topic Re: Timer boundary event not supported for Service Task? in Alfresco Archive

Timer boundary event not supported for Service Task?

xjshangguan — Mon, 17 Dec 2012 19:57:30 GMT

Hi, I have learned in my own testings (jobExecutorActivate=true) and from the forums that timer boundary event is not supported for service task. Can anyone confirm? This will impact us significantly because most of our flow components are service tasks either calling external web services or jav

Re: Timer boundary event not supported for Service Task?

jbarrez — Tue, 18 Dec 2012 17:27:20 GMT

No, Activiti does not support timers on service tasks. The reason for this is transactions: when you have a long-running service task, it keeps the transaction open, which is never a good idea. On top of that, timers in Activiti are also persisted in the database, so when they run, they won't be able to read the 'open' transaction of the service task.

Now, the best practice is to have a short-lived service task, that simply triggers an external something. After the service task, there should be a receive task. the external entity can then trigger the process instance again. That way, the transactions are short, as they should be. If you need a timer, just put it on the receive task.

Re: Timer boundary event not supported for Service Task?

xjshangguan — Thu, 20 Dec 2012 22:01:53 GMT

We do have short lived service task calling external web services. if everything works, we will be fine. The reason why we are looking for timer is when external services are not responsive.
Thanks for the advice. Several of us do have your "Activiti in Action".

Re: Timer boundary event not supported for Service Task?

derikalov — Wed, 20 Feb 2013 04:29:27 GMT

Per BPMN, a ServiceTasks is atomic Activity but nowhere it says it is supposed to be short lived.
Secondly, what would be the semantics of cancelActivity="true" if ServiceTasks are always just asynchronous submit? There is SendTask concept in BPMN for async submits.
Not to mention that DataSet-associated wait may also induce blocking on any Activity, which may be desirable to handle via timeout.

But even in practical terms, what about service tasks that are implemented via Camel (i.e. delegateExpression="${camel}"). The Camel route can take some time and I would like to be able to detect timeouts.

I can rewrite CamelBehaviour myself and i.e. run Camel on a thread pool, then posting an event, and having Timer Boundary event on my ReceiveTask in my process. But it would be nice to (A) have support for it out of the box from Activiti, and (B) this kind of hacking complicates flows, instead of naturally using just one box (ServiceTask) I have to remember/document to use 2 boxes, ServiceTask + ReceiveTask.

Re: Timer boundary event not supported for Service Task?

trademak — Wed, 20 Feb 2013 14:10:52 GMT

Hi,

That's a valid point. Based on this discussion we are thinking to provide out-of-the-box support for this pattern.
We could introduce a new service task type that allows you to add a timer boundary event.
Under the hood the pattern will probably be implemented with Camel in the background and an additional receive task, but you don't need to configure this yourself.
Would that be helpful?

Best regards,

Re: Timer boundary event not supported for Service Task?

derikalov — Wed, 20 Feb 2013 22:07:58 GMT

Yes, this would definitely be helpful.
Just off the top of my head - one way of doing this would be to provide another variety of ActivityBehavior interface, for example:

public interface ActivitiInterruptableBehavior { // Or ActivitiStatefulBehavior
      void setExecution(ActivityExecution execution);
      void execute() throws Exception;
      void interruptExecution(); // best-effort, exceptions ignored, not to confuse with compensation (which is for previous steps)
}

so if my activity:class or activity:delegateExpression resolves to implementation of this interface, the Activiti can assume that (1) boundary timer events should be supported; and (2) optionally, developers can choose to handle cancellation (i.e. stopping long upload/download). This would also mean the instances of ActivitiInterruptableBehavior can be stateful (I think currently instances of ActivitiIBehavior are per-process def, not per execution).
I think BPMN spec does not tell what cancel=True really means for the activity implementation. I may be wrong but I think it may be useful and it does not break the BPMN semantics.

Or, this interrupt-ability and timeout-ability can be communicated to Activiti via Java annotations.

Re: Timer boundary event not supported for Service Task?

mamtag — Mon, 09 Jun 2014 11:47:04 GMT

Hi trademak,
Do we have any update on the service task which allows to add timer boundary event?

Thanx.

Re: Timer boundary event not supported for Service Task?

trademak — Tue, 17 Jun 2014 10:13:07 GMT

Hi,

No we didn't do development in this area yet. What would be your use case for needing this?

Best regards,

Re: Timer boundary event not supported for Service Task?

boekhold — Thu, 19 Feb 2015 06:22:37 GMT

Hmmm, I'm looking into this exact same topic: a process needs to make an external request via JMS request/reply, and the reply could take from seconds to minutes to come back. For the Business Analyst who designs the workflow model, we don't want to complicate his life by requiring him/her to fiddle with servicetask->receive message, plus possible gateways/timers to be able to model this. We want a single task that makes the request and receives the reply, allows us to configure a timeout on it, and doesn't unnecessarily keep any Activiti DB transactions open.

