Creating sensors that react to run statuses

If you want to act on the status of a run, Dagster provides a way to create a sensor that reacts to run statuses. You can use run_status_sensor with a specified DagsterRunStatus to decorate a function that will run when the given status occurs. This can be used to launch other runs, send alerts to a monitoring service on run failure, or report a run success.

Here is an example of a run status sensor that launches a run of status_reporting_job if a run is successful:

src/<project_name>/defs/sensors.py

@dg.run_status_sensor(
    run_status=dg.DagsterRunStatus.SUCCESS,
    request_job=status_reporting_job,
)
def report_status_sensor(context: dg.RunStatusSensorContext):
    # this condition prevents the sensor from triggering status_reporting_job again after it succeeds
    if context.dagster_run.job_name != status_reporting_job.name:
        run_config = {
            "ops": {
                "status_report": {"config": {"job_name": context.dagster_run.job_name}}
            }
        }
        return dg.RunRequest(run_key=None, run_config=run_config)
    else:
        return dg.SkipReason("Don't report status of status_reporting_job")

request_job is the job that will be run when the RunRequest is returned.

Note that in report_status_sensor we conditionally return a RunRequest. This ensures that when report_status_sensor runs status_reporting_job it doesn't enter an infinite loop where the success of status_reporting_job triggers another run of status_reporting_job, which triggers another run, and so on.

Here is an example of a sensor that reports job success in a Slack message:

src/<project_name>/defs/sensors.py

import dagster as dg


@dg.run_status_sensor(run_status=dg.DagsterRunStatus.SUCCESS)
def my_slack_on_run_success(context: dg.RunStatusSensorContext):
    slack_client = WebClient(token=os.environ["SLACK_DAGSTER_ETL_BOT_TOKEN"])

    slack_client.chat_postMessage(
        channel="#alert-channel",
        text=f'Job "{context.dagster_run.job_name}" succeeded.',
    )

When a run status sensor is triggered by a run but doesn't return anything, Dagster will report an event back to the run to indicate that the sensor ran.