Hello Boyang, Thanks for the updated information. A few questions here:
1) Should the quorum-file also update to support multi-raft? 2) In the previous proposal, there's fields in the FetchQuorumRecords like latestDirtyOffset, is that dropped intentionally? 3) I think we also need to elaborate a bit more details regarding when to send metadata request and discover-brokers; currently we only discussed during bootstrap how these requests would be sent. I think the following scenarios would also need these requests 3.a) As long as a broker does not know the current quorum (including the leader and the voters), it should continue periodically ask other brokers via "metadata. 3.b) As long as a broker does not know all the current quorum voter's connections, it should continue periodically ask other brokers via "discover-brokers". 3.c) When the leader's fetch timeout elapsed, it should send metadata request. Guozhang On Wed, Jun 10, 2020 at 5:20 PM Boyang Chen <reluctanthero...@gmail.com> wrote: > Hey all, > > follow-up on the previous email, we made some more updates: > > 1. The Alter/DescribeQuorum RPCs are also re-structured to use multi-raft. > > 2. We add observer status into the DescribeQuorumResponse as we see it is a > low hanging fruit which is very useful for user debugging and reassignment. > > 3. The FindQuorum RPC is replaced with DiscoverBrokers RPC, which is purely > in charge of discovering broker connections in a gossip manner. The quorum > leader discovery is piggy-back on the Metadata RPC for the topic partition > leader, which in our case is the single metadata partition for the version > one. > > Let me know if you have any questions. > > Boyang > > On Tue, Jun 9, 2020 at 11:01 PM Boyang Chen <reluctanthero...@gmail.com> > wrote: > > > Hey all, > > > > Thanks for the great discussions so far. I'm posting some KIP updates > from > > our working group discussion: > > > > 1. We will be changing the core RPCs from single-raft API to multi-raft. > > This means all protocols will be "batch" in the first version, but the > KIP > > itself only illustrates the design for a single metadata topic partition. > > The reason is to "keep the door open" for future extensions of this piece > > of module such as a sharded controller or general quorum based topic > > replication, beyond the current Kafka replication protocol. > > > > 2. We will piggy-back on the current Kafka Fetch API instead of inventing > > a new FetchQuorumRecords RPC. The motivation is about the same as #1 as > > well as making the integration work easier, instead of letting two > similar > > RPCs diverge. > > > > 3. In the EndQuorumEpoch protocol, instead of only sending the request to > > the most caught-up voter, we shall broadcast the information to all > voters, > > with a sorted voter list in descending order of their corresponding > > replicated offset. In this way, the top voter will become a candidate > > immediately, while the other voters shall wait for an exponential > back-off > > to trigger elections, which helps ensure the top voter gets elected, and > > the election eventually happens when the top voter is not responsive. > > > > Please see the updated KIP and post any questions or concerns on the > > mailing thread. > > > > Boyang > > > > On Fri, May 8, 2020 at 5:26 PM Jun Rao <j...@confluent.io> wrote: > > > >> Hi, Guozhang and Jason, > >> > >> Thanks for the reply. A couple of more replies. > >> > >> 102. Still not sure about this. How is the tombstone issue addressed in > >> the > >> non-voter and the observer. They can die at any point and restart at an > >> arbitrary later time, and the advancing of the firstDirty offset and the > >> removal of the tombstone can happen independently. > >> > >> 106. I agree that it would be less confusing if we used "epoch" instead > of > >> "leader epoch" consistently. > >> > >> Jun > >> > >> On Thu, May 7, 2020 at 4:04 PM Guozhang Wang <wangg...