The POST Request node in KNIME works great typically, but if anything goes wrong with the endpoint (e.g. the API goes down, bad URL, a bad API key was passed in via the header, a local web service was stopped, etc.) the node will likely show a spinning progress bar (no progress being made) and will continue to spin even after the user clicks “Cancel all running nodes” or attempts to cancel the POST Request node specifically.
I’ve run into this multiple times. The only way to actually cancel the process is to shut down KNIME. If you close and reopen the workflow, at least you are able to edit the node’s config and try again. However, I confirmed via local testing of an API running on localhost that the POST Request node will continue to send requests regardless of cancellation or even closing the workflow unless the KNIME client is shut down completely.
This has been an issue I’ve run into periodically for over a year, so it has spanned multiple versions and appears to still be an issue in 4.1.2.