Enterprise Architects, Top-Down SOA

I had hoped that the age of non-programming architects was over, but yesterday I was let down. I attended the monthly meeting at the "Practical SOA forum" at SINTEF where an experienced architect ("20+ years of IT experience") presentet his groups work at a large public service company in Norway. The architect explained the EA modelling work going on to build a service-oriented enterprise, showed the EA tool and portal, documented SOA guidelines, refinement of the model into BPMN (but not into BPEL), etc.

All systematic and professional, but then he went on to complain about having to spend too much time with the developers and hired consultants to help them actually understand and implement the model according to the guidelines and policies - which prevented him from playing (my word) with the model to refine it and expand it into new areas of the business...

No wonder many of the pure top-down approach SOA projects are regarded as failures.

WCF: Caching Claims using System.Web.Caching

We use a custom legacy STS (Security Token Service) that assigns a ticket to our consumer applications, that they again pass as to our WCF services for authentication. The passed SAML token contains only the ticket, so we must then use the validated ticket to generate the System.IdentityModel claims used for authorization.

As the services are stateless, each WCF operation must recreate the AuthorizationContext and thus generate the claim sets again. When you compose a set of services into a business process, the claim sets will get generated over and over again. To avoid this, and get better performance, I needed to cache the claim sets by STS ticket for a limited time.

Many might not know this, but the System.Web.Caching.Cache can be used even in systems that are not an ASP.NET application or even hosted by IIS/ASP.NET. You will still get all the goodies, such as cache expiration, dependencies, throwing stuff out of the cache in case of low memory, etc.

We now cache the claim sets in a singleton using a generic <T> getter and setter with ticket-based keys like this:

public static class EApprovalCache
{
private static System.Web.Caching.Cache _cache = HttpRuntime.Cache;

public static Cache Cache
{
get { return _cache; }
}

public static object Add<T>(string ticket, T value)
{
string key = typeof(T).Name +":" + ticket;
return _cache.Add(key, value, null, DateTime.Now.AddHours(1), Cache.NoSlidingExpiration, CacheItemPriority.Normal, null);
}

public static T Get<T>(string ticket)
{
string key = typeof(T).Name +":" + ticket;
return (T)_cache[key];
}
}

The claim set is retrieved and added to the cache like this:

_authorizationContext = EApprovalCache.Get<EApprovalAuthorizationContext> (context.Ticket);
if (_authorizationContext == null)
{
_authorizationContext = new EApprovalAuthorizationContext(session);
EApprovalCache.Add<EApprovalAuthorizationContext> (context.Ticket, _authorizationContext);
}

The claims are cached for max one hour; but if the user logs out and in again, then the user will have gotten another ticket and the claim set would be generated from scratch and not read from the cache.

Getting started with MSE, on SQL Server Express

As you can imagine, I just had to try to install and test the Managed Services Engine for service virtualization when it was made public on CodePlex this week. For a quick intro to MSE, its relation to "Oslo" and SOA governance, and MSE future directions; read this InfoQ interview with William Oellermann.

Not bothering to read the installation guide, I just ran the installer on my Vista machine with SQL Server Express installed - and got a "Failed to create SQL database: MSE6DB" error. The cause of the error is that the installer by default does not target a named SQL Server instance when trying to create the database used by MSE and the sample services provided with the MSE6 toolkit.

The solution is documented in the install guide (but I'm repeating it here for my friend Anders Norås):

• Ensure that SQL Server Express is running on your computer, but close SSE Management Studio
• Open a command windows (CMD.EXE) and navigate to the folder of the MS6.msi installer
• Run the installer (using /i):
  msiexec /i mse6.msi SQLSERVER=.\SQLEXPRESS
• Locate the Microsoft.MSE.Repository.Service.exe.config file in the “~\Program Files\Microsoft Managed Services Engine” folder and change the data source accordingly:
  <DBConnString>Initial Catalog=MSE6DB;Data Source=.\SQLEXPRESS; . . . ;

Note that you must be an administrator the local system if you are not in the SSE server role 'dbcreator' or equivalent.

This gives you the database MSE6DB that contains the MSE repository:
Try starting the Managed Services Engine MMC snap-in. If you get a service repository (net.pipe://localhost/ServiceCatalog/Pipe) connection error, then restart the “MSE Catalog Server” and “MSE Runtime Server” services in that order to reload the database config.

Finally, you must install some missing perf counters to make the service virtualization (hosted endpoints) work at run-time, otherwise you'll get an error when invoking the services. You must also restart the “MSE Catalog Server” and “MSE Runtime Server” services for the changes to take effect.

Now you're set to follow the 30min walkthrough to learn more about MSE and the wonderful world of service virtualization and see why it is important for life-cycle management of services in SOA systems.

PS! all of the walkthrough is correct, just pay attention in the POX step: you need to keep the action as-is from the previous step, only change what the text say you should change (binding XML, etc). Do not rediscover or change the selected operation in the grid.