Udi Dahan - The Software Simplist; a blog on Service Oriented Architecture and Enterprise Software Development

Udi Dahan – The Software Simplist
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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

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 🙂

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

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.”

Comments
Posted on Thursday, February 21st, 2008.

NServiceBus on Virtual TechEd

Posted in NServiceBus | Presentations | WCF | Workflow

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 🙂

Download:

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

Comments
Posted on Thursday, February 21st, 2008.

Advanced Messaging with a dash of DDD

Following my last post (From CRUD to Domain-Driven Fluency) a bunch of questions have started popping up. One that I received via email from a client up in Ireland particularly caught my eye, so here it is:

Hi Udi, I think I see the point about the domain-driven approach but I’m wondering what my messages will look like. If it’s this:

IAppointment InsertInterview(Guid recruiterId, Guid applicantId, Guid appointmentId); OR

IRecuiter UpdateRecuiter(IRecuiter recruiter); (passing in an operation flag attached to the IRecuiter object) OR

IRecuiter UpdateRecuiter(IRecuiter recruiter); (setting a state flag on the relevant object and have the business object check the flag and behave according the state change)

Hope I’m not way off

Sean

Well, Sean, first of all – messages don’t look like functions. They’re a lot more like structures – data transfer objects. In this case, you’d probably be looking at a ScheduleInterviewMessage that had the relevant fields. It would look something like this:

   1:  using System;

   2:  using NServiceBus;

   3:  using System.Xml.Serialization;

4:

   5:  namespace Messages

   6:  {

   7:      [Serializable]

   8:      [Recoverable]

   9:      [TimeToBeReceived("0:01:00.000")]

  10:      public class ScheduleInterviewMessage : IMessage

  11:      {

  12:          public Guid InterviewerId;

  13:          public Guid CandidateId;

  14:          public DateTime RequestedTime;

15:

  16:          [XmlAnyElement]

  17:          public object extra;

  18:      }

  19:  }

Before we go on, I want to explain what we see. The “recoverable” attribute is the way we indicate to the infrastructure that these messages should not be lost in case a server fails, there are network problems, etc. In essence, it does durable, store-and-forward messaging. This will create an environment in which, in the case of network problems, these messages will be written to disk. That’s a good thing, since once connectivity comes back or the server boots back up, the messages will still be around and can be sent.

Now these messages are fairly small, so even at a relatively high load, we shouldn’t be chewing through too much of our expensive, small, high performance local disks. However, if these messages were bigger, we may fill up our disks before connectivity comes back, and we all know what happens to Windows boxes when there’s no room on the file system left:

In order to prevent our system from Denial-of-Servicing itself we need to make those messages clean themselves up. That’s what the “TimeToBeReceived” attribute is for. The amount of time that if a message had not yet been received by the other side that it will be deleted. This could be that the message even made it to the other machine, but the process handling those messages was down. You wouldn’t want to be filling the other side’s disk either causing them to crash, would you? This protects both parties.

The way to figure out how long to set is by looking at the smallest amount of durable storage you have available at your nodes, divide that by the size of the average message, and then again by the rate you need to process messages – and leave yourself at least 100% spare.

In other words, to build a robust system you not only will need to deal with lost messages, but you will be actively throwing messages away.

Finally, that last “XmlAnyElement” attribute is there for versioning. As we version our system and schema, we’ll be adding fields to the message. However, an old client may be talking to a new server, or vice versa. Since we wouldn’t want data to get lost just because of serialization. In a future post, I’ll show how to set up a message handler pipeline exactly for these issues.

Now that we’ve covered all the intricacies around messaging, we can see how the code that handles that above message looks:

   1:  using System;

   2:  using Messages;

   3:  using NServiceBus;

   4:  using NHibernate;

5:

   6:  namespace Server

   7:  {

   8:      public class ScheduleInterviewMessageHandler :

   9:                   BaseMessageHandler<ScheduleInterviewMessage>

  10:      {

  11:          public override void Handle(ScheduleInterviewMessage message)

  12:          {

  13:              using (ISession session = SessionFactory.OpenSession())

  14:              using (ITransaction tx = session.BeginTransaction())

  15:              {

  16:                  ICandidateInterviewer interviewer = session.Get<ICandidateInterviewer>(

  17:                          message.InterviewerId);

  18:                  ICandidate candidate = session.Get<ICandidate>(

  19:                          message.CandidateId);

20:

  21:                  interviewer.ScheduleInterviewWith(candidate)

  22:                          .At(message.RequestedTime);

23:

  24:                  tx.Commit();

  25:              }

26:

  27:              // publish new appointment data

  28:          }

  29:      }

  30:  }

If you’ve read this far and have more questions, please feel free to send them my way. If you’re at a more time-critical part of your project and need an answer quickly, we can set up a skype call. This has been working quite well for many of my overseas clients (shout out to the guys in Ireland and Florida).

