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Archive for the ‘Architecture’ Category



A Pox on your REST! A Pox, I say!

Saturday, December 10th, 2005

After reading Clemens’ “Teaching Indigo to do REST/POX” I, a MEST-er, am compelled to retort. Of course, this has nothing to do with Indigo, or Clemens, who I highly respect. Just that I think the whole REST thing needs to be put to rest. This will doubtless stir the fires of the REST/MEST war again, so I’ll keep to my point – or rather, just raise a question:

A non idempotent message: Withdraw $100 Billion. Easily mapped to REST.
An idempotent message: If transaction #X has not been processed, withdraw $100 Billion as transaction #X. How do you express that REST-fully?

In my opinion, MEST enables idempotency better than REST by simply removing the limitations that the REST verbs put in place.



Ultra scalability for the web

Saturday, December 10th, 2005

On one of the discussion lists I linger in, the following question was raised:

I have a client who wants me to use nHibernate for a ASP.NET Portal we are creating with Visual Basic 2005. Approx. 250,000 users, as many as 40,000 actives at the same time. Does nHibernate introduce significant overhead? Are there known issues?

I figure that the answer I gave there would be valuable to a larger audience, so here it is:

1. No, NHibernate does not introduce significant overhead.
2. Not that that will make any difference for the load described above.

Unless you architect for that level of load, any data access strategy will require very expensive hardware. For example, what better way to handle load than preventing the users from hitting your servers at all? This can be done by generating xml files for data, which are referenced by html pages statically. Look and feel should be done by separate css files. There’s nothing better than using the entire internet as your cache. Manage the expiration of these xml files from the caches of ISPs all over the web. This kind of solution will also enable you to expand your site to Akamai networks much easier, further increasing scalability.

NHibernate gives you the ability to write object oriented business logic in a persistent environment. If your site is light on logic, you might not get much benefit from using an O/R mapper. This has nothing to do with handling very high levels of load.

While the internet places inherent constraints on our ability to develop certain solutions, at the same time we can take advantage of “the rules of the net” – how content is transferred, to handle the highest levels of load. You would be hard pressed to come up with a better, more resilient solution if you were to architect it from scratch.



What you should really know about service contracts

Saturday, December 3rd, 2005

Buddhike from the thinktecture crowd yearns for automation in the mapping between service contract to service implementation – messages to model. It appears to be a worthy goal, doesn’t it?

Well, I’ve been getting my hands dirty on about 3 projects or so over the past couple of years in this whole SOA mess. First of all, you have to understand that the contract isn’t magical – it’s a bitch to get something solid that communicates the intent of how to work with the service. Then, after understanding how the outside world will interact with the service, can you really iron out your domain model. Don’t expect that to occur overnight either.

Finally, this idea of mapping messages to model, it glosses over the fact that you’ll probably need to design/code a service layer over your domain model to encapsulate the workflow of using those domain objects to fulfill a given use case.

In the end, the only real thing left is to map messages to service layer calls, which is something of a waste of time. You’ll only know what you’re mapping after the code is “done” (whatever that means) for both the contract and the service layer – which means much of your domain model is coded up too.

Just write the code to translate message to service layer call. It’s the least of your worries. Don’t waste your time optimizing away the boring typing, although we developers do love trading boring work with more intersting work – if that more intersting work takes longer to do, so be it 😉

I guess I don’t have very high hopes for what the tooling can bring to the table.



So many Dlls, so little time

Sunday, November 27th, 2005

The other day, one of the leads on a project I’m architecting asked me why I insisted on “so many” dlls. In his opinion, increasing the number of “moving parts” would just make things more complicated. It wasn’t the first time I was asked this question, so I thought I’d think it over a bit more this time.

I think that it’s a reasonable and expected response. What’s wrong with what we’re doing now? How is dividing it up more going to make it better?

Before I get into the reasoning, the end result needs to be examined.

Have you ever had a case where you used a dll (let’s call it A) which depended on B, which in turn depended on C. In your project/dll you also use C directly. I’d be willing to bet that almost everyone has run into this scenario. This is the path to dll hell, more appropriately named versioning hell. It is at the root of many an integration gone bad. Reminds me of the commercials “when you sleep with your friend, your also sleeping with all your friend’s friends, and their friends…” and so on.

