topic Re: Exceptions while trying to resume tasks after lengthy jobs in Alfresco Archive

Exceptions while trying to resume tasks after lengthy jobs

raadhakrishnaa — Wed, 30 May 2012 07:53:11 GMT

As a beginner to Activiti,I am struggling to get my Usecase addressed.Details as followsA.Scenario :My ProcessDefinition constitutes multiple activities(predominantly service tasks),of which many of the activities require heavy IO and hence time-taking.For a servicetask that corresponds to one such

Re: Exceptions while trying to resume tasks after lengthy jobs

ronald_van_kuij — Wed, 30 May 2012 22:25:51 GMT

Please (re)format your post next time and use code tags for clearity.

The error is here:

org.activiti.engine.ActivitiException: execution waitServerProvision doesn't exist
Why would there be an execution with an id of 'waitServerProvision'? (I think you only posted part of the stacktrace, right?)

What am I doing wrong here?

You probably stored some wrong reference somewhere to be used to signal the process.

What is the ideal way of passing reference of current execution context to the external logic such that the WorkFlowEngine can be signalled and activated from its wait state for further execution.

Storing/passing on the right information to be used to signal the process. I usually use a combination of business key and receive task name. But it could also be an execution id. Depends…

Re: Exceptions while trying to resume tasks after lengthy jobs

raadhakrishnaa — Fri, 01 Jun 2012 02:09:37 GMT

Thank you Ronald for the quick response and also your suggestion on presenting the query in a readable format .
I had to modify my actual code with alias names for the functions so that it can be easy interpretation for the readers and I missed one such occurrence( 'waitServer…" ) in the stacktrace I pasted ,which probably confused you.I corrected/edited that in my current post.
I do pass the execution id of the current activitytask 'flow1-step1' and also tried the id of receivetask 'flow2-step2' ,but in either case I am reported that the execution does not exist.

Please clarify me on the following
1.If there is a receive task in the definition flow,would there an entry in any of the tables 'act_ru_job' …etc so that the work engine persists the state until then into the tables and waits for a msg signal on the receive task. I did not find any such traces in mysql db tables in my case.

2.For The Java class that corresponds to Service Task,I tried the Java Class as an implementation of 'JavaDelegate' and also an extension of 'TaskActivityBehavior' as understood from the topic http://forums.activiti.org/en/viewtopic.php?f=6&t=3613&p=14092&hilit=Asynchronous+Task#p14092 . All of them result in the same exception

Can someone please give me further direction or hints on this.

Thank you,
RK

Re: Exceptions while trying to resume tasks after lengthy jobs

frederikherema1 — Wed, 13 Jun 2012 07:01:29 GMT

1. A receive task doesn't create any jobs of timers. It just stops the process from flowing (== returning the thread that called startProcessInstance(). You can see this in the ACT_RU_EXECUTION. When you runtimeService.signal() the process, it will start again.

From what I understand, this is what you are trying to reach is the following:
- Start a process from thread A. Since the process is heavy on I/O, you don't want thread A to be blocked by this operation. Rather, you want to return control to the thread and let activiti handle the heavy I/O operation.

The problem is that you're trying to signal an execution from within the same execution. At the time you call "signal()" (in #{myBean.method1…), the process is actually still 'flowing' and not yet ready to receive a signal. Since the process is just started, and hasn't reached a wait-state yet (user task, recieveTask, ..), it's not yet persisted in the DB. This is why you get the "execution not found" exception.

Solution: Use Async continuations http://activiti.org/userguide/index.html#asyncContinuations. Remove the first service-task an signal-task, just use this:


<serviceTask id="step2" activiti:expression="#{myBean.clearThePain(execution)} " activiti:async="true" />