I made a PR with a tweak to Jun's/Becket's proposal: https://github.com/apache/kafka/pull/1484
It just tweaks the fetch behavior specifically for replicas fetching from the __consumer_offsets topic when the fetcher's "replica.fetch.max.bytes" is less than the __consumer_offset leader's "message.max.bytes" to take the max of the two. I'm honestly not that happy with this solution, as I'd rather not change the "replica.fetch.max.bytes" config from being a limit to a recommendation. I'd definitely be happy to hear other alternatives! On Sun, May 29, 2016 at 1:57 PM, Onur Karaman <onurkaraman.apa...@gmail.com> wrote: > Sorry I know next to nothing about Kafka Connect. I didn't understand the > Kafka Connect / MM idea you brought up. Can you go into more detail? > > Otherwise I think our remaining options are: > - Jun's suggestion to bump up the KafkaConfig.messageMaxBytes for > __consumer_offsets topic and change the fetch behavior when message size is > larger than fetch size > - option 6: support sending the regex over the wire instead of the fully > expanded topic subscriptions. This should cut down the message size from > the subscription side. Again this only helps when pattern-based > subscriptions are done. > > minor correction to an earlier comment I made regarding the message size: > message size ~ sum(s_i + a_i for i in range [1, |C|]) > > On Thu, May 26, 2016 at 3:35 PM, Jason Gustafson <ja...@confluent.io> > wrote: > > > Hey Onur, > > > > Thanks for the investigation. It seems the conclusion is that the compact > > format helps, but perhaps not enough to justify adding a new assignment > > schema? I'm not sure there's much more room for savings unless we change > > something more fundamental in the assignment approach. We spent some time > > thinking before about whether we could let the consumers compute their > > assignment locally from a smaller set of information, but the difficulty > > (I'm sure you remember) is reaching consensus on topic metadata. Kafka > > Connect has a similar problem where all the workers need to agree on > > connector configurations. Since all configs are stored in a single topic > > partition, the approach we take there is to propagate the offset in the > > assignment protocol. Not sure if we could do something similar for MM... > > Anyway, it seems like the best workaround at the moment is Jun's initial > > suggestion. What do you think? > > > > -Jason > > > > On Wed, May 25, 2016 at 10:47 PM, Onur Karaman < > > onurkaraman.apa...@gmail.com > > > wrote: > > > > > I gave the topic index assignment trick a try against the same > > environment. > > > The implementation just changed the assignment serialization and > > > deserialization logic. It didn't change SyncGroupResponse, meaning it > > > continues to exclude the subscription from the SyncGroupResponse and > > > assumes the member has kept track of its last subscription. > > > > > > Assignment topic indexing with compression: > > > 1 consumer 34346 bytes > > > 5 consumers 177687 bytes > > > 10 consumers 331897 bytes > > > 20 consumers 572467 bytes > > > 30 consumers 811269 bytes > > > 40 consumers 1047188 bytes * the tipping point > > > 50 consumers 1290092 bytes > > > 60 consumers 1527806 bytes > > > 70 consumers 1769259 bytes > > > 80 consumers 2000118 bytes > > > 90 consumers 2244392 bytes > > > 100 consumers 2482415 bytes > > > > > > Assignment topic indexing without compression: > > > 1 consumer 211904 bytes > > > 5 consumers 677184 bytes > > > 10 consumers 1211154 bytes * the tipping point > > > 20 consumers 2136196 bytes > > > 30 consumers 3061238 bytes > > > 40 consumers 3986280 bytes > > > 50 consumers 4911322 bytes > > > 60 consumers 5836284 bytes > > > 70 consumers 6761246 bytes > > > 80 consumers 7686208 bytes > > > 90 consumers 8611170 bytes > > > 100 consumers 9536132 bytes > > > > > > Assignment topic indexing seems to reduce the size by 500KB without > > > compression and 80KB with compression. So assignment topic indexing > makes > > > some difference in both with and without compression but in our case > was > > > not nearly enough. > > > > > > This can be explained by the fact that we aren't actually hitting the > > worst > > > case scenario of each consumer being assigned a partition from every > > topic. > > > The reason is simple: a topic can only fully span all the consumers if > it > > > has at least as many partitions as there are consumers. Given that > there > > > are 8 partitions per topic and we have 100 consumers, it makes sense > that > > > we aren't close to this worse case scenario where topic indexing would > > make > > > a bigger difference. > > > > > > I tweaked the group leader's assignment code to print out the > assignments > > > and found that each consumer was getting either 238 or 239 partitions. > > Each > > > of these partitions were from unique topics. So the consumers were > really > > > getting partitions from 239 topics instead of the full worst case > > scenario > > > of 3000 topics. > > > > > > On Wed, May 25, 2016 at 1:42 PM, Jason Gustafson <ja...@confluent.io> > > > wrote: > > > > > > > Gwen, Joel: > > > > > > > > That's correct. The protocol does allow us to give an assignor its > own > > > > assignment schema, but I think this will require a couple internal > > > changes > > > > to the consumer to make use of the full generality. > > > > > > > > One thing I'm a little uncertain about is whether we should use a > > > different > > > > protocol type. For a little context, the group membership protocol > > allows > > > > the client to provide a "protocol type" when joining the group to > > ensure > > > > that all members have some basic semantic compatibility. For example, > > the > > > > consumer uses "consumer" and Kafka Connect uses "connect." Currently > > all > > > > assignors using the "consumer" protocol share a common schema for > > > > representing subscriptions and assignment. This is convenient for > tools > > > > (like consumer-groups.sh) since they just need to know how to parse > the > > > > "consumer" protocol type without knowing anything about the > assignors. > > So > > > > introducing another schema would break that assumption and we'd need > > > those > > > > tools to do assignor-specific parsing. Maybe this is OK? > Alternatively, > > > we > > > > could use a separate protocol type (e.g. "compact-consumer"), but > that > > > > seems less than desirable. > > > > > > > > Thanks, > > > > Jason > > > > > > > > On Wed, May 25, 2016 at 11:00 AM, Gwen Shapira <g...