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Archive for the ‘SOA’ Category



Service-Oriented Composition (with video)

Wednesday, July 30th, 2014

When telling people about my approach to SOA, in which a given service would have client/browser-side components running side-by-side in the same process and even in the same page as components from other services, I often get asked this question:

“Doesn’t all of this loosely-coupled composition come with a high cost, in terms of client to server chit-chat?”

So, I’ve finally buckled down and put together a slide to illustrate how the technocratic IT/Ops service I’ve talked about in the past can provide components to resolve these sorts of problems.

After putting the slide together, and realizing some animation would do it good, I went and made a short (5 min) video including some verbal explanation as to how it all works – just for clarity. Check it out or watch it here:




And here’s the image showing everything in one picture:


Service-oriented composition



People, Politics, and the Single Responsibility Principle

Monday, May 26th, 2014

PeopleIn one of Uncle Bob’s recent blog posts on the Single Responsibility Principle he uses the example of using people and organization boundaries as an indication of possible good software boundaries:

When you write a software module, you want to make sure that when changes are requested, those changes can only originate from a single person, or rather, a single tightly coupled group of people representing a single narrowly defined business function. You want to isolate your modules from the complexities of the organization as a whole, and design your systems such that each module is responsible (responds to) the needs of just that one business function.

This is something that often comes up when I teach people about service boundaries when it comes to SOA – organization boundaries are the most intuitive choice.

And, once up on a time, that intuition might have indeed held up.

Stepping back in time

In the age before computers, organizations had a very specific way of structuring themselves.

People who had to work closely together sat in close physical proximity to each other. Data that was required on an ongoing basis would be in file cabinets also physically co-located with the people using that data, and it would be structured in a way that was optimal for their specific purposes. All of this was due to the high cost of communicating with people farther away.

If you needed data from a different department, you had requisition it by filling out a special form, put it in your outbox, and then some guy from the mail room would pick it up, and physically schlep it to the right department, putting it in their inbox, and then someone there would get your data for you – putting it together with your original request, and then the mail guy would schlep it back. This inbox/outbox style of communication should ring a bell from the messaging patterns I talk about with NServiceBus.

As a result, different departments had to have very clearly delineated responsibilities with minimal overlap with each other. The organization just couldn’t function any other way.

And then a bunch of us geeks came along.

Enter the age of computers and networks

By introducing this technology, the cost of communication across large distances started falling – slowly at first, and then quite dramatically.

When anyone in an organization was able access data from anywhere in the blink of an eye, an interesting dynamic started to unfold. All of a sudden, the division of responsibility between departments wasn’t as critical as it was before. When an employee needed to do something, there wasn’t this “that isn’t our job, you need to go to so-and-so” reaction. Because things could be done instantly, that’s exactly what happened.

And then came the politics

By removing the cost of communication, it became possible for more power-hungry people in the organization to start making (or trying to make) decisions that they couldn’t have made before. The introduction of computers into an organization was heralded as a new way of doing business – that the old organizational boundaries were a relic that we should leave behind us.

And thus can the re-org (the first of many).

Responsibilities and people were shuffled around, managers vied for more power, and politics took its’ place as one of the driving forces in the company structure.

Nowadays, if you want a decision made in a company, there isn’t just one person who has the authority to sign off on it anymore. No, you need to have meetings – and more meetings, with people you never knew existed in the company, or why on earth they should have a say on how something is supposed to get done. But that is now our reality: endlessly partially overlapping responsibilities across the organization.

So, what of the Single Responsibility Principle

This just makes it that much harder to decide how to structure our software – there is no map with nice clean borders. We need to be able to see past the organizational dysfunction around us, possibly looking for how the company might have worked 100 years ago if everything was done by paper. While this might be possible in domains that have been around that long (like banking, shipping, etc) but even there, given the networked world we now live in, things that used to be done entirely within a single company are now spread across many different entities taking part in transnational value networks.

In short – it’s freakin’ hard.

But it’s still important.

Just don’t buy too deeply into the idea that by getting the responsibilities of your software right, that you will somehow reduce the impact that all of that business dysfunction has on you as a software developer. Part of the maturation process for a company is cleaning up its’ business processes in parallel to cleaning up its’ software processes.

