# Hands-On: Scenarios (Part 2)¶

In the section above, we saw how to use built-in metrics and checks to monitor the status of datasets and models in Dataiku DSS.

Now let’s see how to use these metrics and checks inside of a scenario to automate workflows.

## Create a Scenario¶

From the Jobs menu, navigate to the Scenarios panel and create a new scenario.

In Dataiku DSS, we can create two kinds of scenarios. We’ll see the Custom Python scenario later. For now, create a step-based scenario named My Scenario.

A scenario has two required components:

• triggers that activate a scenario and cause it to run, and

• steps, or actions, that a scenario takes when it runs.

An optional third component of a scenario is a reporter. Please see the product documentation for more information on reporters.

## Add a Trigger¶

Dataiku DSS allows us to create many kinds of triggers to activate a scenario. These triggers can be based on:

• a change in time,

• a change in a dataset,

• a change in the result of a SQL query,

• or custom code.

Note

If using Dataiku Online, only time-based triggers are available.

Let’s start with the simplest kind of trigger.

• Within the Triggers panel of the Settings tab, click the Add Trigger dropdown button.

• Add a Time-based trigger.

• Name it Every 3 min.

• Change “Repeat every” to 3 minutes.

• If using DSS version 8, change the frequency to Every X minutes and set the interval to 3.

• Make sure its activity status is marked as ON.

Note

For many use cases, it would be unusual to have a scenario run this frequently. This short duration is only to let us see the scenario running in a short amount of time.

Now that we have a trigger in place, we need to provide the steps that the scenario will take when a trigger is activated. In a somewhat contrived example, let’s demonstrate how to rebuild datasets, compute metrics, and set project variables in a scenario.

Navigate to the Steps tab.

• From the Add Step dropdown, first add a Build / Train step. Add transactions_joined_prepared as the dataset to build.

• Note that this step has Build required datasets as the Build mode. Accordingly, because we won’t have “new” data in this tutorial, datasets upstream to transactions_joined_prepared will never be out of date, and this step will only build transactions_joined_prepared.

Note

To learn more about building strategies in Dataiku DSS, see the course Flow Views & Actions.

• Add the step Compute metrics. Choose transactions_joined_prepared as the dataset to compute.

• Earlier we manually computed metrics like the minimum and maximum of card_fico_score. Now the scenario will execute this computation for us.

• Add the step Run checks. Choose transactions_joined_prepared as the dataset to check.

• Checks we created, such as whether the minimum of card_fico_score is greater than or equal to 300, will be recomputed.

• Add the step Check project consistency.

• As our data has not changed, we know that the schema consistency check is going to run smoothly, but in a production use case, it can help detect when the schema of an input dataset has changed.

Add the step Set project variables. The current state_name variable is “Delaware”. Reset it to another state as shown below. You can imagine changing the value of the variable if some condition is met.

{
"state_name": "Rhode Island"
}

• Add a Clear step. Choose merchants_by_state as the dataset to clear.

• This is the output dataset to the Group recipe which uses the state_name variable.

• Add one more Build / Train step. Choose merchants_with_tract_income as the dataset to build.

• With a new state_name variable and an empty merchants_by_state dataset, this section of the Flow will get rebuilt from the Group recipe.

After saving, we could click the green Run button to manually start the scenario. This is important to test out scenario runs.

In this case though, navigate to the Scenario panel in the Jobs menu where all scenarios for the project are listed. Turn the “Auto-triggers” switch to “ON” to have Dataiku DSS start monitoring the triggers of the scenario.

Once the scenario starts running, check its progress in the Jobs panel. Jobs attached to a scenario have a label including the name of the scenario. We can see that this scenario creates two jobs.

• Recall that we chose “Build required datasets” for the build mode instead of an option like “Build only this dataset” or “Force rebuild”. Accordingly, there is “nothing to do” for building transactions_joined_prepared as there is no new data.

• Rebuilding merchants_with_tract_income, however, does require activity because one of the datasets it depends on has been cleared.

Hint

Check the merchants_with_tract_income dataset again. Has the merchant_state column updated from “Delaware” to the new variable?

We can keep tabs on the progress through the Last runs tab of the scenario. Once you have seen a few runs, turn off the scenario from the main Scenarios page.

Note

If we have multiple scenarios, the Automation Monitoring panel in the Jobs menu provides similar information for all scenario activities coming from the project. This feature is not available to community edition users.