying problem I’ve noticed over the past few years is that developers are still thinking in terms of querying when they need more data. When moving to the Domain Model pattern, you have to “simply” represent the domain concepts in code – in other words, see things you aren’t used to seeing. I’ll highlight that part in the question below so that you can see where I’m going to go with this in my answer:

I have an instance where I believe I need access to a service or repository from my entity to evaluate a business rule but I’m using NHibernate for persistence so I don’t have a real good way to inject services into my entity. Can I get some viewpoints on just passing the services to my entity vs. using a facade?

Let me explain my problem to provide more context to the problem.

The core domain revolves around renting video games. I am working on a new feature to allow customers to trade in old video games. Customers can trade in multiple games at a time so we have a TradeInCart entity that works similar to most shopping carts that everybody is familiar with. However there are several rules that limit the items that can be placed into the TradeInCart. The core rules are:

1. Only 3 games of the same title can be added to the cart.
2. The total number of items in the cart cannot exceed 10.
3. No games can be added to the cart that the customer had previously reported lost with regards to their rental membership.
    a. If an attempt is made to add a previously reported lost game, then we need to log a BadQueueStatusAddAttempt to the persistence store.

So the first 2 rules are easily handled internally by the cart through an Add operation. Sample cart interface is below.

   1:  class TradeInCart{
   2:      Account Account{get;}
   3:      LineItem Add(Game game);
   4:      ValidationResult CanAdd(Game game);
   5:      IList<LineItems> LineItems{get;}
   6:  }

However the #3 rule is much more complicated and can’t be handled internally by the cart, so I have to depend on external services. Splitting up the validation logic for a cart add operation doesn’t seem very appealing to me at all. So I have the option of passing in a repository to get the previously reported lost games and a service to log bad attempts. This makes my cart interface ugly real quick.

   1:  class TradeInCart{
   2:      Account Account{get;}
   3:      LineItem Add(
   4:          Game game, 
   5:          IRepository<QueueHistory> repository, 
   6:          LoggingService service);
   8:      ValidationResult CanAdd(
   9:          Game game, 
  10:          IRepository<QueueHistory> repository, 
  11:          LoggingService service);
  13:      IList<LineItems> LineItems{get;}
  14:  }

The alternative option is to have a TradeInCartFacade that handles the validations and adding the items to the cart. The façade can have the repository and services injected though DI which is nice, but the big negative is that the cart ends up totally anemic.

Any thought on this would be greatly appreciated.


As I highlighted above, the thing that will help you with your business rules is to introduce the Customer object (that you probably already have) with the property GamesReportedLost (an IList<Game>). Your TradeInCart would have a reference to the Customer object and could then check the rule in the Add method.

Before I go into the code, it looks like your Account object might be used the same way, but your description of the domain doesn’t mention accounts, so I’m going to assume that that’s unrelated for now:

   1:  public class Customer{
   3:      /* other properties and methods */
   5:      private IList<Game> gamesReportedLost;
   6:      public virtual IList<Game> GamesReportedLost 
   7:      { 
   8:          get
   9:          {
  10:              return gamesReportedLost;
  11:          }
  12:          set
  13:          {
  14:              gamesReportedLost = value;
  15:          }
  16:      }
  17:  }

Keep in mind that the GamesReportedLost is a persistent property of Customer. Every time a customer reports a game lost, this list needs to be kept up to date. Here’s the TradeInCart now:

   1:  public class TradeInCart
   2:  {
   3:      /* other properties and methods */
   5:      private Customer customer;
   6:      public virtual Customer Customer
   7:      { 
   8:          get { return customer; }
   9:          set { customer = value; }
  10:      }
  12:      private IList<LineItem> lineItems;
  13:      public virtual IList<LineItem> LineItems
  14:      {
  15:          get { return lineItems; }
  16:          set { lineItems = value; }
  17:      }
  19:      public void Add(Game game)
  20:      {
  21:          if (lineItems.Count >= CONSTANTS.MaxItemsPerCart)
  22:          {
  23:              FailureEvents.RaiseCartIsFullEvent();
  24:              return;
  25:          }
  27:          if (NumberOfGameAlreadyInCart(game) >=
  28:              CONSTANTS.MaxNumberOfSameGamePerCart)
  29:          {
  30:              FailureEvents
  31:                .RaiseMaxNumberOfSameGamePerCartReachedEvent();
  32:              return;
  33:          }
  35:          if (customer.GamesReportedLost.Contains(game))
  36:              FailureEvents.RaiseGameReportedLostEvent();
  37:          else
  38:              this.lineItems.Add(new LineItem(game));
  39:      }
  41:      private int NumberOfGameAlreadyInCart(Game game)
  42:      {
  43:          int result = 0;
  45:          foreach(LineItem li in this.lineItems)
  46:              if (li.Game == game)
  47:                  result++;
  49:          return result;
  50:      }
  51:  }
  53:  public static class FailureEvents
  54:  {
  55:      public static event EventHandler GameReportedLost;
  56:      public static void RaiseGameReportedLostEvent()
  57:      {
  58:           if (GameReportedLost != null)
  59:               GameReportedLost(null, null);
  60:      }
  62:      public static event EventHandler CartIsFull;
  63:      public static void RaiseCartIsFullEvent()
  64:      {
  65:           if (CartIsFull != null)
  66:               CartIsFull(null, null);
  67:      }
  69:      public static event EventHandler MaxNumberOfSameGamePerCartReached;
  70:      public static void RaiseMaxNumberOfSameGamePerCartReachedEvent()
  71:      {
  72:           if (MaxNumberOfSameGamePerCartReached != null)
  73:               MaxNumberOfSameGamePerCartReached(null, null);
  74:      }
  75:  }

