Credentials Configuration ERROR: The server requested password-based authentication, but no password was provided by plugin null

Hi everybody,
I would need some help in running a certain workflow on the KNIME Server (WebPortal). The workflow correctly run locally in the Analytics Platform but when I try to run it on the server it gives me the following warnings and errors:

WARN  : pool-4-thread-3 : 64423b22-051e-4f41-b903-404412f696aa : Node : Credentials Configuration : 3:30:0:8 : No password set after loading workflow - reconfigure the node to fix it
ERROR : KNIME-Worker-178-PostgreSQL Connector 3:1197:0:3 : 64423b22-051e-4f41-b903-404412f696aa : Node : PostgreSQL Connector : 3:1197:0:3 : Execute failed: The server requested password-based authentication, but no password was provided by plugin null
org.postgresql.util.PSQLException: The server requested password-based authentication, but no password was provided by plugin null

The workflow contains a component with a Credentials Configuration node with which credentials to access a remote PostgreSQL database instance (Amazon RDS) are set. These credentials shouldn’t be asked to the webportal user and for this reason I used a Credentials Configuration instead then a Credentials Widget. I realised that when I export the workflow to the KNIME server, password on the Credential Configuration node is reset.
I tried defining database username and password as workflow credentials, as workflow variables and also inside the workflow, passing them from a Table Creator node to the Credentials Configuration node as flow variables but any of these 3 trials triggered the warning and error reported above.

  • In this case what would be the best practices to allows the workflow to run and so access the RDS?
  • Any suggestion to avoid the error?

Thanks in advance,

The problem resulted to be that if the Credential Configuration node is part of a component, then the password contained in it is removed when the workflow is uploaded to the KNIME server. This is probably a security measure but I think it should be better documented as I didn’t found any reference to it in KNIME Server nor KNIME WebPortal user guides.
A way I found to use credentials in the whole workflow including the user (weekly encrypted) password is simply using a Credential Configuration node but at the workflow level and not embedding it inside a component. Once these credentials variables are on the workflow they can easily be used also inside components by allowing the variables in.
I hope this may be useful also for other users.

Hello @gcincilla ,

how did you configure your Component Output? Did you let out the credential flow variable when you did not manage to deploy to the server?


Hi @dora_gcs, thank you for your reply. Yes, I let the credential flow variables out of the component.
Now the problem is solved but it was the following:
I was confused by the fact that it seems that it’s not possible to use some user credentials present in a flow variable to configure a Credential Configuration node inside a component. Is that correct?
To me it seems that the only way to use a credential flow variable in a component is to let that enter in that component. If that component has its own Credential Configuration node, is not possible to configure it with the credential flow variable. Is this correct or am I missing something?