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This directory/module contains the logic for each of out pollers and an abstraction for running them. Configured pollers also have their infrastructure generated automatically via CDK 🎉

Poller lambdas have their own SQS queues to facilitate long-polling and to allow invoking on a frequency faster than the once per minute allowed by CloudWatch/EventBridge rules.

Starting/Stopping a poller lambda in AWS

To kick-off (start) a poller in AWS, you should navigate to the corresponding SQS queue (in the SQS console) and click the Send and receive messages button, in the message body enter whatever value is useful for that poller (typically an id or timestamp for the polling to begin at).

To stop a poller in AWS, navigate to the Lambda, in the configuration reduce the reserved concurrency to zero (normally it's two). This should result in some throttling alarms for a few mins, before the queue item expires. After that the 'stalled' alarm should fire and stay in alarm until the poller is resumed.

Adding a new poller lambda

  1. add an entry to POLLERS_CONFIG in shared/pollers.ts, which allows you to specify, optionally...
    • idealFrequencyInSeconds if it's a fixed frequency poller (as opposed to long polling)
    • overrideLambdaMemoryMB should this specific poller lambda need more memory than the default (currently 128MB)
    • overrideLambdaTimeoutSeconds should this specific poller lambda need a different timeout than the default (currently 60s)
  2. add a new file in poller-lambdas/src/pollers which exports a named function with a satisfies LongPollFunction or satisfies FixedFrequencyPollFunction on the end. The initial implementation should be as minimal as possible, but does compile, so you can deploy to CODE to generate the secrets in Secrets Manager (which you can subsequently set to the real value).
  3. the TS compiler should enforce that you reference your new function at the bottom of poller-lambdas/src/index.ts (wrapped in pollerWrapper( ))
  4. deploy to CODE, to generate the secrets in Secrets Manager, which you should then populate with real value (ideally CODE & PROD should use different secrets, if the agency/supplier has provided)
  5. iteratively implement your poller, making use of the run command: 
    npm run dev -w poller-lambdas
    ...to run/test your poll logic locally.