Power Platform Community Forum Thread Details

Hi,

The MetadataEvaluationGatewayTimeout error during a dataflow refresh typically indicates that the process of validating the dataflow's schema and metadata against the data source has taken too long and timed out. This issue can occur for several reasons, even if the same dataflow worked previously. Here's a systematic approach to troubleshoot and resolve the issue:

1. Check Data Source Availability

Ensure the data source is available and responsive.
Test the connection to the data source outside of Power BI or Power Apps (e.g., using SQL Server Management Studio, a web browser, or other relevant tools).

2. Inspect Dataflow Complexity

Large Datasets: If the data source has grown significantly, this could increase the time required for metadata evaluation.
Complex Queries: Optimize the queries in your dataflow to minimize computation. Avoid steps like merging, appending, or applying filters in the dataflow where possible.

3. Gateway Performance

Gateway Load: Check if the on-premises data gateway is under heavy load. You can do this in the Power BI Service Gateway settings.
Gateway Update: Ensure the gateway is updated to the latest version.
Gateway Location: If the gateway is geographically far from the data source, latency could contribute to timeouts.

4. Dataflow Settings

Open the dataflow and validate each query individually to identify any problematic transformations or sources.
Check the dataflow refresh policy. If you have incremental refresh enabled, ensure the partitions and range settings are correct.

5. Query Folding

If the data source supports query folding, ensure that transformations in the dataflow can be folded back to the source. You can check this by right-clicking a query step in Power Query and seeing if "View Native Query" is enabled.

6. Increase Gateway Timeout (Advanced)

If you have control over the on-premises data gateway, you can adjust the timeout settings:
1. Open the GatewayConfig.json file on the machine hosting the gateway.
2. Locate the MashupDefaultTimeout or MashupTimeout setting.
3. Increase the value (e.g., from 2 minutes to 5 minutes).
4. Restart the gateway service.

7. Split the Dataflow

If your dataflow handles large or complex datasets, consider splitting it into smaller dataflows. Use one dataflow to extract and transform the data, and another to consume the transformed data.

8. Monitor Logs

Enable and review the gateway logs for more detailed error information. This can help pinpoint where the timeout is occurring.

9. Test in Power BI Desktop

Replicate the dataflow queries in Power BI Desktop. If they fail there as well, the issue likely lies with the source or transformations.

10. Microsoft Support

If the issue persists, open a support ticket with Microsoft. Provide them with the Request ID and a description of the error.

Preventive Measures:

Regularly monitor the size and complexity of your data sources.
Use incremental refresh when dealing with large datasets.
Ensure the gateway machine has sufficient resources (CPU, memory, etc.).

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