image Your service layer class that calls the Add method of TradeInCart would first subscribe to the relevant events in FailureEvents. If one of those events is raised, it would do the necessary logging, external system calls, etc.

As you can see, the API of TradeInCart doesn’t need to make use of any external repositories, nor do you need to inject any other external dependencies in.

One thing I didn’t do in the above code to keep it “short” is to define the relevant custom EventArgs for bubbling up the information as to which game was reported lost or already have 3 of those in the cart. That is something that definitely should be done so that the service layer can pass this information back to the client.

Here’s a look at Service Layer code:

   1:  public class AddGameToCartMessageHandler :
   2:      BaseMessageHandler<AddGameToCartMessage>
   3:  {
   4:      public override void Handle(AddGameToCartMessage m)
   5:      {
   6:          using (ISession session = SessionFactory.OpenSession())
   7:          using (ITransaction tx = session.BeginTransaction())
   8:          {
   9:              TradeInCart cart = session.Get<TradeInCart>(m.CartId);
  10:              Game g = session.Get<Game>(m.GameId);
  12:              Domain.FailureEvents.GameReportedLost +=
  13:                gameReportedLost;
  14:              Domain.FailureEvents.CartIsFull +=
  15:                cartIsFull;
  16:              Domain.FailureEvents.MaxNumberOfSameGamePerCartReached +=
  17:                maxNumberOfSameGamePerCartReached;
  19:              cart.Add(g);
  21:              Domain.FailureEvents.GameReportedLost -=
  22:                gameReportedLost;
  23:              Domain.FailureEvents.CartIsFull -=
  24:                cartIsFull;
  25:              Domain.FailureEvents.MaxNumberOfSameGamePerCartReached -=
  26:                maxNumberOfSameGamePerCartReached;
  28:              tx.Commit();
  29:          }
  30:      }
  32:      private EventHandler gameReportedLost = delegate { 
  33:            Bus.Return((int)ErrorCodes.GameReportedLost);
  34:          };
  36:      private EventHandler cartIsFull = delegate { 
  37:            Bus.Return((int)ErrorCodes.CartIsFull);
  38:          };
  40:      private EventHandler maxNumberOfSameGamePerCartReached = delegate { 
  41:            Bus.Return((int)ErrorCodes.MaxNumberOfSameGamePerCartReached);
  42:          };
  43:      }
  44:  }

It’s important to remember to clean up your event subscriptions so that your Service Layer objects get garbage collected. This is one of the primary causes of memory leaks when using static events in your Domain Model. I’m hoping to find ways to use lambdas to decrease this repetitive coding pattern. You might be thinking to yourself that non-static events on your Domain Model objects would be easier, since those objects would get collected, freeing up the service layer objects for collection as well. There’s just on small problem:

The problem is that if an event is raised by a child (or grandchild object), the service layer object may not even know that that grandchild was involved and, as such, would not have subscribed to that event. The only way the service layer could work was by knowing how the Domain Model worked internally – in essence, breaking encapsulation.

If you’re thinking that using exceptions would be better, you’d be right in thinking that that won’t break encapsulation, and that you wouldn’t need all that subscribe/unsubscribe code in the service layer. The only problem is that the Domain Model needs to know that the service layer had a default catch clause so that it wouldn’t blow up. Otherwise, the service layer (or WCF, or nServiceBus) may end up flagging that message as a poison message (Read more about poison messages). You’d also have to be extremely careful about in which environments you used your Domain Model – in other words, your reuse is shot.


