Udi Dahan   Udi Dahan – The Software Simplist
Enterprise Development Expert & SOA Specialist
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Eureka! AOP is the final piece of the multi-threaded smart client puzzle

Friday, December 7th, 2007

If you’ve read my recent post on the threading issues I’ve been dealing with in Smart Client Applications, then you’re probably beginning to get the picture that its fairly complex. To tell you the truth, it is. And up until this point I haven’t been able to find anything that’ll help – and that includes the CAB/SCSF. But yesterday I had my epiphany. The answer was in AOP.

You see, the main problem that I hadn’t been able to solve was that in order for the code to be thread-safe, you had to make sure that no code in the views would/could change entity data. One solution is not to use data-binding, which sucks, but isn’t enough to be sure. Another solution is to have all supervising-controllers clone an entity before they give it to a view. Even if you could possibly code review every line of those classes, the new guy (or old guy who forgot) will, by accident, write one new line of code that could pass an entity to a view without cloning it first. That’s not a very sustainable solution.

This thing has been bothering me for a couple of months now and I hadn’t found a way around it. Until yesterday, like I said. I was talking to somebody about threading stuff, and somehow my unconscience lobbed me this thought about AOP. Now I’m not the sharpest pencil in the pack, but I know to listen when my unconscience “speaks”.

So I set about going over what I knew about AOP – interceptors, advisors, advice, introductions, etc, etc. And then it dawned on me. I could intercept all calls to any object that implemented IView, check the parameters of those calls, and if they implemented IEntity, to clone them before passing them through.

<Homer-style WOOHOO />

The great thing is that developers don’t need to remember to clone entities – it happens automatically. The even greater thing is that this will lead developers to writing the correct kind of interaction between their views and supervising controllers.

Together with nServiceBus, this is going to make the extremely difficult problem of writing thread-safe smart clients possible.

I’ve never made use of AOP in a framework before so I’d like to get the broader community’s feedback on this before incorporating this in production. I’ve spoken with some serious AOP folks who have allayed most of my uncertainties, but I’d like to hear more. Anyway, here’s the proof of concept (that makes use of Spring).

If this turns out to be a viable solution, I think we’ll have a solid environment for building a software factory on top of. That is something that I’m really excited about. In this multi-core future (present) that is upon us, multi-threading on the client is pretty much a necessity. We need a way to get things safe and stable by default without requiring a member of the CLR team to hold our hand.

Anybody who’s interested in helping, drop a comment below.

Basic Request-Response sample for nServiceBus

Thursday, December 6th, 2007

I’ve been getting more and more requests for tutorials and “getting started” stuff for nServiceBus so the first one is now up on the Sourceforge site.

The sample can be found under /test/RequestResponse and demonstrates the following flow:

Client subscribes to CustomerUpdatedMessage.
Client sends the Server an UpdateCustomerMessage, and passes a CompletionCallback with it.
On the Server side, the UpdateCustomerMessageHandler is activated and passed the message.
On the Server side, the above handler randomly decides upon success or failure of the action:
    Success: Bus.Return((int)ErrorCode.None); // return success code
    Success: Bus.Publish(new CustomerUpdatedMessage());
    Fail: Bus.Return((int)ErrorCode.Fail); // return fail code
On the client side, when the error message containing the error code arrives, the bus dispatches the error code to the CompletionCallback passed originally by the client
On the client side, when (if) the CustomerUpdatedMessage arrives, the bus dispatches it to the CustomerUpdatedMessageHandler.

Some things to note – this is a simplified form of request/response. What we’re doing here is Command/ErrorCode.

The next sample that will be coming up is a full request/response implementation. Let me know if you have any things that you’d specifically like to see done using nServiceBus.

Object Builder – the place to fix system-wide threading bugs

Thursday, December 6th, 2007

Last week I was at a client in their test lab and saw a strange bit of behavior. The system could be described as something like an air traffic control system, showing things moving around on a map. For just a second, a fraction of a second, one of the “planes” disappeared from the map and then reappeared again.

When I asked if anybody else saw it, one of the developers said, “Yeah, that happens sometimes – but it fixes itself right after that.”

“What if the user sends a command to the server making use of that location?”, the PM asked. “Could that cause them to collide?”

You could hear a pin drop.

After everyone got passed the preliminary shock, we got down to work. I asked if I could look at the logs, but after more than an hour, I found nothing. No reason to explain the strange behavior. I suggested doing some more instrumentation so that whenever a location changed on the client-side entities, we’d write that to the log.

After that, we ran the system again in the lab under the expected load (several hundred things moving every second, and the user doing the expected activity) and didn’t notice anything. An intern “volunteered” to keep working the system while the rest of us went to lunch. When we came back, he told us that everything seemed to be working OK.