@gmail.com> > wrote: > >> > >> > Thanks Jun. Further replies are in-lined. > >> > > >> > On Mon, May 4, 2020 at 11:58 AM Jun Rao <j...@confluent.io> wrote: > >> > > >> > > Hi, Guozhang, > >> > > > >> > > Thanks for the reply. A few more replies inlined below. > >> > > > >> > > On Sun, May 3, 2020 at 6:33 PM Guozhang Wang <wangg...@gmail.com> > >> wrote: > >> > > > >> > > > Hello Jun, > >> > > > > >> > > > Thanks for your comments! I'm replying inline below: > >> > > > > >> > > > On Fri, May 1, 2020 at 12:36 PM Jun Rao <j...@confluent.io> wrote: > >> > > > > >> > > > > 101. Bootstrapping related issues. > >> > > > > 101.1 Currently, we support auto broker id generation. Is this > >> > > supported > >> > > > > for bootstrap brokers? > >> > > > > > >> > > > > >> > > > The vote ids would just be the broker ids. "bootstrap.servers" > >> would be > >> > > > similar to what client configs have today, where "quorum.voters" > >> would > >> > be > >> > > > pre-defined config values. > >> > > > > >> > > > > >> > > My question was on the auto generated broker id. Currently, the > broker > >> > can > >> > > choose to have its broker Id auto generated. The generation is done > >> > through > >> > > ZK to guarantee uniqueness. Without ZK, it's not clear how the > broker > >> id > >> > is > >> > > auto generated. "quorum.voters" also can't be set statically if > broker > >> > ids > >> > > are auto generated. > >> > > > >> > > Jason has explained some ideas that we've discussed so far, the > >> reason we > >> > intentional did not include them so far is that we feel it is out-side > >> the > >> > scope of KIP-595. Under the umbrella of KIP-500 we should definitely > >> > address them though. > >> > > >> > On the high-level, our belief is that "joining a quorum" and "joining > >> (or > >> > more specifically, registering brokers in) the cluster" would be > >> > de-coupled a bit, where the former should be completed before we do > the > >> > latter. More specifically, assuming the quorum is already up and > >> running, > >> > after the newly started broker found the leader of the quorum it can > >> send a > >> > specific RegisterBroker request including its listener / protocol / > etc, > >> > and upon handling it the leader can send back the uniquely generated > >> broker > >> > id to the new broker, while also executing the "startNewBroker" > >> callback as > >> > the controller. > >> > > >> > > >> > > > >> > > > > 102. Log compaction. One weak spot of log compaction is for the > >> > > consumer > >> > > > to > >> > > > > deal with deletes. When a key is deleted, it's retained as a > >> > tombstone > >> > > > > first and then physically removed. If a client misses the > >> tombstone > >> > > > > (because it's physically removed), it may not be able to update > >> its > >> > > > > metadata properly. The way we solve this in Kafka is based on a > >> > > > > configuration (log.cleaner.delete.retention.ms) and we expect a > >> > > consumer > >> > > > > having seen an old key to finish reading the deletion tombstone > >> > within > >> > > > that > >> > > > > time. There is no strong guarantee for that since a broker could > >> be > >> > > down > >> > > > > for a long time. It would be better if we can have a more > reliable > >> > way > >> > > of > >> > > > > dealing with deletes. > >> > > > > > >> > > > > >> > > > We propose to capture this in the "FirstDirtyOffset" field of the > >> > quorum > >> > > > record fetch response: the offset is the maximum offset that log > >> > > compaction > >> > > > has reached up to. If the follower has fetched beyond this offset > it > >> > > means > >> > > > itself is safe hence it has seen all records up to that offset. On > >> > > getting > >> > > > the response, the follower can then decide if its end offset > >> actually > >> > > below > >> > > > that dirty offset (and hence may miss some tombstones). If that's > >> the > >> > > case: > >> > > > > >> > > > 1) Naively, it could re-bootstrap metadata log from the very > >> beginning > >> > to > >> > > > catch up. > >> > > > 