Alarms for practice runs

You can specify two CloudWatch alarms for practice runs in zonal autoshift. The first alarm, the outcome alarm, is required. You should configure the outcome alarm to monitor the health of your application when traffic is shifted away from an Availability Zone during each 30-minute practice run.

For a practice run to be effective, specify as an outcome alarm a CloudWatch alarm that monitors metrics for the resource, or your application, that respond with an ALARM state when your application is adversely affected by the loss of one Availability Zone. For more information, see the Alarms that you specify for practice runs section in Best practices when you configure zonal autoshift.

The outcome alarm also provides information for the practice run result that ARC reports for each practice run. If the alarm enters an ALARM state, the practice run is ended and the practice run outcome is returned as FAILED. If the practice run completes the 30 minute scheduled test period and the outcome alarm does not enter an ALARM state, the outcome is returned as SUCCEEDED. A list of all outcome values, with descriptions, is provided in the Outcomes for practice runs section.

Optionally, you can specify a second alarm, the blocking alarm. The blocking alarm blocks practice runs from starting, or continuing, when it’s in an ALARM state. This alarm blocks practice run traffic shifts from being started—and stops any practice runs in progress—when the alarm is in an ALARM state.

For example, in a large architecture with multiple microservices, when one microservice is experiencing a problem, you typically want to stop all other changes in the application environment, which would including blocking practice runs.