[Nitro] OG RFC: Catching an early/fatal exception.

Mark Van De Vyver mvyver at gmail.com
Wed Sep 19 09:19:53 EDT 2007

Hi Devs,

George, now you'll understand why I had no idea about what the effect
of that last patch was :)
Also, try and uncover this without a reasonable debugger :)

You're writing a spec, an Og object is defined at the same 'level' as
the describe's.  'Og.start' is run.
The 'query' call in the first call to sql.rb:create_field_map,
generates an exception.
NOTE: We are within the 'unless map =
klass.instance_variable_get("@field_map")' branch
sql.rb:handle_sql_exception() is called and a new StoreException is raised.

That StoreException is never caught.
The Og.start returns silently.
There is still a connection open to the DB backend, the DB backend is untouched.
manager.rb:put_store is entered, @pool is undefined, and it is from
_here_ that we return to og.rb:start where the exception is _logged_,
but not raised.

So we've seen a fatal error, the spec never receives an exception -
just the Og.start returning 'nil', with a DB connection open and
classes still 'managed'.

Your hint that something is not right might be a later exception:
Error code:
Error message: database is locked(database is locked)

And off you go on that tangent :)
Anyway, I digress.....

1) Where should these exceptions be handled?
There are three places this exception could be handled:
 a) sql.rb:handle_sql_exception
 b) sql.rb:create_field_map
 c) manager.rb:put_store
 d) both a) and b)

Votes? Instructions?

2) What should be done with the DB connection and the manged classes?
>From my understanding, because
'klass.instance_variable_get("@field_map")' returned nil/false in
sql.rb:create_field_map we should really shutdown the DB connection,
unmanage the classes, and scream blue-murder.  The unmanage classes
step is because I think Og's manger doesn't like being given the same
class twice - but this might be an impression left from the OGTABLE
warning just patched?  Anyway, safety first, and I'd vote for
something like the following somewhere (where?) in 1 d):
        if manager.close_store == nil && manager.unmanage_classes == []
          raise <SomeSeriousException>

Comments _please_


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