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#ask-ai
Title
# ask-ai
b

Brandon Peebles

03/04/2024, 9:04 PM
Is there a way I can have a script run when the dagster webserver starts up? For instance, when I run
dagster dev
locally i'd like it to first parse the dbt project before doing anything else
s

Scout

03/04/2024, 9:04 PM
Based on the documentation, there isn't a direct mention of a feature that allows you to run a custom script specifically at the startup of the
dagster dev
command. The
dagster dev
command is used to start a local deployment of Dagster, including the dagster-webserver running on localhost and the dagster-daemon running in the background. The command provides options for setting the working directory, module name, python file, workspace, and various logging and port configurations, but it does not explicitly provide a hook for running custom scripts at startup. However, if you need to ensure that certain actions, such as parsing a dbt project, are performed before running your Dagster jobs, you might consider a couple of approaches: 1. Manual Script Execution: You could manually run a script to parse your dbt project before starting the Dagster webserver with
dagster dev
. This would be an external step in your workflow. 2. Custom Entry Point: If you are deploying Dagster with Docker, you could customize the Docker container's entry point to run a script before starting the Dagster processes. This is mentioned in a discussion where it's suggested to use a custom
ENTRYPOINT
in the Dockerfile that runs any additional commands before executing the Dagster command. 3. Environment Variable: In some cases, setting an environment variable before running
dagster dev
can influence the behavior of the Dagster instance. For example, setting
DAGSTER_DBT_PARSE_PROJECT_ON_LOAD=1
before running
dagster dev
will parse the dbt project on load. This is mentioned in the documentation as part of the steps to inspect a Dagster project in Dagster's UI. 4. Custom Code in Dagster Definitions: If the action you want to perform is related to the initialization of your Dagster assets or resources, you could potentially include the necessary code within the initialization logic of those components. For more specific functionality or if you have a particular use case in mind, you might want to check the latest Dagster documentation or reach out to the Dagster community for more targeted advice.
b

Brandon Peebles

03/04/2024, 9:08 PM
@Scout but doesnt the DAGSTER_DBT_PARSE_PROJECT_ON_LOAD environment variable instruct Dagster to parse the project before executing any op? This seems to slow down my processes
s

Scout

03/04/2024, 9:08 PM
Yes, you are correct. Setting the
DAGSTER_DBT_PARSE_PROJECT_ON_LOAD
environment variable to
1
instructs Dagster to parse the dbt project when the Dagster instance is loaded. This is intended to load dbt models as Dagster assets, which can be useful for inspecting your dbt project within Dagster's UI. However, as you've experienced, this can slow down the startup process because it adds additional overhead to the initialization of the Dagster webserver. If you find that setting
DAGSTER_DBT_PARSE_PROJECT_ON_LOAD=1
is slowing down your processes more than desired, you might consider the following alternatives: 1. Parse dbt Project Manually: Instead of relying on the environment variable, you could parse the dbt project manually before starting the Dagster webserver. This would allow you to control when the parsing happens and potentially optimize the process. 2. Optimize dbt Project Structure: If parsing the dbt project is essential and cannot be avoided, you might look into optimizing your dbt project structure to reduce the time it takes to parse. This could involve simplifying models, reducing dependencies, or breaking the project into smaller, more manageable pieces. 3. Conditional Parsing: You could set up a conditional environment variable that only enables dbt project parsing when needed. For example, you could have a separate script or command that sets
DAGSTER_DBT_PARSE_PROJECT_ON_LOAD=1
only when you want to inspect the dbt models in the UI, and leave it unset or set to
0
for regular development work. 4. Performance Profiling: If the slowdown is significant, you might want to profile the performance to understand where the bottlenecks are. This could reveal specific areas of the dbt project or the Dagster setup that could be optimized. Remember that the
DAGSTER_DBT_PARSE_PROJECT_ON_LOAD
environment variable is specifically for loading dbt models as Dagster assets, which may not be necessary for all development workflows. If you do not need to inspect dbt models as assets in the UI frequently, you may choose to disable this feature during regular development to speed up the startup time. If you continue to experience issues or need further assistance with optimizing your workflow, you may want to reach out to the Dagster community or consult the latest documentation for additional guidance and best practices.
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