Crashed desks

We have endpoints for listing the out-of-order desks and those that have a customer stuck on them. In this exercise, you will add an endpoint that will list all the “crashed” desks. We will say that a desk has crashed if it has not sent status updates in the last 12 seconds.

This is mostly an exercise to check that you understood everything so far: we will not be introducing any new concepts.

Adding the database migration

We need a new column to reflect the last time we received a status update from a desk.

Create a new V3__add-last-status.sql database migration script, with this content:

alter table check_in_desk
add last_status_at timestamp(3);

Updating the entity

Update the CheckInDesk entity to reflect this new column.

Creating the consumer

Create the StatusUpdateConsumer that will consume the CheckInTopics.TOPIC_STATUS records, and update the lastStatusAt field in CheckInDesk to the timestamp of the given Kafka record.

Testing the consumer

As usual, write an automated unit test to ensure that the consumer works as it should.

Extend the controller

Add a GET /desks/crashed endpoint to list the desks whose last status update was from before 12 seconds ago.

You will need to write a custom query in your repository that lists the CheckInDesk whose lastStatusAt was before a given Instant.

Note that you can compute the Instant from 12 seconds ago with:

Instant.now().minusSeconds(12)

Trying everything together

Try running the simulator and your consumers, and checking that crashed desks start appearing once the system has been running for a minute or so.

Once you’re happy with the results, stop the simulator and your consumers, and move on to the final exercise.