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 >