The hell above is the result of sloppiness. Sloppiness with dependencies. If two classes are independent of each other, and do not provide different implementations of the same interface, think twice about putting them in the same project/dll. Minimizing dependencies is the bread and butter of loose coupling. Break dependence on implementations by introducing interfaces in a separate project/dll.

Do it over, and over, and over again.

* You don’t necessarily have to code, in order to refactor your design.

In the end, you should see bunches of projects/dlls which go together, while between the bunches there is almost no dependence whatsoever. The boundaries between bunches will almost always be an interface project/dll.

This will have the pleasant side-effect of enabling concurrent development of bunches with developers hardly ever stepping on each other’s toes. Actually, the number of projects in a given developer’s solution will probably decrease, since they no longer have to deal with all parts of the system.

Bottom line: design is about managing dependencies between classes and dlls.



What SOA means for me

Sunday, November 20th, 2005

A lot of the talk around SOA has coalesced around “connected systems”. I REALLY dislike that term. I think it does distributed systems a world of harm.

Do not think “connected”.

Think “what if this failed at the worst possible time”.

“this” being your connection to the internet, that switch, the server, etc.

Think about every line of code that you write as if the server will restart at that exact moment.

Think that every time you go to the network, things will take 100X as long as you planned.

Think that the server hosting the web service you’re calling isn’t even running.

If you’re not thinking about all this, what will happen to your system when these things DO happen?

Can you really afford to think “connected”?



MEST infrastructure looking for a name

Monday, November 14th, 2005

After Savas has oh so gently prodded me (again) to continue writing about my MEST infrastructure, I thought that first of all I need a name for it. I’m waffling between the cute “MEST-up” and the ego-centric “UdiBus”. Let me know what name you like.

Anyway, alpha testing has been going well. There are currently three configurations in which the product can be run: Client, DbService, and ComplexService. As for benchmarks, it’s not really that interesting what happens in Client mode (it runs fast), but DbService and ComplexService are what matters. On my 2-year old hardward at home, DbService runs at around 45 messages per second (sustained) and ComplexService comes in around 100 messages per second (sustained) with the ability to handle bursts of around 600 messages in one second without adversely affecting latency.

Just so we all understand what’s going on, the purpose of this product is to provide an infrastructure for developing robust distributed systems. This means that despite various environmental failures, no information will be lost and data consistency will not be compromised. These failures include network outages, server reboots at the worst of times… the usual suspects.

In DbService mode, the use of the DTC and transactional messages queues gives the required robustness characteristics, but adversely affects throughput. ComplexService mode splits message handling into a 2 phase process, the first in-memory with message sending tied to the original message receipt with queue level transactions, the second phase acting the same as the DbService. Of course, when handling new information coming into the service, Ids must be generated by phase one, and durably passed to phase 2 for persistence along with all the regular message data.

Finally, as a programming model I’ve based the infrastructure around 3 major elements:

IMessage which represents what messages look like – this being more of an envelope in that it has a header with all the relevant information, but the body isn’t bundled into a separate part – it’s just data on the message.

IMessageHandler represents that code which will run when the appropriate message arrives at the current service.

IServiceBus represents the API to the outside world – subscribe/unsubscribe, publish, send (with it’s many variations…

Let’s talk about send for a second:

you can just send a message and be done with it.
you can send a message to a specific service, regardless of whether you know if that service can understand the message.
you can send a message specifying the code that you want to run when a response arrives, or that the timeout you set has elapsed.

Timeout is an important part of any time-critical process. It can be as little as 1/10 of a second, or as much as several days.

Of course, a service may reject a message (send back the original message with the reject code set in the header) specifying why it did that, and have that information return to the sender. Conversely, a service may acknowledge that it has processed the message successfully.

The really interesting thing I learned (from one of the projects that this product is being used in) is how it looks to implement a broker style architecture with a bus style product.

Anyway, I’ll be looking for beta testers in the coming weeks. Let me know if you’re interested and what kind of system you’re considering using it in. If you want to know more about features, or how it’s built, drop me a line and I’ll put up a post so that everyone will keep updated.



What's wrong with Request/Response

Saturday, October 29th, 2005

RPC thinking leads naturally to Request/Response.