The good news is that you’ll always have a job :-)



Announcing the Particular Service Platform

Wednesday, April 16th, 2014

champaignAfter many months of hinting about the coming of the Particular Service Platform, it’s finally here.

For everybody who has been building message-driven systems on .NET – I really do believe that this is the dawn of a new era (and if you know anything at all about me, you know that I don’t tend to exaggerate).

What is it?

Imagine designing your solution by graphically creating endpoints and messages, seeing the routing laid out in front of you visually, being able to specify system wide error and audit queues, having your cross-cutting authentication applied automatically to all endpoints, correlating events together into sagas, pressing F5, and as everything springs to life, on your second monitor you can see the messages flowing through your specific debug session synchronized in real time as you step through your code.

Well, you don’t have to imagine – that’s now a reality.

Top that off with some nice production monitoring that includes heartbeats for all of your endpoints, notification of message processing failures (with the ability to send them back for reprocessing), and some cool extensibility to plug in your own custom checks.

It’s a whole new world of service-oriented development.

This short video will give you a sense of what it’s like:


Here’s some other things you might find interesting.

Testing you can trust

I’ll bet you didn’t know the level of testing that we’re now putting into each release.

Every time we put out a new release, we test it on cloud servers configured across all permutations of transports, containers, persistence technologies, server operating systems, as well as for compatibility with previously released versions 2 years back (!). This way, when you want to have a new system subscribe to events published by a system already in production, you’ll know that it will all “just work” – no matter what.

Running all of these tests in the cloud is something that we could never afford back when we were a regular free/open-source project, but is definitely worth it. We know you count on us for your mission-critical systems and will continue doing our very best to be worthy of that trust.

The roadmap

Now that the platform is out, the next big thing you can expect is the removal of all distributed transactions.

Over the past months (and even years) we’ve been making preparations for this, making all sorts of small backwards compatible changes and enhancements so that we can fully control the inbound and outbound behavior of messages. The investments we’ve been making in automated tests is also in support of this. We want to be absolutely positive that you will get the exact same logical behavior as before without losing any of the transactional guarantees you’ve come to expect from NServiceBus.

We’ll give you updates on this and the other things we’re working on soon, as part of our larger roadmap so that you’ll know roughly what kind of big features you can expect and when. Of course, we always leave some “slack” in our iterations for working on critical patches, enhancements, and refactoring.

In any case, the main idea here is for you to be able to give us feedback and input on what’s important to you and for us to communicate back what we will be able to commit to and when.

Expressing our thanks

It’s been quite a journey this past year – the company has doubled in size and we’ve really got a great group of people here. While we’re constantly looking ahead and seeing all the wonderful things that we want to do, I wanted to take a moment and look back.

It’s been almost two years of work on ServiceMatrix (previously named NSB Studio) – the absolute biggest investment we’ve made. This past year was really the biggest push, and when taken together with all of the other tools – the production monitoring in ServicePulse that so many people have been clamoring for; the under-the-hood visibility of ServiceInsight; and the unseen glue of ServiceControl tying them all together; well, it was a very ambitious year.

I wanted to thank everyone who took part in our betas – your feedback was absolutely invaluable;

To our Community Champs who keep asking us the difficult questions and pushing us to do better;

To all of you in our community who have believed in us;

To the growing ranks of paying customers who voted with their wallets as well as their hearts;

You have my personal thanks as well as those of the entire team.
It continues to be an honor and a privilege.

Go and get it

That’s it – go to www.particular.net and click the big “download now” button and take the new platform for a spin!

I can’t wait to hear what you all think.



Loosely-coupled orchestration recording now online

Monday, April 7th, 2014

When I was in London a couple of weeks ago teaching my SOA class, I gave an evening presentation called Loosely-Coupled Orchestration which talked about some of the challenges people face when introducing more event-driven and asynchronous patterns into their systems – for example, dealing with out-of-order message delivery.

I’m happy to say that the recording of that session is now online, courtesy of the good folks at Skills Matter, and you can now view that here.

In this presentation, you’ll also see a lot of the new capabilities that will be coming out soon with the release of our new Particular Service Platform – the suite of tools that makes NServiceBus that much more awesome. From monitoring of production issues, to debugging cross-endpoint message flows, to modeling of message-driven & service-oriented systems, it really takes distributed systems development to the next level.