I never said it would be easy :-)

However, the solution is simple (not complex). The same patterns occur over and over. The design is consistent. By focusing on the dependencies we now have a domain model that is reusable across many environments (server, client, sql clr, silverlight). The domain model is also testable without resorting to any fancy mock objects.

One closing comment – while I do my best to write code that is consistent with production quality environments, this code is more about demonstrating design principles. As such, I focus more on the self-documenting aspects of the code and have elided many production concerns.

Do you have a better solution?

Something that I haven’t considered?

Do me a favour – leave me a comment. Tell me what you think.

Comments [65]
Posted on Friday, February 29th, 2008.

Prevent technology blow-ups from killing your project

Posted in General | Workflow

Why should you put a 10 foot pole between yourself and technology?

Well, because Microsoft (or insert vendor of your choice here – they’re all equally guilty of this) tend to deprecate (as in kill) the technology they evangelised just last year/month/week.

Microsoft Sql Server Notification Services are the latest victim.

I hope you don’t have any application code tied to that technology.

Not that it’s the only one.

Workflow Foundation’s warts have started coming out from behind the shiny veneer. It turns out that the threading model is… problematic and requires all sorts of workarounds. Hope those are stable. It’s not like they could have known that we need a high performance way to run our business logic out of the box. I hope you don’t have to change your application code (sorry, pictures diagrams) when you get blocked threads when trying to cancel irrelevant workflows (customer no longer does business with us – cancel order processing workflows).

I forgot to mention that the solution above is for single-box parallelism – if you want true scale-out, you need to go back to solution that “require talented software developer use of call-external-method and handle-external-event activities along with the CLR thread-pool“. That’s OK – I have yet to meet a team/company who attests that they have below average developers.

I apologize for the somewhat sarcastic tone of this post.

It’s just that I’m sick of Microsoft handing developers razor-sharp knives, pointy end forward, and after the developer loses a couple of fingers mentions “oh yah, watch out for these pointy, sharp bits”.

To the developers out there – maybe we need kevlar suits before handling these hazardous materials.

To Microsoft – you think that this doesn’t alienate your customers?

We’re all in the same boat together.

I’m hoping that ALT.NET can help.

Comments [2]
Posted on Wednesday, February 27th, 2008.

"High Priced" architects extremely valuable, even when remote

Posted in General

image When I’m working on a thorny architectural problem, I usually give Arnon a ring and after talking things through with him, reach a much better solution than what I previously was convinced of. These calls have been saving my clients months of effort, increasing revenue through shorter time-to-market, and often have lower total cost of ownership by needing fewer boxes and less admins to keep them running. Simply not-needing a BizTalk (roughly $50K for a dual cpu box) and one less Oracle (between $50K to $75K depending on server size) brings you to 6 figures without breaking a sweat. Imagine what you could buy with that.

It sucks that not enough people have access to guys like Arnon, but he’s pretty busy with his baby now. Although I’ve been trying to jet to clients providing the same kind of value, I’ve pretty much topped out at 10 of these per year each running about a week on average. Frankly, I don’t think my wife would keep me if I did any more than that :-)

Long Distance Relationships

          After doing a bunch of these sessions using Skype, Copilot, Oovoo (for video sharing), and now trying (and liking) Microsoft SharedView I’ve found that I can provide a lot of the architectural guidance and value remotely. This spans all the distributed systems stuff including nServiceBus, using O/R mapping and the Domain Model pattern for logic-rich persistence, asynchronous web architectures, and designing occasionally connected clients (which I’ll be putting more guidance out for shortly).

The fact that Scott said this couldn’t work is a point in it’s favour, though :-) scottbellware120

Just kidding. He had no idea that Big Design Up-Front could be so yummy:

“I think the real value’s in preventative work – where you try to help folks out during the early ideation of their architecture rather than bail them out once they’ve put more investment in designing stuff on paper that doesn’t jive with experience.”

The format that I’ve found works really well for most mid-sized web and enterprise systems is 3 to 4 sessions, each roughly an hour, spread out over a couple of weeks. That gives enough time to cover the non-functional aspects of high-availability (how many 9’s each part of the system really needs), reliability (preventing message and data loss in case of failure), scalability (you know, not that stateless stuff where adding more boxes just causes the DB, and the rest of the system with it, to slow down), etc. We usually end up with several UML diagrams covering structure and behaviour, code samples for each part of the system, config files for the open-source frameworks we use – in other words, a working end-to-end slice.

All that I know how to do.

Clueless image

          What I don’t have a clue about is how to get people who could really benefit from this sort of thing to know that it exists. I’m not a marketing guy and wouldn’t know how to bring a horse to water, let alone make it drink.

