Hi Murali, Thanks for your response. AS1: Thanks for the performance information. Adding this into the KIP is definitely helpful in the motivation.
AS2: Thanks. Sounds good to me. AS3: HIGH and MEDIUM is fine with me, but my suggestion for LOW was because I think it will be rare for people to adjust the per-group config. It's a small point and happy for you to choose. Thanks, Andrew On 2026/07/16 21:12:58 Muralidhar Basani via dev wrote: > Thanks Sushant & Andrew. > > AS1 > On performance testing so far: > > I ran a test on a local 4.3 cluster to see how big the snapshot related > records actually are. > > +++++++++++ > config_value,record_count,snapshot_bytes,update_bytes,snapshot_count,update_count,snapshot_byte_ratio,avg_update_bytes,avg_snapshot_bytes,updates_per_20mb,cliff_ratio_vs_N,broker_restart_load_secs > 50,200000,1284,51561,8,337,0.024,153.0,160.5,137069,2741.4,3 > 100,200000,592,52206,4,339,0.011,154.0,148.0,136179,1361.8,3 > 200,200000,592,52360,4,340,0.011,154.0,148.0,136179,680.9,4 > 300,200000,592,52514,4,341,0.011,154.0,148.0,136179,453.9,4 > 500,200000,592,52206,4,339,0.011,154.0,148.0,136179,272.4,4 > +++++++++++ > > (Note: update_count is low because acks were in-order. pls see the caveat > below.) > > The main finding: each "update" record is tiny, about 154 bytes on average. > This stayed the same no matter what I changed, because these records only > store small (bookkeeping) data (which messages were delivered/acked), not > the message contents. > > Currently the old setting takes a snapshot every N update records (max > 500). The new setting takes a snapshot every 20 MB. Since each update is > only ~154 bytes, 20 MB works out to about 136,000 updates between snapshots. > > So when we eventually remove the old config, a group that used to snapshot > every 500 updates would instead snapshot every ~136,000, roughly ~270× less > often at the old maximum of 500, and even more dramatic at lower settings > (up to ~2700× at N=50). Fewer snapshots means recovery after a restart > takes longer and more log is kept on disk before cleanup, because there are > more update records to replay before reaching a snapshot. It does not > affect throughput. > > In my test, the consumer acknowledged messages in order, so 200,000 > messages collapsed into only ~340 update records. That was enough to > measure the size of an update, but it did not trigger the snapshot limits, > so restart time stayed flat (~3–4s) in every run. To properly measure the > recovery-time difference, I'll use a consumer that acknowledges out of > order, which produces many more (and larger) update records and actually > exercises the snapshot limits, then compare restart time and on-disk log > size at the old vs. new settings. > > Agree, the new code does a little extra work per update (one more counter, > plus measuring each record's size). I'll benchmark that against trunk > during impl, before merge. I will add a performance investigation note to > the KIP's Test Plan to capture this. > > AS2 > > Good point. The name I proposed > (share.coordinator.snapshot.update.bytes.per.snapshot) was derived from the > existing config and swapped "records" for "bytes". > > But this bytes-based design is modeled on > metadata.log.max.record.bytes.between.snapshots, so happy to rename. > I can rename both configs: > > - broker: share.coordinator.snapshot.update.bytes.per.snapshot to > share.coordinator.max.record.bytes.between.snapshots > - per-group: share.snapshot.update.bytes.per.snapshot to > share.max.record.bytes.between.snapshots > > AS3 > > Broker-level HIGH: agree > Group-level LOW: I see the reasoning, but every existing per-group config > in GroupConfig currently is MEDIUM. > (including the other share.* group configs like > share.record.lock.duration.ms). So LOW would make this the only LOW group > config. Slight lean toward MEDIUM for consistency, but no strong objection > to LOW. > > Pls let me know your thoughts. > > Thanks, > Murali > > On Thu, Jul 16, 2026 at 3:55 PM Andrew Schofield <[email protected]> > wrote: > > > Hi Murali, > > Thanks for the KIP. I understand the proposal. > > > > AS1: What performance testing have you done to validate whether there is a > > performance impact due to this change? When we get to the point of removing > > the deprecated configuration, there is a potential behavioural cliff which > > we should have investigated before we get there. > > > > AS2: Is there any reason why you