Check it out!

Oh, I almost forgot, there are still some seats left for my course in New York City. Details here.



On that Microservices thing

Monday, March 31st, 2014

antsSeems that I’m a bit late to the Microservices party – original article here.

But since I’ve been getting repeated requests to weigh in on the topic, I guess I’ll have to risk fanning the flames up again.

Also, since quite a few reactions have already been written on the topic (and I don’t want to repeat them here), I’ll just point to this post by Arnon which sums them all up pretty well.

Now, I don’t entirely agree with all the commentary Arnon pointed to, or all of his thoughts on the topic, but I’ll try to take those up some other time.

And before jumping into it, let me say that there is a lot of good stuff in the article and that, regardless of naming, spreading the word more broadly on these approaches has value.

So, where do I stand on the topic

First of all, for those of you who have been following my blog for a while I’d say this:

Microservices almost equals Autonomous Components.

Why “almost”?

Because an Autonomous Component (AC) isn’t necessarily a physical unit of deployment – very often we’ll see multiple ACs deployed in the same physical process. One of the most common occurrences is in a web front end built as a composite UI. In the same web server process we’ll see components from multiple Services.

This is something that was hardly mentioned in the original article.

On Services and Systems

In my world, Services are a larger organizing principle that are meant to align solution domain boundaries with problem domain boundaries.

Now, that might sound very similar to this passage from the original article:

“The microservice approach to division is different, splitting up into services organized around business capability. Such services take a broad-stack implementation of software for that business area, including user-interface, persistant storage, and any external collaborations. Consequently the teams are cross-functional, including the full range of skills required for the development: user-experience, database, and project management.”

Now, this isn’t entirely surprising because I did have several conversations with both James and Martin on the topic over the past couple of years.

Still, there is something important missing here that I believe is very important to achieve loose-coupling, and that is that Services necessarily have to span system boundaries.

Let me repeat that: a Service will need to have components that are deployed to more than one system.

Here’s why:

Let’s say you have a piece of data like the price of a product. Not only will that data be visible in one system, often it will need to be shown (as well as updated) in other systems too. In order to have appropriate encapsulation of that concept, the owning service will need to be the one that owns the components that operate on that concept in the other systems.

This means that if we need to show the product price on an invoice in a back-end system, then that invoice would have to be a composite UI as well, and the service which owns the price will have a component deployed there which would be responsible for showing the price on the invoice.

In this manner, no code outside the service boundary would know about the concept of the product price and thus could not end up coupled to it.

Although the original article does get into this to some degree (when talking about Decentralized Data Management), I don’t really see how a microservice/AC could end up having this level of ownership of data.

Still, the point made about different persistence technologies is valid at the level of services (though not ACs).

How big is a service

Now, if the price is not shared outside the boundary of the service, then how would order totals be calculated?

The answer is that the totals must (MUST) be calculated in the same service.

This shouldn’t be surprising as it’s just good old OO – encapsulating data with the logic that operates on it. Or, if you’d like, call it the Single Responsibility Principle: there should only be a single service impacted by a change to the definition of this data.

As a result, you’ll tend to see services that aren’t all that small, and probably not so many of them. In my experience, I’ve seen between 7 and 15 services the majority of the time.

Cross-service collaboration

Although I am glad to see the recommendation for event-based interactions between microservices, the focus on cross-process communication ignores some extremely important collaboration scenarios – the most important of which is in the client tier.

In a web application, it is quite common to have components written in javascript from multiple services interacting among themselves in the browser – one publishing events, others subscribing to those JS events. It is also quite common to see those JS components request some data from back-end components in the same service in response to those JS events.

This type of synchronous RPC communication within a service boundary is perfectly acceptable, although it stands in contrast to the recommendations of the microservices approach.

Caveat on sharing data

I’ve been going on and on about the importance of not sharing data, but there is one exception to that rule.

There is a special service that I call IT/Ops which (among other things) is responsible for integration with 3rd party systems. As a part of this integration, it encapsulates data transformation logic and, as a result, needs to be able to receive data from the other more business-centric services.