Messaging thinking enables Request/Response1, Response2, Response3,…

RPC folks ask “why on earth would you need more than one response?”

I ask “what would anyone need more than 64K for?”
If you have the power, you’ll use it.



Code is Model, is Software, is Computer, is … Thing

Tuesday, October 11th, 2005

The feedback is beginning to swell on Harry’s post “Code is Model” and I think that it’s about time for me to join the fray.

First of all, I don’t like “is-a” relationships so much outside the field of software design (a dog is-a mammal is-a animal is-a thing). I think that it pays to be precise. What don’t I like? I don’t like comparing things that exist at different levels.

Is code the same as a model? Does it serve the same purpose? If code is-a model, does that mean that model is-a code? From a purely logical analysis of “is-a” relationships we know that this isn’t necessarily the case. In most cases, the level of precision of the left-hand-side is higher than the right-hand-side. A dog barks, we can’t be that specific about an animal.

Why then does Harry suggest that the model be as precise as the code?

After boiling down the content of the article we find that a different relationship emerges. Both the code and the model are views of something else, the logical program. I find this statement more in line with my views on DSLs, and architecture in general.

When analyzing a problem, we do not holistically solve all facets at the same time. Rather, we create a solution for each facet. To be more precise, we explain one view of The Solution (which we don’t fully grasp yet) that speaks to the given facet. The static structure of the system is one facet we analyze with class diagrams. The behaviour of the system is another facet analyzed with sequence diagrams. Durable storage of data is another facet analyzed with an ERD. And so on.

In my opinion, these models, these views will always be incorrect/imprecise exactly because they speak to one specific facet at a time. The main purpose of these models is to raise the level of abstraction so that the main idea is better understood.

This brings me back to the question of purpose. The purpose of code is to be compiled, runned, and maintained/changed over time. The purpose of a model is to communicate our understanding of the solution to someone else. The success criteria of code is much more stringent than that of the model. It’s also much faster to draw up a quick sketch of certain elements of a system to explain how things work than to start going over code, line by line.

Code is Model?

The CASE is dead. Long live the CASE.



Service Oriented Weakness

Tuesday, October 4th, 2005

So you’ve swallowed the SOA koolaid, you’re the best MEST’er there is, and you’re all ready to begin your first, full-blown, SOA project.

Well, you’ve obviously read “MEST up”, and you’re ready to pub-sub your way to glory.

There’s just one, teeny-tiny thing that may have slipped by you: the GUI. That client-side code that just ISN’T a service. It may sub, but it sure ain’t pubbin’.

There’s also those nasty multi-threading issues that you just can’t get around. The user WILL click when a message comes by and updates that very same object you want to refresh.

Even when you get past all that, you’ve got to accept the fact that the client will never be loosely coupled like other services. Not only that, a large section of a given service’s contract will exist solely for the client.

May this post be one of many (by me and the rest of the guys down in the trenches writing the code that will be called service oriented) to take down the SOA/ESB/EDA/”whatever TLA comes next” hype. I’m sick of business people arguing architecture with me after returning from their last, vendor sponsored, SOA conference.

We do software. We’ve been doing it a long time. We will continue doing it after this hype, and many after it, wither and die. We do not try to tell you how to run your business. Please, stop telling us how you think the software that runs your business needs to be technically built. Please DO tell us what the software should do. Good requirements are hard to come by, SOA or not.

Oh, and to all the vendors out there, where do YOU get the audacity to tell us how the software that runs our businesses should be built – with nary a requirement to be seen?

Wow, that’s been building up for some time. Good to get it off my chest.



Devx SOA Article published for IBM

Friday, September 30th, 2005

My latest article “SOA Support, SOA Therapy, SOA Treatment” (http://www.devx.com/ibm/Article/29325
) has just been published for the IBM section of DevX. Please leave comments here, though.

As for orchestration, which was subtely(?) editted out, my thoughts are as follows:

If you have a bus-style architecture, orchestration/choreography is out. If you have a broker-style architecture, you could try it. On the other hand, orchestration will only be good for the broker, all the other spoke-services are out. And if you understand what Activities really are (long running business processes is such a misnomer), you could implement them yourself with such a performance gain that you’d laugh at the benchmarks all the vendors are pushing.



   


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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 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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