@confluent.io> > > > wrote: > > > > > > > > > ah, right - we can add as many strategies as we want. > > > > > > > > > > On Wed, May 25, 2016 at 10:54 AM, Joel Koshy <jjkosh...@gmail.com> > > > > wrote: > > > > > > > > > > > > Yes it would be a protocol bump. > > > > > > > > > > > > > > > > > > > Sorry - I'm officially confused. I think it may not be required - > > > since > > > > > the > > > > > > more compact format would be associated with a new assignment > > > strategy > > > > - > > > > > > right? > > > > > > > > > > > > > > > > > > > smaller than the plaintext PAL, but the post-compressed binary > > PAL > > > is > > > > > > just > > > > > > > 25% smaller than the post-compressed plaintext PAL. IOW using a > > > > symbol > > > > > > > table helps a lot but further compression on that already > compact > > > > > format > > > > > > > would yield only marginal return. > > > > > > > > > > > > > > > > > > > > So basically I feel we could get pretty far with a more compact > > > field > > > > > > > format for assignment and if we do that then we would > potentially > > > not > > > > > > even > > > > > > > want to do any compression. > > > > > > > > > > > > > > > > > > > Also just wanted to add that this compression on the binary PAL > did > > > > help > > > > > > but the compression ratio was obviously not as high as plaintext > > > > > > compression. > > > > > > > > > > > > > > > > > > > > > > > > > > On Tue, May 24, 2016 at 4:19 PM, Gwen Shapira < > g...@confluent.io > > > > > > > > wrote: > > > > > > > > > > > > > >> Regarding the change to the assignment field. It would be a > > > protocol > > > > > > bump, > > > > > > >> otherwise consumers will not know how to parse the bytes the > > > broker > > > > is > > > > > > >> returning, right? > > > > > > >> Or did I misunderstand the suggestion? > > > > > > >> > > > > > > >> On Tue, May 24, 2016 at 2:52 PM, Guozhang Wang < > > > wangg...@gmail.com> > > > > > > >> wrote: > > > > > > >> > > > > > > >> > I think for just solving issue 1), Jun's suggestion is > > > sufficient > > > > > and > > > > > > >> > simple. So I'd prefer that approach. > > > > > > >> > > > > > > > >> > In addition, Jason's optimization on the assignment field > > would > > > be > > > > > > good > > > > > > >> for > > > > > > >> > 2) and 3) as well, and I like that optimization for its > > > simplicity > > > > > and > > > > > > >> no > > > > > > >> > format change as well. And in the future I'm in favor of > > > > considering > > > > > > to > > > > > > >> > change the in-memory cache format as Jiangjie suggested. > > > > > > >> > > > > > > > >> > Guozhang > > > > > > >> > > > > > > > >> > > > > > > > >> > On Tue, May 24, 2016 at 12:42 PM, Becket Qin < > > > > becket....@gmail.com> > > > > > > >> wrote: > > > > > > >> > > > > > > > >> > > Hi Jason, > > > > > > >> > > > > > > > > >> > > There are a few problems we want to solve here: > > > > > > >> > > 1. The group metadata is too big to be appended to the > log. > > > > > > >> > > 2. Reduce the memory footprint on the broker > > > > > > >> > > 3. Reduce the bytes transferred over the wire. > > > > > > >> > > > > > > > > >> > > To solve (1), I like your idea of having separate messages > > per > > > > > > member. > > > > > > >> > The > > > > > > >> > > proposal (Onur's option 8) is to break metadata into small > > > > records > > > > > > in > > > > > > >> the > > > > > > >> > > same uncompressed message set so each record is small. I > > agree > > > > it > > > > > > >> would > > > > > > >> > be > > > > > > >> > > ideal if we are able to store the metadata separately for > > each > > > > > > >> member. I > > > > > > >> > > was also thinking about storing the metadata into multiple > > > > > messages, > > > > > > >> too. > > > > > > >> > > What concerns me was that having multiple messages seems > > > > breaking > > > > > > the > > > > > > >> > > atomicity. I am not sure how we are going to deal with the > > > > > potential > > > > > > >> > > issues. For example, What if group metadata is replicated > > but > > > > the > > > > > > >> member > > > > > > >> > > metadata is not? It might be fine depending on the > > > > implementation > > > > > > >> though, > > > > > > >> > > but I am not sure. > > > > > > >> > > > > > > > > >> > > For (2) we want to store the metadata onto the disk, which > > is > > > > what > > > > > > we > > > > > > >> > have > > > > > > >> > > to do anyway. The only question is in what format should > we > > > > store > > > > > > >> them. > > > > > > >> > > > > > > > > >> > > To address (3) we want to have the metadata to be > > compressed, > > > > > which > > > > > > is > > > > > > >> > > contradict to the the above solution of (1). > > > > > > >> > > > > > > > > >> > > I think Jun's suggestion is probably still the simplest. > To > > > > avoid > > > > > > >> > changing > > > > > > >> > > the behavior for consumers, maybe we can do that only for > > > > > > >> offset_topic, > > > > > > >> > > i.e, if the max fetch bytes of the fetch request is > smaller > > > than > > > > > the > > > > > > >> > > message size on the offset topic, we always return at > least > > > one > > > > > full > > > > > > >> > > message. This should avoid the unexpected problem on the > > > client > > > > > side > > > > > > >> > > because supposedly only tools and brokers will fetch from > > the > > > > the > > > > > > >> > internal > > > > > > >> > > topics, > > > > > > >> > > > > > > > > >> > > As a modification to what you suggested, one solution I > was > > > > > thinking > > > > > > >> was > > > > > > >> > to > > > > > > >> > > have multiple messages in a single compressed message. > That > > > > means > > > > > > for > > > > > > >> > > SyncGroupResponse we still need to read the entire > > compressed > > > > > > messages > > > > > > >> > and > > > > > > >> > > extract the inner messages, which seems not quite > different > > > from > > > > > > >> having a > > > > > > >> > > single message containing everything. But let me just put > it > > > > here > > > > > > and > > > > > > >> see > > > > > > >> > > if that makes