Thanks Jason, We would only return the metadata for the latest fetches. So, if someone wanted to use this to lazily maintain a client-side metadata map for all partitions, they'd have to store it separately and merge in new updates as they arrive.
This way: 1. We don't need to increase the complexity of the client by storing that metadata 2. Users will be able to treat all returned metadata as "fresh" without having to reason about the timestamps. 3. All parts of the returned ConsumerRecords object have the same lifecycle: all the data and metadata are the results of the most recent round of fetch responses that had not been previously polled. Does that seem sensible to you? I'll update the KIP to clarify this. Thanks, -John On Wed, 2020-12-16 at 10:29 -0800, Jason Gustafson wrote: > Hi John, > > Just one question. It wasn't very clear to me exactly when the metadata > would be returned in `ConsumerRecords`. Would we /always/ include the > metadata for all partitions that are assigned, or would it be based on the > latest fetches? > > Thanks, > Jason > > On Fri, Dec 11, 2020 at 4:07 PM John Roesler <vvcep...@apache.org> wrote: > > > Thanks, Guozhang! > > > > All of your feedback sounds good to me. I’ll update the KIP when I am able. > > > > 3) I believe it is the position after the fetch, but I will confirm. I > > think omitting position may render beginning and end offsets useless as > > well, which leaves only lag. That would be fine with me, but it also seems > > nice to supply this extra metadata since it is well defined and probably > > handy for others. Therefore, I’d go the route of specifying the exact > > semantics and keeping it. > > > > Thanks for the review, > > John > > > > On Fri, Dec 11, 2020, at 17:36, Guozhang Wang wrote: > > > Hello John, > > > > > > Thanks for the updates! I've made a pass on the KIP and also the POC PR, > > > here are some minor comments: > > > > > > 1) nit: "receivedTimestamp" -> it seems the metadata keep getting > > updated, > > > and we do not create a new object but just update the values in-place, so > > > maybe calling it `lastUpdateTimstamp` is better? > > > > > > 2) It will be great to verify in javadocs that the new API > > > "ConsumerRecords#metadata(): Map<TopicPartition, Metadata>" may return a > > > superset of TopicPartitions than the existing API that returns the data > > by > > > partitions, in case users assume their map key-entries would always be > > the > > > same. > > > > > > 3) The "position()" API of the call needs better clarification: is it the > > > current position AFTER the records are returned, or is it BEFORE the > > > records are returned? Personally I'd suggest we do not include it if it > > is > > > not used anywhere yet just to avoid possible misuage, but I'm fine if you > > > like to keep it still; in that case just clarify its semantics. > > > > > > > > > Other than that，I'm +1 on the KIP as well ! > > > > > > > > > Guozhang > > > > > > > > > On Fri, Dec 11, 2020 at 8:15 AM Walker Carlson <wcarl...@confluent.io> > > > wrote: > > > > > > > Thanks for the KIP! > > > > > > > > +1 (non-binding) > > > > > > > > walker > > > > > > > > On Wed, Dec 9, 2020 at 11:40 AM Bruno Cadonna <br...@confluent.io> > > wrote: > > > > > > > > > Thanks for the KIP, John! > > > > > > > > > > +1 (non-binding) > > > > > > > > > > Best, > > > > > Bruno > > > > > > > > > > On 08.12.20 18:03, John Roesler wrote: > > > > > > Hello all, > > > > > > > > > > > > There hasn't been much discussion on KIP-695 so far, so I'd > > > > > > like to go ahead and call for a vote. > > > > > > > > > > > > As a reminder, the purpose of KIP-695 to improve on the > > > > > > "task idling" feature we introduced in KIP-353. This KIP > > > > > > will allow Streams to offer deterministic time semantics in > > > > > > join-type topologies. For example, it makes sure that > > > > > > when you join two topics, that we collate the topics by > > > > > > timestamp. That was always the intent with task idling (KIP- > > > > > > 353), but it turns out the previous mechanism couldn't > > > > > > provide the desired semantics. > > > > > > > > > > > > The details are here: > > > > > > https://cwiki.apache.org/confluence/x/JSXZCQ > > > > > > > > > > > > Thanks, > > > > > > -John > > > > > > > > > > > > > > > > > > > > > > > > -- > > > -- Guozhang > > > > >
