Free Tool: Create Reliable Services with NServiceBus
NServiceBus can help you create more reliable .NET services. It may not be as "free" as it appears, though.
NServiceBus was suggested by a reader who commented on my WCF article
about handling long-running processes in an SOA environment. NServiceBus is an open-source tool for creating services in .NET. But I'm stretching the definition of "free tool" a little because NServiceBus is only "sort of" free. The Express Edition is free but has some limitations: It's a single threaded application (able to handle up to 30 requests a second), and can only be run on a single production server with a maximum of four cores.
NServiceBus is a flexible tool, though. It handles creating a wide variety of services (including full duplex services where the consumer can call the server and the server can call the consumer). Unlike WCF, NServiceBus is a lot more about writing code and defining interfaces than putting entries in config or XAML files. The publish/subscribe model is also an important part of the NServiceBus way of doing things.
The major difference between WCF and NServiceBus is message handling. WCF is based around remote procedure calls: A request is sent by a consumer, caught by some host, and then passed to a "WCF-enabled" class for processing. With NServiceBus, on the other hand, incoming requests are queued. Those requests are pulled from the queue and handed over to an "NServiceBus-enabled" class for processing. This makes fault tolerance considerably easier to implement in NServiceBus than in WCF (in a queuing system, it's very difficult to lose a request). You can get to that level of reliability with WCF but it will require an additional tool (probably an enterprise service bus that implements queuing).
If you decide to investigate NServiceBus and, eventually, decide to upgrade to the standard edition it'll cost you either $25 a month or a single payment of $500 to $2000. Like I said: Not really free, just "sort of" free. But if reliability is what matters to you then this is a tool worth looking at.
Peter Vogel is a system architect and principal in PH&V Information Services. PH&V provides full-stack consulting from UX design through object modeling to database design. Peter tweets about his VSM columns with the hashtag #vogelarticles. His blog posts on user experience design can be found at http://blog.learningtree.com/tag/ui/.