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From Dale Harvey <d...@arandomurl.com>
Subject Re: Checkpointing on read only databases
Date Sun, 13 Apr 2014 17:46:57 GMT
We and couch dont have this or the opposite problem since the checkpoint is
recorded on both databases and only used if it matches

As for storing rev, do you mean storing the rev at the point of the stored
update_seq, then checking it matches before using the checkpoint? that
seems like it could work, with couchdb's deterministic revisions it would
be possible to trick the replicator into thinking its up to date, but thats
getting into a very niche edge case


On 13 April 2014 18:31, Calvin Metcalf <calvin.metcalf@gmail.com> wrote:

> Though currently we have the opposite problem right if we delete the target
> db? (this on me brain storming)
>
> Could we store last rev in addition to last seq?
> On Apr 13, 2014 1:15 PM, "Dale Harvey" <dale@arandomurl.com> wrote:
>
> > If the src database was to be wiped, when we restarted replication
> nothing
> > would happen until the source database caught up to the previously
> written
> > checkpoint
> >
> >    create A, write 5 documents
> >    replicate 5 documents A -> B, write checkpoint 5 on B
> >    destroy A
> >    write 4 documents
> >    replicate A -> B, pick up checkpoint from B and to ?since=5
> >    .. no documents written
> >
> >
> >
> https://github.com/pouchdb/pouchdb/blob/master/tests/test.replication.js#L771is
> > our test that covers it
> >
> >
> > On 13 April 2014 18:02, Calvin Metcalf <calvin.metcalf@gmail.com> wrote:
> >
> > > If we were to unilaterally switch to checkpoint on target what would
> > > happen, replication in progress would loose their place?
> > > On Apr 13, 2014 11:21 AM, "Dale Harvey" <dale@arandomurl.com> wrote:
> > >
> > > > So with checkpointing we write the checkpoint to both A and B and
> > verify
> > > > they match before using the checkpoint
> > > >
> > > > What happens if the src of the replication is read only?
> > > >
> > > > As far as I can tell couch will just checkout a
> checkpoint_commit_error
> > > and
> > > > carry on from the start, The only improvement I can think of is the
> > user
> > > > specifies they know the src is read only and to only use the target
> > > > checkpoint, we can 'possibly' make that happen automatically if the
> src
> > > > specifically fails the write due to permissions.
> > > >
> > >
> >
>

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