Thanks Bill for the updated wiki. I have a couple of more comments:
1. Setting StateRestoreListener on the KafkaStreams granularity may not be
sufficient, as in the listener callback we do not which store it is
restoring right now: if the topic is a changelog topic then from the
`TopicPartition` we may be able to infer the state store name, but if the
topic is the source topic read as a KTable then we may not know which store
it is restoring right now; plus forcing users to infer the state store name
from the topic partition name would not be intuitive as well. Plus for
different stores the listener may be implemented differently, and setting a
global listener would force users to branch on the topic-partition names,
similarly to what we did in the global timestamp extractor. On the other
hand, I also agree that setting the listener on the per-store granularity
may be a bit cumbersome since if users want to override it on a specific
store it needs to expose some APIs maybe at StateStoreSupplier. So would
love to hear other people's opinions.
If we think that different implemented restoring callback may be less
common, then I'd suggest at least replace the `TopicPartition` parameter
with the `String` store name and the `TaskId`?
2. I think we can pass in the `long endOffset` in the `onRestoreStart`
function as well, as we will have read the endOffset already by then;
otherwise users can still not be able to track the restoration progress
(e.g. how much percentage I have been restoring so far, to estimate on how
long I still need to wait).
Guozhang
On Wed, Jun 14, 2017 at 12:25 PM, Bill Bejeck <bbej...@gmail.com> wrote:
> Eno,
>
> Thanks for the comments.
>
> 1. As for having both restore and restoreAll, I kept the restore method for
> backward compatibility as that is what is used by current implementing
> classes. However as I think about it makes things cleaner to have a single
> restore method taking a collection. I'll wait for others to weigh in, but
> I'm leaning towards having a single restore method.
>
> 2. The "onBatchRestored" method is for keeping track of the restore process
> as we load records from each poll request.
>
> For example if the change log contained 5000 records and
> MAX_POLL_RECORDS is set to 1000, the "onBatchRestored" method would get
> called 5 times each time with the ending offset of the last record in the
> batch and the count of the batch. I'll update the KIP to add comments
> above the interface methods.
>
>
> Thanks,
> Bill
>
>
> On Wed, Jun 14, 2017 at 11:49 AM, Eno Thereska <eno.there...@gmail.com>
> wrote:
>
> > Thanks Bill,
> >
> > A couple of questions:
> >
> >
> 1. why do we need both restore and restoreAll, why can't we just have one,
> > that takes a collection (i.e., restore all)? Are there cases when people
> > want to restore one at a time? In that case, they could still use
> > restoreAll with just 1 record in the collection right?
> >
> > 2. I don't quite get "onBatchRestored". Could you put a small comment on
> > top of all three methods. An example might help here.
> >
> > Thanks
> > Eno
> >
> >
> > > On 8 Jun 2017, at 18:05, Bill Bejeck <bbej...@gmail.com> wrote:
> > >
> > > Guozhang, Damian thanks for the comments.
> > >
> > > Giving developers the ability to hook into StateStore recovery phases
> was
> > > part of my original intent. However the state the KIP is in now won't
> > > provide this functionality.
> > >
> > > As a result I'll be doing a significant revision of KIP-167. I'll be
> > sure
> > > to incorporate all your comments in the new revision.
> > >
> > > Thanks,
> > > Bill
> > >
> > > On Wed, Jun 7, 2017 at 5:24 AM, Damian Guy <damian....@gmail.com>
> wrote:
> > >
> > >> I'm largely in agreement with what Guozhang has suggested, i.e.,
> > >> StateRestoreContext shouldn't have any setters on it and also need to
> > have
> > >> the end offset available such that people can use it derive progress.
> > >> Slightly different, maybe the StateRestoreContext interface could be:
> > >>
> > >> long beginOffset()
> > >> long endOffset()
> > >> long currentOffset()
> > >>
> > >> One further thing, this currently doesn't provide developers the
> > ability to
> > >> hook into this information if they are using the built-in StateStores.
> > Is
> > >> this something we should be considering?
