Hey Joel, Yeah the clock issues would arrive when leadership changed or the time on the machine changed.
Don't you see all the same issues you see with client-defined timestamp's if you let mm control the timestamp as you were proposing? That means time is no longer monotonic. A mixture of mirrored data from two source clusters may be arbitrarily skewed just as from two clients. Also, Joel, can you just confirm that you guys have talked through the whole timestamp thing with the Samza folks at LI? The reason I ask about this is that Samza and Kafka Streams (KIP-28) are both trying to rely on *client-defined* notions of time and there is a really well thought out rationale for why it needs to be client-defined. In the absence of these I think I would also have agreed with you guys about preferring server time. But because of those, I think it may be super confusing if one part of Kafka has a mandatory notion of time that means X and another part has a mandatory notion that means Y. WRT your idea of a FollowerFetchRequestI had thought of a similar idea where we use the leader's timestamps to approximately set the follower's timestamps. I had thought of just adding a partition metadata request that would subsume the current offset/time lookup and could be used by the follower to try to approximately keep their timestamps kosher. It's a little hacky and doesn't help with MM but it is also maybe less invasive so that approach could be viable. -Jay On Thu, Sep 10, 2015 at 3:36 PM, Joel Koshy <jjkosh...@gmail.com> wrote: > I just wanted to comment on a few points made earlier in this thread: > > Concerns on clock skew: at least for the original proposal's scope > (which was more for honoring retention broker-side) this would only be > an issue when spanning leader movements right? i.e., leader migration > latency has to be much less than clock skew for this to be a real > issue wouldn’t it? > > Client timestamp vs broker timestamp: I’m not sure Kafka (brokers) are > the right place to reason about client-side timestamps precisely due > to the nuances that have been discussed at length in this thread. My > preference would have been to the timestamp (now called > LogAppendTimestamp) have nothing to do with the applications. Ewen > raised a valid concern about leaking such “private/server-side” > timestamps into the protocol spec. i.e., it is fine to have the > CreateTime which is expressly client-provided and immutable > thereafter, but the LogAppendTime is also going part of the protocol > and it would be good to avoid exposure (to client developers) if > possible. Ok, so here is a slightly different approach that I was just > thinking about (and did not think too far so it may not work): do not > add the LogAppendTime to messages. Instead, build the time-based index > on the server side on message arrival time alone. Introduce a new > ReplicaFetchRequest/Response pair. ReplicaFetchResponses will also > include the slice of the time-based index for the follower broker. > This way we can at least keep timestamps aligned across brokers for > retention purposes. We do lose the append timestamp for mirroring > pipelines (which appears to be the case in KIP-32 as well). > > Configurable index granularity: We can do this but I’m not sure it is > very useful and as Jay noted, a major change from the old proposal > linked from the KIP is the sparse time-based index which we felt was > essential to bound memory usage (and having timestamps on each log > index entry was probably a big waste since in the common case several > messages span the same timestamp). BTW another benefit of the second > index is that it makes it easier to roll-back or throw away if > necessary (vs. modifying the existing index format) - although that > obviously does not help with rolling back the timestamp change in the > message format, but it is one less thing to worry about. > > Versioning: I’m not sure everyone is saying the same thing wrt the > scope of this. There is the record format change, but I also think > this ties into all of the API versioning that we already have in > Kafka. The current API versioning approach works fine for > upgrades/downgrades across official Kafka releases, but not so well > between releases. (We almost got bitten by this at LinkedIn with the > recent changes to various requests but were able to work around > these.) We can clarify this in the follow-up KIP. > > Thanks, > > Joel > > > On Thu, Sep 10, 2015 at 3:00 PM, Jiangjie Qin <j...@linkedin.com.invalid> > wrote: > > Hi Jay, > > > > I just changed the KIP title and updated the KIP page. > > > > And yes, we are working on a general version control proposal to make the > > protocol migration like this more smooth. I will also create a KIP for > that > > soon. > > > > Thanks, > > > > Jiangjie (Becket) Qin > > > > > > On Thu, Sep 10, 2015 at 2:21 PM, Jay Kreps <j...@confluent.io> wrote: > > > >> Great, can we change the name to something related to the > change--"KIP-31: > >> Move to relative offsets in compressed message sets". > >> > >> Also you had mentioned before you were going to expand on the mechanics > of > >> handling these log format changes, right? > >> > >> -Jay > >> > >> On Thu, Sep 10, 2015 at 12:42 PM, Jiangjie Qin > <j...