These Heisenbugs are the things that keep me up at night.

“Watching the system changes its behavior”, one of the older devs nodded his head sagely.

Just as we were about to leave the lab another one of the developers gave a shout, “It did it again!”. We quickly stopped the system. Opened the (rather huge) log files and looked for the latest entries.

There it was.

A context switch between setting the latitude and longitude of an entity.

That should not have happened. Not that context switches don’t happen, but rather that it should have been impossible by design. We had made use of synchronization domains and the appropriate patterns so that two threads could never concurrently be working on the same instance of an entity. The synchronization features baked in to nServiceBus had taken care of everything up to that point.

Before getting into the threading solution, I want to address a specific alternate patch that was deployed in the meantime:

The solution for the long/lat problem was simple – just make Location a value object and use a single setter for it rather than one for Latitide and another for Longitude. We were still worried about other bits of data that were correllated in the domain – things that couldn’t be solved the same way.

After getting 3 grizzled C++ veterans in the room, we did a code walkthrough of the threading model of nServiceBus. We went through the nitty gritty details of synchronization domains, how the Bus object was outside of the domain, why that was important for user experience, how the message handlers couldn’t be ContextBoundObjects because of the performance impact of creating and destroying them at a high rate, why they couldn’t just be singletons, why they still had to run in the synchronization domain, so that the UI thread couldn’t work on the same (or related) objects at the same time, etc, etc.

And then it hit me.

The bus was communicated directly with the message handlers.

After the Object Builder created the message handler, the bus dispatched the message to the handler directly. And since the bus was outside the synchronization domain, then the thread calling into the handler wouldn’t have locked the domain, leaving the UI thread open to go in and touch those very same objects.

They say that really understanding the problem is 90% of the solution. I’m hoping to meet them some day, because they’re really smart.

All that we needed to do was have the Object Builder dispatch the message to the handler instead of the bus – since the builder was configured to be in the synchronization domain (on the client side). Something as simple as just adding the method:

void BuildAndDispatch(Type typeToBuild, string methodName, params object[] methodArgs);

So, instead of the bus using this code:

object handler = this builder.Build(messageHandlerType);
MethodInfo method = messageHandlerType.GetMethod(“Handle”);
method.Invoke(handler, messageToBeDispatched);

It would do:

this.builder.BuildAndDispatch(messageHandlerType, “Handle”, messageToBeDispatched);

[Just FYI, this is now up on the sourceforge site]

We redeployed the system to the lab, ran all the functional, stress, load, etc tests and everything appeared to be stable. The system has been under scrutiny for the past 4 days by batteries of testers instructed specifically to look for those strage kinds of behavior. Other developers are running scripts on the log files looking for other kinds of context switches that may have been missed by the testers. I am happy to report that they haven’t found anything.

Not that this means that the problem isn’t there. We really can’t be sure. However, the PM has decided that we are stable enough to go into pilot mode – deploying into production beside the current system; having users work on both systems at the same time. I’m optimistic.

I’m personally involved in two more production-projects that are making use of nServiceBus in similarly high-end situations and we’ve never had these threading problems – now two years running.

That was an interesting week.

[Podcast] Migrating from N-Tier to SOA

Wednesday, December 5th, 2007

In this podcast we’ll be discussing certain methodologies for migrating an architecture from N-Tier to SOA. We’ll see what parts can be used almost unchanged, and which N-Tier concepts have no place in this new, service-oriented world.

Ketan asks:

Hello Udi,

I am Ketan, working as Analyst Programmer in India. I want some information regarding SOA Architecture. I have visited several blogs and sites and I do have enough knowledge regarding technical terms of SOA. I have worked a lot in 3-tier mechanism a lot and now want to switch on SOA Architecture in Visual Studio 2005.

I read your blog post How to migrate to SOA and liked the contents and am interested in doing it. Can you please be more precise about how to migrate from 3-tier to SOA? Actually, I have read whole content of above link and you have explained enough. But, still I want you to keep me out from dark. You have described it functionally, but I want some technical description of this process. Please help me in this.

If you can provide me some example/application (in which SOA Architecture has been implemented), then it will be very helpful to me.

Thanks in advance. Waiting for your favorable reply.



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Additional References

Want more?

Check out the “Ask Udi” archives.

Got a question?

Send Udi your question to answer on the show.

UdiDahan.com – past, present, and future

Sunday, November 25th, 2007

4 years ago I had just started this blog and had a handful of subscribers. Now you all number over 1200. I am just totally blown away, and thankful for your support. I’ve been thinking to myself over the past few weeks that I should be doing more for you, but was wondering exactly what.