As you can imagine, this puts IT/Ops in the risky position of coupling itself to a lot of things and thus needs to be done carefully. As a result, I recommend that many of the most skilled technical people work within the IT/Ops team, also serving in a consultative capacity to the other service teams.

In closing

I am extremely thankful to Martin and James for writing the Microservices article.

I think that the conversations it has sparked are timely, and hopefully more people will ponder these questions of how to structure their code-bases in order to avoid them becoming monolithic.

And while I think that it’s great to consider aligning team boundaries with service boundaries, people need to understand that it will need to be an evolutionary process – it will take time to transition an existing code base and an existing team structure to this new model, especially since these teams will have to continue to deliver features and bug fixes through the transition period. Jumping to the new model directly may cause more harm than good.

This is actually one of the most salient topics of my course (next one in NYC in May) – how do you get there from here. In my experience there are 4 phases that companies go through, often taking at least a couple of years, with larger environments taking potentially longer.

In any case, let’s keep the conversation going.

What are your thoughts? Have you been applying the Microservices approach, or possibly the one I talk about (I really should give it a name). What’s been working well for you? What hasn’t?

Leave me a comment or write your own blog post.



and now the ADSD Unconference!

Friday, March 14th, 2014

ADSD unconferenceIn addition to NSBcon, we’re also going to be running the first ADSD conference in London too – the day before, in fact.

Well, it would be more accurate to say the first ADSD UNconference.

For the thousand+ people I’ve trained over the past 7 years who have been applying the principles of the course and want to discuss what’s been working for them, what hasn’t been working, and how new tools and technologies can be applied to achieve loosely-coupled bliss, this is the place for you.

Important: This is unconference is limited to people who have taken the red pill ADSD course.

Join us in London on June 25 – register here.
Or in New York City on October 1 – register here.

We will be meeting the evening before to set the agenda and then go out for drinks and dinner.

What’s ADSD?

That’s the acronym for the Advanced Distributed Systems Design with SOA and DDD course I’ve been teaching for the past 7+ years.

If you want to know about Service-Oriented Architecture (or Microservices as it’s now being called – separate blog post coming on that topic), Domain-Driven Design, Command-Query Responsibility Separation, and how to gradually transition your way there – this is the course for you.

The next one is in London March 24-28 – register here.
The one after that is in NYC May 12-16 – register here.

What’s an “unconference”?

Taken from Wikipedia:

An unconference is a participant-driven meeting. The term “unconference” has been applied, or self-applied, to a wide range of gatherings that try to avoid one or more aspects of a conventional conference, such as high fees, sponsored presentations, and top-down organization.

Typically at an unconference, the agenda is created by the attendees at the beginning of the meeting. Anyone who wants to initiate a discussion on a topic can claim a time and a space. Unconferences typically feature open discussions rather than having a single speaker at the front of the room giving a talk, although any format is permitted.

In closing

I know some people have gotten so much value from the course that they’ve actually attended the course a second time.

Most probably wouldn’t be able to convince their boss.

So it is my hope that this format can serve as a kind of continuation to the course for people in the ADSD community to maintain contact and learn from each other, on top of the online discussion group.

Hope to see you there!



Last round of training

Saturday, February 23rd, 2013

Update: Videos now for sale here.

If you’d asked me last year how long I saw myself jetting around the world giving my SOA course, I probably would have said that I could see myself doing this well into “retirement”. But things change – usually when you least expect it.

In any case, I’ll be giving the course 4 more times, and that’ll be it.

Date City Address Register
Mar 18 Oslo, NO Program Utvikling
Martin Lingesvei 17 – 25
Register
Apr 8 New York, US New Horizons
290 Madison Ave
Register
May 13 Stockholm, Sweden Cornerstone
Svärdvägen 3A, 182 11 Danderyd
Register
June 3 London UK Skills Matter
107-111 Fleet Street
Register

When I was in Denver last month, I had the SOA course professionally recorded so if you can’t make any of these dates, you’ll still be able to get the videos. If you bought the videos in the past, don’t worry, I’ll be getting you the new videos as soon as they’re available. The NServiceBus courses delivered by other trainers will continue to run the same as before.

This change is part of a larger change in priorities for me. There are some big things coming that I’m very excited about that require quite a bit more of my attention.

