How can I troubleshoot latency issues in Azure Stream Analytics job output?

@Stephen27

To troubleshoot latency issues in your Azure Stream Analytics job output, consider the following steps:

Check for Throttling - Ensure that neither the downstream sink (Azure SQL Database) nor the upstream source (Event Hub) is throttled. Throttling can lead to delays in processing and output.

Examine Resource Utilization - Monitor the resource utilization of your Stream Analytics job. If resource utilization is consistently high (over 80%), it may indicate that the job is nearing its maximum allocated resources, which can contribute to latency. You might consider increasing the number of streaming units to improve throughput.

Job Diagram Analysis - Use the job diagram in the Azure portal to visualize the flow of data and identify any bottlenecks. This can help you see if there are any backlogged events or if the processing logic is compute-intensive.

Output Retry Logic - Be aware that the SQL output can experience transient errors which may cause delays. The job attempts to connect to SQL and fetch the schema, and any issues during this process can lead to increased latency.

Common Pitfalls - Ensure that your query logic is not inadvertently filtering out events or causing delays. For example, check for any WHERE clauses that may be filtering out all events or for any casting errors that could prevent output from being generated.

By following these steps, you should be able to diagnose and potentially resolve the latency issues you are experiencing.

For more details refer: Troubleshoot Azure Stream Analytics outputs

• Troubleshoot Azure Stream Analytics queries

I hope this information helps.

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Hello @Stephen27 ,

welcome to this moderated Azure community forum.

As already mentioned above, there can be multiple reasons why you experience latency.

I would check the CPU usage first to see if the current number of streaming unit is still sufficient, eg. because the amount of messages has increased over time.

You say you forward your messages to a Sql database. Check if this database performs as expected.

In general a relational database is not optimized for data like telemetry. I suggest checking out Azure Data Explorer, a timeseries database that is optimized for insert only storage for immutable, events, observations, facts.

If you have a test environment next to the production environment, please check if you can replay the same observations there.

It's also recommended to tune the query using the Visual Studio code extension for Stream Analytics so you can test it before deployment..

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