During the development of a small prototype we discovered an issue when using EDRA with the Remoting interface. We had to build this prototype to demonstrate the changes we made to EDRA and prove that the way we want to make use off EDRA really works. The prototype contained 3 services: 1 user interface service, 1 business process service and 1 business information service. The application flow is very simple: the user interface service does an EDRA call to the business process services and the business process service does an EDRA call to the business information service. This is a little different as for example the Global Bank implementation where only 1 EDRA call is made (from the user interface to the service).

The above means that the business action of the business process service does an EDRA call to the business information service. When executing this with the remoting interface transport and ‘inProc’ dispatching we got the following error: ‘tcp channel already registered’. After some investigation we noticed the following line in the ‘RemotingInterfaceListenerController.cs’ file

Transport = new TcpServerChannel(props, bsfsp);

Because in this statement, no name is supplied for the TcpServerChannel that is created (not part of ‘props’), the remoting runtime uses the default name ‘tcp’. When this piece of code is executed twice, this is causing the exception ‘tcp channel already registered’.

Because during development of our services we like to use remoting interface and ‘inproc’ dispatching (easy debugging), we had to solve this issue.

The most easy way to solve this issue is supplying an empty string (“”) to the constructor of the TcpServerChannel as part of the IDictionary ‘props’.

This should look something like

props [“port”] = _port;

props [“name”] = “”;

Transport = new TcpServerChannel(props, bsfsp);

But… maybe it’s better to get the name out of the configuration file and decide, based on the information returned by the ChannelServices.RegisteredChannels property, if the channel is already registered!

Ever asked yourself the question: “Am I (still) doing the right thing?” Well, I did!
I was triggered by someone that asked me why we are making all these changes to EDRA and why we are making all those guidelines about “how to use EDRA”. Isn’t EDRA the perfect SOA framework without all that changes, he asked. Well…. To be honest, I said, I don’t think so. Then of course the next question was: why should we use it? This made me think, are we doing the right thing?

Of course it is much easier to continue talking about SOA for a couple of months or even years, dreaming about al the good thinks SOA will bring us in the future. But he… we have to start somewhere, so why not start now!
There are tons of articles or writings about SOA on the internet, however there are only a few successful SOA implementations in real life projects (that I know off). In my opinion implementing a perfect SOA architecture cannot be done by just selecting the right framework, or tool (at least not at this moment). Implementing SOA needs a different way of thinking! For most of us, getting familiar with this “new way” of thinking takes time. To reduce this time as much as possible, adopting a framework might be the right thing to do. While using a framework, we will encounter all kind off issues that we wouldn’t have found when we only continued reading about the perfect world of SOA.

Whether to adopt a specific framework or not isn’t a decision we can make in one minute. We have to make sure that the framework meets you own architectural requirements. If some (or more) of our requirements are not covered by the framework, we have to find out how easy it is to introduce these requirements in the framework.
This is exactly what we are doing at the moment. We have our own set of requirements and we are mapping these requirements to EDRA features. Requirements that we think are important and are not available in EDRA will be implemented by our self. Of course we have to make sure that our own requirements are up to date with the latest ideas about SOA. This is why requirements are not static but can change in time, based on articles that we read or changes in technology and tools that we use.

For me, Adopting EDRA wasn’t based on its complete set of SOA features. In fact I don’t even think that Microsoft is positioning EDRA as a SOA framework. In my opinion the most important features of EDRA are: supplying a way to separate the business logic from the cross-cutting concerns (logging, authorization, etc.) and separate the business logic from the underlying transport that is used. I think these features give you a good starting point for building distributed systems. SOA features that we think are missing in EDRA (some of them I wrote about in previous posts) will be added to EDRA by our self.

One very important thing I try to keep in mind is to “abstract” the usage of EDRA away as much as possible. For me EDRA is just a piece of infrastructure that is used in our architecture. In the end it must be possible to replace EDRA by any other technology or framework that comes available without having to change all your services within the architecture (or at least as little as possible). So, it’s not only a question IF you want to use EDRA but also HOW you will use EDRA. Spending some time on writing design guidelines for services (interfaces) build against EDRA might give you more flexibility in the near future when switching to another version of EDRA or even a totally new framework or technology.

After spending a considerable amount of time thinking about the above issues, I think using EDRA as a starting point is a good thing to do (for our situation) and resources needed for introducing new (SOA) features will not be a waste of our time. By introducing some good design guidelines for our service we keep enough flexibility for changes in framework or technology in the near future.
So, in my opinion: Yes we are still doing the right thing!!

