Reports occasionally fail: ERROR: Value cannot be null

[Lauri]

I have an HTML report that mostly runs successfully but occasionally fails with this type of error:

5/2/2023 4:31:53 PM    Warn     Failed generation of report 156a6bef-8931-4a5a-b013-e7ede15cf55c for user 01c4d6e6-6420-4da7-b736-3acf60cc7678. ERROR: Exception during content resolution while processing request with id 10171d03-9312-4ec9-8f79-be2fa8218b67. Check Engine logs for details. ERROR: Value cannot be null.

Parameter name: value

I waited a few minutes, ran the Publish Task again and it succeeded. Any idea why it failed? The log isn't helpful to me but I can post some of it. 

I'm running NPrinting May 2022 SR4 and Sense Enterprise Feb 2023 Patch 1.

[Lech_Miszkiewicz · Accepted solution]

Hi @Lauri 

Can you give us a context what type of objects does this report contain?

• Are there any unsupported objects - MAKE SURE YOU CHECK THIS!!
  • QS: https://help.qlik.com/en-US/nprinting/May2022/Content/NPrinting/GettingStarted/HowCreateConnections/...
  • QV: https://help.qlik.com/en-US/nprinting/May2022/Content/NPrinting/GettingStarted/HowCreateConnections/...
• Are there any filters (on fields or variables)
• Are there any conditions? What are they
• Are there any Pages/Levels
  • If they are, are those running over some sort of tables and not actual fields?
• Do you have calculated dimensions?
• Do you use variables or formulas in your template - what are they?
• Are you using any variables in file or folder names, email content, or email subject?
• Ho big is your app? Is it opening quick in Qlik Sense and is responsive when you apply selections? or is it rather slow and takes time to produce date when you open it from the hub?
  • Please define size of the app and size in the memory
  • Please maybe give us an idea if it is just regular basic star schema or some sort of different model?
  • Are there any island tables in your data model?

I am suspecting first point to be a problem as usually those are causing similar behaviour, but all other points are also important and would have to be investigated.

If it happens frequently I would also enable debug logging to maybe get more info about the problem: https://help.qlik.com/en-US/nprinting/May2022/Content/NPrinting/Troubleshooting/Troubleshooting-logs...

regards

Lech 

[Lauri · Accepted solution]

hi Lech, 

Thank you for the detailed reply. I just found that the QS app reload is overlapping in time with the NPrinting publish task, which I have to think is a likely cause of my NPrinting error.  (The reload is taking longer than it used to. I'd better figure out how to make it more efficient.)

I have a clarifying question about the help article, which states:

You should not create connections to Qlik Sense apps that use the following:

• Always one selected value for fields

• Calculated dimensions, etc.

Does it mean that I should not create a connection to a QS app that contains a calculated dimension ANYWHERE in the app, even if that dimension is in an object (e.g., table) that I don't use in NPrinting?

[Lech_Miszkiewicz]

Hi Lauri,

good point - I was always approaching it same as you... moreover I actually use calculated dimensions in straight tables sometimes. Those cannot be used as levels but often can be used just as tables.

@Ruggero_Piccoli - Is the below statement from help site wrong? I mean we should probably categorize what is causing whole qvw/qvf to be not supported and what causes some UI objects only partially supported. This is link to unsupported objects: https://help.qlik.com/en-US/nprinting/May2022/Content/NPrinting/GettingStarted/HowCreateConnections/... 

Then in the same document we have this: https://help.qlik.com/en-US/nprinting/May2022/Content/NPrinting/ReportsDevelopment/Qlik-objects-supp...

It is not clear and is limiting to state that calculated dimensions are not supported. We use them very often also in Qlik Sense straight tables. We understand that those cannot be used as levels or pages, but can be used as straight tables.

Do you think we could clarify this in help document? I would suggest split between things which disqualify Qlik app from use with NPrinting (like always one selected value) and things which dont have full functionality when used.

.... or maybe I am getting this wrong assuming that "always one selected value" is more unsupported then any other object as indeed if used with any filters "always one selected value" can still work with NPrinting, but we will have no control over it....

[Ruggero_Piccoli · Accepted solution]

Hi @Lech_Miszkiewicz 

Good point. I can ask for a revision of those pages to add more details, where possible. 

About calculated dimensions there is, for example, also the limitation:

Qlik Sense On-Demand reports with selections on calculated dimensions fails

Jira issue ID: OP-8382
Qlik Sense On-Demand reports with selections applied on calculated dimensions will fail. However, you can apply selections on dimensions based on Qlik Sense fields. The workaround is to move the formula to the load script and use the calculated fields to apply selections to your On-Demand reports.

from https://community.qlik.com/t5/Release-Notes/Qlik-NPrinting-Release-notes-May-2022-Initial-Release/ta...

Supporting calculated dimensions means that a user, after seeing it in the UI, could create a filter on an On-Demand request and suppose it works.  

Best Regards,

Ruggero

[Frank_S]

HI @Ruggero_Piccoli 

Please send me  the internal JIRA to the HLP so I can track the clarifications suggested by @Lech_Miszkiewicz 

I agree they are very good points.

Thanks

[Ruggero_Piccoli]

Hi @Frank_S 

This kind of request can be addressed via private message as we usually do.

Best Regards,

Ruggero