Event Hub Connection

Question

Our tech partner is having difficulty connecting to a new Event Hub. They asked me to open a ticket. Please assist so I may reply to our vendor.

Here is the error they are receiving:

EventProcessor instance '914850a1-9568-4eab-94aa-a2b1b7b7d99f' of eventhub 'SIEM365' consumer group '$Default'. An error occurred while load-balancing and claiming ownership. The exception is AuthenticationError('CBS Token authentication failed.\nStatus code: None\nError: client-error\nCBS Token authentication failed.\nStatus code: None'). Retrying after 33.68647457185955 seconds

Answer 1

Hello Eric Cobb,

Thank you for posting your question on the Microsoft Q&A portal.

I understood the issue as the Event Processor is failing CBS token authentication while attempting to claim partition ownership in your Event Hub, which typically points to credential or network-related problems.

This error often occurs when the authentication credentials are invalid, expired, or lack the necessary permissions. It could be due to an incorrect connection string, an Entra ID (Azure AD) token issue, network restrictions like firewalls blocking the authentication flow, or even clock skew on the client machine. I recommend starting by verifying the connection string or Entra ID (Azure AD) credentials used by your tech partner, ensuring they have the correct permissions (e.g., Listen or Manage rights) for the Event Hub and consumer group. Also, check if any network rules or private endpoints are configured that might be blocking access.

Let me know if you need detailed steps on the above-mentioned steps.

To help pinpoint the root cause, could you share more details? For example, what authentication method are they using (SAS connection string or Entra ID (Azure AD)), is the Event Hub namespace set up with public access or private endpoints, and have there been any recent changes to keys or roles? Additionally, confirming the client SDK version and checking for clock sync issues might be useful.

Additional Considerations

The error mentions load-balancing and claiming ownership, which suggests this is part of a consumer group scenario. Verify that the consumer group '$Default' exists and that there aren't multiple competing consumers causing conflicts during the partition ownership claims.

You can share the above details leveraging the private message for this thread.

For further guidance, you can refer to these resources:

• Event Hubs authentication overview: https://learn.microsoft.com/azure/event-hubs/authenticate-application
• Managing connection strings: https://learn.microsoft.com/azure/event-hubs/event-hubs-get-connection-string

If you provide more context, I can offer more tailored advice. Thanks again for reaching out!

Please "Accept as Answer" if the answer provided is useful, so that you can help others in the community looking for remediation for similar issues.

Thanks

Pratyush