Any advise on exception / error handling approaches/prinicip

Hi,

Can I ask for some advise re what the best practice is for handling
exceptions & errors through my rails code from the point of view of how
to
display them back to the user? Some items I’d love to be covered
include:

  • is the principle that ALL exceptions (even those the application might
    not
    to be able to do anything about) should be caught and then the
    application
    then decides what text and view .rhtml? Or should the approach be to
    allow
    exceptions to occur and the rails framework to then pass this to a
    general
    error page?

  • errors/exceptions that may occur in the action record / data layer -
    what
    categories of errors/exceptions here should be either (a) returned as
    call
    didn’t work or (b) exception. That is, from a best practice point of
    view
    are there 2 categories of errors/exceptions in the data layer that
    should be
    acknowledged and handed differently in terms of how they are captured
    and
    passed back to the controller layer? (e.g. catch exception and process
    in
    model code and return appropriate response, OR through to an approach
    like:
    any issue that occur in the rails or database itself that get raised as
    an
    exception, don’t try to catch them, but let the exception be thrown back
    to
    the controller (at which point my first question kicks in re whether the
    controller should catch these areas and process or let the rails
    framework
    through to a general application error page)

  • where can I see all the possible errors like RoutingError,
    UnknownAction…? Is it enough to stick with the standard rails
    rescue_action_in_public method (see below)?

    def rescue_action_in_public(exception) #:doc:
      case exception
        when RoutingError, UnknownAction
          render_text(IO.read(File.join(RAILS_ROOT, 'public', 
    

‘404.html’)),
“404 Not Found”)
else
render_text(IO.read(File.join(RAILS_ROOT, ‘public’,
‘500.html’)),
“500 Internal Error”)
end
end

  • allocation of specific error numbers against each specific error the
    application catches/can create?

  • separate log file for error details in a specific parseable/setout
    format
    (e.g. for a paging system to reference) in additional to standard log
    file
    which contains various other details like rails SQL / timing
    information, or
    full exception stack details

  • an action’s render - this won’t be reached if I through an exception
    before this point or there is a rails exception I don’t catch before
    this
    point no?

  • anything else related to monitoring application health?

Thanks
Greg

[bump - still very keen to hear back if possible:) ]

dont let the user see the raw error and give them a nice page,
explaining that it aint their fault. (most users will blame there
self’s)

There is also a nice plugin out there that will email every time a error
occur’s

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