Appian 19.4 Node Timer Exception with Rule Expression

RE: Appian 19.4 Node Timer Exception with Rule Expression

Thanos.Michos — Tue, 06 Apr 2021 06:30:40 GMT

Chris, thanks for your help as well.

We have shifted our implementation of the time event just as you have noted, directly using the caladddays function with a constant.

However, with the link to the KB article that Stefan has sent we have understood the cause of this issue which was the use of keyword syntax when calling the rule expression. This is not supported in events and various other components, including case as the ones you have indicated in your note.

Again, thank you for your help!

RE: Appian 19.4 Node Timer Exception with Rule Expression

Thanos.Michos — Tue, 06 Apr 2021 06:27:21 GMT

Stefan, thank you for this very helpful link. You have helped a lot in this case.

It makes it clear that the issue is due to calling the rule expression using keyword syntax, which we do. And it states clearly in Appian's documentation that this is not supported in events, process reports and various other components.

I also considered adding a script task before the user task, but the expression was too simple to add another node to the process.

And to answer you last question, apart from having to integrate with other systems to retrieve some pieces of information before the task is shown to the user, we have requirements (for reporting purposes) to depict that a new business process was initiated and that the initial submission was not completed by the user. So we do a bit of work before the user task.

RE: Appian 19.4 Node Timer Exception with Rule Expression

Chris — Mon, 05 Apr 2021 15:08:53 GMT

Agree with Stefan that while expressions can be used for escalation timers, they are very picky. Especially in the use of expressions containing localVariables, with() or load(), we will calculate the exception timer in a prior script task into pv! as he suggests.

If you want to ensure the timer is more dynamic, include a constant with the day value - and you can use this directly in the User Input Task:

caladddays(ri!entryDate, cons!YOUR_CONSTANT_HERE)

RE: Appian 19.4 Node Timer Exception with Rule Expression

Stefan Helzle — Mon, 05 Apr 2021 07:20:08 GMT

I think this is a known issue with doing date/time calculations in process nodes via expressions. Add a script task just before the user task do the calculation and store it into a PV. Then use the PV in the exception. Or omit keyword syntax as described here

community.appian.com/.../kb-1794-details-error-eval-reason-index-error-thrown-when-using-escalations-timers-and-exception-flows

Out of curiosity. Why do you need an exception in that task? Following your description this is just the start of that process. Why not a start form?

RE: Appian 19.4 Node Timer Exception with Rule Expression

Thanos.Michos — Mon, 05 Apr 2021 05:27:51 GMT

The status of the user task is Paused and the status of the process instance is Paused by Exception. The process history shows the task as assigned.

The error that is displayed in the process monitoring view of appian designer is "ERROR:EVAL:@reason=index". The db log of the execution engine running that process instance has the following ERROR entries.

2021-04-02 07:39:50 [PX021] {pe4747.kdb ,3655838} (Default) ERROR .a.p.PROCESS.i "Event Mapping Runtime 149, attached to Node instance 17823: 'LWS_formStep10', Process 536915545: 'LWS Submit New Case'" "Timer absolute schedule expression (=#"_a-0000e616-f8b9-8000-928d-010000010000_743179"(entryDate: pv!caseBasicData.entryDate)): ERROR:EVAL:@reason=index"
2021-04-02 07:39:50 [PX021] {pe4747.kdb ,3655838} (Default) ERROR .events.timer "Timer event errors: 209, Error Messages: "ERROR:EVAL:@reason=index""

RE: Appian 19.4 Node Timer Exception with Rule Expression

Stefan Helzle — Sun, 04 Apr 2021 10:54:07 GMT

Do you see any errors in process instance details? Is the task skipped in task history?

RE: Appian 19.4 Node Timer Exception with Rule Expression

Thanos.Michos — Sun, 04 Apr 2021 07:38:19 GMT

Hello Chris,

Thank you for your response.

The Rule Expression, named "LWS_timerStep10" has a single rule input "entryDate" of type Date and Time.

Its definition is the following simple expression: caladddays(ri!entryDate, 5)

Then, the rule expression "LWS_timerStep10" is used inside the exception timer definition of the User Task, which is enabled through Activity Chaining, meaning the user clicks on an Action and the process leads to this User Task through activity chaining.

That is when we (as users) see the error described in my original note. Just to rule any possible security issues, the same error is thrown for both Basic Users and System Administrators.

As I mentioned in my original note, if we use the definition of the Rule Expression directly in the exception timer then everything works just fine.

RE: Appian 19.4 Node Timer Exception with Rule Expression

Chris — Fri, 02 Apr 2021 17:26:02 GMT

We utilize rules to determine exception flows in many locations without issues. Are you able to share your rule definition?