Cloud Native Development in Practice

Availability

VMware Tanzu Labs

You will demonstrate how pal-tracker application works with Tanzu Application Service availability characteristics.

Learning outcomes

After completing the lab, you will be able to:

• Demonstrate how Tanzu Application Service handles availability.

Getting started

Review the Availability slides.

Codebase and manifest

1. You must have completed (or fast-forwarded to) the Hardening lab. You must have your pal-tracker application associated with the scaling-availability-solution codebase deployed and running on Tanzu Application Service.

2. In a terminal window, make sure you start in the ~/workspace/pal-tracker directory.

Monitoring

In this lab you will exercise your pal-tracker application under load, monitor it, and tune it.

You can monitor the pal-tracker application through the following:

• Command line via the following cf commands:

  • cf app pal-tracker
  • cf events pal-tracker

• Apps Manager user interface.

If you choose to monitor via the command line you will need a minimum of four terminal windows open.

If you choose to monitor with Apps Manager you will need only one.

Verify availability characteristics

1. In a dedicated terminal window, run a load test:

   docker run -i -t --rm -e DURATION=300 -e NUM_USERS=10 -e REQUESTS_PER_SECOND=5 -e URL=http://pal-tracker-${UNIQUE_IDENTIFIER}.${DOMAIN} pivotaleducation/loadtest
   

   Watch for 30 seconds or more to verify no errors.

2. In a separate terminal window, invoke a failure:

   curl -v -XPOST -H "Content-Length:0"  http://${APP_URL}/actuator/palTrackerFailure
   

3. Verify that a crash and restart occurs. You can see this either in Apps Manager or the window in which you are watching cf events output. This restart may occur very quickly, which demonstrates disposability characteristics of your application.

4. Verify whether or not you see errors in your load test output.

   Notice that you may see some transient failures during the disposal and recovery of the failed instance. Keep in mind the Diego subsystem coordinates with the Gorouter to remove instances from its IP table during disposal, but there might be some requests in flight during the shutdown event.

   Your application design should accommodate such transient failures.

5. Let your load test complete, or terminate it by Ctrl+C.

Wrap up

Review the Availability slides about how processes are monitored and recovered in Tanzu Application Service.

Now that you have completed the lab, you should be able to:

• Demonstrate how Tanzu Application Service handles availability.

Extras