Re-send failed emails

[CarlosNZ]

Currently, if emails fail to send, they never get re-sent. The notification table keeps track of if the email send successfully, so we've got the information we need.

Just need to add a periodic scheduled task to check and re-attempt any failed ones, perhaps once a day I guess, and on server re-start.

[CarlosNZ]

Estimate: 4 hours

[CarlosNZ]

There's a few other considerations for this:

• How long do we keep trying? Cos eventually the email might become irrelevant -- e.g. if the user has already gone to the site on their own and made changes and re-submitted, then getting the email for the original request for changes would be confusing.
  • Is there any other ways to determine when to give up?
• We should probably send an email to Support or Admin letting them known that an email has failed.
• Need a way to suppress notifications if they've failed for reasons that will never change (e.g. invalid recipients). (Probably need another field in addition to "email_sent".)
• Probably want to add a "email_attempt_timestamp" field which will be useful in determine time limits etc.

[CarlosNZ]

Schema changes

On notification table:

• New column: "email_status", with possible enum values:
  • NULL -- initial state, will remain like this if no email is attempted (i.e configured not to, or no valid addresses)
  • "SENT" -- sent successfully
  • "PENDING" -- when first attempting to send email
  • "ERROR" -- after initial failure
  • "GIVEN_UP" -- after exceeding maxAttempts or maxAge -- won't try any more
• Remove "email_sent" field and migrate to new field: true -> "SENT", false -> "GIVEN_UP"
• New column "email_send_attempt_timestamps" which is an array of timestamps which we keep adding to (default: [])

New "scheduler"

• add to 'action' | 'cleanup' | 'backup' | 'archive' => "email"

New Server prefs:

• emailSchedule
• emailMaxAttempts (number)
• emailMaxAge (days)