sense. > > > > > > >> > > > > > > > > >> > > We can have a map of GroupMetadataKey -> > > > > GroupMetadataValueOffset. > > > > > > >> > > > > > > > > >> > > The GroupMetadataValue is stored in a compressed message. > > The > > > > > inner > > > > > > >> > > messages are the following: > > > > > > >> > > > > > > > > >> > > Inner Message 0: Version GroupId Generation > > > > > > >> > > > > > > > > >> > > Inner Message 1: MemberId MemberMetadata_1 (we can > compress > > > the > > > > > > bytes > > > > > > >> > here) > > > > > > >> > > > > > > > > >> > > Inner Message 2: MemberId MemberMetadata_2 > > > > > > >> > > .... > > > > > > >> > > Inner Message N: MemberId MemberMetadata_N > > > > > > >> > > > > > > > > >> > > The MemberMetadata format is the following: > > > > > > >> > > MemberMetadata => Version Generation ClientId Host > > > > Subscription > > > > > > >> > > Assignment > > > > > > >> > > > > > > > > >> > > So DescribeGroupResponse will just return the entire > > > compressed > > > > > > >> > > GroupMetadataMessage. SyncGroupResponse will return the > > > > > > corresponding > > > > > > >> > inner > > > > > > >> > > message. > > > > > > >> > > > > > > > > >> > > Thanks, > > > > > > >> > > > > > > > > >> > > Jiangjie (Becket) Qin > > > > > > >> > > > > > > > > >> > > > > > > > > >> > > > > > > > > >> > > On Tue, May 24, 2016 at 9:14 AM, Jason Gustafson < > > > > > > ja...@confluent.io> > > > > > > >> > > wrote: > > > > > > >> > > > > > > > > >> > > > Hey Becket, > > > > > > >> > > > > > > > > > >> > > > I like your idea to store only the offset for the group > > > > metadata > > > > > > in > > > > > > >> > > memory. > > > > > > >> > > > I think it would be safe to keep it in memory for a > short > > > time > > > > > > after > > > > > > >> > the > > > > > > >> > > > rebalance completes, but after that, it's only real > > purpose > > > is > > > > > to > > > > > > >> > answer > > > > > > >> > > > DescribeGroup requests, so your proposal makes a lot of > > > sense > > > > to > > > > > > me. > > > > > > >> > > > > > > > > > >> > > > As for the specific problem with the size of the group > > > > metadata > > > > > > >> message > > > > > > >> > > for > > > > > > >> > > > the MM case, if we cannot succeed in reducing the size > of > > > the > > > > > > >> > > > subscription/assignment (which I think is still probably > > the > > > > > best > > > > > > >> > > > alternative if it can work), then I think there are some > > > > options > > > > > > for > > > > > > >> > > > changing the message format (option #8 in Onur's initial > > > > > e-mail). > > > > > > >> > > > Currently, the key used for storing the group metadata > is > > > > this: > > > > > > >> > > > > > > > > > >> > > > GroupMetadataKey => Version GroupId > > > > > > >> > > > > > > > > > >> > > > And the value is something like this (some details > > elided): > > > > > > >> > > > > > > > > > >> > > > GroupMetadataValue => Version GroupId Generation > > > > > [MemberMetadata] > > > > > > >> > > > MemberMetadata => ClientId Host Subscription > Assignment > > > > > > >> > > > > > > > > > >> > > > I don't think we can change the key without a lot of > pain, > > > but > > > > > it > > > > > > >> seems > > > > > > >> > > > like we can change the value format. Maybe we can take > the > > > > > > >> > > > subscription/assignment payloads out of the value and > > > > introduce > > > > > a > > > > > > >> new > > > > > > >> > > > "MemberMetadata" message for each member in the group. > For > > > > > > example: > > > > > > >> > > > > > > > > > >> > > > MemberMetadataKey => Version GroupId MemberId > > > > > > >> > > > > > > > > > >> > > > MemberMetadataValue => Version Generation ClientId Host > > > > > > Subscription > > > > > > >> > > > Assignment > > > > > > >> > > > > > > > > > >> > > > When a new generation is created, we would first write > the > > > > group > > > > > > >> > metadata > > > > > > >> > > > message which includes the generation and all of the > > > > memberIds, > > > > > > and > > > > > > >> > then > > > > > > >> > > > we'd write the member metadata messages. To answer the > > > > > > DescribeGroup > > > > > > >> > > > request, we'd read the group metadata at the cached > offset > > > > and, > > > > > > >> > depending > > > > > > >> > > > on the version, all of the following member metadata. > This > > > > would > > > > > > be > > > > > > >> > more > > > > > > >> > > > complex to maintain, but it seems doable if it comes to > > it. > > > > > > >> > > > > > > > > > >> > > > Thanks, > > > > > > >> > > > Jason > > > > > > >> > > > > > > > > > >> > > > On Mon, May 23, 2016 at 6:15 PM, Becket Qin < > > > > > becket....@gmail.com > > > > > > > > > > > > > >> > > wrote: > > > > > > >> > > > > > > > > > >> > > > > It might worth thinking a little further. We have > > > discussed > > > > > this > > > > > > >> > before > > > > > > >> > > > > that we want to avoid holding all the group metadata > in > > > > > memory. > > > > > > >> > > > > > > > > > > >> > > > > I am thinking about the following end state: > > > > > > >> > > > > > > > > > > >> > > > > 1. Enable compression on the offset topic. > > > > > > >> > > > > 2. Instead of holding the entire group metadata in > > memory > > > on > > > > > the > > > > > > >> > > brokers, > > > > > > >> > > > > each broker only keeps a [group -> Offset] map, the > > offset > > > > > > points > > > > > > >> to > > > > > > >> > > the > > > > > > >> > > > > message in the offset topic which holds the latest > > > metadata > > > > of > > > > > > the > > > > > > >> > > group. > > > > > > >> > > > > 3. DescribeGroupResponse will read from the offset > topic > > > > > > directly > > > > > > >> > like > > > > > > >> > > a > > > > > > >> > > > > normal consumption, except that only exactly one > message > > > > will > > > > > be > > > > > > >> > > > returned. > > > > > > >> > > > > 4. SyncGroupResponse will read the message, extract > the > > > > > > assignment > > > > > > >> > part > > > > > > >> > > > and > > > > > > >> > > > > send back the partition assignment. We can compress > the > > > > > > partition > > > > > > >> > > > > assignment before sends it out if we want. > > > > > > >> > > > > > > > > > > >> > > > > Jiangjie (Becket) Qin > > > > > > >> > > > > > > > > > > >> > > > > On Mon, May 23, 2016 at 5:08 PM, Jason Gustafson < > > > > > > >> ja...