I have been trying to keep busy besides “just” the blog.

I finally set nServiceBus free. And am probably more pleased with myself than I should be 🙂

The Ask Udi podcast does a bit towards getting some feedback from you, but I’m pretty sure that you feel (as do I) that it’s too “fire-and-forget” since it can take a month or more for my answer to come online. I do want to give a quick shout out to Bill who has been extremely patient with me and keeps sending me nice meaty questions. Thanks Bill!

Just recently I’ve floated a new endeavour called ArchiTips, hoping to get some of you to share your tips with the rest of the community because, let’s face it, I talk way too much as it is already. Even if you don’t have a big write-up for your tip, just fire me an email with a sentence or two and I’ll find the way to package it for mass consumption.

Finally, I’ve recently started doing some remote consulting with a couple of my blog’s readers, one in Florida, the other in Ireland. I must say that it’s working quite a bit better than I would have imagined and that they’re getting value from it. Both are in the initial phases of a serious web system upgrade and are looking at their architecture again with an eye on scalability and simplicity (my two favorite ‘S’ words). For me, it was great really getting to know them and I’d like to do more of this.

So here’s what I had in mind (bonus for you for reading this far!)

I want to give away 10 remote consulting sessions, each of them half-an-hour long. I know that it’s not enough for everybody but I want to see if this will work at all before trying to scale it up. Leave a comment below if you’re interested – or an email if you really need the privacy. Tell me a bit about yourself, what kind of work you’re doing, and how you think I could help. Also, let me know if you’d be willing to have yourself recorded so that we can put our conversation up as a podcast for others to benefit from – you’ll always have the right to veto this should you regret you’re initial decision later.

I’m hoping this lower latency communication will help turn things up a notch, and I’m looking forward to hearing from you.

BTW, I won’t necessarily be choosing the first 10 that I receive. I’ll try to get an even split between those who agree to have their conversation come online and those who require more privacy. Believe me, I’ve worked at some places who were pretty over-the-top when it came to confidentiality and IP and all that – I know what you guys have to deal with.

So, umm, let’s go.

(Gosh, I hope the comments won’t stay empty. Wouldn’t I look dumb.)

[Podcast] Versioning and SOA–There is no IDog2

Friday, November 9th, 2007

In this podcast we’ll look at the issues around versioning and SOA and how the asynchronous nature of messaging obviates the need for previously accepted interface-based versioning practices.

Jarrod asks:

Hi Udi,

I have some questions around versioning and SOA:

Over the years I’ve been fairly adamant about the practice of versioning interfaces should a method change be needed.

Hence, IDog and IDog2

Generally I would also say that a method addition would need a new interface as much as a change to an existing method or property (sometimes requiring completely deprecating the old interface).

With SOA being used more and contract first designs coming down the pipe…an addition of a method or operation to a contract in SOA does not mean its a breaking change.

So, do you continue to create a new interface and version the name within an SOA environment? Even if its just one method that is being added?

A service contract, in general…with just a single method in my opinion is a bad design. Sure, there are exceptions to that but I can just see changes made to the service contracts over the course of a few years with many 1-2 method interfaces.

Day 1 : 12 methods on interface IDog

6 months later : 1 new method, create IDog2 which implements IDog

15 months later : 2 new methods, create IDog3 which implements IDog2

Some can argue that if you’re having to add methods like this, the original design was flawed. That may be…or you could just be in a volatile business environment in which SOA must adapt.

So my main questions are:

1) Do you think its the best practice to continue to version interfaces for non-breaking method additions in an SOA environment in which you also have control of the consumers (internal consumers)?

2) Do you think its the best practice to continue to version interfaces for non-breaking method additions in an SOA environment in which you do not have control of the consumers (external consumers)?

3) If the answer to the above is yes, is a single method on a new interface acceptable?

4) If you know of a problem in an existing interface on a method and have control of the consumers – do you “fix” the method and redeploy to the consumers? Or do you deprecate the entire interface and begin anew?

I’m interested in seeing your responses 🙂



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Additional References

Want more?

Check out the “Ask Udi” archives.

Got a question?

Send Udi your question to answer on the show.

NServiceBus available on SourceForge

Monday, November 5th, 2007

I’ve taken the next step in making NServiceBus truly open source. You can now find it on SourceForge here:


Having never run an open source project before, I’d appreciate it if one of my trusted friends would step up and help me run the logistical aspects of it – to whom to give developer access, manage the writing of documentation, etc.