@linkedin.com.invalid> > >> wrote: > >> > >> > Neha and Jay, > >> > > >> > Thanks a lot for the feedback. Good point about splitting the > >> discussion. I > >> > have split the proposal to three KIPs and it does make each discussion > >> more > >> > clear: > >> > KIP-31 - Message format change (Use relative offset) > >> > KIP-32 - Add CreateTime and LogAppendTime to Kafka message > >> > KIP-33 - Build a time-based log index > >> > > >> > KIP-33 can be a follow up KIP for KIP-32, so we can discuss about > KIP-31 > >> > and KIP-32 first for now. I will create a separate discussion thread > for > >> > KIP-32 and reply the concerns you raised regarding the timestamp. > >> > > >> > So far it looks there is no objection to KIP-31. Since I removed a few > >> part > >> > from previous KIP and only left the relative offset proposal, it > would be > >> > great if people can take another look to see if there is any concerns. > >> > > >> > Thanks, > >> > > >> > Jiangjie (Becket) Qin > >> > > >> > > >> > On Tue, Sep 8, 2015 at 1:28 PM, Neha Narkhede <n...@confluent.io> > wrote: > >> > > >> > > Becket, > >> > > > >> > > Nice write-up. Few thoughts - > >> > > > >> > > I'd split up the discussion for simplicity. Note that you can always > >> > group > >> > > several of these in one patch to reduce the protocol changes people > >> have > >> > to > >> > > deal with.This is just a suggestion, but I think the following split > >> > might > >> > > make it easier to tackle the changes being proposed - > >> > > > >> > > - Relative offsets > >> > > - Introducing the concept of time > >> > > - Time-based indexing (separate the usage of the timestamp field > >> from > >> > > how/whether we want to include a timestamp in the message) > >> > > > >> > > I'm a +1 on relative offsets, we should've done it back when we > >> > introduced > >> > > it. Other than reducing the CPU overhead, this will also reduce the > >> > garbage > >> > > collection overhead on the brokers. > >> > > > >> > > On the timestamp field, I generally agree that we should add a > >> timestamp > >> > to > >> > > a Kafka message but I'm not quite sold on how this KIP suggests the > >> > > timestamp be set. Will avoid repeating the downsides of a broker > side > >> > > timestamp mentioned previously in this thread. I think the topic of > >> > > including a timestamp in a Kafka message requires a lot more thought > >> and > >> > > details than what's in this KIP. I'd suggest we make it a separate > KIP > >> > that > >> > > includes a list of all the different use cases for the timestamp > >> (beyond > >> > > log retention) including stream processing and discuss tradeoffs of > >> > > including client and broker side timestamps. > >> > > > >> > > Agree with the benefit of time-based indexing, but haven't had a > chance > >> > to > >> > > dive into the design details yet. > >> > > > >> > > Thanks, > >> > > Neha > >> > > > >> > > On Tue, Sep 8, 2015 at 10:57 AM, Jay Kreps <j...@confluent.io> > wrote: > >> > > > >> > > > Hey Beckett, > >> > > > > >> > > > I was proposing splitting up the KIP just for simplicity of > >> discussion. > >> > > You > >> > > > can still implement them in one patch. I think otherwise it will > be > >> > hard > >> > > to > >> > > > discuss/vote on them since if you like the offset proposal but not > >> the > >> > > time > >> > > > proposal what do you do? > >> > > > > >> > > > Introducing a second notion of time into Kafka is a pretty massive > >> > > > philosophical change so it kind of warrants it's own KIP I think > it > >> > isn't > >> > > > just "Change message format". > >> > > > > >> > > > WRT time I think one thing to clarify in the proposal is how MM > will > >> > have > >> > > > access to set the timestamp? Presumably this will be a new field > in > >> > > > ProducerRecord, right? If so then any user can set the timestamp, > >> > right? > >> > > > I'm not sure you answered the questions around how this will work > for > >> > MM > >> > > > since when MM retains timestamps from multiple partitions they > will > >> > then > >> > > be > >> > > > out of order and in the past (so the max(lastAppendedTimestamp, > >> > > > currentTimeMillis) override you proposed will not work, right?). > If > >> we > >> > > > don't do this then when you set up mirroring the data will all be > new > >> > and > >> > > > you have the same retention problem you described. Maybe I missed > >> > > > something...? > >> > > > > >> > > > My main motivation is that given that both Samza and Kafka streams > >> are > >> > > > doing work that implies a mandatory client-defined notion of > time, I > >> > > really > >> > > > think introducing a different mandatory notion of time in Kafka is > >> > going > >> > > to > >> > > > be quite odd. We should think hard about how client-defined time > >> could > >> > > > work. I'm not sure if it can, but I'm also not sure that it can't. > >> > Having > >> > > > both will be odd. Did you chat about this with Yi/Kartik on the > Samza > >> > > side? > >> > > > > >> > > > When you are saying it won't work you are assuming some particular > >> > > > implementation? Maybe that the index is a monotonically increasing > >> set > >> > of > >> > > > pointers to the least record with a timestamp larger than the > index > >> > time? > >> > > > In other words a search for time X gives the largest offset at > which > >> > all > >> > > > records are <= X? > >> > > > > >> > > > For retention, I agree with the problem you point out, but I think > >> what > >> > > you > >> > > > are saying in that case is that you want a size limit too. If you > use > >> > > > system time you actually hit the same problem: say you do a full > dump > >> > of > >> > > a > >> > > > DB table with a setting of 7 days retention, your retention will > >> > actually > >> > > > not get enforced for the first 7 days because the data is "new to > >> > Kafka". > >> > > > > >> > > > -Jay > >> > > > > >> > > > > >> > > > On Mon, Sep 7, 2015 at 10:44 AM, Jiangjie Qin > >> > <j...