@confluent.io > > > > > > >> > > > > > > > > >> > > > > wrote: > > > > > > >> > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > Jason, doesn't gzip (or other compression) > basically > > > do > > > > > > this? > > > > > > >> If > > > > > > >> > > the > > > > > > >> > > > > > topic > > > > > > >> > > > > > > is a string and the topic is repeated throughout, > > > won't > > > > > > >> > compression > > > > > > >> > > > > > > basically replace all repeated instances of it > with > > an > > > > > index > > > > > > >> > > > reference > > > > > > >> > > > > to > > > > > > >> > > > > > > the full string? > > > > > > >> > > > > > > > > > > > >> > > > > > > > > > > > >> > > > > > Hey James, yeah, that's probably true, but keep in > > mind > > > > that > > > > > > the > > > > > > >> > > > > > compression happens on the broker side. It would be > > nice > > > > to > > > > > > >> have a > > > > > > >> > > more > > > > > > >> > > > > > compact representation so that get some benefit over > > the > > > > > wire > > > > > > as > > > > > > >> > > well. > > > > > > >> > > > > This > > > > > > >> > > > > > seems to be less of a concern here, so the bigger > > gains > > > > are > > > > > > >> > probably > > > > > > >> > > > from > > > > > > >> > > > > > reducing the number of partitions that need to be > > listed > > > > > > >> > > individually. > > > > > > >> > > > > > > > > > > > >> > > > > > -Jason > > > > > > >> > > > > > > > > > > > >> > > > > > On Mon, May 23, 2016 at 4:23 PM, Onur Karaman < > > > > > > >> > > > > > onurkaraman.apa...@gmail.com> > > > > > > >> > > > > > wrote: > > > > > > >> > > > > > > > > > > > >> > > > > > > When figuring out these optimizations, it's worth > > > > keeping > > > > > in > > > > > > >> mind > > > > > > >> > > the > > > > > > >> > > > > > > improvements when the message is uncompressed vs > > when > > > > it's > > > > > > >> > > > compressed. > > > > > > >> > > > > > > > > > > > > >> > > > > > > When uncompressed: > > > > > > >> > > > > > > Fixing the Assignment serialization to instead be > a > > > > topic > > > > > > >> index > > > > > > >> > > into > > > > > > >> > > > > the > > > > > > >> > > > > > > corresponding member's subscription list would > > usually > > > > be > > > > > a > > > > > > >> good > > > > > > >> > > > thing. > > > > > > >> > > > > > > > > > > > > >> > > > > > > I think the proposal is only worse when the topic > > > names > > > > > are > > > > > > >> > small. > > > > > > >> > > > The > > > > > > >> > > > > > > Type.STRING we use in our protocol for the > > > assignment's > > > > > > >> > > > TOPIC_KEY_NAME > > > > > > >> > > > > is > > > > > > >> > > > > > > limited in length to Short.MAX_VALUE, so our > strings > > > are > > > > > > first > > > > > > >> > > > > prepended > > > > > > >> > > > > > > with 2 bytes to indicate the string size. > > > > > > >> > > > > > > > > > > > > >> > > > > > > The new proposal does worse when: > > > > > > >> > > > > > > 2 + utf_encoded_string_payload_size < > > index_type_size > > > > > > >> > > > > > > in other words when: > > > > > > >> > > > > > > utf_encoded_string_payload_size < index_type_size > - > > 2 > > > > > > >> > > > > > > > > > > > > >> > > > > > > If the index type ends up being Type.INT32, then > the > > > > > > proposal > > > > > > >> is > > > > > > >> > > > worse > > > > > > >> > > > > > when > > > > > > >> > > > > > > the topic is length 1. > > > > > > >> > > > > > > If the index type ends up being Type.INT64, then > the > > > > > > proposal > > > > > > >> is > > > > > > >> > > > worse > > > > > > >> > > > > > when > > > > > > >> > > > > > > the topic is less than length 6. > > > > > > >> > > > > > > > > > > > > >> > > > > > > When compressed: > > > > > > >> > > > > > > As James Cheng brought up, I'm not sure how things > > > > change > > > > > > when > > > > > > >> > > > > > compression > > > > > > >> > > > > > > comes into the picture. This would be worth > > > > investigating. > > > > > > >> > > > > > > > > > > > > >> > > > > > > On Mon, May 23, 2016 at 4:05 PM, James Cheng < > > > > > > >> > wushuja...@gmail.com > > > > > > >> > > > > > > > > > >> > > > > > wrote: > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > On May 23, 2016, at 10:59 AM, Jason Gustafson > < > > > > > > >> > > > ja...@confluent.io> > > > > > > >> > > > > > > > wrote: > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > 2. Maybe there's a better way to lay out the > > > > > assignment > > > > > > >> > without > > > > > > >> > > > > > needing > > > > > > >> > > > > > > > to > > > > > > >> > > > > > > > > explicitly repeat the topic? For example, the > > > leader > > > > > > could > > > > > > >> > sort > > > > > > >> > > > the > > > > > > >> > > > > > > > topics > > > > > > >> > > > > > > > > for each member and just use an integer to > > > represent > > > > > the > > > > > > >> > index > > > > > > >> > > of > > > > > > >> > > > > > each > > > > > > >> > > > > > > > > topic within the sorted list (note this > depends > > on > > > > the > > > > > > >> > > > subscription > > > > > > >> > > > > > > > > including the full topic list). > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > Assignment -> [TopicIndex [Partition]] > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > Jason, doesn't gzip (or other compression) > > basically > > > > do > > > > > > >> this? > > > > > > >> > If > > > > > > >> > > > the > > > > > > >> > > > > > > topic > > > > > > >> > > > > > > > is a string and the topic is repeated > throughout, > > > > won't > > > > > > >> > > compression > > > > > > >> > > > > > > > basically replace all repeated instances of it > > with > > > an > > > > > > index > > > > > > >> > > > > reference > > > > > > >> > > > > > to > > > > > > >> > > > > > > > the full string? > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > -James > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > You could even combine these two options so > that > > > you > > > > > > have > > > > > > >> > only > > > > > > >> > > 3 > > > > > > >> > > > > > > integers > > > > > > >> > > > > > > > > for each topic assignment: > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > Assignment -> [TopicIndex MinPartition > > > MaxPartition] > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > There may even be better options with a little > > > more > > > > > > >> thought. > > > > > > >> > > All > > > > > > >> > > > of > > > > > > >> > > > > > > this > > > > > > >> > > > > > > > is > > > > > > >> > > > > > > > > just part of the client-side protocol, so it > > > > wouldn't > > > > > > >> require > > > > > > >> > > any > > > > > > >> > > > > > > version > > > > > > >> > > > > > > > > bumps on the broker. What do you think? > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > Thanks, > > > > > > >> > > > > > > > > Jason > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > On Mon, May 23, 2016 at 9:17 AM, Guozhang > Wang < > > > > > > >> > > > wangg...