So I’m asking for your help.

If you know someone who’s at that phase in their project where they need to make a bunch of decisions in terms of which technologies to use and how to use them, or someone who’s looking for a sounding board for their ideas before diving into code, or anyone else for that matter who you’d feel would be well served here – help me help them.

Just so everything’s above board here, and you know what you’re pointing your trusting colleagues to, here’s the full deal:

For less than what most UI control suites will cost, you get 3 full video, app-sharing, design and coding sessions which will save your project between 10 to 100 times as much money as you spent. I’m serious. My track record is currently 8 for 8.

That’s it. The bottom line. $750 to save up to $75,000.



Leave a comment. Let me know what you think. Please.

If I’m totally off my rocker here, save me some embarrassment.

If you think this is a great deal, then give the nay-sayers above a run for their money.

If you’d really like to see a different offering, or have any other ideas, do me a favour and tell me.


Finally, a big thank you to all my readers and subscribers. I don’t express my gratitude nearly as much as I should and get so much from this blog and have you to thank for it. Here’s hoping the next 4 years will be as fulfilling as the last 4.

Keep It Simple.

Comments [3]
Posted on Monday, February 25th, 2008.

NServiceBus.com information

Posted in NServiceBus

www.NServiceBus.com is online.

It’s not “done” yet, but I’m pretty sure it’s past time that nServiceBus had its own site separate from this blog. I’m still working out the DNS and other domain forwarding and hosting stuff, but we’re live.

There is some information on the “overview” page about one-way messaging, store-and-forard, and why those patterns were chosen for nServiceBus.

Check it out.

Comments [2]
Posted on Friday, February 22nd, 2008.

Beware the Data Services Platform (DSP)

Posted in Uncategorized


Done it again, the analysts have.

Dreamt up a (not) new acronym around SOA, they have.

Written up a useless 53 page report on it, they have.

The grizzled veterans over at the SOA yahoo group have already weighed in.

Back in the beginning of 2006 I called it out as a Common SOA Pitfall. Later on in mid 2007, InfoQ quoted me on this same theme for Astoria – now ADO.NET Data Services.

“Stopped they must be; on this all depends.”

Posted on Thursday, February 21st, 2008.

NServiceBus on Virtual TechEd

Well, I had almost forgot about that interview.

When I was at TechEd Barcelona last November (07), the morning after I flew in I experienced “the fish bowl” and Virtual TechEd for the first time. Anyway, after a short chat – and quite to my surprise, my interviewer, Paul Foster, decided that we should talk about nServiceBus.

So here it is. The Microsoft/Marketing friendly description of what nServiceBus is and how nicely it plays with things like WCF and WF. Always be a gracious guest. Don’t bite the hand that feeds you. But a nibble here and there – well, that you can get away with :-)


Virtual TechEd site is gone and in it’s place is something else, not related to software.

Posted on Thursday, February 21st, 2008.


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Bryan Wheeler, Director Platform Development at msnbc.com
Udi Dahan is the real deal.

We brought him on site to give our development staff the 5-day “Advanced Distributed System Design” training. The course profoundly changed our understanding and approach to SOA and distributed systems.

Consider some of the evidence: 1. Months later, developers still make allusions to concepts learned in the course nearly every day 2. One of our developers went home and made her husband (a developer at another company) sign up for the course at a subsequent date/venue 3. Based on what we learned, we’ve made constant improvements to our architecture that have helped us to adapt to our ever changing business domain at scale and speed If you have the opportunity to receive the training, you will make a substantial paradigm shift.

If I were to do the whole thing over again, I’d start the week by playing the clip from the Matrix where Morpheus offers Neo the choice between the red and blue pills. Once you make the intellectual leap, you’ll never look at distributed systems the same way.

Beyond the training, we were able to spend some time with Udi discussing issues unique to our business domain. Because Udi is a rare combination of a big picture thinker and a low level doer, he can quickly hone in on various issues and quickly make good (if not startling) recommendations to help solve tough technical issues.” November 11, 2010

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A man I respect immensely.”

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Shy Cohen Shy Cohen, Senior Program Manager at Microsoft
“Udi is a world renowned software architect and speaker. I met Udi at a conference that we were both speaking at, and immediately recognized his keen insight and razor-sharp intellect. Our shared passion for SOA and the advancement of its practice launched a discussion that lasted into the small hours of the night.
It was evident through that discussion that Udi is one of the most knowledgeable people in the SOA space. It was also clear why – Udi does not settle for mediocrity, and seeks to fully understand (or define) the logic and principles behind things.
Humble yet uncompromising, Udi is a pleasure to interact with.”

