Azure Data Explorer Cluster

Question

Azure Data Explorer Cluster

Luis Loaysa Admin 0

Hi there,

I am having some issues with KQL in Azure Data Explorer Cluster, I have made sure that I have admin permissions to the Cluster and the database itself but when running KQL queries they just get stuck in Preparing to run, no matter how big or small.

This wasn't the case before, I am a little lost with how to troubleshoot this. The automated troubleshooting is not helping much.

I hope someone can help with this.

Regards,

Luis

Chandra Boorla 14,510 Reputation points Microsoft External Staff Moderator

2025-06-26T16:52:12.99+00:00

@Luis Loaysa Admin

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

1 answer

Your answer

Chandra Boorla 14,510 Reputation points Microsoft External Staff Moderator

2025-06-26T16:52:12.99+00:00

@Luis Loaysa Admin

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

Answer 1

J N S S Kasyap 3,625 Microsoft External Staff Moderator

Hi @Luis Loaysa Admin
You're having a frustrating time with your KQL queries getting stuck in the "Preparing to run" state in Azure Data Explorer here are some targeted troubleshooting tips:

In the Azure portal, navigate to your ADX cluster > Monitoring > Metrics or Cluster Health, and look for signs of degraded engine nodes or backpressure.
If the cluster is experiencing high ingestion load or query concurrency, new queries may not be dispatched. Check CPU/memory and concurrent query limits.
In a working query window, run .show operations to see if your queries are stuck in a pre-execution state. This can confirm whether they reached the engine at all.
If you’re using tools like the web UI or Azure portal, try switching to Kusto Explorer or Kusto CLI to rule out frontend browser/session issues.

If these steps don’t resolve the issue, it might be helpful to gather additional information. Here are some follow-up questions you could consider:

Can you confirm if this issue occurs with all queries or just specific ones?
Have there been any changes to the cluster configuration or workload patterns recently?
Are there any error messages in the query history?
How long have the queries been stuck in the "Preparing to run" state?
Are you able to run any simpler queries successfully, or are they all impacted?

I hope this helps you get back on track! Let me know if you have any other questions or need further assistance.

Luis Loaysa Admin 0 Reputation points

2025-06-20T09:22:29.9233333+00:00

Hi there,

I have followed your the troubleshooting steps above. I have checked the health and monitoring but I can't see anything odd, no Data Loss at all. It feels like this is more an UI issue. I have also run the automated health check but said nothing was in bad state.

I've tried to run the .show operations command but is still stuck in preparing to run. All queries no matter how small, for example adding the | take 5 get stuck in Preparing to run.

I think this is an UI issue because when I select a table and click on Get data and try to save it to a file in my computer it does show the logs, I can also save them successfully.

Any ideas?

Thank you for the support.
Sander van de Velde | MVP 36,761 Reputation points MVP Volunteer Moderator

2025-06-23T06:05:37.5666667+00:00

Hello @Luis Loaysa Admin ,

welcome to this moderated Azure community forum.

Better questions with more information lead to better answers from our community members.

Please provide information about the steps you have taken, the guide you follow, and the errors you receive so fellow members can understand your question better.

What rights do you have and what queries do you want to execute? What errors do you see?
J N S S Kasyap 3,625 Reputation points Microsoft External Staff Moderator

2025-06-24T16:23:51.9733333+00:00
@Luis Loaysa Admin ,
To help diagnose the issue more effectively, it would be helpful if you could provide some additional details. Understanding exactly what steps you've taken, any documentation or guides you’ve followed, and the specific behavior you're encountering will help others assist you better.

Please share more about:

The exact KQL queries you're running (even simple ones that are failing).

Whether this issue affects all queries or just certain ones.

What permissions your account has (e.g., database viewer, contributor, etc.).

Any error messages or logs visible in the Azure portal.

Whether any recent changes were made to the cluster configuration or permissions.

What troubleshooting steps you’ve already tried.

This information will make it easier for others to provide targeted advice and possible solutions.
Chandra Boorla 14,510 Reputation points Microsoft External Staff Moderator

2025-06-25T19:19:18.36+00:00

@Luis Loaysa Admin

We haven’t heard from you on the last response and was just checking back to see if you have a resolution yet. In case if you have any resolution, please do share that same with the community as it can be helpful to others. Otherwise, will respond with more details and we will try to help.

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