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.”
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, 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.”
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, 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
July 9th, 2012 at 2:36 am
All your arguments are compelling, but I still can’t see the advantage of composing in the UI with Javascript over composing in a tiny piece of server-side code that’s coupled to the UI.
The obvious problem with this approach you have not mentioned… What do you do about non-Javascript users – do you just ignore them? I would find amazing if you have been using these techniques for 5 years and not considered the non-Javascript case.
The other thing that springs to mind with this approach is that you have to expose all your services. Does this not mean that a cunning user could in theory book a hotel room without sending any card details. A malicious user could in fact fill up a hotel with reservations by making direct calls to the relevant service? Just thinking out loud here…
July 9th, 2012 at 6:05 am
“In general, failed credit card payments are handled pretty much the same way for all ecommerce – an email is sent to the customer asking for an alternative form of payment, also saying that their purchase won’t be processed until payment is made.”
I’m pretty sure this is a false statement. I have seen, and worked on, plenty of ecommerce sites where if the payment is not accepted it errors out on the screen you are on. The only time that has been different is when the price of the item was high and the shipping address was not my billing but that was a manual intervention and a phone call.
July 9th, 2012 at 10:32 am
Udi,
As I understand it, there are 2 phases of obtaining payment via a credit card:
1. Authorization, where the funds to pay for the transaction are reserved (i.e. a “hold”).
2. Capture, where the credit card is actually charged (typically when the order ships).
When you say “In general, failed credit card payments are handled pretty much the same way for all ecommerce”, are you referring specifically to authorization or capture (or either)?
July 9th, 2012 at 10:46 am
This is just COBOL/VSAM/3270 screen edits from the 1960s. Codd devised the RM just to avoid client side messes. While OO folk preen about data and method being encapsulated, when it’s pointed out that transactional methods (semantics) *belong* with the data, they get all huffy about losing control of *their* application. If one wishes to continue with 1960s siloed application development, then go for it. But do know that you’ll be writing orders of magnitude more LoC. Perhaps that’s the point? Permanent employment??
Perhaps a rear-guard action against code generation from the database schema? More of those frameworks are coming into existence. After all, with a 5NF database, all constraints are defined in the schema/catalog as plain text, and so can be used to generate client screens just as some do with messy xml files.
July 10th, 2012 at 12:25 am
Chris,
First of all, the proportion of the population without JS is dropping all the time. Second, the risk that you’re calling out is easily handled by the event-processing mechanisms in the back – users would only be hurting themselves.
July 10th, 2012 at 12:31 am
Josh (2+3 assuming you’re the same person),
I shouldn’t have spoken in such broad strokes – yes, I guess there are plenty of ecommerce systems that don’t work the way I described, but that doesn’t mean they should.
The issue is that we can’t assume perfect connectivity between our systems and that of our credit card processor. It doesn’t make sense to tie up resources on our system, limiting our ability to accept more orders and handle more customers, by performing a blocking call here.
This is true for both payments and authorizations.
July 10th, 2012 at 12:44 am
Robert,
I’ve seen the size of code bases decrease dramatically when building systems this way (as compared to the traditional layered/tiered architectures). Now, it could be that you’re against those as well, in which case we have something in common.
On the issue of the primacy of the relational model, in my work with business stakeholders in many domains, I’ve found that they don’t require “up to the microsecond” referential integrity in many cases and can live quite happily with Eventual Consistency.
With regards to generating code (a.k.a behavior) off of the constraints defined in a database, I’d be interested to see how one would model temporal rules like: When an order is placed, wait with its processing for 30 min (in case it gets cancelled during that time), or N minutes based on other rules (high priced item, preferred customer, etc).
We also tend to need to be able to run multiple versions of the same long-running processes side-by-side, something that most databases don’t tend to make very easy. An example of this is a mortgage application process – we should be able to upgrade the system at any time such that existing applications continue behaving according to the rules that were in place at the start of the application.
July 11th, 2012 at 11:51 am
@Udi,
We’re actually not the same person. I only wrote #3.
And your reply makes perfect sense. Thanks!
July 13th, 2012 at 2:04 pm
There are still quite a few users who are running browser add-ons like NoScript or using Blackberries that have limited JavaScript support.
