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Session 4: Randomize the generation of viruses with Step Functions

For the moment, we scheduled the creation of one virus every minute. It is slow, but the rate and cron scheduling expressions does not allow shorter frequencies! And even if it did, it would be nice to have some randomization...

We can do that thanks to EventBridge and Step Functions! Our goal is the make the scheduled lambda send 3 EventBridge messages every minute. Each message will launch a Step Function that will wait a random amount of time between 0 and 60s before creating a virus.

Deploy your first Event Bus and Step Function

Checkout session-4 branch

git checkout session-4-v2
  • Notice the new event-bridge.ts in the ressource folder
  • Add it to the ressources in the serverless.ts (end of file)
  • Give your lambdas the right to dispatch messages on this event bus by uncommenting the correct blocks in the provider section of the serverless.ts.
  • Run yarn and deploy your stack.
cd backend
yarn
sls deploy

Now, it's your turn 💪

  • Replace the requestNothing lambda by a spreadVirus lambda that sends 3 events of type VIRUS_CREATION_REQUESTED in the dojo-serverless Event Bus
  • Rename the doNothing Step Function to have 3 steps:
    • A ChooseWaitTime state of Task type, which triggers a lambda returning a number of seconds to wait (random between 1 and 60)
    • A WaitXSeconds state of Wait type, that waits for the given number of seconds before triggering the next step (use the SecondsPath property)
    • A final CreateVirus state of Task type that calls the createVirus lambda

Done ? Nice work ! Don't forget to kill your stack by running serverless remove in the backend folder ! You just have created an app which trigger a lambda every minute! Don't forget it or it could be expensive ;)

To see final result, checkout master branch!