When running dagster dev - is there a way to find the port that the webserver is running from within an execution context?

When you run

dagster dev

, it launches both the Dagster webserver/UI and the Dagster daemon. The documentation does not explicitly mention a method to find the port that the webserver is running on from within an execution context. Typically, the command will print out the URL you can access the UI from in the browser, which is usually on port 3000. If you need to specify a different port or determine the port programmatically from within an execution context, the documentation does not provide direct guidance on how to do this. However, it's common practice to set the

DAGSTER_HOME

environment variable and use consistent port configurations to ensure that services can discover and communicate with each other as expected. For more specific use cases or advanced configurations, you might need to refer to the source code, community discussions, or reach out for support directly if the documentation does not cover your scenario.

@Scout I want to be able to construct a URL to the UI from within a sensor

Constructing a URL to the Dagster UI from within a sensor is not a typical use case covered directly in the documentation. Sensors in Dagster are designed to evaluate conditions and yield

RunRequest

objects or emit skip reasons, and they do not inherently have knowledge of the webserver's network configuration. However, if you need to construct a URL to the UI within a sensor, you would typically need to know the hostname and port where the Dagster UI is running. This information is not available in the sensor's execution context. The webserver's host and port are usually determined by the environment in which Dagster is running and are often specified in the Dagster instance configuration or through environment variables. If you have a fixed host and port for your Dagster UI, you could hardcode the URL within your sensor code. Alternatively, you could set environment variables for the host and port and read these from within your sensor to construct the URL dynamically. Here's a conceptual example of how you might approach this:

python import os from dagster import sensor, RunRequest  @sensor def my_sensor(context):     # Assuming you have set DAGSTER_UI_HOST and DAGSTER_UI_PORT as environment variables     dagster_ui_host = os.getenv('DAGSTER_UI_HOST', 'localhost')     dagster_ui_port = os.getenv('DAGSTER_UI_PORT', '3000')      # Construct the URL to the Dagster UI     dagster_ui_url = f"http://{dagster_ui_host}:{dagster_ui_port}"      # You can now use dagster_ui_url in your sensor logic     # For example, you might want to include it in a message or alert     message = f"Check the Dagster UI for more details: {dagster_ui_url}"      # Your sensor logic here...     # ...      yield RunRequest(run_key="example", run_config={})

Please note that this is a conceptual example and may not directly apply to your specific setup. You would need to ensure that the environment variables

DAGSTER_UI_HOST

and

DAGSTER_UI_PORT

are set in the environment where your Dagster instance is running. Keep in mind that this approach assumes that the sensor has access to the environment variables at runtime, which may not always be the case depending on your deployment setup. If you have a more dynamic environment or need to retrieve the host and port from the Dagster instance configuration, you may need to explore other options or reach out to the community for more specific guidance.