Your approach sounds really good for a lot of scenarios but I would still have a fallback plan if a submit button goes through without triggering JS/AJAX.
July 16th, 2012 at 10:11 am
Hi, awesome set of posts. Judging by the hostility in these comments you’re really challenging some people’s world view, which is great.
A very smart developer once told me: “If you look at a design and think that it is stupid you have to take a moment and think that it may be you who is stupid.”
To Chris: You’re making a fool of yourself. I would seriously suggest taking Udi’s “Advanced Distributed Systems Design with SOA” course, if you can. I took it a couple of years ago and it really put this kind of thing into perspective. But its when you start implementing these concepts that it really starts to fall into place.
These approaches don’t make design, development or deployment easier in the short term. However they are easier to support, scale and add features to.
Disclosure: I have no link to Udi. Other than taking the course and using his consulting services.
July 16th, 2012 at 2:03 pm
Udi,
I agree completely with what you are saying and I love the idea of the approach. But I just want to be able to do it server-side rather than client-side, or at least know there is an option to do so.
On the server side, can’t we just call RenderAction() for each component (in the cases where we do not need to compose from multiple services into a table), and merge the html? We keep every aspect of our controllers de-coupled from each other, including our views.
Tabular data composition:
The example of tabular data composition using knockout.js shows that all we have to do is create a new viewmodel, composed from the various services, and which is then rendered with a view/template on the client side.
The remaining problem is where we have to compose into a table, server side. In this case don’t we just aggregate the data into a new view model and RenderPartial from one controller – this would be one of a few places where a single controller and a single View interacts with multiple services, but currently, I cannot fathom any way around this minimal coupling.
Or do you have another suggestion for solving this problem? It seems that many of us want to be able to do this server-side after all…
Darran
July 17th, 2012 at 12:24 pm
@Dimitry
If someone is running NoScript, I say *bleep*-em. This is 2012.
For stuff like ecommerce, the requirement I’ve most often seen is that you need to provide a path through purchasing and checkout, but it doesn’t have to be pleasant.
July 24th, 2012 at 11:48 pm
@Josh
So what do you do when you are building software for government services (tax payments, online health care, etc.) and you have accessibility requirements to meet? What if you are building software for a company or charity who actually cares about people with disabilities and where a “pleasant path through…” can make a real difference?
Do you just say *bleep*-em then? What do you do next out of interest, I’m genuinely curious? Surely writing good software can be an inclusive pursuit rather than one where we just raise the bird to anyone who doesn’t fit into our neatly packaged world view whether by choice or circumstance?
Or do you actually try to find a good solution? I like to find solutions to problems, personally, but in this domain (SOA) I’m a little out of my depth (for now) so I’ll take the time to ask the experts while mulling things over myself.
July 25th, 2012 at 5:41 am
@Darran
Josh’s statement is derived from the “general” e-commerce attitude that it is 2012 and it might not be worth the extra effort to support non-js clients. If the particular business cared a lot about these clients, then a different implementation might be required.
If you follow Udi and read his blog posts, one of the biggest messages he makes is the fact there is no cookie cutter solution. No solution that you can apply to everything. If something doesn’t work in your context, do what makes sense for the context, business, and project.
July 25th, 2012 at 10:07 pm
@Gary
Thanks, I agree completely that it comes down to what the business wants/needs and that there’s no one size fits all. It’s one of the biggest messages from Udi that I’m taking on.
What I found disagreeable on this thread however was that there is a clearly stated desire to learn about how to maintain our service boundaries on all tiers of our architectures. Many of us have asked the question: how do you do this server-side with tables? We’re asking the guys that have the most experience…
And, I think that on the one hand: screw the client, and on the other hand: abandon that desire to maintain boundaries because you can’t use Javascript, is a bit, disappointing.
July 27th, 2012 at 5:40 am
Darran,
Microsoft has been making it gradually easier to do more involved server-side composition with things like MVC Razor using Sections, but it still has a ways to go.
There also isn’t a good built-in event model for loading things server side – ie when the product IDs have been found for a certain search string, that another service will get a callback and be able to bring in other product info for those IDs.
