Cluster Access mode set to Shared on Databricks, results in connection refused on Exasol

[Gembo]

I am trying to run a TRUNCATE command on my exasol DWH from Databricks using the pyexasol. This works perfectly fine when I have the cluster access mode as "No Isolation Shared" which does not have access to our Unity Catalog. When I change the cluster access mode to "Shared" and now has access to Unity Catalog, the cluster fails to connect to Exasol DWH with the following error message:

"Could not connect to Exasol: [Errno 111] Connection refused"

Any ideas how to solve this?

[SSundaram]

Interesting. Did you try with "Single User" mode, which also has UC support? 

[Gembo]

@SSundaram "Single user" access mode works when connecting using pyexasol, but this cluster is being accessed by our whole Data Engineering team and would not really be a viable solution. 

[SSundaram]

Understood. So UC is not the problem, but the access mode is what causing this issue. There are few limitations with shared access mode on UC. I am guessing it might be the credentials passthrough, not sure. 

[Kaniz]

Hi @Gembo, When connecting to Exasol using pyexasol, encountering a “Connection refused” error can be frustrating.

Let’s troubleshoot this issue step by step:

1. Database Availability:
   • Ensure that your Exasol database is online. Sometimes, databases automatically shut down after a period of inactivity.
2. IP Address Whitelisting:
   • Check if the IP address of your Databricks cluster is added to the allow list in the Exasol SaaS UI. This step is crucial for successful connections.
3. Network Connectivity:
   • Verify that your Databricks cluster can reach the Exasol host and port specified in the SaaS UI. You can use tools like telnet to test connectivity on port 8563.
4. Firewall Considerations:
   • Ensure that no firewall is blocking access to the Exasol database. Firewalls can sometimes prevent connections.
5. Exasol Trial Mode Limitations:
   • Since you mentioned you’re using the trial mode, be aware that there might be limitations. Confirm if trial mode affects your connection.

[Gembo]

It is not a problem of connectivity/firewall as I am able to connect using pyexasol when setting the access mode to different values on Databricks Cluster. Our Exasol and Databricks are not trial modes as these are our main DWH/Data Lakehouse for our data.

[Kaniz]

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