did not follow a similar naming scheme as > > the existing metadata log configs, such as > > share.coordinator.max.record.bytes.between.snapshots? > > > > AS3: I suggest that the broker-level config would be HIGH and the > > group-level config would be LOW importance. > > > > Thanks, > > Andrew > > > > On 2026/07/16 05:13:29 Sushant Mahajan wrote: > > > Thanks for the change. > > > > > > All comments from my side are addressed. > > > > > > Regards, > > > Sushant Mahajan > > > > > > On Wed, 15 Jul 2026, 00:37 Muralidhar Basani via dev, < > > [email protected]> > > > wrote: > > > > > > > Thanks Sushanth. > > > > > > > > I updated KIP to remove the module dependency, create a helper > > interface in > > > > share-coordinator, and add a new metric. > > > > Please take a look. > > > > > > > > Thanks, > > > > Murali > > > > > > > > On Mon, Jul 13, 2026 at 5:39 PM Sushant Mahajan <[email protected]> > > > > wrote: > > > > > > > > > Hi, > > > > > Thanks for the response. > > > > > > > > > > Regarding > > > > > > > > > > sm01 - I would prefer not a add group coordinator dependency on share > > > > > coordinator. Thats why we created coordinator-common. > > > > > > > > > > Could we instead create a helper interface in share-coordinator to > > access > > > > > the relevant configs and pass the impl from BrokerServer (which has > > > > access > > > > > to relevant group config managers) to the share coordinator service? > > > > > > > > > > sm04 - yes, lets add that one. > > > > > > > > > > Rest of the answers are good. > > > > > > > > > > Regards, > > > > > Sushant Mahajan > > > > > > > > > > On Fri, 10 Jul 2026, 22:55 Muralidhar Basani via dev, < > > > > > [email protected]> > > > > > wrote: > > > > > > > > > > > Thanks again Sushant for the nice review. > > > > > > > > > > > > sm01 > > > > > > > > > > > > True. share-coordinator has no compile dependency on > > group-coordinator. > > > > > The > > > > > > KIP adds implementation project(':group-coordinator') to the > > > > > > share-coordinator build. There is no cyclic dep. > > > > > > > > > > > > ShareGroupConfigProvider gets a new accessor > > > > > > snapshotUpdateBytesPerSnapshotOrDefault(groupId, brokerDefault) > > > > > > ShareCoordinatorShard.Builder gets a new setter > > > > > > withShareGroupConfigProvider(.....) and > > ShareCoordinatorService.Builder > > > > > > gets the same setter. > > > > > > With these, BrokerServer can now construct the provider and pass > > it in. > > > > > The > > > > > > shard can then communicate with the provider on both the write path > > > > > > (generateShareStateRecord) and the replay path > > (handleShareSnapshot), > > > > > > falling back to the broker-level default (when the group has no > > > > > override). > > > > > > > > > > > > sm02 > > > > > > > > > > > > Good point. A default value is not distinguishable from an explicit > > > > value > > > > > > via getLong() alone. > > > > > > > > > > > > I have updated KIP Public interfaces -> deprecated config section. > > > > > > 1. If share.coordinator.snapshot.update.bytes.per.snapshot is in > > > > > > originals() -> bytes mode. > > > > > > 2. Else if share.coordinator.snapshot.update.records.per.snapshot > > is in > > > > > > originals() -> records mode (deprecated path). > > > > > > 3. Else (neither explicitly set) -> bytes mode at the 20 mb > > default. > > > > > > 4. If both are in originals() -> bytes mode wins and a warn is > > logged. > > > > > > > > > > > > This resolution happens once at startup in ShareCoordinatorConfig, > > not > > > > > > per-record. > > > > > > > > > > > > sm03 > > > > > > > > > > > > Cluster-roll backward compatibility > > > > > > > > > > > > During a rolling upgrade, yes brokers run mixed versions. Each > > broker's > > > > > > shard independently decides snapshot cadence, from its own local > > > > config. > > > > > A > > > > > > newer broker replaying records written by an older broker (or > > other way > > > > > > around) interprets them identically. So cadence may differ in the > > > > > mid-roll, > > > > > > but there is no on-disk format change and no coordination required > > I > > > > > see. A > > > > > > broker that hasn't yet had the new config set, will simply use the > > 20 > > > > MB > > > > > > default. I have updated Compatibility section in the kip. > > > > > > > > > > > > sm04 > > > > > > > > > > > > Currently the records-based didn't have any. A new metric > > > > > > bytes-since-snapshot (per __share_group_state