Until next time 🙂

Comments [5]
Posted on Monday, February 18th, 2008.

From CRUD to Domain-Driven Fluency

I got a question about how to stay away from CRUD based service interfaces when the logic itself is like that, and I’ve found that this shift in thinking really needs more examples, so I’ve decided to put this out there:

For instance, in an HR system, the process of interviewing candidates – wouldn’t you just insert, update, and delete these Appointment objects?

If I were to put on my domain-driven hat, I would describe those requirements differently – interview appointments have a lifecycle: proposed, accepted, cancelled, etc. It seems that only a user of the role HR Interviewer should be able to make appointments for themselves, so the service layer code would probably look something like this:

using (ISession session = SessionFactory.OpenSession())
using (ITransaction tx = session.BeginTransaction())
{
    ICandidateInterviewer interviewer = session.Get<ICandidateInterviewer>(message.InterviewerId);
    ICandidate candidate = session.Get<ICandidate>(message.CandidateId);

    interviewer.ScheduleInterviewWith(candidate).At(message.RequestedTime);  
    tx.Commit();
}

The “ScheduleInterviewWith” method accepts an ICandidate and returns an IAppointment. IAppointment has a method “At” which accepts a DateTime parameter and returns void – just changes the data of the appointment. The state of the appointment at creation time would probably be proposed. The appointment object would probably be added to the list of appointments for that interviewer – that’s what will cause it to be persisted automatically.

Later, when the candidate accepts the meeting, we could have the following method on ICandidate – void Accept(IAppointment); that would obviously check that the candidate is the right person for that interview, the appointment’s current state (not cancelled), etc – finally updating its state. What part of this looks like create, update, delete? If that’s what your service layer to domain interaction looks like, do you now know what your messages will be looking like?CRUD seems to be what most of us are familiar with. Moving to domain-driven thinking takes time and practice, but is well worth it. Contrast this with a more traditional O/R mapping solution:

using (ISession session = SessionFactory.OpenSession())
using (ITransaction tx = session.BeginTransaction())
{
    ICandidateInterviewer interviewer = session.Get<ICandidateInterviewer>(message.InterviewerId);
    ICandidate candidate = session.Get<ICandidate>(message.CandidateId); 

    Appointment a = new Appointment(); 

    a.Interviewer = interviewer; 
    interviewer.Appointments.Add(a); 

    a.Candidate = candidate;
    candidate.Appointments.Add(a); 

    a.Time = message.RequestedTime; 

    session.Save(a);  

    tx.Commit(); 
}

As you can see, we’ve got simpler, more expressive, and more testable code when employing the domain model pattern, than using “just” O/R mapping. I’m not saying that the domain model pattern doesn’t need O/R mapping in the background for it to work. But that’s just it – the persistence gunk needs to be in the background and the business logic needs to be encapsulated.

So, while I’ll agree with Dave that the Domain Model is more lifestyle than pattern, I would argue against these conclusions:

If this post had a point, it’s only to share the idea that Domain Model is a big, big thing. It’s probably overkill in a lot of cases where you have simple applications that have very simple purposes.

As you just saw in the example above, there is no “overkill” to be seen. The domain model in the example wasn’t “a big, big thing”.

The domain model. Use it.

Why not have a better lifestyle? ;-)

Comments [26]
Posted on Friday, February 15th, 2008.

NServiceBus Version 1.7 Available

Posted in NServiceBus

Get it here.