Anyway, hope to see you either in Oslo, New York, Stockholm, or London.



Service-Oriented API implementations

Monday, December 10th, 2012

gearsIt’s quite common for our systems to need to expose an API for external parties to call that isn’t exactly aligned with our service boundaries – at least, when you follow the “vertical services” model rather than the “layered services” approach. I’ve blogged many times about the problems with layering, so I won’t go into that now beyond to say that you really, REALLY, should avoid it.

A short intro to SOA, done right

In the “vertical services” approach I espouse, you often see components from multiple services deployed to any given endpoint. While these services usually don’t need to communicate with each other at all, occasionally you’ll see them leaving “breadcrumbs” behind for each other – things like UserId or OrderId in the session. What’s especially important is that these IDs are accessible even before the entity is finalized – this enables each service to collect its own data without needing any other service to know about that data.

In an ecommerce environment, we would see one service owning money, another the product catalog (excluding prices, those would be owned by the previous service), another service owning the customers’ payment info (credit cards, etc), and yet another owning shipping addresses – all of these separate from the one that owns the shopping cart. Let’s call these Finance, Catalog, Payment, Shipping, and finally Shopping – just so that we have something to reference later.

The API

While we can do all sorts of cool browser composition with the UI in our own system, enabling each service to collect and display its own information, if we want to expose an API for clients to call, we wouldn’t want to force those clients to have to make a separate call to each service in order to make a purchase. Instead, we’d want something that looks like:

MakePurchase(Guid orderId, Dictionary cart, CreditCardInfo cc, Address shippingAddress)

In case you were wondering, the service which owns the definition of this API is different from all of the above services – it is a service that is primarily technical in nature and is responsible for things like integration and data transformations. I call this service IT/Ops.

Getting the data from the API to the services

So, we don’t want any of our business-centric services to know about anybody else’s data structures, so that leaves it to IT/Ops to pass the data to them. The thing is that we still want to do that in the most loosely-coupled way possible – with messaging being a good candidate for that.

So, what we’ll do is have IT/Ops send a message containing the data to the other services, but with a slight twist.

Here’s what the code would look like with NServiceBus:

Bus.SendLocal(new Order { Id = orderId, Cart = cart,
                          CreditCard = cc, ShippingAddress = shippingAddress });



Why the SendLocal?

So that the components from the other services can all run together with IT/Ops in the same process giving a nice tight deployment model.

UPDATE:

If you’re using a transport like RabbitMQ that is set up as a remote broker, the overhead of going back through the broker might not be worth the improved reliability you’d get by going through messaging. In that case, you might want to consider the Domain Events approach. This would give you a similar level of decoupling but then IT/Ops would need to set up an surrounding transaction, well, that is if you want all the services processing to succeed/fail as one unit. If you don’t, you’d probably be better off just sending messages from IT/Ops to endpoints that host each of the components of the other services.

End Update

Before we get to the services, let me show you the Order class – specifically, the interfaces it implements:

public class Order : ShoppingOrder, PaymentsOrder, ShippingOrder
{
    public Guid OrderId { get; set; }
    public Dictionary<Guid, int> Cart { get; set; }
    public CreditCardInfo CreditCard { get; set; }
    public Address ShippingAddress { get; set; }
}

public interface ShoppingOrder
{
    Guid OrderId { get; set; }
    Dictionary<Guid, int> Cart { get; set; }
}

public interface PaymentsOrder
{
    Guid OrderId { get; set; }
    CreditCardInfo CreditCard { get; set; }
}

public interface ShippingOrder
{
    Guid OrderId { get; set; }
    Address ShippingAddress { get; set; }
}




Each of the above interfaces represents the data that each service cares about. Therefore, each service will provide an assembly that handles that message/data and persists it to its database, like this:


public class ShoppingAPIHandler : IHandleMessages<ShoppingOrder>
{
    public void Handle(ShoppingOrder message)
    {
        //persist to shopping service db
    }
}

public class PaymentsAPIHandler : IHandleMessages<PaymentsOrder>
{
    public void Handle(PaymentsOrder message)
    {
        //persist to payment service db
    }
}

public class ShippingAPIHandler : IHandleMessages<ShippingOrder>
{
    public void Handle(ShippingOrder message)
    {
        //persist to shipping service db
    }
}



Since the Order object being sent is a polymorphic match for all of these interfaces, NServiceBus knows to invoke all of these handlers. By the way, if you care about the order of invocation, then you can control that as well (but I won’t get into that here).

