[DGD]upgrading kernel library

[Felix A. Croes]

Two in one.

Geir Harald Hansen <geirhans at ifi.uio.no> wrote:

> > > Dworkin wrote:
> > Possible variants:
> > 
> >  - keep track of different issues of compiled objects, including their
> >    sources.
> >  - don't keep track of different issues; instead, ensure that only
> >    one issue exists of an object at any time by making the upgrade
> >    operation atomic.  Disallow destructing of lib objects that are
> >    still inherited other than by the upgrade operation.
>
> How can I make the upgrade operation atomic if I need to split it over
> several callouts to permit DGD to swap out objects during the upgrade?
> The recompilation of a non-inheritable could fail and leave separate
> versions of inheritables in existence.

You can't.  You would have to do it all on one thread to make the
operation atomic.


> Another thing, I suspend callouts.. Should I also somehow block all user
> input and block new logins while upgrading?  How?

You can block new connections by temporarily setting the login
timeout to -1.  You can block input on connections using
block_input() in /kernel/lib/connection.c.


Stephen Schmidt <schmidsj at union.edu> wrote:

>[...]
> 1) I gather that by "global upgrade" we mean that, when we
> update object A, we also want to update all objects B that
> inherit A, and probably update all clones of A and B also.
> Since this is not default behavior (by default, A's clones,
> B, and B's clones would keep the pre-upgrade behavior until
> they were reloaded) the mudlib has to keep track of everything
> that inherits A and systematically replace old code with
> new code. Is that about right, or have I missed a step?

You may not realize that with "upgrading" I mean something other
than "updating".  Global upgrading is the process of recompiling
a set of objects without destructing them first, allowing them
to retain state in the form of variables and callouts.  Of all
the LPC servers, only DGD has this capability.

However, it can only do so for one object (and all of its clones)
at a time, and only if the object is not inherited by another.
The division between inherited objects and other objects, enforced
by the kernel library, ensures that there always is a way to
upgrade any single object.  Global upgrading must coordinate
the process for a set of objects, usually all those that inherit
some specific object or objects.

Regards,
Dworkin

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