Errors overwriting node settings with flow variables: Unknown variable "output_file"

Hi forum,

I get this error message with my fairly simple workflow:

Errors overwriting node settings with flow variables: Unknown variable "output_file"

This error message comes with the "Project Writer (FXX)" node, that uses the flow variable "output_file" to write a project file.  The 2 nodes Project Reader and Writer are from BioSolveIT.

I've found some threads dealing with this "unknown variable" error, but as far as I could see, no real solution anywhere.  I'm using 2.11.3 on linux32 (ubuntu) and (preview) on win32, both in cli/script mode.  Since I could not find any entry in the changelog for 2.12, I did not try the 2.12.0 release so far.

Also, this error message is not always issued.  When I start the workflow interactively with 2.11.3 on linux64 (suse), no error.  Also no error on the same machine when running in cli/script mode.

There was a proposal in one thread to just ignore this message, but my workflow exits with a traceback and return code 4.

Does anyone have some hints for this problem?


No hints?  Do you need more input to reproduce this issue?  Would a more generic example without vendor specific nodes be more helpful?  I think, the main problem is the connection between the node that creates the variable and the nodes that use it.

Is this a known issue, possibly with some workarounds available?


Sorry for the late reply. That sounds serious if the workflow behaves differently between commandline and interactive execution.

Is it possible that the create temp dir node is not reset when you run it after load (although I would expect a different error message then). If you can create a test case for us to reproduce/clarify that would be appreciated.

Hi, I have the same problem. In the beginning of the workflow I am setting variables in a metanode via python script that reads from a file (created apart from the WF). The file exists and has correct values but gets stuck on the following message and does not advance anymore:
“INFO main BatchExecutor ===== Executing workflow C:\Users\Public\Documents\BH_poc_2019-01-02 =====
WARN main Node Errors overwriting node settings with flow variables: Unknown variable “variables_file”
WARN main Node Errors overwriting node settings with flow variables: Unknown variable “variables_file””

In the graphical editor I can launch it without problems. May you please help me with that issue?

Hi there!

It is only a warning :slight_smile: Do you exit from batch mode after this is shown? How long does workflow execution last in GUI? You should get message like “Workflow (did not) finished successfully” at the end…


Hello, My first post so hopefully this goes well :grinning:. So I ran across this issue today when cleaning up a workflow working to remove all errors & warnings. I received this warning, but the workflow completed normally and seemed all was well. But not wanting to stress users I searched how to remove the warning and found this thread.

Seems a reproducible workflow was needed so I successfully created a reproducible workflow with the problem using only KNIME base nodes, and variables. The simple workflow has the user enter a folder (like C:\Temp), then the folder will be scanned for files, then save the scan list as FileScan.csv into the original user selected folder. Variables were used to convert the user selected path to a string, add \FileScan.csv to it, then feed this to the .csv writer and auto save the file list.

Based on the behavior, it “seems” the CSV Writer is ready to write the .csv before the variables have created the filename using the user’s path. So then .csv writer warns - “Errors overwriting node settings with flow variables …” etc. Verified the variable does exist, but I’m guessing doesn’t exist when the table arrives to be written. Then the variables catch up and the node writes the .csv correctly.

I’ve included the exported workflow to anyone to test and two images. Image 1 of the error, Image 2 of the workflow used to create the error (the same was uploaded here as well).

CSV Variable Scan and Auto Save
CSV Variable Scan and Auto Save.knwf (18.6 KB)

My Setup for Reference:
Win10 - Enterprise
i7 CPU - 32GB RAM - Dell Latitude 5511 Laptop
KNIME 4.4.1

1 Like

Hello All, Exported my simple Windows workflow to Linux. Recreated the warning on Linux (after modifying Windows to Linux). Attached are screenshots and the Linux workflow.

Lastly, all completed normally both on Windows and Linux. The .csv file was auto created within the folder that was scanned.

Linux Workflow
Linux CSV Variable Scan and Auto Save.knwf (18.4 KB)

Linux Setup:
Linux Mint 20.1
i9 CPU - 8GB RAM - Dell XPS 8930 desktop
KNIME 4.4.1

Hi @morvayd,

You can safely ignore this warning, you have configured the CSV writer to use a flow variable which you are creating during the workflow. When then CSV writer tries to check if it can execute, it detects that the configured flow variable is missing.
If you need to suppress this warning message, you can wrap the CSV Writer in a Component (don’t forget to configure the Input Flow variables to allow the target file variable in).
BTW you can use the new Create File/Folder Variables – KNIME Hub node to create such folder based file path variables, its a bit easier to use than what you are doing it right now.


Thank you for the reply! The Create File/Folder Variables node was helpful, and now there’s a workaround to prevent the warning from appearing.


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