Glenn Block Glenn Block, Senior Program Manager - WCF at Microsoft
“I have known Udi for many years having attended his workshops and having several personal interactions including working with him when we were building our Composite Application Guidance in patterns & practices. What impresses me about Udi is his deep insight into how to address business problems through sound architecture. Backed by many years of building mission critical real world distributed systems it is no wonder that Udi is the best at what he does. When customers have deep issues with their system design, I point them Udi's way.”

Karl Wannenmacher Karl Wannenmacher, Senior Lead Expert at Frequentis AG
“I have been following Udi’s blog and podcasts since 2007. I’m convinced that he is one of the most knowledgeable and experienced people in the field of SOA, EDA and large scale systems.
Udi helped Frequentis to design a major subsystem of a large mission critical system with a nationwide deployment based on NServiceBus. It was impressive to see how he took the initial architecture and turned it upside down leading to a very flexible and scalable yet simple system without knowing the details of the business domain. I highly recommend consulting with Udi when it comes to large scale mission critical systems in any domain.”

Simon Segal Simon Segal, Independent Consultant
“Udi is one of the outstanding software development minds in the world today, his vast insights into Service Oriented Architectures and Smart Clients in particular are indeed a rare commodity. Udi is also an exceptional teacher and can help lead teams to fall into the pit of success. I would recommend Udi to anyone considering some Architecural guidance and support in their next project.”

Ohad Israeli Ohad Israeli, Chief Architect at Hewlett-Packard, Indigo Division
“When you need a man to do the job Udi is your man! No matter if you are facing near deadline deadlock or at the early stages of your development, if you have a problem Udi is the one who will probably be able to solve it, with his large experience at the industry and his widely horizons of thinking , he is always full of just in place great architectural ideas.
I am honored to have Udi as a colleague and a friend (plus having his cell phone on my speed dial).”

Ward Bell Ward Bell, VP Product Development at IdeaBlade
“Everyone will tell you how smart and knowledgable Udi is ... and they are oh-so-right. Let me add that Udi is a smart LISTENER. He's always calibrating what he has to offer with your needs and your experience ... looking for the fit. He has strongly held views ... and the ability to temper them with the nuances of the situation.
I trust Udi to tell me what I need to hear, even if I don't want to hear it, ... in a way that I can hear it. That's a rare skill to go along with his command and intelligence.”

Eli Brin, Program Manager at RISCO Group
“We hired Udi as a SOA specialist for a large scale project. The development is outsourced to India. SOA is a buzzword used almost for anything today. We wanted to understand what SOA really is, and what is the meaning and practice to develop a SOA based system.
We identified Udi as the one that can put some sense and order in our minds. We started with a private customized SOA training for the entire team in Israel. After that I had several focused sessions regarding our architecture and design.
I will summarize it simply (as he is the software simplist): We are very happy to have Udi in our project. It has a great benefit. We feel good and assured with the knowledge and practice he brings. He doesn’t talk over our heads. We assimilated nServicebus as the ESB of the project. I highly recommend you to bring Udi into your project.”

Catherine Hole Catherine Hole, Senior Project Manager at the Norwegian Health Network
“My colleagues and I have spent five interesting days with Udi - diving into the many aspects of SOA. Udi has shown impressive abilities of understanding organizational challenges, and has brought the business perspective into our way of looking at services. He has an excellent understanding of the many layers from business at the top to the technical infrstructure at the bottom. He is a great listener, and manages to simplify challenges in a way that is understandable both for developers and CEOs, and all the specialists in between.”

Yoel Arnon Yoel Arnon, MSMQ Expert
“Udi has a unique, in depth understanding of service oriented architecture and how it should be used in the real world, combined with excellent presentation skills. I think Udi should be a premier choice for a consultant or architect of distributed systems.”

Vadim Mesonzhnik, Development Project Lead at Polycom
“When we were faced with a task of creating a high performance server for a video-tele conferencing domain we decided to opt for a stateless cluster with SQL server approach. In order to confirm our decision we invited Udi.

After carefully listening for 2 hours he said: "With your kind of high availability and performance requirements you don’t want to go with stateless architecture."

One simple sentence saved us from implementing a wrong product and finding that out after years of development. No matter whether our former decisions were confirmed or altered, it gave us great confidence to move forward relying on the experience, industry best-practices and time-proven techniques that Udi shared with us.
It was a distinct pleasure and a unique opportunity to learn from someone who is among the best at what he does.”

Jack Van Hoof Jack Van Hoof, Enterprise Integration Architect at Dutch Railways
“Udi is a respected visionary on SOA and EDA, whose opinion I most of the time (if not always) highly agree with. The nice thing about Udi is that he is able to explain architectural concepts in terms of practical code-level examples.”