partition) could be > > > > useful. > > > > > > Let me know if this is good, or any other suggestion? > > > > > > > > > > > > sm05 > > > > > > > > > > > > The threshold is measured on uncompressed serialized record bytes. > > > > There > > > > > is > > > > > > a little note in the kip mentioning that "Compression is not > > accounted > > > > > for; > > > > > > the threshold is on uncompressed record bytes." > > > > > > Actually share.coordinator.state.topic.compression.codec defaults > > to > > > > > NONE. > > > > > > So by default on-disk bytes equal the measured bytes; So it will > > not > > > > > affect > > > > > > the 20mb limit, in default deploymnt. > > > > > > > > > > > > Thanks, > > > > > > Murali > > > > > > > > > > > > On Thu, Jul 9, 2026 at 7:25 PM Sushant Mahajan < > > [email protected]> > > > > > > wrote: > > > > > > > > > > > > > Hi, > > > > > > > Went over the new byte based approach. > > > > > > > > > > > > > > Few questions: > > > > > > > > > > > > > > sm01 - currently share coord module does not depend on the group > > > > > > > coordinator. Could you detail out how the new group level config > > will > > > > > be > > > > > > > injected in the share coordinator? > > > > > > > > > > > > > > sm02 - since we have default defined as 20MB, how to > > differentiate > > > > > > between > > > > > > > older update count set vs byte limit set? The kip mentions if set > > > > byte > > > > > > > level will be honored. How to determine set vs default? > > > > > > > > > > > > > > sm03 - could you drop a line about backward compatibility in > > case of > > > > > > > cluster roll? > > > > > > > > > > > > > > sm04 - should we also add any new metrics? > > > > > > > > > > > > > > sm05 - do measurements need to take compression into account? > > Does it > > > > > > > affect the 20 MB limit? > > > > > > > > > > > > > > Regards, > > > > > > > Sushant Mahajan > > > > > > > > > > > > > > On Sun, 14 Jun 2026, 18:50 Muralidhar Basani via dev, < > > > > > > > [email protected]> > > > > > > > wrote: > > > > > > > > > > > > > > > Hi, > > > > > > > > Apologies for the delayed reply. > > > > > > > > > > > > > > > > Sushant, thanks for the reply. Just to flag the KIP has > > switched to > > > > > > > > bytes-based control (pls see below), which supersedes most of > > the > > > > > > > > records-based tuning discussion. > > > > > > > > > > > > > > > > Chia, thank you for the suggestions. Both the points are now > > in the > > > > > > KIP: > > > > > > > > - chia_00: broker floor stays at 0 (no compatibility break) > > > > > > > > - chia_01: bytes-based control adopted, matching > > > > > > > > metadata.log.max.record.bytes.between.snapshots, default 20 MB. > > > > > > > > > > > > > > > > Records-based config will be marked as deprecated. > > > > > > > > > > > > > > > > Updated KIP: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-1349%3A+Bytes-based+configurable+snapshot+frequency+for+share+groups > > > > > > > > > > > > > > > > Please take a look again. > > > > > > > > > > > > > > > > Thanks, > > > > > > > > Murali > > > > > > > > > > > > > > > > On Thu, Jun 11, 2026 at 5:20 AM Chia-Ping Tsai < > > > > [email protected]> > > > > > > > > wrote: > > > > > > > > > > > > > > > > > hi > > > > > > > > > > > > > > > > > > chia_00: Changing the lower bound of the existing config is a > > > > > > > > > compatibility issue. If we want to avoid heavy snapshots, we > > can > > > > > set > > > > > > > the > > > > > > > > > lower bound of the new group-level configuration to 200 by > > > > default. > > > > > > > Also, > > > > > > > > > the broker-level constraint should be changed to 0-1000, > > which > > > > > won’t > > > > > > > > bring > > > > > > > > > compatibility issues > > > > > > > > > > > > > > > > > > chia_01: Have you considered using bytes instead of records > > as > > > > the > > > > > > > > > controlled unit? > > > > > > > > > > > > > > > > > > > > > > > > > > > On 2026/05/22 19:30:38 Muralidhar Basani via dev wrote: > > > > > > > > > > Hi all, > > > > > > > > > > > > > > > > > > > > I would like to start a discussion on KIP-1349, which > > allows > > > > > > > > configurable > > > > > > > > > > snapshot frequency of share groups. > > > > > > > > > > > > > > > > > > > > KIP : > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-1349%3A+Configurable+snapshot+frequency+for+share+groups > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > Murali > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