@gmail.com > > > > > > >> > > > > > > > > > > > >> > > > > > > > wrote: > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > >> The original concern is that regex may not be > > > > > > efficiently > > > > > > >> > > > > supported > > > > > > >> > > > > > > > >> across-languages, but if there is a neat > > > > workaround I > > > > > > >> would > > > > > > >> > > love > > > > > > >> > > > > to > > > > > > >> > > > > > > > learn. > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > > > >> Guozhang > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > > > >> On Mon, May 23, 2016 at 5:31 AM, Ismael Juma > < > > > > > > >> > > ism...@juma.me.uk > > > > > > >> > > > > > > > > > > >> > > > > > > wrote: > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > > > >>> +1 to Jun's suggestion. > > > > > > >> > > > > > > > >>> > > > > > > >> > > > > > > > >>> Having said that, as a general point, I > think > > we > > > > > > should > > > > > > >> > > > consider > > > > > > >> > > > > > > > >> supporting > > > > > > >> > > > > > > > >>> topic patterns in the wire protocol. It > > requires > > > > > some > > > > > > >> > > thinking > > > > > > >> > > > > for > > > > > > >> > > > > > > > >>> cross-language support, but it seems > > > surmountable > > > > > and > > > > > > it > > > > > > >> > > could > > > > > > >> > > > > make > > > > > > >> > > > > > > > >> certain > > > > > > >> > > > > > > > >>> operations a lot more efficient (the fact > > that a > > > > > basic > > > > > > >> > regex > > > > > > >> > > > > > > > subscription > > > > > > >> > > > > > > > >>> causes the consumer to request metadata for > > all > > > > > topics > > > > > > >> is > > > > > > >> > not > > > > > > >> > > > > > great). > > > > > > >> > > > > > > > >>> > > > > > > >> > > > > > > > >>> Ismael > > > > > > >> > > > > > > > >>> > > > > > > >> > > > > > > > >>> On Sun, May 22, 2016 at 11:49 PM, Guozhang > > Wang > > > < > > > > > > >> > > > > > wangg...@gmail.com> > > > > > > >> > > > > > > > >>> wrote: > > > > > > >> > > > > > > > >>> > > > > > > >> > > > > > > > >>>> I like Jun's suggestion in changing the > > > handling > > > > > > >> logics of > > > > > > >> > > > > single > > > > > > >> > > > > > > > large > > > > > > >> > > > > > > > >>>> message on the consumer side. > > > > > > >> > > > > > > > >>>> > > > > > > >> > > > > > > > >>>> As for the case of "a single group > > subscribing > > > to > > > > > > 3000 > > > > > > >> > > > topics", > > > > > > >> > > > > > with > > > > > > >> > > > > > > > >> 100 > > > > > > >> > > > > > > > >>>> consumers the 2.5Mb Gzip size is reasonable > > to > > > me > > > > > > (when > > > > > > >> > > > storing > > > > > > >> > > > > in > > > > > > >> > > > > > > ZK, > > > > > > >> > > > > > > > >> we > > > > > > >> > > > > > > > >>>> also have the znode limit which is set to > 1Mb > > > by > > > > > > >> default, > > > > > > >> > > > though > > > > > > >> > > > > > > > >>> admittedly > > > > > > >> > > > > > > > >>>> it is only for one consumer). And if we do > > the > > > > > change > > > > > > >> as > > > > > > >> > Jun > > > > > > >> > > > > > > > suggested, > > > > > > >> > > > > > > > >>>> 2.5Mb on follower's memory pressure is OK I > > > > think. > > > > > > >> > > > > > > > >>>> > > > > > > >> > > > > > > > >>>> > > > > > > >> > > > > > > > >>>> Guozhang > > > > > > >> > > > > > > > >>>> > > > > > > >> > > > > > > > >>>> > > > > > > >> > > > > > > > >>>> On Sat, May 21, 2016 at 12:51 PM, Onur > > Karaman > > > < > > > > > > >> > > > > > > > >>>> onurkaraman.apa...@gmail.com > > > > > > >> > > > > > > > >>>>> wrote: > > > > > > >> > > > > > > > >>>> > > > > > > >> > > > > > > > >>>>> Results without compression: > > > > > > >> > > > > > > > >>>>> 1 consumer 292383 bytes > > > > > > >> > > > > > > > >>>>> 5 consumers 1079579 bytes * the tipping > > point > > > > > > >> > > > > > > > >>>>> 10 consumers 1855018 bytes > > > > > > >> > > > > > > > >>>>> 20 consumers 2780220 bytes > > > > > > >> > > > > > > > >>>>> 30 consumers 3705422 bytes > > > > > > >> > > > > > > > >>>>> 40 consumers 4630624 bytes > > > > > > >> > > > > > > > >>>>> 50 consumers 5555826 bytes > > > > > > >> > > > > > > > >>>>> 60 consumers 6480788 bytes > > > > > > >> > > > > > > > >>>>> 70 consumers 7405750 bytes > > > > > > >> > > > > > > > >>>>> 80 consumers 8330712 bytes > > > > > > >> > > > > > > > >>>>> 90 consumers 9255674 bytes > > > > > > >> > > > > > > > >>>>> 100 consumers 10180636 bytes > > > > > > >> > > > > > > > >>>>> > > > > > > >> > > > > > > > >>>>> So it looks like gzip compression shrinks > > the > > > > > > message > > > > > > >> > size > > > > > > >> > > by > > > > > > >> > > > > 4x. > > > > > > >> > > > > > > > >>>>> > > > > > > >> > > > > > > > >>>>> On Sat, May 21, 2016 at 9:47 AM, Jun Rao < > > > > > > >> > j...