Neil Robbins Neil Robbins, Applications Architect at Brit Insurance
“Having followed Udi's blog and other writings for a number of years I attended Udi's two day course on 'Loosely Coupled Messaging with NServiceBus' at SkillsMatter, London.

I would strongly recommend this course to anyone with an interest in how to develop IT systems which provide immediate and future fitness for purpose. An influential and innovative thought leader and practitioner in his field, Udi demonstrates and shares a phenomenally in depth knowledge that proves his position as one of the premier experts in his field globally.

The course has enhanced my knowledge and skills in ways that I am able to immediately apply to provide benefits to my employer. Additionally though I will be able to build upon what I learned in my 2 days with Udi and have no doubt that it will only enhance my future career.

I cannot recommend Udi, and his courses, highly enough.”

Nick Malik Nick Malik, Enterprise Architect at Microsoft Corporation
You are an excellent speaker and trainer, Udi, and I've had the fortunate experience of having attended one of your presentations. I believe that you are a knowledgable and intelligent man.”

Sean Farmar Sean Farmar, Chief Technical Architect at Candidate Manager Ltd
“Udi has provided us with guidance in system architecture and supports our implementation of NServiceBus in our core business application.

He accompanied us in all stages of our development cycle and helped us put vision into real life distributed scalable software. He brought fresh thinking, great in depth of understanding software, and ongoing support that proved as valuable and cost effective.

Udi has the unique ability to analyze the business problem and come up with a simple and elegant solution for the code and the business alike.
With Udi's attention to details, and knowledge we avoided pit falls that would cost us dearly.”

Børge Hansen Børge Hansen, Architect Advisor at Microsoft
“Udi delivered a 5 hour long workshop on SOA for aspiring architects in Norway. While keeping everyone awake and excited Udi gave us some great insights and really delivered on making complex software challenges simple. Truly the software simplist.”

Motty Cohen, SW Manager at KorenTec Technologies
“I know Udi very well from our mutual work at KorenTec. During the analysis and design of a complex, distributed C4I system - where the basic concepts of NServiceBus start to emerge - I gained a lot of "Udi's hours" so I can surely say that he is a professional, skilled architect with fresh ideas and unique perspective for solving complex architecture challenges. His ideas, concepts and parts of the artifacts are the basis of several state-of-the-art C4I systems that I was involved in their architecture design.”

Aaron Jensen Aaron Jensen, VP of Engineering at Eleutian Technology
Awesome. Just awesome.

We’d been meaning to delve into messaging at Eleutian after multiple discussions with and blog posts from Greg Young and Udi Dahan in the past. We weren’t entirely sure where to start, how to start, what tools to use, how to use them, etc. Being able to sit in a room with Udi for an entire week while he described exactly how, why and what he does to tackle a massive enterprise system was invaluable to say the least.

We now have a much better direction and, more importantly, have the confidence we need to start introducing these powerful concepts into production at Eleutian.”

Gad Rosenthal Gad Rosenthal, Department Manager at Retalix
“A thinking person. Brought fresh and valuable ideas that helped us in architecting our product. When recommending a solution he supports it with evidence and detail so you can successfully act based on it. Udi's support "comes on all levels" - As the solution architect through to the detailed class design. Trustworthy!”

Chris Bilson Chris Bilson, Developer at Russell Investment Group
“I had the pleasure of attending a workshop Udi led at the Seattle ALT.NET conference in February 2009. I have been reading Udi's articles and listening to his podcasts for a long time and have always looked to him as a source of advice on software architecture.
When I actually met him and talked to him I was even more impressed. Not only is Udi an extremely likable person, he's got that rare gift of being able to explain complex concepts and ideas in a way that is easy to understand.
All the attendees of the workshop greatly appreciate the time he spent with us and the amazing insights into service oriented architecture he shared with us.”

Alexey Shestialtynov Alexey Shestialtynov, Senior .Net Developer at Candidate Manager
“I met Udi at Candidate Manager where he was brought in part-time as a consultant to help the company make its flagship product more scalable. For me, even after 30 years in software development, working with Udi was a great learning experience. I simply love his fresh ideas and architecture insights.
As we all know it is not enough to be armed with best tools and technologies to be successful in software - there is still human factor involved. When, as it happens, the project got in trouble, management asked Udi to step into a leadership role and bring it back on track. This he did in the span of a month. I can only wish that things had been done this way from the very beginning.
I look forward to working with Udi again in the future.”