2) During that time, it would refrain itself from answering > >> > > MetadataRequest > >> > > > from any clients. > >> > > > > >> > > > > >> > > I am not sure that the "FirstDirtyOffset" field fully addresses the > >> > issue. > >> > > Currently, the deletion tombstone is not removed immediately after a > >> > round > >> > > of cleaning. It's removed after a delay in a subsequent round of > >> > cleaning. > >> > > Consider an example where a key insertion is at offset 200 and a > >> deletion > >> > > tombstone of the key is at 400. Initially, FirstDirtyOffset is at > >> 300. A > >> > > follower/observer fetches from offset 0 and fetches the key at > offset > >> > 200. > >> > > A few rounds of cleaning happen. FirstDirtyOffset is at 500 and the > >> > > tombstone at 400 is physically removed. The follower/observer > >> continues > >> > the > >> > > fetch, but misses offset 400. It catches all the way to > >> FirstDirtyOffset > >> > > and declares its metadata as ready. However, its metadata could be > >> stale > >> > > since it actually misses the deletion of the key. > >> > > > >> > > Yeah good question, I should have put more details in my explanation > >> :) > >> > > >> > The idea is that we will adjust the log compaction for this raft based > >> > metadata log: before more details to be explained, since we have two > >> types > >> > of "watermarks" here, whereas in Kafka the watermark indicates where > >> every > >> > replica have replicated up to and in Raft the watermark indicates > where > >> the > >> > majority of replicas (here only indicating voters of the quorum, not > >> > counting observers) have replicated up to, let's call them Kafka > >> watermark > >> > and Raft watermark. For this special log, we would maintain both > >> > watermarks. > >> > > >> > When log compacting on the leader, we would only compact up to the > Kafka > >> > watermark, i.e. if there is at least one voter who have not replicated > >> an > >> > entry, it would not be compacted. The "dirty-offset" is the offset > that > >> > we've compacted up to and is communicated to other voters, and the > other > >> > voters would also compact up to this value --- i.e. the difference > here > >> is > >> > that instead of letting each replica doing log compaction > independently, > >> > we'll have the leader to decide upon which offset to compact to, and > >> > propagate this value to others to follow, in a more coordinated > manner. > >> > Also note when there are new voters joining the quorum who has not > >> > replicated up to the dirty-offset, of because of other issues they > >> > truncated their logs to below the dirty-offset, they'd have to > >> re-bootstrap > >> > from the beginning, and during this period of time the leader learned > >> about > >> > this lagging voter would not advance the watermark (also it would not > >> > decrement it), and hence not compacting either, until the voter(s) has > >> > caught up to that dirty-offset. > >> > > >> > So back to your example above, before the bootstrap voter gets to 300 > no > >> > log compaction would happen on the leader; and until later when the > >> voter > >> > have got to beyond 400 and hence replicated that tombstone, the log > >> > compaction would possibly get to that tombstone and remove it. Say > >> later it > >> > the leader's log compaction reaches 500, it can send this back to the > >> voter > >> > who can then also compact locally up to 500. > >> > > >> > > >> > > > > 105. Quorum State: In addition to VotedId, do we need the epoch > >> > > > > corresponding to VotedId? Over time, the same broker Id could be > >> > voted > >> > > in > >> > > > > different generations with different epoch. > >> > > > > > >> > > > > > >> > > > Hmm, this is a good point. Originally I think the "LeaderEpoch" > >> field > >> > in > >> > > > that file is corresponding to the "latest known leader epoch", not > >> the > >> > > > "current leader epoch". For example, if the current epoch is N, > and > >> > then > >> > > a > >> > > > vote-request with epoch N+1 is received and the voter granted the > >> vote > >> > > for > >> > > > it, then it means for this voter it knows the "latest epoch" is N > + > >> 1 > >> > > > although it is unknown if that sending candidate will indeed > become > >> the > >> > > new > >> > > > leader (which would only be notified via begin-quorum request). > >> > However, > >> > > > when persisting the quorum state, we would encode leader-epoch to > >> N+1, > >> > > > while the leaderId to be the older leader. > >> > > > > >> > > > But now thinking about this a bit more, I feel we should use two > >> > separate > >> > > > epochs, one for the "lates known" and one for the "current" to > pair > >> > with > >> > > > the leaderId. I will update the wiki page. > >> > > > > >> > > > > >> > > Hmm, it's kind of weird to bump up the leader epoch before the new > >> leader > >> > > is actually elected, right. > >> > > > >> > > > >> > > > > 106. "OFFSET_OUT_OF_RANGE: Used in the FetchQuorumRecords API to > >> > > indicate > >> > > > > that the follower has fetched from an invalid offset and should > >> > > truncate > >> > > > to > >> > > > > the offset/epoch indicated in the response." Observers can't > >> truncate > >> > > > their > >> > > > > logs. What should they do with OFFSET_OUT_OF_RANGE? > >> > > > > > >> > > > > > >> > > > I'm not sure if I understand your question? Observers should still > >> be > >> > > able > >> > > > to truncate their logs as well. > >> > > > > >> > > > > >> > > Hmm, I thought only the quorum nodes have local logs and observers > >> don't? > >> > > > >> > > > 107. "The leader will continue sending BeginQuorumEpoch to each > >> known > >> > > > voter > >> > > > > until it has received its endorsement." If a voter is down for a > >> long > >> > > > time, > >> > > > > sending BeginQuorumEpoch seems to add unnecessary overhead. > >> > Similarly, > >> > > > if a > >> > > > > follower stops sending FetchQuorumRecords, does the leader keep > >> > sending > >> > > > > BeginQuorumEpoch? > >> > > > > > >> > > > > >> > > > Regarding BeginQuorumEpoch: that is a good point. The > >> > begin-quorum-epoch > >> > > > request is for voters to quickly get the new leader information; > >> > however > >> > > > even if they do not get them they can still eventually learn about > >> that > >> > > > from others via gossiping FindQuorum. I think we can adjust the > >> logic > >> > to > >> > > > e.g. exponential back-off or with a limited num.retries. > >> > > > > >> > > > Regarding FetchQuorumRecords: if the follower sends > >> FetchQuorumRecords > >> > > > already, it means that follower already knows that the broker is > the > >> > > > leader, and hence we can stop retrying BeginQuorumEpoch; however > it > >> is > >> > > > possible that after a follower sends FetchQuorumRecords already, > >> > suddenly > >> > > > it stops send it (possibly because it learned about a higher epoch > >> > > leader), > >> > > > and hence this broker may be a "zombie" leader and we propose to > use > >> > the > >> > > > fetch.timeout to let the leader to try to verify if it has already > >> been > >> > > > stale. > >> > > > > >> > > > > >> > > It just seems that we should handle these two cases in a consistent > >> way? > >> > > > >> > > Yes I agree, on the leader's side, the FetchQuorumRecords from a > >> follower > >> > could mean that we no longer needs to send BeginQuorumEpoch anymore > --- > >> and > >> > it is already part of our current implementations in > >> > https://github.com/confluentinc/kafka/commits/kafka-raft > >> > > >> > > >> > > Thanks, > >> > > > >> > > Jun > >> > > > >> > > > > >> > > > > > >> > > > > Jun > >> > > > > > >> > > > > On Wed, Apr 29, 2020 at 8:56 PM Guozhang Wang < > wangg...@gmail.com > >> > > >> > > > wrote: > >> > > > > > >> > > > > > Hello Leonard, > >> > > > > > > >> > > > > > Thanks for your comments, I'm relying in line below: > >> > > > > > > >> > > > > > On Wed, Apr 29, 2020 at 1:58 AM Wang (Leonard) Ge < > >> > w...