@confluent.io > > > > > > >> > > > > > > > > > >> > > > > > wrote: > > > > > > >> > > > > > > > >>>>> > > > > > > >> > > > > > > > >>>>>> Onur, > > > > > > >> > > > > > > > >>>>>> > > > > > > >> > > > > > > > >>>>>> Thanks for the investigation. > > > > > > >> > > > > > > > >>>>>> > > > > > > >> > > > > > > > >>>>>> Another option is to just fix how we deal > > > with > > > > > the > > > > > > >> case > > > > > > >> > > > when a > > > > > > >> > > > > > > > >>> message > > > > > > >> > > > > > > > >>>> is > > > > > > >> > > > > > > > >>>>>> larger than the fetch size. Today, if the > > > fetch > > > > > > size > > > > > > >> is > > > > > > >> > > > > smaller > > > > > > >> > > > > > > > >> than > > > > > > >> > > > > > > > >>>> the > > > > > > >> > > > > > > > >>>>>> fetch size, the consumer will get stuck. > > > > Instead, > > > > > > we > > > > > > >> can > > > > > > >> > > > > simply > > > > > > >> > > > > > > > >>> return > > > > > > >> > > > > > > > >>>>> the > > > > > > >> > > > > > > > >>>>>> full message if it's larger than the > fetch > > > size > > > > > w/o > > > > > > >> > > > requiring > > > > > > >> > > > > > the > > > > > > >> > > > > > > > >>>>> consumer > > > > > > >> > > > > > > > >>>>>> to manually adjust the fetch size. On the > > > > broker > > > > > > >> side, > > > > > > >> > to > > > > > > >> > > > > serve > > > > > > >> > > > > > a > > > > > > >> > > > > > > > >>> fetch > > > > > > >> > > > > > > > >>>>>> request, we already do an index lookup > and > > > then > > > > > > scan > > > > > > >> the > > > > > > >> > > > log a > > > > > > >> > > > > > bit > > > > > > >> > > > > > > > >> to > > > > > > >> > > > > > > > >>>>> find > > > > > > >> > > > > > > > >>>>>> the message with the requested offset. We > > can > > > > > just > > > > > > >> check > > > > > > >> > > the > > > > > > >> > > > > > size > > > > > > >> > > > > > > > >> of > > > > > > >> > > > > > > > >>>> that > > > > > > >> > > > > > > > >>>>>> message and return the full message if > its > > > size > > > > > is > > > > > > >> > larger > > > > > > >> > > > than > > > > > > >> > > > > > the > > > > > > >> > > > > > > > >>>> fetch > > > > > > >> > > > > > > > >>>>>> size. This way, fetch size is really for > > > > > > performance > > > > > > >> > > > > > optimization, > > > > > > >> > > > > > > > >>> i.e. > > > > > > >> > > > > > > > >>>>> in > > > > > > >> > > > > > > > >>>>>> the common case, we will not return more > > > bytes > > > > > than > > > > > > >> > fetch > > > > > > >> > > > > size, > > > > > > >> > > > > > > but > > > > > > >> > > > > > > > >>> if > > > > > > >> > > > > > > > >>>>>> there is a large message, we will return > > more > > > > > bytes > > > > > > >> than > > > > > > >> > > the > > > > > > >> > > > > > > > >>> specified > > > > > > >> > > > > > > > >>>>>> fetch size. In practice, large messages > are > > > > rare. > > > > > > >> So, it > > > > > > >> > > > > > shouldn't > > > > > > >> > > > > > > > >>>>> increase > > > > > > >> > > > > > > > >>>>>> the memory consumption on the client too > > > much. > > > > > > >> > > > > > > > >>>>>> > > > > > > >> > > > > > > > >>>>>> Jun > > > > > > >> > > > > > > > >>>>>> > > > > > > >> > > > > > > > >>>>>> On Sat, May 21, 2016 at 3:34 AM, Onur > > > Karaman < > > > > > > >> > > > > > > > >>>>>> onurkaraman.apa...@gmail.com> > > > > > > >> > > > > > > > >>>>>> wrote: > > > > > > >> > > > > > > > >>>>>> > > > > > > >> > > > > > > > >>>>>>> Hey everyone. So I started doing some > > tests > > > on > > > > > the > > > > > > >> new > > > > > > >> > > > > > > > >>>>>> consumer/coordinator > > > > > > >> > > > > > > > >>>>>>> to see if it could handle more strenuous > > use > > > > > cases > > > > > > >> like > > > > > > >> > > > > > mirroring > > > > > > >> > > > > > > > >>>>>> clusters > > > > > > >> > > > > > > > >>>>>>> with thousands of topics and thought I'd > > > share > > > > > > >> > whatever I > > > > > > >> > > > > have > > > > > > >> > > > > > so > > > > > > >> > > > > > > > >>>> far. > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>>> The scalability limit: the amount of > group > > > > > > metadata > > > > > > >> we > > > > > > >> > > can > > > > > > >> > > > > fit > > > > > > >> > > > > > > > >> into > > > > > > >> > > > > > > > >>>> one > > > > > > >> > > > > > > > >>>>>>> message > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>>> Some background: > > > > > > >> > > > > > > > >>>>>>> Client-side assignment is implemented in > > two > > > > > > phases > > > > > > >> > > > > > > > >>>>>>> 1. a PreparingRebalance phase that > > > identifies > > > > > > >> members > > > > > > >> > of > > > > > > >> > > > the > > > > > > >> > > > > > > > >> group > > > > > > >> > > > > > > > >>>> and > > > > > > >> > > > > > > > >>>>>>> aggregates member subscriptions. > > > > > > >> > > > > > > > >>>>>>> 2. an AwaitingSync phase that waits for > > the > > > > > group > > > > > > >> > leader > > > > > > >> > > to > > > > > > >> > > > > > > > >> decide > > > > > > >> > > > > > > > >>>>> member > > > > > > >> > > > > > > > >>>>>>> assignments based on the member > > > subscriptions > > > > > > across > > > > > > >> > the > > > > > > >> > > > > group. > > > > > > >> > > > > > > > >>>>>>> - The leader announces this decision > > with a > > > > > > >> > > > > SyncGroupRequest. > > > > > > >> > > > > > > > >> The > > > > > > >> > > > > > > > >>>>>>> GroupCoordinator handles > SyncGroupRequests > > > by > > > > > > >> appending > > > > > > >> > > all > > > > > > >> > > > > > group > > > > > > >> > > > > > > > >>>> state > > > > > > >> > > > > > > > >>>>>>> into a single message under the > > > > > __consumer_offsets > > > > > > >> > topic. > > > > > > >> > > > > This > > > > > > >> > > > > > > > >>>> message > > > > > > >> > > > > > > > >>>>> is > > > > > > >> > > > > > > > >>>>>>> keyed on the group id and contains each > > > member > > > > > > >> > > subscription > > > > > > >> > > > > as > > > > > > >> > > > > > > > >> well > > > > > > >> > > > > > > > >>>> as > > > > > > >> > > > > > > > >>>>>> the > > > > > > >> > > > > > > > >>>>>>> decided assignment for each member. > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>>> The environment: > > > > > > >> > > > > > > > >>>>>>> - one broker > > > > > > >> > > > > > > > >>>>>>> - one __consumer_offsets partition > > > > > > >> > > > > > > > >>>>>>> - offsets.topic.compression.codec=1 // > > this > > > is > > > > > > gzip > > > > > > >> > > > > > > > >>>>>>> - broker has my pending KAFKA-3718 patch > > > that > > > > > > >> actually > > > > > > >> > > > makes > > > > > > >> > > > > > use > > > > > > >> > > > > > > > >> of > > > > > > >> > > > > > > > >>>>>>> offsets.topic.compression.codec: > > > > > > >> > > > > > > > >>>>>> > https://github.com/apache/kafka/pull/1394 > > > > > > >> > > > > > > > >>>>>>> - around 3000 topics. This is an actual > > > subset > > > > > of > > > > > > >> > topics > > > > > > >> > > > from > > > > > > >> > > > > > one > > > > > > >> > > > > > > > >>> of > > > > > > >> > > > > > > > >>>>> our > > > > > > >> > > > > > > > >>>>>>> clusters. > > > > > > >> > > > > > > > >>>>>>> - topics have 8 partitions > > > > > > >> > > > > > > > >>>>>>> - topics are 25 characters long on > average > > > > > > >> > > > > > > > >>>>>>> - one group with a varying number of > > > consumers > > > > > > each > > > > > > >> > > > hardcoded > > > > > > >> > > > > > > > >> with > > > > > > >> > > > > > > > >>>> all > > > > > > >> > > > > > > > >>>>>> the > > > > > > >> > > > > > > > >>>>>>> topics just to make the tests more > > > consistent. > > > > > > >> > > wildcarding > > > > > > >> > > > > with > > > > > > >> > > > > > > > >> .