It’s kind of weird, really. I’ve managed the development of much larger code bases with many, many developers but just can’t seem to get my head around this open source philosophy. The one thing that I am sure about is that NServiceBus needs to be open source. So, please bear with me while I figure out this brave new world. If I do happen to slight anyone, believe me that it is entirely out of ignorance of the accepted decorums and manners, so I offer this apology a-priori.

Now that that’s out of the way, here are some things people have been interested in putting into NServiceBus:

  • Support for ActiveMQ
  • Port to VS 2008
  • Documentation!

Any other ideas? Send them my way either via the comments here, or on the SourceForge project site.

[ArchiTips] Stand UP!

Friday, November 2nd, 2007

Welcome to the first instalment of ArchiTips. I’m Udi Dahan, The Software Simplist and together with IASA we’re going to be providing you with quick titbits of information designed for architects.

This week is going to be the opening of a new series of tips about presentation skills.

As architects, many of us have grown from highly technical positions where our success derived mainly from our ability to talk with machines. However, in the role of architect much of our communication is now done with our fellow human beings. Moreover, our use of machines now focuses on creating content for human consumption.

As much as we wish it weren’t so, the “rightness” of our guidance won’t necessarily make developers or managers accept it. And, truth be told, an architect whose guidance is consistently not followed may need those same communication skills in the interviews coming his way 🙂

Although many books can be written on the topic (and, indeed, many have), this week I wanted to call out one simple, practical, easy to employ tip that will increase the effectiveness of your presentations.

If you’re in any situation where you’re talking to more than one person about your guidance, stand up.

This may be a formal design review, or an informal discussion over some diagrams, it doesn’t matter. Especially if everyone else is sitting down, standing up automatically communicates authority and self confidence. You’ll also notice that once you stand, you’ll start making more
use of your hands and other body language. When speaking to groups of 10 or more people, standing up will also ensure you can make eye contact with everybody. These two factors account for 55% of communication.

What this means is that if you’ve been using the perfect words, pitch, speed, volume, and tone of voice, you’ll more than double your effectiveness.

I can only imagine what this little tip could have done for my career when I was just starting out, so I’d like to hear from those of you who are using this tip and how its working for you. Also, if you have any tips of your own that you think will help other architects, send it in! You also can check out my blog for more information for architects.

Interesting hidden jobs

Thursday, November 1st, 2007

A while ago I put up a jobs network thing on the right bar of my blog but didn’t give it much thought. The other day I thought I’d take a look around and see if there’s anything of value there, or if I should just take it down. I must say that I found some interesting stuff – interesting enough to warrant its own post. Here are some of them:

Senior Technology Architect
Are you a rock star architect? A programming champion? An expert in enterprise architecture and high-performance, event-driven systems? An authority on software development process and methodologies? Are you challenged by understanding the business problem and mapping out a clear path to solving it? Does leading a team to meet big obstacles head on excite you? If so, Bridgewater Associates wants you to help us revolutionize our mission-critical technologies.

Architect/Technical Lead at ThoughtWorks
If you would like to…

  • Architect, and subsequently help develop, Enterprise-scale Applications and Systems from the ground up.
  • Guide a team to consistency and creativity throughout the software development lifecycle
  • Take a technical leadership role and help shape the “big picture” on projects
  • Collaborate on architecture and design decisions with a team of exceptionally talented developers in an non-hierarchical environment
  • Help ThoughtWorks to continue to build robust, technically leading edge systems for clients, across a variety of domains that continually raise the bar in delivering business value.

We want to hear from you!

The full job listing can be found here, and you can also subscribe for the RSS feed. If you’re looking to recruit the kind of people who read my blog and others like it, take a look here.

I’d also be happy to hear about anyone who found a job through this network and hear about their experiences.

I think that covers the topic.

[TechEd] Speaking about High-Performance Persistent Domain Models

Friday, October 26th, 2007

Apparently, I didn’t screw up my talk last year at TechEd so they’re having me back. Here’s hoping this esoteric topic doesn’t scare too many people away:

ARC401 Designing High Performance, Persistent Domain Models
Discover how denormalizing your OLTP database schemas and your object models can improve your systems performance – even for complex business logic scenarios. We’ll be touching on tips and tricks that Amazon and EBay employ to improve throughput. This session will show you when to use lazy loading, eager fetching, and other high-performance persistence techniques as well as how to encapsulate this complexity keeping client code loosely coupled.
Thu Nov 8 13:30 – 14:45 Room 117

You can find the slides I’m going to be presenting here in zipped PDF form.

I recently presented this session to the Jerusalem user group and they seemed to like it, so all that’s left to do is take that 2 and a half hour presentation and make it just as good in half the time. I’m optimistic. Really.

Stop reading.

You’re ruining my optimism.

I mean it.


Don't miss my best content


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

Ian Robinson 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 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.”

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