@confluent.io> > >> > > > > > wrote: > >> > > > > > > >> > > > > > > Hi Kafka developers, > >> > > > > > > > >> > > > > > > It's great to see this proposal and it took me some time to > >> > finish > >> > > > > > reading > >> > > > > > > it. > >> > > > > > > > >> > > > > > > And I have the following questions about the Proposal: > >> > > > > > > > >> > > > > > > - How do we plan to test this design to ensure its > >> > correctness? > >> > > Or > >> > > > > > more > >> > > > > > > broadly, how do we ensure that our new ‘pull’ based model > >> is > >> > > > > > functional > >> > > > > > > and > >> > > > > > > correct given that it is different from the original RAFT > >> > > > > > implementation > >> > > > > > > which has formal proof of correctness? > >> > > > > > > > >> > > > > > > >> > > > > > We have two planned verifications on the correctness and > >> liveness > >> > of > >> > > > the > >> > > > > > design. One is via model verification (TLA+) > >> > > > > > https://github.com/guozhangwang/kafka-specification > >> > > > > > > >> > > > > > Another is via the concurrent simulation tests > >> > > > > > > >> > > > > > > >> > > > > > >> > > > > >> > > > >> > > >> > https://github.com/confluentinc/kafka/commit/5c0c054597d2d9f458cad0cad846b0671efa2d91 > >> > > > > > > >> > > > > > - Have we considered any sensible defaults for the > >> > configuration, > >> > > > i.e. > >> > > > > > > all the election timeout, fetch time out, etc.? Or we > want > >> to > >> > > > leave > >> > > > > > > this to > >> > > > > > > a later stage when we do the performance testing, etc. > >> > > > > > > > >> > > > > > > >> > > > > > This is a good question, the reason we did not set any default > >> > values > >> > > > for > >> > > > > > the timeout configurations is that we think it may take some > >> > > > benchmarking > >> > > > > > experiments to get these defaults right. Some high-level > >> principles > >> > > to > >> > > > > > consider: 1) the fetch.timeout should be around the same scale > >> with > >> > > zk > >> > > > > > session timeout, which is now 18 seconds by default -- in > >> practice > >> > > > we've > >> > > > > > seen unstable networks having more than 10 secs of transient > >> > > > > connectivity, > >> > > > > > 2) the election.timeout, however, should be smaller than the > >> fetch > >> > > > > timeout > >> > > > > > as is also suggested as a practical optimization in > literature: > >> > > > > > https://www.cl.cam.ac.uk/~ms705/pub/papers/2015-osr-raft.pdf > >> > > > > > > >> > > > > > Some more discussions can be found here: > >> > > > > > > https://github.com/confluentinc/kafka/pull/301/files#r415420081 > >> > > > > > > >> > > > > > > >> > > > > > > - Have we considered piggybacking `BeginQuorumEpoch` with > >> the > >> > ` > >> > > > > > > FetchQuorumRecords`? I might be missing something obvious > >> but > >> > I > >> > > am > >> > > > > > just > >> > > > > > > wondering why don’t we just use the `FindQuorum` and > >> > > > > > > `FetchQuorumRecords` > >> > > > > > > APIs and remove the `BeginQuorumEpoch` API? > >> > > > > > > > >> > > > > > > >> > > > > > Note that Begin/EndQuorumEpoch is sent from leader -> other > >> voter > >> > > > > > followers, while FindQuorum / Fetch are sent from follower to > >> > leader. > >> > > > > > Arguably one can eventually realize the new leader and epoch > via > >> > > > > gossiping > >> > > > > > FindQuorum, but that could in practice require a long delay. > >> > Having a > >> > > > > > leader -> other voters request helps the new leader epoch to > be > >> > > > > propagated > >> > > > > > faster under a pull model. > >> > > > > > > >> > > > > > > >> > > > > > > - And about the `FetchQuorumRecords` response schema, in > >> the > >> > > > > `Records` > >> > > > > > > field of the response, is it just one record or all the > >> > records > >> > > > > > starting > >> > > > > > > from the FetchOffset? It seems a lot more efficient if we > >> sent > >> > > all > >> > > > > the > >> > > > > > > records during the bootstrapping of the brokers. > >> > > > > > > > >> > > > > > > >> > > > > > Yes the fetching is batched: FetchOffset is just the starting > >> > offset > >> > > of > >> > > > > the > >> > > > > > batch of records. > >> > > > > > > >> > > > > > > >> > > > > > > - Regarding the disruptive broker issues, does our pull > >> based > >> > > > model > >> > > > > > > suffer from it? If so, have we considered the Pre-Vote > >> stage? > >> > If > >> > > > > not, > >> > > > > > > why? > >> > > > > > > > >> > > > > > > > >> > > > > > The disruptive broker is stated in the original Raft paper > >> which is > >> > > the > >> > > > > > result of the push model design. Our analysis showed that with > >> the > >> > > pull > >> > > > > > model it is no longer an issue. > >> > > > > > > >> > > > > > > >> > > > > > > Thanks a lot for putting this up, and I hope that my > questions > >> > can > >> > > be > >> > > > > of > >> > > > > > > some value to make this KIP better. > >> > > > > > > > >> > > > > > > Hope to hear from you soon! > >> > > > > > > > >> > > > > > > Best wishes, > >> > > > > > > Leonard > >> > > > > > > > >> > > > > > > > >> > > > > > > On Wed, Apr 29, 2020 at 1:46 AM Colin McCabe < > >> cmcc...@apache.org > >> > > > >> > > > > wrote: > >> > > > > > > > >> > > > > > > > Hi Jason, > >> > > > > > > > > >> > > > > > > > It's amazing to see this coming together :) > >> > > > > > > > > >> > > > > > > > I haven't had a chance to read in detail, but I read the > >> > outline > >> > > > and > >> > > > > a > >> > > > > > > few > >> > > > > > > > things jumped out at me. > >> > > > > > > > > >> > > > > > > > First, for every epoch that is 32 bits rather than 64, I > >> sort > >> > of > >> > > > > wonder > >> > > > > > > if > >> > > > > > > > that's a good long-term choice. I keep reading about > stuff > >> > like > >> > > > > this: > >> > > > > > > > https://issues.apache.org/jira/browse/ZOOKEEPER-1277 . > >> > > Obviously, > >> > > > > > that > >> > > > > > > > JIRA is about zxid, which increments much faster than we > >> expect > >> > > > these > >> > > > > > > > leader epochs to, but it would still be good to see some > >> rough > >> > > > > > > calculations > >> > > > > > > > about how long 32 bits (or really, 31 bits) will last us > in > >> the > >> > > > cases > >> > > > > > > where > >> > > > > > > > we're using it, and what the space savings we're getting > >> really > >> > > is. > >> > > > > It > >> > > > > > > > seems like in most cases the tradeoff may not be worth it? > >> > > > > > > > > >> > > > > > > > Another thing I've been thinking about is how we do > >> > > > bootstrapping. I > >> > > > > > > > would prefer to be in a world where formatting a new Kafka > >> node > >> > > > was a > >> > > > > > > first > >> > > > > > > > class operation explicitly initiated by the admin, rather > >> than > >> > > > > > something > >> > > > > > > > that happened implicitly when you started up the broker > and > >> > > things > >> > > > > > > "looked > >> > > > > > > > blank." > >> > > > > > > > > >> > > > > > > > The first problem is that things can "look blank" > >> accidentally > >> > if > >> > > > the > >> > > > > > > > storage system is having a bad day. Clearly in the > non-Raft > >> > > world, > >> > > > > > this > >> > > > > > > > leads to data loss if the broker that is (re)started this > >> way > >> > was > >> > > > the > >> > > > > > > > leader for some partitions. > >> > > > > > > > > >> > > > > > > > The second problem is that we have a bit of a chicken and > >> egg > >> > > > problem > >> > > > > > > with > >> > > > > > > > certain configuration keys. For example, maybe you want > to > >> > > > configure > >> > > > > > > some > >> > > > > > > > connection security settings in your cluster, but you > don't > >> > want > >> > > > them > >> > > > > > to > >> > > > > > > > ever be stored in a plaintext config file. (For example, > >> SCRAM > >> > > > > > > passwords, > >> > > > > > > > etc.) You