* > > > > > > >> > > > > > > > >>>>> should > > > > > > >> > > > > > > > >>>>>>> have the same effect once the > subscription > > > > hits > > > > > > the > > > > > > >> > > > > coordinator > > > > > > >> > > > > > > > >> as > > > > > > >> > > > > > > > >>>> the > > > > > > >> > > > > > > > >>>>>>> subscription has already been fully > > expanded > > > > out > > > > > > to > > > > > > >> the > > > > > > >> > > > list > > > > > > >> > > > > of > > > > > > >> > > > > > > > >>>> topics > > > > > > >> > > > > > > > >>>>> by > > > > > > >> > > > > > > > >>>>>>> the consumers. > > > > > > >> > > > > > > > >>>>>>> - I added some log messages to Log.scala > > to > > > > > print > > > > > > >> out > > > > > > >> > the > > > > > > >> > > > > > message > > > > > > >> > > > > > > > >>>> sizes > > > > > > >> > > > > > > > >>>>>>> after compression > > > > > > >> > > > > > > > >>>>>>> - there are no producers at all and auto > > > > commits > > > > > > are > > > > > > >> > > > > disabled. > > > > > > >> > > > > > > > >> The > > > > > > >> > > > > > > > >>>> only > > > > > > >> > > > > > > > >>>>>>> topic with messages getting added is the > > > > > > >> > > __consumer_offsets > > > > > > >> > > > > > topic > > > > > > >> > > > > > > > >>> and > > > > > > >> > > > > > > > >>>>>>> they're only from storing group metadata > > > while > > > > > > >> > processing > > > > > > >> > > > > > > > >>>>>>> SyncGroupRequests. > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>>> Results: > > > > > > >> > > > > > > > >>>>>>> The results below show that we exceed > the > > > > > 1000012 > > > > > > >> byte > > > > > > >> > > > > > > > >>>>>>> KafkaConfig.messageMaxBytes limit > > relatively > > > > > > quickly > > > > > > >> > > > (between > > > > > > >> > > > > > > > >> 30-40 > > > > > > >> > > > > > > > >>>>>>> consumers): > > > > > > >> > > > > > > > >>>>>>> 1 consumer 54739 bytes > > > > > > >> > > > > > > > >>>>>>> 5 consumers 261524 bytes > > > > > > >> > > > > > > > >>>>>>> 10 consumers 459804 bytes > > > > > > >> > > > > > > > >>>>>>> 20 consumers 702499 bytes > > > > > > >> > > > > > > > >>>>>>> 30 consumers 930525 bytes > > > > > > >> > > > > > > > >>>>>>> 40 consumers 1115657 bytes * the tipping > > > point > > > > > > >> > > > > > > > >>>>>>> 50 consumers 1363112 bytes > > > > > > >> > > > > > > > >>>>>>> 60 consumers 1598621 bytes > > > > > > >> > > > > > > > >>>>>>> 70 consumers 1837359 bytes > > > > > > >> > > > > > > > >>>>>>> 80 consumers 2066934 bytes > > > > > > >> > > > > > > > >>>>>>> 90 consumers 2310970 bytes > > > > > > >> > > > > > > > >>>>>>> 100 consumers 2542735 bytes > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>>> Note that the growth itself is pretty > > > gradual. > > > > > > >> Plotting > > > > > > >> > > the > > > > > > >> > > > > > > > >> points > > > > > > >> > > > > > > > >>>>> makes > > > > > > >> > > > > > > > >>>>>> it > > > > > > >> > > > > > > > >>>>>>> look roughly linear w.r.t the number of > > > > > consumers: > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>> > > > > > > >> > > > > > > > >>>>> > > > > > > >> > > > > > > > >>>> > > > > > > >> > > > > > > > >>> > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > > > > > > > > > > > > > > > > https://www.wolframalpha.com/input/?i=(1,+54739),+(5,+261524),+(10,+459804),+(20,+702499),+(30,+930525),+(40,+1115657),+(50,+1363112),+(60,+1598621),+(70,+1837359),+(80,+2066934),+(90,+2310970),+(100,+2542735) > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>>> Also note that these numbers aren't > > averages > > > > or > > > > > > >> medians > > > > > > >> > > or > > > > > > >> > > > > > > > >> anything > > > > > > >> > > > > > > > >>>>> like > > > > > > >> > > > > > > > >>>>>>> that. It's just the byte size from a > given > > > > run. > > > > > I > > > > > > >> did > > > > > > >> > run > > > > > > >> > > > > them > > > > > > >> > > > > > a > > > > > > >> > > > > > > > >>> few > > > > > > >> > > > > > > > >>>>>> times > > > > > > >> > > > > > > > >>>>>>> and saw similar results. > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>>> Impact: > > > > > > >> > > > > > > > >>>>>>> Even after adding gzip to the > > > > __consumer_offsets > > > > > > >> topic > > > > > > >> > > with > > > > > > >> > > > > my > > > > > > >> > > > > > > > >>>> pending > > > > > > >> > > > > > > > >>>>>>> KAFKA-3718 patch, the AwaitingSync phase > > of > > > > the > > > > > > >> group > > > > > > >> > > fails > > > > > > >> > > > > > with > > > > > > >> > > > > > > > >>>>>>> RecordTooLargeException. This means the > > > > combined > > > > > > >> size > > > > > > >> > of > > > > > > >> > > > each > > > > > > >> > > > > > > > >>>> member's > > > > > > >> > > > > > > > >>>>>>> subscriptions and assignments exceeded > the > > > > > > >> > > > > > > > >>>> KafkaConfig.messageMaxBytes > > > > > > >> > > > > > > > >>>>> of > > > > > > >> > > > > > > > >>>>>>> 1000012 bytes. The group ends up dying. > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>>> Options: > > > > > > >> > > > > > > > >>>>>>> 1. Config change: reduce the number of > > > > consumers > > > > > > in > > > > > > >> the > > > > > > >> > > > > group. > > > > > > >> > > > > > > > >> This > > > > > > >> > > > > > > > >>>>> isn't > > > > > > >> > > > > > > > >>>>>>> always a realistic answer in more > > strenuous > > > > use > > > > > > >> cases > > > > > > >> > > like > > > > > > >> > > > > > > > >>>> MirrorMaker > > > > > > >> > > > > > > > >>>>>>> clusters or for auditing. > > > > > > >> > > > > > > > >>>>>>> 2. Config change: split the group into > > > smaller > > > > > > >> groups > > > > > > >> > > which > > > > > > >> > > > > > > > >>> together > > > > > > >> > > > > > > > >>>>> will > > > > > > >> > > > > > > > >>>>>>> get full coverage of the topics. This > > gives > > > > each > > > > > > >> group > > > > > > >> > > > > member a > > > > > > >> > > > > > > > >>>> smaller > > > > > > >> > > > > > > > >>>>>>> subscription.