Error Handling


Very important!
Requires quite a bit of forethought and discipline
Your API should export sensible error codes and messages at all levels
All syscalls and other API calls should be checked for error codes and handled "correctly"
Sometimes failure modes aren't as easy as they appear
Example - if you try to deliver a piece of mail and it fails, do you
Stop delivering for that single attempt, and backoff?
Stop delivery for all mail to that host/MX, and backoff?
.. and then, how do you start delivery up again?