Proxy and connection to KNIME server

KNIME Server
1

Hi all,

I have to fill the proxy entries in KNIME Preference if a workflow need an access to Internet. Do you know if is it possible to indicate the proxy information (Active Provider Direct, Schema, Host, Port) directly in a node of a workflow and use it (and let the preference by default) ?

Moreover, I noticed that I can not connect to my KNIME server when a proxy is given in preference → then I get this issue in KNIME: “Error while retrieving server information for login, probably because the server is not reachable.”
There is no issue when I go back without Proxy (with Active Provider “Direct”). Other users using the same proxy, same station and same server have not this issue so it looks like there is something special in my configuration. Do you have an idea why I have this issue?

Best,
Cyrille

2

Hello @Cyrille,

Thank you for contacting KNIME regarding this issue.

My understanding of the issue is that you are

  1. seeking for information on how to set proxy information in a node in a workflow and to use it by default;
  2. unable to connect to your KS when a proxy is set in AP preferences (which would probably be resolved if (1) is possible); and
  3. this issue is unique to your configuration (ie it is not happening to others).

If this is correct, please confirm and I will research the issue further.

Please provide the following for additional information/troubleshooting:

  • What operating system is your KNIME AP software running on?
  • What version(s) of KNIME Server (KS) and KNIME Analytics Platform (AP) are being used?
  • Have there been any changes to the environment that could explain the issue (e.g. configuration changes, new patch applied, new version of component)
  • Are you in the same operating environment as others (for example, are they in office and you are working from home via VPN, etc)
  • Are you able to provide logs from AP for the time period covering this issue?

I look forward to helping you resolve this issue!

Regards,
Nickolaus

3

Hi Nickolaus,

Yes exactly, thanks for this summary!

I’m using Knime AP 4.2.2 and KS 4.11.3 both on CentOS Linux 7. To my knowledge everything looks similar for other users, they are using same AP and KS installation and same environment. I have no idea why I have this issue, I didn’t test it previously.
This issue is the same with/without VPN and on site, and it appears for all our KS installation.

You will find attached the Knime log file. knime-2021-06-23.log (2.8 KB)
This issue seems not registered in log file but the Error “Service Unavailable” for checking licenses is probably related to the same issue because I think that I didn’t have this error message before when proxy information was empty in KNIME preference.

Best,
Cyrille

4

Hello Cyrille,

Thank you for that additional information.

  1. You have to fill in proxy entries in KNIME AP preferences if a wf needs access to the Internet.
  2. You cannot connect to KNIME server when a proxy is given in preferences.
  3. a. Error message when attempting:
2021-06-23 09:24:04,832 : ERROR : Worker-2: Check for new licenses :  : BackgroundFetchLicensesJob :  :  : Error while fetching licenses from license server 'http://x-sknil01:8080/knime/rest': <HTML><TITLE>503 Service Unavailable</TITLE>^M
<H1>503 Service Unavailable</H1>^M
Failed to resolve the name of server <B>x-sknil01</B></HTML>^M
javax.ws.rs.ServiceUnavailableException: <HTML><TITLE>503 Service Unavailable</TITLE>
<H1>503 Service Unavailable</H1>
Failed to resolve the name of server <B>x-sknil01</B></HTML>
  1. This issue is the same with/without VPN and on-site (I assume this means in-office on office network.)
503 Service Unavailable
The HyperText Transfer Protocol (HTTP) 503 Service Unavailable server error response code indicates that the server is not ready to handle the request.
Common causes are a server that is down for maintenance or that is overloaded.

Hypothesis:
When operating with proxy entries, AP appears to be making a request to a license server, which it is unable to reach due to failed name resolution; it then times out, yielding HTTP 503 error.

I strongly suspect that configuring access via proxy allows internet access but changes the routing in such a way that resources on the internal portion of the network are no longer accessible;

This seems to be borne out by being able to access KS when you clear the proxy settings once more.

You mention that others use this proxy with no issues; I would suggest that you would have to compare/contrast all of your networking/knime proxy/vpn settings with another working sample to determine what difference in settings may be causing a difference in results.

Please let me know your thoughts on this.

Regards,
Nickolaus

2 Likes
5

Hi Nickolaus,

Thanks for your reply. Yes exactly, I’m thinking the same things but we haven’t found what difference is in the settings. By the way, we deleted this proxy restriction and everything is fine now.

Best regards
Cyrille

6

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