Some important features:

TimeoutMessages now handled by separate endpoint

allows for scaling out timeout handling – can use a distributor behind that endpoint

improves performance of other endpoints – less messages to handle

When sagas complete, TimeoutMessages for those sagas get cleared as well

improves throughput when sagas that can take a long time complete quickly

this is done by sending a TimeoutMessage with a Clear flag

Testing environment for sagas (example available)

Reminder class removed to make testing more explicit

Timeout Manager address now configured like all other messages

Change number of worker threads for an endpoint dynamically

After finding a bottleneck (most messages in queue), can increase the number of resources allocated to that endpoint by sending a message

Enables writing scripts which monitor all endpoints and use rules to allocate resources at runtime – like a grid

Simple UI available for monitoring queues and allocating threads

Configure queues by using transport independent format: queueName@MachineName

SagaMessageHandler designed to be inherited from and overridden for simpler business process handling – see saga sample message handlers

One Message Handler class can now handle more than one type of message without needing to handle IMessage

Even when configured incorrectly, messages don’t get lost – they’re forwarded to an error queue, which is how admins will know to fix the config, and then can replay those messages again.

You might enjoy reading this as a comparison for how WF tries to support multiple hosts running the same process.

Here’s the download link again – download here.

Comments [2]
Posted on Monday, February 11th, 2008.

Interested in SOA Training Videos?

Posted in Architecture | Courses | EDA | ESB | NServiceBus | SOA

This past 2 weeks I was in Australia doing some in-depth training on Service Oriented Architecture, Enterprise Development, and nServiceBus implementation. We managed to record one full week of sessions and are in the process of compressing, editing, and other video whatever stuff.

I was wondering if any of my loyal subscribers would be interested in getting a set of DVDs containing Udi talking for hours and hours about how to identify services, map out cross-service business processes, zero in on business fracture points to further decompose services into business components, and decompose those into autonomous components by analyzing non-functional message properties, summing up with using all that information for choosing cost-effective technologies for each autonomous component.

In other words, get 5 days of training you can pause, think about, and replay as many times as you need. There’s something for almost every phase of an enterprise project, from top level architecture, through coding, testing, to deployment tips and monitoring tactics, so you can pick up what you need – right when you need it.

Please bear with me as I get the processes in place for getting this out.

I’m wondering – how valuable do you think it would be to have weekly live online Q&A sessions as opposed to the more asynchronous (and scalable) simple forum thing?

Just so I can see what I need to be preparing myself for, please leave a comment below expressing your interest. If you also know someone else who might benefit from this, drop them a link. The last thing I want to have happen is for this to take months and months to get out because I didn’t prepare things in advance that I could have.

And a big thanks to Simon and the gang in Australia for helping make this happen. It was a great two weeks and I thank you for that.

Comments [34]
Posted on Friday, February 8th, 2008.

NServiceBus implements Erlang Concurrency

Going over the concurrency features of Erlang, the language famed for nine 9’s of uptime, I find that nServiceBus covers almost every single one.

Here’s the core list from Joe Armstrong’s book, Programming Erlang:

“In Erlang:

Creating and destroying processes is very fast.

Sending messages between processes is very fast.

Processess behave the same way on all operating systems.

We can have very large numbers of processes.

Processes share no memory and are completely independent.

The only way for processes to interact is through message passing.”

In nServiceBus, we don’t create or destroy processes – that’s a Windows issue. Instead, we just do messaging with endpoints. If there’s a process behind that endpoint, and it responds, then other interesting things can occur.

In the continued list:

Message passing is asynchronous.

Processes can monitor each other.

It is possible to selectively receive messages.

Remote processes appear largely the same as local processes.

All of this is part of the design philosophy of nServiceBus. While I have yet to see a carrier-grade implementation of nServiceBus, we are enjoying very impressive system-wide uptimes in production. Oh, and the programming model is still plain-old .NET, so you don’t have to learn any new languages or environments (even though I think that you might learn something – I know I did).

Comments
Posted on Friday, February 8th, 2008.

Recommendations

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

Sam Gentile, Independent WCF & SOA Expert
“Udi, one of the great minds in this area.
A man I respect immensely.”

Ian Robinson, Principal Consultant at ThoughtWorks
"Your blog and articles have been enormously useful in shaping, testing and refining my own approach to delivering on SOA initiatives over the last few years. Over and against a certain 3-layer-application-architecture-blown-out-to- distributed-proportions school of SOA, your writing, steers a far more valuable course."

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, 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.”

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“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, 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, 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, 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, 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, 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.”

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“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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, .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, 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, 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, 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, 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, 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, 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, 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, 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

Article: The Enterprise Service Bus and Your SOA

97 Things Every Software Architect Should Know

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