How would you implement this "WorkerChain" functionality in .NET?
- by Dan Tao
Sorry for the vague question title -- not sure how to encapsulate what I'm asking below succinctly. (If someone with editing privileges can think of a more descriptive title, feel free to change it.)
The behavior I need is this. I am envisioning a worker class that accepts a single delegate task in its constructor (for simplicity, I would make it immutable -- no more tasks can be added after instantiation). I'll call this task T. The class should have a simple method, something like GetToWork, that will exhibit this behavior:
If the worker is not currently running T, then it will start doing so right now.
If the worker is currently running T, then once it is finished, it will start T again immediately.
GetToWork can be called any number of times while the worker is running T; the simple rule is that, during any execution of T, if GetToWork was called at least once, T will run again upon completion (and then if GetToWork is called while T is running that time, it will repeat itself again, etc.).
Now, this is pretty straightforward with a boolean switch. But this class needs to be thread-safe, by which I mean, steps 1 and 2 above need to comprise atomic operations (at least I think they do).
There is an added layer of complexity. I have need of a "worker chain" class that will consist of many of these workers linked together. As soon as the first worker completes, it essentially calls GetToWork on the worker after it; meanwhile, if its own GetToWork has been called, it restarts itself as well. Logically calling GetToWork on the chain is essentially the same as calling GetToWork on the first worker in the chain (I would fully intend that the chain's workers not be publicly accessible).
One way to imagine how this hypothetical "worker chain" would behave is by comparing it to a team in a relay race. Suppose there are four runners, W1 through W4, and let the chain be called C. If I call C.StartWork(), what should happen is this:
If W1 is at his starting point (i.e., doing nothing), he will start running towards W2.
If W1 is already running towards W2 (i.e., executing his task), then once he reaches W2, he will signal to W2 to get started, immediately return to his starting point and, since StartWork has been called, start running towards W2 again.
When W1 reaches W2's starting point, he'll immediately return to his own starting point.
If W2 is just sitting around, he'll start running immediately towards W3.
If W2 is already off running towards W3, then W2 will simply go again once he's reached W3 and returned to his starting point.
The above is probably a little convoluted and written out poorly. But hopefully you get the basic idea. Obviously, these workers will be running on their own threads.
Also, I guess it's possible this functionality already exists somewhere? If that's the case, definitely let me know!
