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6. Introduce System Change

The application is running correctly. It is time to introduce a change into the system.

This simulates releasing new functionality to your users in production.

Inform Dynatrace#

First, inform Dynatrace that a change is about to occur. Namely, you are going to make a change to the my-otel-demo-cartservice service by changing the cartServiceFailure feature flag from off to on.

Tell Dynatrace about the upcoming change by sending an event (note: This event does not actually make the change; you need to do this).

Run the following:

./runtimeChange.sh my-otel-demo-cartservice cartServiceFailure on

Refresh the my-otel-demo-cartservice page and near the bottom you should see the configuration change event.

configuration changed event

Make Change#

Open this file: flags.yaml

Change the defaultValue of cartServiceFailure from "off" to "on" (scroll to line 75)

feature flag YAML

Now apply the change by running this command:

kubectl apply -f $CODESPACE_VSCODE_FOLDER/flags.yaml

You should see:

configmap/my-otel-demo-flagd-config configured

Be Patient

The application will now generate errors when emptying the users cart. It will do this 1/10th of the time, so be patient, it can take a few moments for the errors to occur.

Generate Your Own Traffic#

There is a load generator running, but you can generate traffic by accessing the site.

See access user interface

Repeatedly add an item to your cart, go to the cart and empty it. Hope you're "lucky" that you generate a backend failure.

Open Problems App#

In Dynatrace:

  • Press ctrl + k. Search for problems
  • Open the problems app

Wait for the problem to appear.

You can also open the my-otel-demo-cartservice Service screen to monitor for failures.

  • Press ctrl + k. Search for Services
  • Open the services app + navigate to the my-otel-demo-cartservice
  • Monitor the Failed requests chart