index > Windows Workflow Foundation > Custom queue and persistance

Custom queue and persistance

Hi,

I created a custom Activity implementing IActivityEventListener to manager my own events.

My problem is when the workflow host is closed and relaunch, all events registered previously are not recreated during rehydratation and my activities aren't responding anymore.

How can i solve this ?
Do i need to persist each queue myself ? If yes, where (or when...) should i do that ?

Thanks for any help,

Hadrien

Hadrienlc

How, and where, are you subscribing to the events in your queues?

Tomas Restrepo [MVP]

Tomas Restrepo

Subscriptions are normally created in IEventActivty.Subscribe().
(I also tried to recreate them during OnActivityExecutionLoad() but without success.)

The queue management is very similar to the one showed in the CustomActivity Framework sample...

I insist on the fact that this problem only occurs in close and relaunch the workflow host...

Thanks for your help !

Hadrienlc

I think you're creating the subscriptions in the right place.

I have a theory, however, but it is just that, a theory, so it would be nice if someone could confirm/reject it.

I believe that WF will *never* force event activities to recreate subscriptions when a persisted workflow is loaded again. Subscriptions are persisted in the sense that they are handled and remembered by the WorkflowQueuing service. However, if your external runtime service that does the work (i.e. that reacts to subscriptions and fires event) has to do something when a new subscription is created (such as polling or attaching to events in an external data source), then this won't quite work because the subscription is not recreated when the workflow instance is loaded again.

In that case, I *think* that it's the developers responsability to create the helper runtime service so that it "remembers" any subscriptions that were created and uses that information to respawn any processes that had been started as a consecuence (such as start polling the external data source again).

I may be wrong on this though (and hopefully I am, because it sure seems for the built-in support to be half baked without this).

Tomas Restrepo [MVP]

Tomas Restrepo

reply 4