(ex: g1 has topics starting > > > with > > > > > a-m > > > > > > >> while > > > > > > >> > > g2 > > > > > > >> > > > > has > > > > > > >> > > > > > > > >>> topics > > > > > > >> > > > > > > > >>>>>>> starting ith n-z). This would be > > > operationally > > > > > > >> painful > > > > > > >> > to > > > > > > >> > > > > > manage. > > > > > > >> > > > > > > > >>>>>>> 3. Config change: split the topics among > > > > members > > > > > > of > > > > > > >> the > > > > > > >> > > > > group. > > > > > > >> > > > > > > > >>> Again > > > > > > >> > > > > > > > >>>>> this > > > > > > >> > > > > > > > >>>>>>> gives each group member a smaller > > > > subscription. > > > > > > This > > > > > > >> > > would > > > > > > >> > > > > also > > > > > > >> > > > > > > > >> be > > > > > > >> > > > > > > > >>>>>>> operationally painful to manage. > > > > > > >> > > > > > > > >>>>>>> 4. Config change: bump up > > > > > > >> KafkaConfig.messageMaxBytes > > > > > > >> > (a > > > > > > >> > > > > > > > >>> topic-level > > > > > > >> > > > > > > > >>>>>>> config) and > > KafkaConfig.replicaFetchMaxBytes > > > > (a > > > > > > >> > > > broker-level > > > > > > >> > > > > > > > >>> config). > > > > > > >> > > > > > > > >>>>>>> Applying messageMaxBytes to just the > > > > > > >> __consumer_offsets > > > > > > >> > > > topic > > > > > > >> > > > > > > > >> seems > > > > > > >> > > > > > > > >>>>>>> relatively harmless, but bumping up the > > > > > > broker-level > > > > > > >> > > > > > > > >>>>> replicaFetchMaxBytes > > > > > > >> > > > > > > > >>>>>>> would probably need more attention. > > > > > > >> > > > > > > > >>>>>>> 5. Config change: try different > > compression > > > > > > codecs. > > > > > > >> > Based > > > > > > >> > > > on > > > > > > >> > > > > 2 > > > > > > >> > > > > > > > >>>> minutes > > > > > > >> > > > > > > > >>>>> of > > > > > > >> > > > > > > > >>>>>>> googling, it seems like lz4 and snappy > are > > > > > faster > > > > > > >> than > > > > > > >> > > gzip > > > > > > >> > > > > but > > > > > > >> > > > > > > > >>> have > > > > > > >> > > > > > > > >>>>>> worse > > > > > > >> > > > > > > > >>>>>>> compression, so this probably won't > help. > > > > > > >> > > > > > > > >>>>>>> 6. Implementation change: support > sending > > > the > > > > > > regex > > > > > > >> > over > > > > > > >> > > > the > > > > > > >> > > > > > wire > > > > > > >> > > > > > > > >>>>> instead > > > > > > >> > > > > > > > >>>>>>> of the fully expanded topic > > subscriptions. I > > > > > think > > > > > > >> > people > > > > > > >> > > > > said > > > > > > >> > > > > > in > > > > > > >> > > > > > > > >>> the > > > > > > >> > > > > > > > >>>>>> past > > > > > > >> > > > > > > > >>>>>>> that different languages have subtle > > > > differences > > > > > > in > > > > > > >> > > regex, > > > > > > >> > > > so > > > > > > >> > > > > > > > >> this > > > > > > >> > > > > > > > >>>>>> doesn't > > > > > > >> > > > > > > > >>>>>>> play nicely with cross-language groups. > > > > > > >> > > > > > > > >>>>>>> 7. Implementation change: maybe we can > > > reverse > > > > > the > > > > > > >> > > mapping? > > > > > > >> > > > > > > > >> Instead > > > > > > >> > > > > > > > >>>> of > > > > > > >> > > > > > > > >>>>>>> mapping from member to subscriptions, we > > can > > > > > map a > > > > > > >> > > > > subscription > > > > > > >> > > > > > > > >> to > > > > > > >> > > > > > > > >>> a > > > > > > >> > > > > > > > >>>>> list > > > > > > >> > > > > > > > >>>>>>> of members. > > > > > > >> > > > > > > > >>>>>>> 8. Implementation change: maybe we can > try > > > to > > > > > > break > > > > > > >> > apart > > > > > > >> > > > the > > > > > > >> > > > > > > > >>>>>> subscription > > > > > > >> > > > > > > > >>>>>>> and assignments from the same > > > SyncGroupRequest > > > > > > into > > > > > > >> > > > multiple > > > > > > >> > > > > > > > >>> records? > > > > > > >> > > > > > > > >>>>>> They > > > > > > >> > > > > > > > >>>>>>> can still go to the same message set and > > get > > > > > > >> appended > > > > > > >> > > > > together. > > > > > > >> > > > > > > > >>> This > > > > > > >> > > > > > > > >>>>> way > > > > > > >> > > > > > > > >>>>>>> the limit become the segment size, which > > > > > shouldn't > > > > > > >> be a > > > > > > >> > > > > > problem. > > > > > > >> > > > > > > > >>> This > > > > > > >> > > > > > > > >>>>> can > > > > > > >> > > > > > > > >>>>>>> be tricky to get right because we're > > > currently > > > > > > >> keying > > > > > > >> > > these > > > > > > >> > > > > > > > >>> messages > > > > > > >> > > > > > > > >>>> on > > > > > > >> > > > > > > > >>>>>> the > > > > > > >> > > > > > > > >>>>>>> group, so I think records from the same > > > > > rebalance > > > > > > >> might > > > > > > >> > > > > > > > >>> accidentally > > > > > > >> > > > > > > > >>>>>>> compact one another, but my > understanding > > of > > > > > > >> compaction > > > > > > >> > > > isn't > > > > > > >> > > > > > > > >> that > > > > > > >> > > > > > > > >>>>> great. > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>>> Todo: > > > > > > >> > > > > > > > >>>>>>> It would be interesting to rerun the > tests > > > > with > > > > > no > > > > > > >> > > > > compression > > > > > > >> > > > > > > > >> just > > > > > > >> > > > > > > > >>>> to > > > > > > >> > > > > > > > >>>>>> see > > > > > > >> > > > > > > > >>>>>>> how much gzip is helping but it's > getting > > > > late. > > > > > > >> Maybe > > > > > > >> > > > > tomorrow? > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>>> - Onur > > > > > > >> > > > > > > > >>>>>>> > > > > > > >> > > > > > > > >>>>>> > > > > > > >> > > > > > > > >>>>> > > > > > > >> > > > > > > > >>>> > > > > > > >> > > > > > > > >>>> > > > > > > >> > > > > > > > >>>> > > > > > > >> > > > > > > > >>>> -- > > > > > > >> > > > > > > > >>>> -- Guozhang > > > > > > >> > > > > > > > >>>> > > > > > > >> > > > > > > > >>> > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > > > >> -- > > > > > > >> > > > > > > > >> -- Guozhang > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > -- > > > > > > >> > -- Guozhang > > > > > > >> > > > > > > > >> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