Also, since all of these handler assemblies are deployed to the same endpoint, and the Order object is sent just once, this means that all the handlers will be invoked in a single transaction on a single thread – either all of them succeeding, or all failing. Since they’re all connected on the same Order Id, referential integrity can be preserved as well.

Wrapping up

When you are building a system on SOA principles, you’ll often find that you need a service like IT/Ops to handle data transformation and other broker-centric tasks. While much of SOA is based on the Bus Architectural Style – meaning primarily publish/subscribe interaction between services – that doesn’t mean that your business-centric services cannot have their components deployed in the same process.

I’d go so far as to say that if you aren’t deploying components from multiple services in process with each other at least some of the time then it’s quite likely that your service boundaries are probably incorrect.

Anyway, I hope you found this post interesting. Shout out to Slawek who gave me the idea for this post.

By the way, if you’d like to learn more about these kinds of patterns, the next batch of courses is open for registration – but the early bird prices are almost over, so you’d better hurry.

Register for   Denver CO, USA,     Bad Ems, Germany,     Perth, Australia.



High Availability a la Dennis

Monday, September 3rd, 2012

I thought I’d give a bit of a shout-out to Dennis van der Stelt whose been applying many of the principles from my course on his project and now has something of a success story to share. Although all he put out was a little tweet about it, I think if more people bug him, we can tease some more out:

It’s not just about getting the system built quickly the first time, and it’s not just about having a maintainable code base longer term, equally important is the ability to quickly deploy major releases to the system without downtime – ‘cuz when you’re system is down, it’s not providing any business value (which is what being Agile is all about).

What do you say, Dennis? Tell us some more!

UPDATE

Dennis gives the full story here.



Data Duplication and Replication

Tuesday, August 28th, 2012

agent_smith_replicationOccasionally I’ll get questions from people who have been going down the CQRS path about why I’m so against data duplication. Aren’t the performance benefits of a denormalized view model justified, they ask. This is even more pronounced in geographically distributed systems where the “round-trip” may involve going outside your datacenter over a relatively slow link to another site.

CQRS

As his been said several times before by many others, it’s not the denormalized view model that defines CQRS.

One of the things that sometimes surprising people after going through my course is that in most cases you don’t need a denormalized view model, or at least, not the kind you think. Yes, that’s right: MOST cases.

But I don’t want to get too deep into the CQRS thing in this post – that can wait.

SOA

The big thing I’m against is raw business data being duplicated between services.

Data that can be expected to be accessible in multiple services includes things like identifiers, status information, and date-times. These date-times are used to anchor the status changes in time so that our system will behave correctly even if data/messages are processed out of order. Not all status information necessarily needs to be anchored in time explicitly – sometimes this can be implicit to the context of a given flow through the system.

For example, the Amazon.com checkout workflow.

In that flow, if you provide a shipping address that is in the US, you are presented with one set of options for shipping speed, whereas an international address will lead you to a different set of options.

Assuming that the address information of the customer and the shipping speed options are in different services, we need to propagate the status InternationalAddress(true/false) between these services in that same flow. In this case, there isn’t a need to explicitly anchor that status in time.

But what’s so bad about duplication of data between services?

The danger is that functionality ultimately follows raw business data.

You start with something small like having product prices in the catalog service, the order service, and the invoice service. Then, when you get requirements around supporting multiple currencies, you now need to implement that logic in multiple places, or create a shared library that all the services depend on.

These dependencies creep up on you slowly, tying your shoelaces together, gradually slowing down the pace of development, undermining the stability of your codebase where changes to one part of the system break other parts. It’s a slow death by a thousand cuts, and as a result nobody is exactly sure what big decision we made that caused everything to go so bad.

That’s the thing, it wasn’t viewed as a “big decision” but rather as just one “pragmatic choice” for that specific case. The first one excuses the second, which paves the way for third, and from that point on, it’s a “pattern” – how we do things around here; the proverbial slippery slope.

