Transaction coordinator for wcf distributed transactions

Question

I know that Transaction coordinators are used for coordinating transaction between different types of resources such as 1)SQL Server 2)Oracle 3)MSMQ 4)File System etc. and it is their responsibility to keep tracks of transactions and if transaction of any of this resources failed it should rollback transaction of all other resources in WCF.

I would like to know a) Which transaction coordinator to choose and why b) Can we choose transaction coordinator by itself or it will be done automatically by wcf itself for following conditions :-

1)If wcf uses transactions for same Microsoft technology(Microsoft SQL Server & Microsoft Message Queue)

2)If wcf uses transaction for different database technology(Microsoft SQL Server, Oracle and MySQL)

3)If wcf uses transaction for all different types of resources with different technlogies(Microsoft SQL Server, Oracle, File System etc.)

Answer 1

I would strongly advice against using DTC in such a heterogeneous environment. There are multiple risks involved. Only one of them is limiting your future choices: what if you have to use a file system that cannot enlist it a transaction (say, network fileshare)? Or cloud frontend? Or some 3rd party service?

Also DTC couples parts of your system together very badly. All sorts of coupling are involved: spatial, temporal, even platform (because everyone must know how to enlist in a specific DTC).

Despite performance (which is thousands of times worst with DTC than without) aspects, DTC works great until it doesn't. You should be prepared to "transaction is in doubt" situations and all sorts of troubleshooting if you use DTC. And it should be a part of your design.

There are cases when DTC is needed for some rare specific cases in systems, but if you find yourself in a situation when you look at transactions and DTC as at a holy golden hammer (we just start transaction, and if something fails we "just" rollback everything) I recommend you to stop right now. You will save tons of time, bugs, nerves, money, resources if you stop here.

I believe it would be more logical and much better to make a proper design that would not require DTC. Remember: business does not rollback. We do, programmers. When money are being transferred from one account to another (possible in different banks), there is no DTC involved, it would be crazy. They do not rollback, they compensate. There are patterns and ways to do it properly, we cannot just wrap the whole world in a transaction.

So design your systems against independent contexts that can operate autonomously and communicate to each other naturally and you will find yourself in a much better world :)

Answer 2

I'd say if you are running your application on a windows server, Ms DTC would be the most natural choice as it is a part of the OS already as a native windows service. http://blogs.msdn.com/b/florinlazar/archive/2004/03/04/what-is-msdtc-and-why-do-i-need-to-care-about-it.aspx

I've used it before for WCF-services in a custom software project and it does the job. If it was me I would use it again for a new project, unless there was a very specific reason not to.