Notifications for successful or failed checkin

[aaron-pham]

Are you interested in adding text or email notifications using Amazon SNS?

I have a few friends using this checkin service with my frontend, and this is a highly requested feature. I may start working on this soon and will create a PR if interested!

[swtools0]

I think this is a great idea. Here's what I suggest:

1. Checkin succeeded notification: Create a new SNS topic to which the HandleScheduledCheckin function will publish messages upon successful checkin.
2. Checkin failed notification: Create an SQS DLQ processor lambda function which simply fires off an SNS "checkin failed" notification to a new checkin failed topic. This queue doesn't exist yet, but I'd really like to start triggering HandleScheduledCheckin from an SQS queue. Then, on any type of failure of the HandleScheduledCheckin function, we simply throw an error, the message goes to the DLQ, and the new queue processor lambda function is responsible for the message from there. In the future, we can even consider allowing HandleScheduledCheckin to retry a couple of times before the message goes to the DLQ.

In the meantime, I'll set up the aforementioned queue and DLQ

[swtools0]

#13 changes the flow to

ScheduleCheckin function -> trigger-scheduled-checkin-* rule -> SqsScheduledCheckinReadyQueue queue -> HandleScheduledCheckin function

When an error is thrown by HandleScheduledCheckin, the SQS message which triggered the invocation goes to SqsScheduledCheckinReadyDlq. So, to enable failure notifications, create a lambda queue consumer of SqsScheduledCheckinReadyDlq which fires off a notification to a new checkin failed SNS topic.