[ZODB-Dev] replicated ZEO idea

[Toby Dickenson]

On Monday 16 Sep 2002 4:15 am, Anthony Baxter wrote:
> >>> Toby Dickenson wrote
> >
> > I have been thinking about the storages 'copyTransactionsFrom' method=
,
> > which uses another storages 'iterator' method to copy all of the
> > transactions from one storage to another. This is usually used for
> > transferring data between different storage implementations, but I th=
ink
> > this technique could also be used as the basis for a lightweight
> > replication option....
>
> Packing storage A would result in needing to re-sync the whole storage,
> wouldn't it?

You need to avoid specifying a 'pack age' for A that is shorter than your=
=20
inter-replication gap.

> What would happen if storage B (the target storage) got
> packed?

Nothing. Thats like throwing away your old backup tapes.

> It seems to me like the way to do this would be to make sure the normal
> clients of storage B are always in read-only mode...

Yes

> otherwise you're going
> to be in a potential world of pain...

Yes, this could get very bad if we are not careful.

The replication process needs to ensure that B has not forked since the=20
preceeding replication event.