I'm developing some Workflow 4 activities that will continuously loop and do some work. For example, one may watch an RSS feed and execute some steps as new items are added. I would like to be able to stop and restart this process cleanly (ie, in a windows service or Azure Worker Role). Currently, I have a While loop with an expression that always resolves to true, and just let the instance die when the app closes. But it seems like this is not a very clean way to stop the workflow.
How should I stop and restart the workflow?
The exact system depends a bit in the way you host your workflow but I am assuming you are using the WorkflowApplication. In that case simple option is to use the WorkflowApplication which has a Cancel method you can use to cancel execution of the workflow. You can also create a bookmarked activity and resume a stop bookmark or something similar but that might be overkill.
Related
We have a service hook created for one of our projects in ADO. It was going fine until last weekend. Suddenly few webhooks started queued and I am not sure how to force it to get processed. Can someone help me if there is a way to force those items to get processed.
Thanks,
Venu
I am afraid that you cannot get that you want during process.
Under the process, the queued service hooks will not be picked again and will not be processed again.
When the main thread, such as a work item, is running, you cannot forcefully intervene or exit the content that is already queued.
And there is a similar issue also discussing about this situation.
And waiting service hooks are actually coupled, which also depends on your memory, because they actually run in memory. If there are occasional memory loss and other problems during execution, this cannot ensure that all service hooks can be executed as expected.
Or you should interrupt the current process and reduce the service hooks for it. But it is not a good solution.
So it is the best way to add a function that can handle the queued service hooks in the process. But currently there is no such function. Therefore we recommend you submit the suggestion ticket to the Team to suggest them add that feature.
In AEM CQ , I am using asset manager api to write content(images uploaded from) in dam. This triggers out of the box Dam Update Asset workflow. I require to read renditions and asset properties that would be written available once the workflow is completed.
My question is how to wait until the workflow is completed for reading the asset properties instead of thread.sleep.
I tried with a recursive function call to iterate while the asset property is present. This gave null pointer exception. But when I put a thread.sleep of 50 ms inside the iteration it works for me.
Another approach I tried to get the workflow object inside the service to read workflow status but found that it takes few milliseconds for the ootb workflow to start after the content is written. Here also had to give thread.sleep.
One more attempt to use a event handler to listen workflow events. We are able to enter the event type as workflow completed. How to notify the service or jsp that the workflow is completed and we can read the asset properties and renditions?
It would be great if someone can share their suggestions feedback on the approach. Thank you.
You have the wrong approach to solve this problem. In my eyes you have exactly 2 reasonable solutions on this.
Create workflow process/step and extend the Dam Update Asset Workflow with your custom step.
OR
Create JCR observation listener and listen for Event.PROPERTY_ADDED for example or use the higher sling APIs and create event handler with the appropriate topic and than execute your business logic as soon the property you look for is added or changed.
Why not to use Thread.sleep() or other similar solution:
you don't know when the workflow is executed exactly. it may be
delayed if many asssets are uploaded or just get stuck
you cannot assure that your thread will be able to execute it's
logic. the instance may be stopped for example
creating a new tread for every resource uploaded may be expensive task. you also waste resources when you create an infinite loop and put those threads to sleep, than wake them and check again and again ... and so on until eventually the thread is able to do it's job
Is it possible to cancel a long running activity while still keep the whole workflow alive. The workflow itself is hosted in WorkflowApplication.
The real user case is we've got a long running activity which polls the price from an external web service, and once it gets the price the activity should complete and the workflow will move to its next step. However, the price is something nice to have but not mandatory, so in some cases we want to cancel the polling activity and let the WF carry on its execution.
So the question is how can I notify a running workflow to cancel (actually skip) its current activity.. if this is not possible at all, can someone please share your thoughts and point me the right direction to achieve this goal.
Thanks a lot.
Dan
You can do this using a Pick activity. Use one PickBranch trigger to poll for the price and add a skip polling bookmarked activity to the other branch. Whatever branch completes first continue and the other will be canceled.
I'd like to move my scheduled tasks into workflows so I can better monitor their execution. Currently I'm using a Window's scheduled task to call a web service that starts the process. Is there a facility that you use to schedule execution of a sequence so that it occurs every N minutes?
My optimal solution would:
Easy to configure
Provide useful feedback on errors
Be 'fire and forget'
PS - Trying out AppFabric for Windows Server if that adds any options.
The most straightforward way I know of would be to make an executable for each workflow (could be console or windows app), and have it host the workflow through code.
This way you can continue to use scheduled tasks to manage the tasks, the main issue is feedback/monitoring the process. For this you could output to console, write to the event log, or even have a more advanced visualisation with a windows app - although you'd have to write this yourself (or google for something!). This MS Workflow Monitoring sample might be of interest, haven't used it myself.
Similar deal with errors, although writing to the event log would be the normal course of action in this case.
I'm not aware of any other hosts for WF, aside from things like Dynamics CRM, but that won't help you with what you're trying to do.
You need to use a scheduler. Either roll your own, use AppFabic as mentioned or use Quartz.NET:
http://quartznet.sourceforge.net/
If you use Quartz, it's either roll your own service host or use the ready-made one and configure it using xml. I rolled my own and it worked fine.
Autorun is another free option... http://autorun.codeplex.com/
I have a web application that I am adding workflow functionality to using Windows Workflow Foundation. I have based my solution around K. Scott Allen's Orders Workflow example on OdeToCode. At the start I didn't realise the significance of the caveat "if you use Delay activities with and configure active timers for the manual scheduling service, these events will happen on a background thread that is not associated with an HTTP request". I now need to use Delay activities and it doesn't work as is with his solution architecture. Has anyone come across this and found a good solution to this? The example is linked to from a lot of places but I haven't seen anyone else come across this issue and it seems like a bit of a show stopper to me.
Edit: The problem is that the results from the workflow are returned to the the web application via HttpContext. I am using the ManualWorkflowSchedulerService with the useActiveTimers and this works fine for most situations because workflow events are fired from the web app and HttpContext still exists when the workflow results are returned and the web app can continue processing. When a delay activity is used processing happens on a background thread and when it tries to return results to the web app, there is no valid HttpContext (because there has been no Http Request), so further processing fails. That is, the webapp is trying to process the workflow results but there has been no http request.
I think I need to do all post Delay activity processing within the workflow rather than handing off to the web app.
Cheers.
You didn't describe the problem you are having. But maybe this is of some help.
You can use the ManualWorkflowSchedulerService with the useActiveTimers and the workflow will continue on another thread. Normally this is fine because your HTTP request has already finished and it doesn't really matter.
If however you need full control the workflow runtime will let you get a handle on all loaded workflows using the GetLoadedWorkflows() function. This will return acollection of WorkflowInstance objects. usign these you can can call the GetWorkflowNextTimerExpiration() to check which is expired. If one is you can manually resume it. In this case you want to use the ManualWorkflowSchedulerService with the useActiveTimers=false so you can control the last thread as well. However in most cases using useActiveTimers=true works perfectly well.