I'm running into this error:

dagster.daemon.AssetDaemon - ERROR - Auto-materialize daemon caught an error

Following up with:

dagster.daemon.AssetDaemon - ERROR - Caught error:
dagster._check.CheckError: Expected non-None value: None

I'm not quite sure what the cause of this is My partitions are being created properly, but non of the downstream lineage Assets were started. What might be plausible causes of this?

The error message you're encountering indicates that the Dagster daemon, specifically the AssetDaemon, has caught an error related to an expectation of a non-None value that was not met (

Expected non-None value: None

). This error is a type of

CheckError

which typically occurs when Dagster's internal validation checks fail, often due to an unexpected

None

value where a non-

None

value was required. Based on the information provided, it seems that the error occurred during the auto-materialization process managed by the AssetDaemon. Auto-materialization is a feature that allows Dagster to automatically materialize assets according to a defined schedule or sensor. If the partitions are being created properly but the downstream assets are not being materialized, there could be several potential causes: 1. Misconfiguration of Assets or Dependencies: There might be a misconfiguration in the way assets are defined or how their dependencies are set up. Ensure that all assets and their dependencies are correctly configured. 2. Issues with the Asset Daemon: The AssetDaemon might be encountering issues when trying to materialize the assets. This could be due to a variety of reasons, such as incorrect permissions, missing configurations, or other operational issues. 3. Problems with Upstream Assets: If there are issues with the upstream assets, such as failed materializations or missing data, this could prevent downstream assets from being materialized. 4. Code Version Mismatch: If the code version associated with the asset definitions has changed without proper migration or update, this could lead to issues during auto-materialization. 5. Dagster Version Issues: If you recently upgraded Dagster, there might be breaking changes or bugs introduced in the new version that could affect the auto-materialization process. To troubleshoot this issue, you can take the following steps: - Check the Asset Definitions: Ensure that all asset definitions and dependencies are correct and that there are no missing values that could lead to a

None

value where a non-

None

value is expected. - Review the Dagster Daemon Logs: Look at the logs for the Dagster daemon to see if there are any additional error messages or stack traces that can provide more context about the failure. - Verify Permissions and Configurations: Make sure that the Dagster daemon has the necessary permissions to access and materialize the assets and that all configurations are correct. - Test Materialization Manually: Try to manually materialize the assets using the Dagster API or CLI to see if the issue is specific to the auto-materialization process. - Check for Version Compatibility: If you recently upgraded Dagster, review the release notes for any

@Scout how could I do this:

Test Materialization Manually: Try to manually materialize the assets using the Dagster API or CLI to see if the issue is specific to the auto-materialization process.

To manually materialize assets using the Dagster API, you can use the

materialize

function. This function allows you to execute a single-threaded, in-process run which materializes the provided assets. Here's a general example of how you might use the

materialize

function:

python from dagster import materialize from your_project.assets import your_asset  # Replace 'your_asset' with the actual asset you want to materialize result = materialize([your_asset])  # Check if the materialization was successful assert result.success

Make sure to replace

your_project.assets

and

your_asset

with the actual module path and asset name that you want to materialize. To use the CLI for manual materialization, you can use the

dagster asset materialize

command. Here's how you might call it from your terminal:

shell dagster asset materialize -a your_asset

Again, replace

your_asset

with the name of the asset you want to materialize. Before running these commands, ensure that your Dagster environment is properly configured, and you have the necessary dependencies installed. If you encounter any errors during manual materialization, the error messages may provide additional context that can help diagnose the issue with the auto-materialization process.

@Scout and how could I do that from the web UI?

To manually materialize assets from the Dagster web UI, you can follow these steps: 1. Start the Dagster web UI by running the following command in your terminal:

shell    dagit -f path_to_your_python_file.py

Replace

path_to_your_python_file.py

with the path to the Python file that contains your asset definitions. 2. Open your web browser and navigate to the URL where the Dagster UI is hosted, typically

<http://localhost:3000>

. 3. In the Dagster UI, navigate to the Assets tab where you will see a list of your defined assets. 4. Find the asset you want to materialize. You can use the search bar to filter assets by name if you have many assets. 5. Click on the asset to view its details. 6. On the asset's detail page, you should see a Materialize button. Click this button to start the materialization process. 7. A dialog may appear asking you to confirm the materialization and to provide any required configuration. Fill in the necessary details if prompted. 8. After confirming, Dagster will initiate the materialization process. You can monitor the progress and view logs directly in the UI. 9. Once the materialization is complete, you can inspect the logs to ensure that the process succeeded without errors. By following these steps, you can manually trigger the materialization of assets from the Dagster web UI and verify that the assets are materializing as expected. If the manual materialization succeeds without issues, but the auto-materialization process is still failing, the problem may be specific to the auto-materialization configuration or daemon.