Jason Gofford
03/08/2024, 9:18 AMconfigure_at_launch()
, and explain the pros and cons of this mechanism of instantiating a resource.Scout
03/08/2024, 9:18 AMconfigure_at_launch()
method is used when you want to defer the configuration of a resource until the time a job or asset is launched. This can be particularly useful in scenarios where the configuration is dynamic and determined at runtime, rather than being static or known upfront.
### Examples of when to use `configure_at_launch()`:
1. Database Connections with Dynamic Parameters: If you have a job that interacts with different databases or tables based on some runtime condition, you might use configure_at_launch()
to specify the target database or table at launch time.
2. Environment-Specific Resources: In cases where you have multiple deployment environments (development, staging, production), you might want to configure resources differently in each environment. Using configure_at_launch()
, you can pass environment-specific configurations when the job is triggered.
3. User-Driven Workflows: If the configuration of a resource depends on user input or some external event, you can use configure_at_launch()
to provide the necessary parameters when the job is initiated in response to that input or event.
4. Testing and Mocking: When writing tests, you might want to configure a resource with different settings or mock implementations. configure_at_launch()
allows you to provide these configurations at the time the test job is run.
### Pros and Cons of `configure_at_launch()`:
Pros:
- Flexibility: It allows for dynamic configuration of resources based on runtime conditions, user inputs, or other external factors.
- Environment Agnosticism: It enables the same job or asset code to be used across different environments with different configurations.
- Simplicity: It can simplify the configuration management by allowing you to specify resource configurations in one place at launch time, rather than having to manage multiple configuration files or environment variables.
- Security: It can enhance security by allowing sensitive information to be passed at runtime, reducing the exposure of secrets in code or configuration files.
Cons:
- Complexity: It can add complexity to the launch process, as you need to ensure that the correct configurations are provided every time a job is launched.
- Observability: It might make it harder to understand the configuration that was used for a particular run, as it is not statically defined in the codebase.
- Error-Prone: There is a risk of misconfiguration or forgetting to provide necessary configuration parameters at launch time, which can lead to runtime errors.
The documentation provides an example of how to use configure_at_launch()
with a sensor, where the sensor dynamically provides the table name to a database resource for eaScout
03/08/2024, 9:19 AMpython from dagster import ConfigurableResource, Definitions, asset class DatabaseResource(ConfigurableResource): table: str def read(self): ... @asset def data_from_database(db_conn: DatabaseResource): return db_conn.read() defs = Definitions( assets=[data_from_database], resources={"db_conn": DatabaseResource.configure_at_launch()}, )
In this example, the DatabaseResource
is configured to read from a specific table, and the table name is provided at launch time, allowing for dynamic selection of the table to be queried by the asset.Jason Gofford
03/08/2024, 9:21 AMtable
defined in this example. Show me a complete example of how a configurable property of a resource is set at launch time in an asset.Scout
03/08/2024, 9:21 AMDatabaseResource
with a configurable property table
and how you can set this property at launch time using a sensor. First, define the DatabaseResource
class with a configurable property `table`: python from dagster import ConfigurableResource, asset class DatabaseResource(ConfigurableResource): table: str def read(self): # Here you would have logic to read from the specified table # For example, using an SQL query like f"SELECT * FROM {self.table}" ...