For a service task that does the request/reply, I just found the following post: http://forums.activiti.org/comment/9956#comment-9956. However this doesn't yet address any timeout handling via a timer boundary event.

Anything that can be done in this area to make modeling these scenarios simple and quick for Business Analysts?

Maarten

Re: Timer boundary event not supported for Service Task?

jbarrez — Sat, 28 Feb 2015 08:51:18 GMT

If you take that implementation from that post, you can put a regular timer event on it.
A more complex implementation could mimic this behaviour and hide the event in the diagram by creating a TimerEntity in the execute() method there.

Re: Timer boundary event not supported for Service Task?

javacorner — Sun, 22 Mar 2015 10:45:45 GMT

<html>

<head>
<meta http-equiv=Content-Type content="text/html; charset=windows-1252">
<meta name=Generator content="Microsoft Word 14 (filtered)">
<style>
<!–
/* Font Definitions */
@font-face
{font-family:Batang;
panose-1:2 3 6 0 0 1 1 1 1 1;}
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
@font-face
{font-family:"\@Batang";
panose-1:2 3 6 0 0 1 1 1 1 1;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin-top:0in;
margin-right:0in;
margin-bottom:10.0pt;
margin-left:0in;
line-height:115%;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{colorurple;
text-decoration:underline;}
.MsoChpDefault
{font-family:"Calibri","sans-serif";}
.MsoPapDefault
{margin-bottom:10.0pt;
line-height:115%;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
–>
</style>

</head>

<body lang=EN-US link=blue vlink=purple>

<div class=WordSection1>

Dears jbarrez
, ALL,

For the work
around that you sent here before of <a
href="http://forums.activiti.org/comment/14426#comment-14426">#2</a> which is “

"Now,
the best practice is to have a short-lived service task, that simply triggers
an external something. After the service task, there should be a receive task.
the external entity can then trigger the process instance again. That way, the
transactions are short, as they should be. If you need a timer, just put it on
the receive task."

I have similar scenario [My the
process calls external backend system]
and I am trying to use the receivetask .

You told “that simply triggers an external
something” Now I
want some timer to send this signal to “receivetask” in order to let the process to retry to call the external backend
system.

How can I
implement timer ? Is it Timer catching event or timer boundary event or what ?

My process definition
is like the following:

<process
id="TimerProcess" name="Timer Process" isExecutable="true">

 <startEvent
id="startevent1" name="Start">

 <extensionElements>

 <activiti:executionListener event="start"
class="me.ffusion.bpm.listeners.InmaEventListener"></activiti:executionListener>

 </extensionElements>

 </startEvent>

 <serviceTask id="servicetaskInitialize" name="initialize" activiti:class="me.ffusion.bpm.javaDelegates.Initialize">

 <extensionElements>

 <activiti:executionListener event="start"
class="me.ffusion.bpm.listeners.InmaEventListener"></activiti:executionListener>

 </extensionElements>

 </serviceTask>

 <serviceTask id="servicetaskCallBackend" name="Call Backend" activiti:class="me.ffusion.bpm.javaDelegates.CallBackend">

 <extensionElements>

 <activiti:executionListener event="start"
class="me.ffusion.bpm.listeners.InmaEventListener"></activiti:executionListener>

 </extensionElements>

 </serviceTask>

 <sequenceFlow id="flow1" sourceRef="servicetaskInitialize"
targetRef="servicetaskCallBackend"></sequenceFlow>

 <sequenceFlow id="flow4" sourceRef="startevent1"
targetRef="servicetaskInitialize"></sequenceFlow>

 <sequenceFlow id="flow5" sourceRef="servicetaskCallBackend"
targetRef="isCallBackendSuccess"></sequenceFlow>

 <serviceTask id="servicetaskContinue" name="Continue" activiti:class="me.ffusion.bpm.javaDelegates.NoAction"></serviceTask>

 <endEvent
id="endevent1" name="End"></endEvent>

 <sequenceFlow id="flow10" sourceRef="servicetaskContinue"
targetRef="endevent1"></sequenceFlow>

 <receiveTask id="receivetask1" name="wait for timer"></receiveTask>

 <exclusiveGateway id="isCallBackendSuccess" name="Is Call Backend Success" default="continue"></exclusiveGateway>

 <sequenceFlow id="continue" sourceRef="isCallBackendSuccess"
targetRef="servicetaskContinue"></sequenceFlow>

 <sequenceFlow id="backerror" sourceRef="isCallBackendSuccess"
targetRef="receivetask1"></sequenceFlow>

 <sequenceFlow id="flow13" sourceRef="receivetask1"
targetRef="servicetaskCallBackend"></sequenceFlow>

 </process>

 

 

</div>

</body>

</html>

Re: Timer boundary event not supported for Service Task?

jbarrez — Tue, 24 Mar 2015 13:35:16 GMT

Yes, a boundary timer event on the receive task would do that.