could use a broker API to set the > configuration, > >> but > >> > > > that > >> > > > > > > brings > >> > > > > > > > up the chicken and egg problem. The broker needs to be > >> > > configured > >> > > > to > >> > > > > > > know > >> > > > > > > > how to talk to you, but you need to configure it before > you > >> can > >> > > > talk > >> > > > > to > >> > > > > > > > it. Using an external secret manager like Vault is one > way > >> to > >> > > > solve > >> > > > > > > this, > >> > > > > > > > but not everyone uses an external secret manager. > >> > > > > > > > > >> > > > > > > > quorum.voters seems like a similar configuration key. In > >> the > >> > > > current > >> > > > > > > KIP, > >> > > > > > > > this is only read if there is no other configuration > >> specifying > >> > > the > >> > > > > > > quorum > >> > > > > > > > voter set. If we had a kafka.mkfs command, we wouldn't > need > >> > this > >> > > > key > >> > > > > > > > because we could assume that there was always quorum > >> > information > >> > > > > stored > >> > > > > > > > locally. > >> > > > > > > > > >> > > > > > > > best, > >> > > > > > > > Colin > >> > > > > > > > > >> > > > > > > > > >> > > > > > > > On Thu, Apr 16, 2020, at 16:44, Jason Gustafson wrote: > >> > > > > > > > > Hi All, > >> > > > > > > > > > >> > > > > > > > > I'd like to start a discussion on KIP-595: > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > >> > > > >> > > >> > https://cwiki.apache.org/confluence/display/KAFKA/KIP-595%3A+A+Raft+Protocol+for+the+Metadata+Quorum > >> > > > > > > > . > >> > > > > > > > > This proposal specifies a Raft protocol to ultimately > >> replace > >> > > > > > Zookeeper > >> > > > > > > > > as > >> > > > > > > > > documented in KIP-500. Please take a look and share your > >> > > > thoughts. > >> > > > > > > > > > >> > > > > > > > > A few minor notes to set the stage a little bit: > >> > > > > > > > > > >> > > > > > > > > - This KIP does not specify the structure of the > messages > >> > used > >> > > to > >> > > > > > > > represent > >> > > > > > > > > metadata in Kafka, nor does it specify the internal API > >> that > >> > > will > >> > > > > be > >> > > > > > > used > >> > > > > > > > > by the controller. Expect these to come in later > >> proposals. > >> > > Here > >> > > > we > >> > > > > > are > >> > > > > > > > > primarily concerned with the replication protocol and > >> basic > >> > > > > > operational > >> > > > > > > > > mechanics. > >> > > > > > > > > - We expect many details to change as we get closer to > >> > > > integration > >> > > > > > with > >> > > > > > > > > the controller. Any changes we make will be made either > as > >> > > > > amendments > >> > > > > > > to > >> > > > > > > > > this KIP or, in the case of larger changes, as new > >> proposals. > >> > > > > > > > > - We have a prototype implementation which I will put > >> online > >> > > > within > >> > > > > > the > >> > > > > > > > > next week which may help in understanding some details. > It > >> > has > >> > > > > > > diverged a > >> > > > > > > > > little bit from our proposal, so I am taking a little > >> time to > >> > > > bring > >> > > > > > it > >> > > > > > > in > >> > > > > > > > > line. I'll post an update to this thread when it is > >> available > >> > > for > >> > > > > > > review. > >> > > > > > > > > > >> > > > > > > > > Finally, I want to mention that this proposal was > drafted > >> by > >> > > > > myself, > >> > > > > > > > Boyang > >> > > > > > > > > Chen, and Guozhang Wang. > >> > > > > > > > > > >> > > > > > > > > Thanks, > >> > > > > > > > > Jason > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > -- > >> > > > > > > Leonard Ge > >> > > > > > > Software Engineer Intern - Confluent > >> > > > > > > > >> > > > > > > >> > > > > > > >> > > > > > -- > >> > > > > > -- Guozhang > >> > > > > > > >> > > > > > >> > > > > >> > > > > >> > > > -- > >> > > > -- Guozhang > >> > > > > >> > > > >> > > >> > > >> > -- > >> > -- Guozhang > >> > > >> > > > -- -- Guozhang
