WF (for the record: Windows Workflow Foundation) is great. If you need it, you really need it. If you have the engine and one workflow running, adding other workflows is no sweat at all. If your workflows are persisted, you won‘t have to care for shutdowns. If you carefully designed your workflow you can use the graphical view for discussions with the user. If you set it up correctly, even errors can be handled by workflows.
Well, WF is great. But there certainly are a lot of “if”s here…
I was at the PDC 05 where Microsoft introduced the WWF (later to be renamed to WF due to some concerned Pandas ;-) ) as THE big surprise. But I had to wait until earlier this year to get my “production hands” on it. Curiously that happened more or less simultaneously in more than one project. And curiously, despite the different nature of the task at hand they turned out to be very similar. Similar in terms of the problems, similar in terms of the pitfalls, similar in terms of the solutions. And also very similar in the demand for knowledge of things that are not WF specific but are far from common knowledge for the average developer… (and with that I mean the average knowledge areas, not developers of average knowledge… did that make sense? I have no intention to disqualify someone for not knowing all the stuff that‘s following!)
Curiously^3 while there is so much information available about WF—hosting, data exchange, and what else—it still did not answer our questions. I rather got the impression that my problems were largely ignored. Or if they were mentioned it stopped right there. “Here is something you will have to think about!” Period. “You should use XY.” Period. “That will be a problem.” Period.
So I had to rely on my BizTalk background to fill the gaps (and my knowlegde about multithreading even goes back to OS/2, sic! Am I in danger of becomming a dinosaur?). In the following posts I will dig in one or the other topic and some of the “best practices” (if it can be called that) we came about with, which might help the next developer.
At SDX people work for various customers, usually on-site. If I would like to go to vacation I might have something to say about the matter myself. So does the customer. So does my account manager. And the back office. And… you get the idea. To manage that you need an informal workflow at least, once the head count of your company goes up you need it formalized. And this is what our example application (let‘s call it Vacations@SDX) does:
- Show me how many vacation days I have left.
- Let me request a new vacation.
- Let all people concerned with my vacation have their say.
- If everyone involved acknowledged the vacation write the information to the payroll application.
Of course since most people are mostly out of office, the application has to be a web application, the workflow long running, and notifications done by email. And the payroll application could be offline. And most importantly: DON‘T MESS WITH MY VACATION! Losing my request somewhere along the way simply WON‘T DO!
Nothing special here at all. Some kind of document review, order processing, or whatever workflow would have similar demands. Actually this is a very simple real world example. And yet, if done correctly it is a far from simple undertaking. Certainly it is not as simple as drawing a workflow and hooking up the basics as described in the available documentation.
On the list of things to talk about is workflow instance state, workflow communication, hosting, and error handling. This will be fairly basic stuff from an “architectural” point of view, but I will assume that you know or read up about the WF basics. I‘m not going to repeat the dozen lines of code it takes to host WF in a console application.
If that sounds interesting for you, stay tuned.
That’s all for now folks,