topic Re: Competing for tasks in Alfresco Archive

Competing for tasks

ritchieannand — Thu, 22 Oct 2015 21:00:15 GMT

If you're writing something that uses the Activiti API to automatically handle something, but there could be multiple copies of it, is there a good way to have it work with the workflow and handle the inevitable collisions?I was thinking about having the workflow split into a "queued" user/manual ta

Re: Competing for tasks

jbarrez — Wed, 28 Oct 2015 18:51:30 GMT

I'm not fully following here, why wouldn't you use an async service task for this? The job executor solves the competing already for you?

Re: Competing for tasks

ritchieannand — Wed, 28 Oct 2015 19:39:39 GMT

Service tasks are outbound, right? You'd need to either be running multiple Activiti servers or put together something for a single Activiti server that can do a "round robin" technique of handing out the service task (or do the "round robin" from a bean), I take it.

Not that it's not possible, it's just that running the Activiti API from multiple machines and querying manual/user tasks is SO much easier than configuring servers to be registered and visible from something called by a JavaDelegate

I did attempt 'Asynchronous' using an API client, but that really is Activiti-server-only; clients can't really see that "between the task and the sequence flow" state (at least not until the due date happens.

The code above works pretty nicely in my testing, but I haven't tried running multiple instances yet. I'm guessing there would be two major cases that Activiti's API might already handle:

* Optimistic locking failure trying to complete the task at the same time as someone else?
* Losing the battle when trying to complete the task because it's already been completed by someone else

It's fun starting processes manually and watching the agent grab them, do its work and then proceed or move to the failure state. I *really* like the "My instances" view in the Process section of Activiti Explorer. Nice red highlights showing where the tasks are now and where they've been. Sweet

– Ritchie

Re: Competing for tasks

jbarrez — Tue, 03 Nov 2015 11:59:08 GMT

Service tasks are not outbound, you write any logic you want in it. You also can use script tasks, no jar deployment needed.

The Job Executor of Activiti will do retries in case of failures. It also catches optimistic locking exceptions and assumes it has been picked up by another job executor.

Clients can indeed not see that state, but should they? Would you rather have them wait until the -possibly long- logic has been executed?