> > >>
> > >>
> > >> On Tue, 6 Jun 2017 at 23:32 Guozhang Wang <wangg...@gmail.com> wrote:
> > >>
> > >>> Thanks for the updated KIP Bill, I have a couple of comments:
> > >>>
> > >>> 1) I'm assuming beginRestore / endRestore is called only once per
> store
> > >>> throughout the whole restoration process, and restoreAll is called
> per
> > >>> batch. In that case I feel we can set the StateRestoreContext as a
> > second
> > >>> parameter in restoreAll and in endRestore as well, and let the
> library
> > to
> > >>> set the corresponding values instead and only let users to read
> (since
> > >> the
> > >>> collection of key-value pairs do not contain offset information
> anyways
> > >>> users cannot really set the offset). The "lastOffsetRestored" would
> be
> > >> the
> > >>> starting offset when called on `beginRestore`.
> > >>>
> > >>> 2) Users who wants to implement their own batch restoration callbacks
> > >> would
> > >>> now need to implement both `restore` and `restoreAll` while they
> either
> > >> let
> > >>> `restoreAll` to call `restore` or implement the logic in `restoreAll`
> > >> only
> > >>> and never call `restore`. Maybe we can provide two abstract impl of
> > >>> BatchingStateRestoreCallbacks which does beginRestore / endRestore as
> > >>> no-ops, with one callback implementing `restoreAll` to call abstract
> > >>> `restore` while the other implement `restore` to throw "not supported
> > >>> exception" and keep `restoreAll` abstract.
> > >>>
> > >>> 3) I think we can also return the "offset limit" in
> > StateRestoreContext,
> > >>> which is important for users to track the restoration progress since
> > >>> otherwise they could not tell how many percent of restoration has
> > >>> completed. I.e.:
> > >>>
> > >>> public interface BatchingStateRestoreCallback extends
> > >> StateRestoreCallback
> > >>> {
> > >>>
> > >>> void restoreAll(Collection<KeyValue<byte[], byte []>> records,
> > >>> StateRestoreContext
> > >>> restoreContext);
> > >>>
> > >>> void beginRestore(StateRestoreContext restoreContext);
> > >>>
> > >>> void endRestore(StateRestoreContext restoreContext);
> > >>> }
> > >>>
> > >>> public interface StateRestoreContext {
> > >>>
> > >>> long lastOffsetRestored();
> > >>>
> > >>> long endOffsetToRestore();
> > >>>
> > >>> int numberRestored();
> > >>> }
> > >>>
> > >>>
> > >>> Guozhang
> > >>>
> > >>>
> > >>>
> > >>> On Fri, Jun 2, 2017 at 9:16 AM, Bill Bejeck <bbej...@gmail.com>
> wrote:
> > >>>
> > >>>> Guozhang, Matthias,
> > >>>>
> > >>>> Thanks for the comments. I have updated the KIP, (JIRA title and
> > >>>> description as well).
> > >>>>
> > >>>> I had thought about introducing a separate interface altogether, but
> > >>>> extending the current one makes more sense.
> > >>>>
> > >>>> As for intermediate callbacks based on time or number of records, I
> > >> think
> > >>>> the latest update to the KIP addresses this point of querying for
> > >>>> intermediate results, but it would be per batch restored.
> > >>>>
> > >>>> Thanks,
> > >>>> Bill
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>> On Fri, Jun 2, 2017 at 8:36 AM, Jim Jagielski <j...@jagunet.com>
> > wrote:
> > >>>>
> > >>>>>
> > >>>>>> On Jun 2, 2017, at 12:54 AM, Matthias J. Sax <
> > >> matth...@confluent.io>
> > >>>>> wrote:
> > >>>>>>
> > >>>>>> With regard to backward compatibility, we should not change the
> > >>> current
> > >>>>>> interface, but add a new interface that extends the current one.
> > >>>>>>
> > >>>>>
> > >>>>> ++1
> > >>>>>
> > >>>>>
> > >>>>
> > >>>
> > >>>
> > >>>
> > >>> --
> > >>> -- Guozhang
> > >>>
> > >>
> >
> >
>
--
-- Guozhang
