Error Indexing Map in MNI Script Process Node

RE: Error Indexing Map in MNI Script Process Node

jonathanf_kr — Tue, 13 May 2025 14:04:36 GMT

Alberto, this change fixed my issue right away. Thanks.

RE: Error Indexing Map in MNI Script Process Node

jonathanf_kr — Tue, 13 May 2025 13:53:26 GMT

Thanks for all the tips and areas to look for. I'm currently working on a POC / Demo project just learning the ins and outs for our future projects. I specifically was trying out the MNI approach. I'm going to continueto work on that approach for my understanding even though I fully agree the foreach method separated into it's own rule would be the most scalable / maintainable approach in the future for this specific situation.

RE: Error Indexing Map in MNI Script Process Node

Alberto Cortés — Tue, 13 May 2025 08:43:31 GMT

Hi,

From what I can tell, the issue is related to using "is appended to list" in the output of a node that is configured as a Multiple Node Instance (MNI) with the "Run all instances at the same time" option enabled.

When this setting is used, all node instances execute in parallel, and if they all try to append to the same process variable simultaneously, you can run into race conditions.

Suggested fix:

Instead of "is appended to list", switch to "is stored at index" and store each result at tp!instanceIndex. This ensures each instance writes to a specific index in the array, avoiding concurrency issues.

Recommended approach:

As Mathie and Harsa mentioned, it’s usually better to avoid MNI altogether for these scenarios. Using a!forEach() in a script task or expression rule is much safer and more maintainable, since it runs sequentially and avoids shared variable conflicts.

Hope this helps!

RE: Error Indexing Map in MNI Script Process Node

Harsha Sharma — Tue, 13 May 2025 06:55:06 GMT

To better debug this and for future scalability as well I would suggest you create an expression rule for the script tasks expression.

You can pass pv!event, pv!eventIId etc all the process variables, configure the code using a!foreach() and test that your expression rule works as expected with null handlings, date formats etc so that it returns expected output always.

RE: Error Indexing Map in MNI Script Process Node

David Jimenez — Tue, 13 May 2025 06:47:12 GMT

Seems that some of the instances is receiving a null.... check it...

RE: Error Indexing Map in MNI Script Process Node

Mathieu Drouin — Tue, 13 May 2025 00:28:12 GMT

Why do you need to do this via MNI in a script task instead of a forEach in an expression rule?