[c-lightning] Replicated backups

[ZmnSCPxj]

Good morning Christian,

> > > If the plugin dies at some point and `lightningd` auto-removes the hook,
> > > some queries will not get backed up. Some of those queries may update
> > > channels that end up not getting updated for a good while (maybe the
> > > other side just goes offline for a long while), so you cannot even know
> > > that you do not know of an update until too late.
> >
> > I figured in these scenarios you can start over from a new update
> > counter. The plugin would have to save uncommitted logs incase the
> > remote goes down.
>
> We should likely mandate that plugins with hooks registered should be
> treated as critical and we should die alongside the plugin in those
> cases.

There is always the possibility that a plugin dies before its hook gets registered.
In that case, `lightningd` cannot possibly have known that the plugin *should* have been hooked in, and cannot know it should die.
(admittedly this is a very unlikely edge case, but still --- if you are talking about a backup facility...)

This is why I suggested using a flag, to indicate "some plugin must have this hook registered, if not, die after all plugins have either given `getmanifest` or failed to start up".

Regards,
ZmnSCPxj