Generic error when running a Synapse pipeline containing a dataflow or trying to start a debug session

Question

Generic error when running a Synapse pipeline containing a dataflow or trying to start a debug session

MS 0

I have 2 Synapse instances in UK South. Error only occurs in one of them and doesn't seem to show up in the workspace logs - 'Internal server error executing the request.' This happens when trying to start debug cluster or run a pipeline with a dataflow inside it.

Manoj Kumar Boyini 330 Reputation points Microsoft External Staff Moderator

2025-10-21T02:41:52.6666667+00:00

Hi MS,
I hope you had a chance to review the information shared earlier, and I hope this information has been helpful! If you still have questions, please let us know what is needed in the comments so the question can be answered.

Thanks,
Manoj
Manoj Kumar Boyini 330 Reputation points Microsoft External Staff Moderator

2025-10-23T08:54:45.5033333+00:00

Hi MS,

We haven't heard back from you. Please reply if you have any questions in this matter and we will gladly continue the discussion.

Thanks,
Manoj

2 answers

Your answer

Manoj Kumar Boyini 330 Reputation points Microsoft External Staff Moderator

2025-10-21T02:41:52.6666667+00:00

Hi MS,
I hope you had a chance to review the information shared earlier, and I hope this information has been helpful! If you still have questions, please let us know what is needed in the comments so the question can be answered.

Thanks,
Manoj
Manoj Kumar Boyini 330 Reputation points Microsoft External Staff Moderator

2025-10-23T08:54:45.5033333+00:00

Hi MS,

We haven't heard back from you. Please reply if you have any questions in this matter and we will gladly continue the discussion.

Thanks,
Manoj

Answer 1

Hi MS,

Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.

The error 'Internal server error executing the request' usually means Synapse had trouble starting the compute that runs your data flow. Since this only happens in one of your workspaces, it’s likely something in that workspace’s setup or environment.

Please check if the debug cluster is able to start from the Data Flow Debug or Integration Runtime section in Synapse Studio. If the cluster can’t start, it could be due to limited capacity in the region, missing permissions, or a network rule blocking Synapse from creating the compute.

If the workspace uses a Managed Virtual Network or private endpoints, please make sure the needed Azure services (like Storage and Synapse control plane) are allowed through your firewall or NSG. Sometimes blocked outbound traffic causes this exact error.

Try creating and running a very simple data flow (for example, one that just reads and writes data). If that fails too, it confirms the issue is with the workspace setup or compute, not your pipeline.

Also, check the Azure Service Health page for UK South to make sure there’s no ongoing Synapse issue in that region.

Kindly let me know if you have any further questions. I’ll be glad to assist you.

Thanks,
Manoj

Answer 2

MS 0

Hi Manoj, I agree with you it may be network related as its the workspace using the Managed Virtual Network and Private endpoints where the debug cluster is failing to start. However I can't see a means of configuring outbound traffic from Synapse with this setup? I've checked that there are no firewalls or nsg's impacting traffic.

Kind regards, Mark

Manoj Kumar Boyini 330 Reputation points Microsoft External Staff Moderator

2025-10-21T17:15:45.8866667+00:00

Hi MS,

You’re right when a Synapse workspace uses a Managed VNet with private endpoints, you don’t get a way to manually set or control outbound traffic. Synapse handles all outbound communication on its own using Microsoft-managed connections.

In this setup, Synapse needs to reach a few key services (like your storage account, Azure Data Lake, and the Synapse control plane) to start the debug cluster. If it can’t reach any of these, the cluster start will fail and show that same “Internal server error” message.

Few quick things you can check:

1.Make sure all your private endpoints are in Succeeded state and approved especially for your workspace storage and any linked resources like Key Vault or SQL.

2.If your storage account has firewall rules, make sure the Synapse managed outbound IPs are allowed in that list. You can find these IPs in your workspace under Networking or Managed private endpoints.

3.Also check that public network access isn’t fully turned off for required services unless all private endpoints are properly set up.

If you need to control outbound network rules yourself (like adding NSGs or custom routes), you’d have to use a customer-managed VNet instead of a managed one that’s the only option where outbound traffic can be customized.

Please check those points and let me know how it goes. I’ll be happy to help you go through the private endpoint or firewall settings if it’s still not working.

Thanks,
Manoj
Manoj Kumar Boyini 330 Reputation points Microsoft External Staff Moderator

2025-10-24T08:53:57.5633333+00:00

Hi MS,

I hope the steps provided above were helpful. Please let me know if there's anything else I can assist you with.

Thanks,
Manoj

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Generic error when running a Synapse pipeline containing a dataflow or trying to start a debug session

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