Christopher Bennage Christopher Bennage, President at Blue Spire Consulting, Inc.
“My company was hired to be the primary development team for a large scale and highly distributed application. Since these are not necessarily everyday requirements, we wanted to bring in some additional expertise. We chose Udi because of his blogging, podcasting, and speaking. We asked him to to review our architectural strategy as well as the overall viability of project.
I was very impressed, as Udi demonstrated a broad understanding of the sorts of problems we would face. His advice was honest and unbiased and very pragmatic. Whenever I questioned him on particular points, he was able to backup his opinion with real life examples. I was also impressed with his clarity and precision. He was very careful to untangle the meaning of words that might be overloaded or otherwise confusing. While Udi's hourly rate may not be the cheapest, the ROI is undoubtedly a deal. I would highly recommend consulting with Udi.”

Robert Lewkovich, Product / Development Manager at Eggs Overnight
“Udi's advice and consulting were a huge time saver for the project I'm responsible for. The $ spent were well worth it and provided me with a more complete understanding of nServiceBus and most importantly in helping make the correct architectural decisions earlier thereby reducing later, and more expensive, rework.”

Ray Houston Ray Houston, Director of Development at TOPAZ Technologies
“Udi's SOA class made me smart - it was awesome.

The class was very well put together. The materials were clear and concise and Udi did a fantastic job presenting it. It was a good mixture of lecture, coding, and question and answer. I fully expected that I would be taking notes like crazy, but it was so well laid out that the only thing I wrote down the entire course was what I wanted for lunch. Udi provided us with all the lecture materials and everyone has access to all of the samples which are in the nServiceBus trunk.

Now I know why Udi is the "Software Simplist." I was amazed to find that all the code and solutions were indeed very simple. The patterns that Udi presented keep things simple by isolating complexity so that it doesn't creep into your day to day code. The domain code looks the same if it's running in a single process or if it's running in 100 processes.”

Ian Cooper Ian Cooper, Team Lead at Beazley
“Udi is one of the leaders in the .Net development community, one of the truly smart guys who do not just get best architectural practice well enough to educate others but drives innovation. Udi consistently challenges my thinking in ways that make me better at what I do.”

Liron Levy, Team Leader at Rafael
“I've met Udi when I worked as a team leader in Rafael. One of the most senior managers there knew Udi because he was doing superb architecture job in another Rafael project and he recommended bringing him on board to help the project I was leading.
Udi brought with him fresh solutions and invaluable deep architecture insights. He is an authority on SOA (service oriented architecture) and this was a tremendous help in our project.
On the personal level - Udi is a great communicator and can persuade even the most difficult audiences (I was part of such an audience myself..) by bringing sound explanations that draw on his extensive knowledge in the software business. Working with Udi was a great learning experience for me, and I'll be happy to work with him again in the future.”

Adam Dymitruk Adam Dymitruk, Director of IT at Apara Systems
“I met Udi for the first time at DevTeach in Montreal back in early 2007. While Udi is usually involved in SOA subjects, his knowledge spans all of a software development company's concerns. I would not hesitate to recommend Udi for any company that needs excellent leadership, mentoring, problem solving, application of patterns, implementation of methodologies and straight out solution development.
There are very few people in the world that are as dedicated to their craft as Udi is to his. At ALT.NET Seattle, Udi explained many core ideas about SOA. The team that I brought with me found his workshop and other talks the highlight of the event and provided the most value to us and our organization. I am thrilled to have the opportunity to recommend him.”

Eytan Michaeli Eytan Michaeli, CTO Korentec
“Udi was responsible for a major project in the company, and as a chief architect designed a complex multi server C4I system with many innovations and excellent performance.”

Carl Kenne Carl Kenne, .Net Consultant at Dotway AB
“Udi's session "DDD in Enterprise apps" was truly an eye opener. Udi has a great ability to explain complex enterprise designs in a very comprehensive and inspiring way. I've seen several sessions on both DDD and SOA in the past, but Udi puts it in a completly new perspective and makes us understand what it's all really about. If you ever have a chance to see any of Udi's sessions in the future, take it!”

Avi Nehama, R&D Project Manager at Retalix
“Not only that Udi is a briliant software architecture consultant, he also has remarkable abilities to present complex ideas in a simple and concise manner, and...
always with a smile. Udi is indeed a top-league professional!”

Ben Scheirman Ben Scheirman, Lead Developer at CenterPoint Energy
“Udi is one of those rare people who not only deeply understands SOA and domain driven design, but also eloquently conveys that in an easy to grasp way. He is patient, polite, and easy to talk to. I'm extremely glad I came to his workshop on SOA.”

