[DPC-5272] add additional logging to ecr-cleanup lambda

[lukey-luke]

🎫 Ticket

DPC-5272

🛠 Changes

• add additional logging statement at end of lambda_handler() to indicate lambda has completed
• add unit test to ensure completion message is emitted

ℹ️ Context

• This is intended as a low-lift effort to ensure that this lambda is running.
• This logging statement enables me to create new alerts on Splunk for ECR-cleanup to ensure logs are being emitted.
  • DPC Prod - ECR Cleanup Failed to Run
  • DPC Test - ECR Cleanup Failed to Run
  • NOTE: These are currently disabled and should not be enabled until terraform is updated to be a module which can be imported and monitored independently by each team (DPC-5296)
• See example of monitoring another lambda to ensure it's running: DPC Prod - Opt Out Import Failed to Run

🧪 Validation

• see test_lambda_function.py
  • pytest passes locally
• verified that log message shows up in Splunk from test environment:
  • Note: expect log messages to show up under /aws/lambda/<subscriber-team>-<env>-ecr-cleanup in the future (flagged in context section above)

[jdettmannnava]

Unsure why the low-effort version, when the ticket you wrote indicates much more effort?

[lukey-luke]

Unsure why the low-effort version, when the ticket you wrote indicates much more effort?

@jdettmannnava Good question — I scoped this small on purpose for a couple of reasons: first, to avoid stepping on your PR with a larger diff (#410), and second, because getting DPC-5296 done sooner is the real priority. Once that move to using a module is completed, DPC as well as other teams can benefit from independent monitoring of the shared lambda code.

[Jose-verdance]

LGTM!

[lukey-luke]

I made a couple updates to cover failures in the response for list_tasks() and batch_delete_images(). When there are failures "error" on the message will trigger the splunk alert conditions for "DPC Prod - ECR Cleanup Failure" or "DPC Test - ECR Cleanup Failure"