Updating the Definitions object

As with your other Dagster definitions, the final step is to add the sensor, its related asset, and job into the Definitions object. This will be done in the top-level __init__.py file.

1. Import the new asset, job, and sensor into the __init__.py file by updating the following imports:

   from .assets import trips, metrics, requests
   ...
   from .jobs import trip_update_job, weekly_update_job, adhoc_request_job
   ...
   from .sensors import adhoc_request_sensor
   

2. Beneath metric_assets, create a request_assets variable that loads the assets from requests:

   request_assets = load_assets_from_modules([requests])
   

3. Add the adhoc_request_job to all_jobs :

   all_jobs = [trip_update_job, weekly_update_job, adhoc_request_job]
   

4. Beneath all_schedules, create a new variable named all_sensors and add the adhoc_request_sensor to it:

   all_sensors = [adhoc_request_sensor]
   

5. Lastly, update the Definitions object by:

   1. Adding the new asset (request_assets) to the assets parameter:

      assets=[*trip_assets, *metric_assets, *request_assets],
      

   2. Adding the sensors parameter and setting it to all_sensors:

      sensors=all_sensors,
      

At this point, __init__.py should look like this:

from dagster import Definitions, load_assets_from_modules

from .assets import trips, metrics, requests
from .resources import database_resource
from .jobs import trip_update_job, weekly_update_job, adhoc_request_job
from .schedules import trip_update_schedule, weekly_update_schedule
from .sensors import adhoc_request_sensor

trip_assets = load_assets_from_modules([trips])
metric_assets = load_assets_from_modules([metrics])
request_assets = load_assets_from_modules([requests])

all_jobs = [trip_update_job, weekly_update_job, adhoc_request_job]
all_schedules = [trip_update_schedule, weekly_update_schedule]
all_sensors = [adhoc_request_sensor]

defs = Definitions(
    assets=[*trip_assets, *metric_assets, *request_assets],
    resources={
        "database": database_resource,
    },
    jobs=all_jobs,
    schedules=all_schedules,
    sensors=all_sensors
)

Congratulations on creating a sensor! We’ll discuss how to enable the sensor in a bit, but let’s start by going through the Dagster UI.