Today we finished a first version of our “deployment strategy” for services build with EDRA. Because we decided some time earlier to host all our services within 1 instance of EDRA (even if they are built for different projects/applications) we encountered some issues when using the “deployment strategy” that come with EDRA.

We noticed the first issue when trying to install two services on our development server created by two different developers on their local machines. Both developers had an EDRA installation on their machine. On both machines the EDRA assemblies had a different “PublicKeyToken”, of course this caused all kind of problems when deploying these services to our central instance of EDRA. The services were both compiled against a different set of EDRA assemblies. Installing these two services on our development server hosting one instance of EDRA caused all kind of compatibility issues between the different “PublicKeyTokens” in the EDRA assemblies and publicKeyTokens in the configuration files.

To solve this issue we build our “own” release set of EDRA assemblies. These assemblies are the ones that will be used for every project that is using EDRA. Also we made some changes in the ‘CreateNewTemplate.swf’ script and the “ApplicationTemplate.sln” that is used in this script. We deleted the ‘ReferenceArchitecure’ enterprise template from the solution to make sure no EDRA code files are available for our developers. Further we made some changes in the “Deploy.swf” and “SetupHelpers.swf” script to support only using the compiled assemblies within the Visual Studio solution created by our new “CreateNewTemplate.swf” script.

All this is included in the image that we created for setting up a .NET development machine. After installing this image on a machine, the developer ends up with machine containing all necessary Microsoft development tools, all EDRA assemblies installed in the GAC and a shortcut from the start menu to our modified “CreateNewTemplate” script. So now our developers are ready to build their EDRA based services without first installing EDRA.

After defining how to use the EDRA framework we had to define a strategy for our development, test and production servers. We decided to go for the “two server” option. This means hosting the service interface and service implementation on different servers.
We created a list with all files necessary for the two different server types. So only the necessary assemblies are installed on the machine (GAC). The EDRA configuration file is installed on both machines. On the server hosting the service interface we tested the WebService and Remoting transport. On the server hosting the service implementation we tested the WebService and DCOM dispatching transport. All combinations worked perfectly fine.

We think that the work described above brings us a relatively simple way of deploying an EDRA based service on either our development, test or production server. All the developer has to deliver is the “message”, “business action”and “interface transport” assemblies. And of course some EDRA configuration settings that will be included in the EDRA configuration files on the servers by our server administrator.

Today we finished version 1.0 of our directory service. This service is the first in a range of changes/additions we will make to the EDRA framework. All functionality as described in my previous posts is implemented in this first release. Below some implementation details for this service:
As a datastore for this ‘directory service’ we decided to use Active Directory. Of course using UDDI as a source for this is also a very (maybe even more) logical choice , but some requirements of our client made us decide to use Active Directory.
Because it is not that easy to implement a schema change in a company Active Directory, we used ADAM (Active Directory Application Mode) during development so we didn't have to wait before the schema change is implemented in the Active Directory.

After defining and implementing the schema in ADAM on our development server, the directory services was build using the default EDRA structure, created by the ‘CreateNewTemplate’ script. A simple caching mechanism is implemented within the service to reduce the relatively low performance of querying ADAM. The actual communication with ADAM is implemented in a ‘AdamProvider’ class that is registered in the directory service configuration file. This makes it relatively easy to implement an ‘UDDIProvider’ class in the (near) future.
The directory service is available through remoting and webservice interface. Because every service consumer within the architecture is allowed to use the directory service, none of the EDRA handlers for authentication or authorization are used for this service. During development no issues were found in using EDRA.
During the ‘deployment’ phase of our service however, we did encounter some (potential) issues. We think some adjustment need to be made in de setup and deployment scripts that come with EDRA. Especially in the situation that a ‘new service’ needs to be installed on the server that is already running an EDRA instance (and some services) we see some issues.

More on these deployment issues (and hopefully our solutions!) in a later post.

So this is the moment, I am starting my own blog. Working as an architect on several .NET projects my main interest is SOA. After some time of evaluation the Microsoft EDRA (aka Shadowfax) initiative I am about to start using EDRA in real life. This made me decide to share my thoughts, issues (and frustration??) in this process. Besides EDRA I also keep an eye on another 'new product' called FABRIQ. So maybe you will find some writting about this too.