Scott C. Reynolds Scott C. Reynolds, Director of Software Engineering at CBLPath
“Udi is consistently advancing the state of thought in software architecture, service orientation, and domain modeling.
His mastery of the technologies and techniques is second to none, but he pairs that with a singular ability to listen and communicate effectively with all parties, technical and non, to help people arrive at context-appropriate solutions. Every time I have worked with Udi, or attended a talk of his, or just had a conversation with him I have come away from it enriched with new understanding about the ideas discussed.”

Evgeny-Hen Osipow, Head of R&D at PCLine
“Udi has helped PCLine on projects by implementing architectural blueprints demonstrating the value of simple design and code.”

Rhys Campbell Rhys Campbell, Owner at Artemis West
“For many years I have been following the works of Udi. His explanation of often complex design and architectural concepts are so cleanly broken down that even the most junior of architects can begin to understand these concepts. These concepts however tend to typify the "real world" problems we face daily so even the most experienced software expert will find himself in an "Aha!" moment when following Udi teachings.
It was a pleasure to finally meet Udi in Seattle Alt.Net OpenSpaces 2008, where I was pleasantly surprised at how down-to-earth and approachable he was. His depth and breadth of software knowledge also became apparent when discussion with his peers quickly dove deep in to the problems we current face. If given the opportunity to work with or recommend Udi I would quickly take that chance. When I think .Net Architecture, I think Udi.”

Sverre Hundeide Sverre Hundeide, Senior Consultant at Objectware
“Udi had been hired to present the third LEAP master class in Oslo. He is an well known international expert on enterprise software architecture and design, and is the author of the open source messaging framework nServiceBus. The entire class was based on discussion and interaction with the audience, and the only Power Point slide used was the one showing the agenda.
He started out with sketching a naive traditional n-tier application (big ball of mud), and based on suggestions from the audience we explored different solutions which might improve the solution. Whatever suggestions we threw at him, he always had a thoroughly considered answer describing pros and cons with the suggested solution. He obviously has a lot of experience with real world enterprise SOA applications.”

Raphaël Wouters Raphaël Wouters, Owner/Managing Partner at Medinternals
“I attended Udi's excellent course 'Advanced Distributed System Design with SOA and DDD' at Skillsmatter. Few people can truly claim such a high skill and expertise level, present it using a pragmatic, concrete no-nonsense approach and still stay reachable.”

Nimrod Peleg Nimrod Peleg, Lab Engineer at Technion IIT
“One of the best programmers and software engineer I've ever met, creative, knows how to design and implemet, very collaborative and finally - the applications he designed implemeted work for many years without any problems!

Jose Manuel Beas
“When I attended Udi's SOA Workshop, then it suddenly changed my view of what Service Oriented Architectures were all about. Udi explained complex concepts very clearly and created a very productive discussion environment where all the attendees could learn a lot. I strongly recommend hiring Udi.”

Daniel Jin Daniel Jin, Senior Lead Developer at PJM Interconnection
“Udi is one of the top SOA guru in the .NET space. He is always eager to help others by sharing his knowledge and experiences. His blog articles often offer deep insights and is a invaluable resource. I highly recommend him.”

Pasi Taive Pasi Taive, Chief Architect at Tieto
“I attended both of Udi's "UI Composition Key to SOA Success" and "DDD in Enterprise Apps" sessions and they were exceptionally good. I will definitely participate in his sessions again. Udi is a great presenter and has the ability to explain complex issues in a manner that everyone understands.”

Eran Sagi, Software Architect at HP
“So far, I heard about Service Oriented architecture all over. Everyone mentions it – the big buzz word. But, when I actually asked someone for what does it really mean, no one managed to give me a complete satisfied answer. Finally in his excellent course “Advanced Distributed Systems”, I got the answers I was looking for. Udi went over the different motivations (principles) of Services Oriented, explained them well one by one, and showed how each one could be technically addressed using NService bus. In his course, Udi also explain the way of thinking when coming to design a Service Oriented system. What are the questions you need to ask yourself in order to shape your system, place the logic in the right places for best Service Oriented system.

I would recommend this course for any architect or developer who deals with distributed system, but not only. In my work we do not have a real distributed system, but one PC which host both the UI application and the different services inside, all communicating via WCF. I found that many of the architecture principles and motivations of SOA apply for our system as well. Enough that you have SW partitioned into components and most of the principles becomes relevant to you as well. Bottom line – an excellent course recommended to any SW Architect, or any developer dealing with distributed system.”

Consult with Udi

Guest Authored Books
Chapter: Introduction to SOA    Article: The Enterprise Service Bus and Your SOA

97 Things Every Software Architect Should Know

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