So what’s with the word “Replication” in the title of this post?

While data duplication between services is very dangerous, replication of business data WITHIN a service is perfectly alright.

Let’s get back into multi-site scenarios, like a retail chain that has a headquarters (HQ) and many stores. Prices are pushed out from the HQ and orders are pushed back from the stores according to some schedule.

We know that we can’t guarantee a perfect connection between all stores and the HQ at all times, therefore we copy the prices published from the HQ and store them locally in the store. Also, since we want to perform top-level analytics on the orders made at the various stores, that would be best done by having all of those orders copied locally at the HQ as well.

We should not view this movement of data from one physical location to another as duplication, but rather as replication done for performance reasons. If there were some magical always-on zero-latency network that existed, we wouldn’t need to do any of this replication.

And that’s just the thing – logical boundaries should not be impacted by these types of physical infrastructure choices (generally speaking). Since services are aligned with logical boundaries, we should expect to see them cross physical boundaries – this includes SYSTEM boundaries (since a system is really nothing more than a unit of deployment).

I know that you might be reading that and thinking “What!?” but there isn’t enough time to get into this in any more depth here. You can read some of my previous posts on the topic of SOA for more info here.

Cross-site integration without replication

There are some domains where sensitive data cannot be allowed to “rest” just anywhere. Let’s look at a healthcare environment where we’re integrating data from multiple hospitals and care providers. While all of these partners are interested in working together to make sure that patients get the best care, which means that they need to share their data with each other, they don’t want any of THEIR data to remain at any partner sites afterwards (and are quite adamant about this).

In these cases, the decision was made that performance is less important than data ownership. Personally, I don’t agree with this mindset. The fact that data is “at rest” in a location as opposed to “in flight” does not change ownership. It could be stored in an encrypted manner so that only a certain application could use it, resulting in the same overall effect, but this is an argument that I’ve never won.

People (as physical beings) put a great deal of emphasis on the physical locations of things. It’s understandable but quite counterproductive when dealing with the more abstract domain of software.

In closing

By virtue of the fact that we don’t duplicate raw business data between services, that means that the regular data structures inside a service already look very different from what they would have looked like in a traditional layered architecture with an ORM-persisted entity model.

In fact, you probably wouldn’t see very many relationships between entities at all.

Going beyond that, you probably wouldn’t see the same entities you had before. An Order wouldn’t exist the way you expect; addresses (billing and shipping) would be stored (indexed by OrderID) in one service whereas the shipping speed (also indexed by OrderId) would be in another, and the prices may well be in yet another.

It is in this manner that data does not end up being duplicated between services, but rather is composed by many services whether that is in the UI of one system, the print-outs down by a second system, or in the integration with 3rd parties done by a third system.

If performance needs to be improved, look at having these services replicate their data from one physical system to another – in-memory caching is one way of doing this, denormalized view models might be though of as another (until you realize there isn’t very much normalization within a service to begin with).

And a word from our sponsor :-)

For those of you on “rewrite that big-ball-of-mud” projects looking to use these principles, I strongly suggest coming on one of my courses. The next one is in San Francisco and I’ve just opened up the registration for Miami.

For those of you on the other side of the Atlantic, the next courses will be in Stockholm in October and in London this December.

The schedule for next year is also coming together and it will include South Africa and Australia too.

Anyway, here’s what one attendee had to say after taking the course earlier this month:

I wanted to thank you for the excellent workshop in Toronto last week. I spent the better part of the weekend reflecting over what was presented, the insights we learned through the group exercises, and how my preconceptions of SOA have changed. By the end of the course, all the tidbits of (usually) rather ambiguous information that I’ve collected from various blogs, books, and other sources, finally coalesced into something more intelligible – one big A-HA moment if you will. Overall, I found the content of the workshop to be incredibly enlightening and it left me feeling invigorated and excited to learn more.
- Joel from Canada

Hope you’ll be able to make it.

If travel is out of the question for you, you can also look at get a recording of the course here.

One final thing

If your employer won’t foot the bill for these, please get in touch with me.
I wouldn’t want you not to be able to come just because you’re paying out of pocket.

There are very substantial discounts available.

Contact me.



   


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

97 Things Every Software Architect Should Know



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