In short, we’re missing quite a lot of infrastructure. This means either building it ourselves or allowing some coupling to come creeping back in there.
July 28th, 2012 at 10:37 am
Udi,
Thanks for UI Composition article series. It seems to me that problem of the UI design is quite often overlooked in the context of DDD and complex systems.
Could you explain how to use Razor sections to compose view on the server-side. I wonder how to provide data for each section.
July 29th, 2012 at 12:18 am
Thanks Udi. I’m happy to accept a little server-side coupling for the case where I’m merging data from multiple services into a table. It seems largely avoidable in most other use-cases. Cheers.
August 13th, 2012 at 9:06 am
I actually appreciate the questions that Chris asked. I think the weakest link in “Udi SOA” has been the lack of a clarified client side technique implemented with real code and a real stack instead of just abstract hand waving.
August 14th, 2012 at 4:17 am
Just a quick note regarding the JavaScript vs server side. In ‘SOA Patterns – Manning’ they talk about having server side composition to support legacy systems. I.e. the point is about keeping the responsibility separate, if you can do that with server side components then great. If you can do that with JavaScript then great too. In my experience I am using a combination of both. For services that I do not care too much about I use server side composition as it’s faster for my .net team to implement. For more important/sensitive/fragile parts these are implemented with JS as it provides more opportunity for async, resistance to server failure, etc. NB it doesn’t have to be web, rich native apps also have the same pros/cons of js wrt composition.
March 4th, 2013 at 6:45 pm
How do you handle server-side orchestration when you have to do it, for example a REST API?
Make the endpoint belong to a service, and duplicate any data it needs inside that service, or, have the web application do the orchestration and call multiple services?
April 21st, 2013 at 10:33 pm
I don’t quite follow – what do you mean by saying that NServiceBus helps to mitigate server-side failures? I thought it’s just a message-passing layer. Or does it have some sort of retry-after-exception policy?
April 22nd, 2013 at 12:16 am
Gleb,
Yes – NServiceBus is what invokes your code, catches any exceptions you throw, retries (with a back-off policy), logs, moves to a separate queue, and provides tooling for returning the message back to the original queue for reprocessing as well.
And that’s just the simple stuff 🙂
April 25th, 2014 at 11:01 pm
What happens if you want to display a server side validation message to the client after they have clicked submit? For example, say the hotel has a no overbooking policy, and upon clicking submit, the service in charge of booking rooms returns a “sorry, that room is now sold out” message and this needs to be displayed on the client. We might also want that validation failure to stop the submission to all other services as well.
I understand that we could just accept all bookings perform a compensation action later like sending an email, but sometimes, ui’s may demand immediate feedback for the user that can only be performed from the server side. Any idea’s on how to tackle this with a composite ui?
April 27th, 2014 at 8:12 pm
Terrence,
If that is a requirement, we can model things differently.
For example, implementing the client-side logic such that only after Service1 completes its server-side validation – returning a response to the client-side code of Service1 which will in turn raise a client-side event indicating that everything’s good, and that will call back to the client-side code of Service2 which is subscribed to it, which will kick off the server-side logic of Service2.
March 8th, 2015 at 5:11 am
Hi Udi,
One thing i have not been able to figure out for myself (nor find code snippets for) is how UI composition would work within a table kind of display. This essentially will require correlation between responses received from different services. So suppose in a vanilla case, i want to display a few products and their prices in a table. If I assume that product name and description come from the Marketing service, and price from the Finance service, how does the correlation between the data received from these two services happen? Assuming that both services will return data in the same order (as was done in one sample code you had referred to on some other site) seems to me not a production-ready algorithm.
UI composition in other scenarios where no such correlation is needed is, as you say, not a big deal to achieve. But this table thing has me beat.
Warm Regards
Rajesh
March 29th, 2015 at 2:46 pm
Rajesh,
There would be a Branding Service which owns the table layout, and has a ViewModel with properties for each of the service – each property being a dictionary from the product ID to the relevant value. Each service would set the property for which it has the data, and the ViewModel, when all properties would be set, would trigger the rendering logic.
Does that answer your question?