Next, define an asset that uses this resource: python @asset(required_resource_keys={"db_conn"}) def data_from_database(db_conn: DatabaseResource): return db_conn.read()
Now, define a sensor that triggers runs of a job that includes this asset. The sensor will dynamically provide the table
name to the DatabaseResource
at launch time: python from dagster import sensor, RunRequest, RunConfig, define_asset_job update_data_job = define_asset_job( name="update_data_job", selection=[data_from_database] ) @sensor(job=update_data_job) def table_update_sensor(): tables = ["table1", "table2"] # This could be dynamically generated for table_name in tables: yield RunRequest( run_config=RunConfig( resources={ "db_conn": {"config": {"table": table_name}}, }, ), )
In this example, the table_update_sensor
sensor yields RunRequest
objects that include a RunConfig
. The RunConfig
specifies the configuration for the db_conn
resource, setting the table
property to the name of the table that you want to read from in each run. When the sensor triggers a run, it will pass the table
configuration to the DatabaseResource
, and the data_from_database
asset will read from the specified table. This example shows how you can set a configurable property of a resource at launch time in an asset using Dagster's sensor mechanism. The actual implementation details of the DatabaseResource.read
method would depend on the specifics of your database interaction, such as using an ORM or executing raw SQL queries.Jason Gofford
03/08/2024, 9:44 AMScout
03/08/2024, 9:44 AMpython from dagster import job @job(resource_defs={"db_conn": db_resource}) def my_data_processing_job(): data_from_database()
When you go to launch a run of my_data_processing_job
through the Dagster UI, you would be presented with a configuration editor where you can input the dynamic configuration for the db_conn
resource. Alternatively, you could use the GraphQL API to launch the run with a provided configuration. It's important to note that while you can provide dynamic configuration at launch time, the asset itself is not directly receiving configuration; rather, it's the resources or ops within the job that are being configured. The asset will use these configured resources or ops as part of its computation. If you need to configure assets dynamically and frequently, using sensors or schedules to automate this process might be more efficient. However, for one-off runs or testing purposes, manually providing configuration at launch time is a suitable approach.Jason Gofford
03/08/2024, 9:58 AMScout
03/08/2024, 9:58 AMDefinitions
and then filling in the remaining configuration at launch time. Resources must be either fully configured at definition time or configured at launch time. However, there has been discussion in the community about the desire for such a feature, where users can provide some configuration when defining the resource and then supply the rest of the configuration at runtime. This feature would allow for more flexible resource configuration patterns, especially in cases where some resource parameters are known upfront, and others are only known at runtime. As of now, if you want to configure a resource at launch time, you would use the configure_at_launch()
method when defining the resource in Definitions
. This means that all configuration for the resource must be provided at launch time, and none of it is specified in the Definitions
. Here's an example of how you would define a resource that is fully configured at launch time: python from dagster import ConfigurableResource, Definitions, asset class MyResource(ConfigurableResource): # Configuration schema for the resource foo: str bar: str # ... @asset(required_resource_keys={"my_resource"}) def my_asset(context): # Use the resource within the asset resource = context.resources.my_resource # ... # Define the resource to be configured at launch time defs = Definitions( assets=[my_asset], resources={"my_resource": MyResource.configure_at_launch()}, )
In this example, when you launch a run that includes my_asset
, you would need to provide the configuration for my_resource
, including values for both foo
and bar
. If the feature for partial configuration becomes available in a future release, the documentation will be updated to reflect how to use it. For now, you would need to manage partial configurations outside of Dagster's resource system, such as by using environment variables or other mechanisms to supply the additional configuration at runtime.Jason Gofford
03/08/2024, 10:00 AMmy_asset
asset? Show me a full example.Scout
03/08/2024, 10:00 AMfoo
and bar
properties of the MyResource
resource in a run containing the my_asset
asset, you would provide a run configuration that specifies the values for these properties. This configuration is typically provided as a YAML file or a dictionary when launching the run through the Dagster UI, the Dagster CLI, or programmatically. Here's an example of how you might provide this configuration as a YAML file: yaml resources: my_resource: config: foo: "value_for_foo" bar: "value_for_bar"
If you're using the Dagster UI, you would paste this configuration into the appropriate field in the launchpad when triggering a run. Alternatively, if you're launching the run programmatically, you would provide the configuration as a dictionary to the run_config
parameter. Here's an example of how you might do this using the materialize
function: python from dagster import materialize result = materialize( [my_asset], run_config={ "resources": { "my_resource": { "config": { "foo": "value_for_foo", "bar": "value_for_bar", } } } } )
In this example, the materialize
function is used to execute a run that materializes the my_asset
asset with the provided resource configuration. The run_config
dictionary specifies the configuration for the my_resource
resource, including the foo
and bar
properties. Please note that the actual implementation of the MyResource
class and how it uses the foo
and bar
properties would depend on your specific use case. The above examples show how to pass configuration values for these properties when launching a run.