[cs615asa] HW2 Required Arguments

[Jan Schaumann]

David Q Sevilla <dsevilla at stevens.edu> wrote:
 
> The manual page for ec2-backup-v1(1) has conflicting
> information, in that, the synopsis indicates that -v
> volume-id is a required option, but the options
> description indicates that the tool's behavior is to
> create a new volume if one is not provided. Is the
> latter interpretation a mistaken carry-over from the
> final version of this assignment

Yes, that's what it is.

I've updated the manual page.  Your program will not
create a volume.

> Also, I am kind of confused about how to handle
> regions and availability zones. Does it make sense
> to switch the AMI that I spin an instance out of
> based on the region / availability zone of the given
> volume?

Yes.  Given that the user provides the volume, you
will need to handle the case that the volume is in a
region your preferred instance is not available in.

You have a few options:

- only accept volumes in a single region and fail out
  if the given volume is not in the specified region
  (this is not very nice for the user, but very easy
  for you to handle)

- accept volumes in any region; for this, you may want
  to keep a mapping of AMIs to regions so that you can
  spin up an instance based on the given volume's
  region
  (this is much nicer for the user, and only
  marginally more complicated for you)

The manual page does not specify any restrictions on
the volume, so the user is reasonable to expect that
any volume in any region can be specified.

In either case, your program needs to handle any
failures gracefully and generate meaningful error
messages to the user.

-Jan