@linkedin.com.invalid > >> > > > > >> > > > wrote: > >> > > > > >> > > > > Jay, > >> > > > > > >> > > > > Thanks for the comments. Yes, there are actually three > proposals as > >> > you > >> > > > > pointed out. > >> > > > > > >> > > > > We will have a separate proposal for (1) - version control > >> mechanism. > >> > > We > >> > > > > actually thought about whether we want to separate 2 and 3 > >> internally > >> > > > > before creating the KIP. The reason we put 2 and 3 together is > it > >> > will > >> > > > > saves us another cross board wire protocol change. Like you > said, > >> we > >> > > have > >> > > > > to migrate all the clients in all languages. To some extent, the > >> > effort > >> > > > to > >> > > > > spend on upgrading the clients can be even bigger than > implementing > >> > the > >> > > > new > >> > > > > feature itself. So there are some attractions if we can do 2 > and 3 > >> > > > together > >> > > > > instead of separately. Maybe after (1) is done it will be > easier to > >> > do > >> > > > > protocol migration. But if we are able to come to an agreement > on > >> the > >> > > > > timestamp solution, I would prefer to have it together with > >> relative > >> > > > offset > >> > > > > in the interest of avoiding another wire protocol change (the > >> process > >> > > to > >> > > > > migrate to relative offset is exactly the same as migrate to > >> message > >> > > with > >> > > > > timestamp). > >> > > > > > >> > > > > In terms of timestamp. I completely agree that having client > >> > timestamp > >> > > is > >> > > > > more useful if we can make sure the timestamp is good. But in > >> reality > >> > > > that > >> > > > > can be a really big *IF*. I think the problem is exactly as Ewen > >> > > > mentioned, > >> > > > > if we let the client to set the timestamp, it would be very hard > >> for > >> > > the > >> > > > > broker to utilize it. If broker apply retention policy based on > the > >> > > > client > >> > > > > timestamp. One misbehave producer can potentially completely > mess > >> up > >> > > the > >> > > > > retention policy on the broker. Although people don't care about > >> > server > >> > > > > side timestamp. People do care a lot when timestamp breaks. > >> Searching > >> > > by > >> > > > > timestamp is a really important use case even though it is not > used > >> > as > >> > > > > often as searching by offset. It has significant direct impact > on > >> RTO > >> > > > when > >> > > > > there is a cross cluster failover as Todd mentioned. > >> > > > > > >> > > > > The trick using max(lastAppendedTimestamp, currentTimeMillis) > is to > >> > > > > guarantee monotonic increase of the timestamp. Many commercial > >> system > >> > > > > actually do something similar to this to solve the time skew. > About > >> > > > > changing the time, I am not sure if people use NTP like using a > >> watch > >> > > to > >> > > > > just set it forward/backward by an hour or so. The time > adjustment > >> I > >> > > used > >> > > > > to do is typically to adjust something like a minute / week. So > >> for > >> > > each > >> > > > > second, there might be a few mircoseconds slower/faster but > should > >> > not > >> > > > > break the clock completely to make sure all the time-based > >> > transactions > >> > > > are > >> > > > > not affected. The one minute change will be done within a week > but > >> > not > >> > > > > instantly. > >> > > > > > >> > > > > Personally, I think having client side timestamp will be useful > if > >> we > >> > > > don't > >> > > > > need to put the broker and data integrity under risk. If we > have to > >> > > > choose > >> > > > > from one of them but not both. I would prefer server side > timestamp > >> > > > because > >> > > > > for client side timestamp there is always a plan B which is > putting > >> > the > >> > > > > timestamp into payload. > >> > > > > > >> > > > > Another reason I am reluctant to use the client side timestamp > is > >> > that > >> > > it > >> > > > > is always dangerous to mix the control plane with data plane. IP > >> did > >> > > this > >> > > > > and it has caused so many different breaches so people are > >> migrating > >> > to > >> > > > > something like MPLS. An example in Kafka is that any client can > >> > > > construct a > >> > > > > > LeaderAndIsrRequest/UpdateMetadataRequest/ContorlledShutdownRequest > >> > > (you > >> > > > > name it) and send it to the broker to mess up the entire > cluster, > >> > also > >> > > as > >> > > > > we already noticed a busy cluster can respond quite slow to > >> > controller > >> > > > > messages. So it would really be nice if we can avoid giving the > >> power > >> > > to > >> > > > > clients to control the log retention. > >> > > > > > >> > > > > Thanks, > >> > > > > > >> > > > > Jiangjie (Becket) Qin > >> > > > > > >> > > > > > >> > > > > On Sun, Sep 6, 2015 at 9:54 PM, Todd Palino <tpal...@gmail.com> > >> > wrote: > >> > > > > > >> > > > > > So, with regards to why you want to search by timestamp, the > >> > biggest > >> > > > > > problem I've seen is with consumers who want to reset their > >> > > timestamps > >> > > > > to a > >> > > > > > specific point, whether it is to replay a certain amount of > >> > messages, > >> > > > or > >> > > > > to > >> > > > > > rewind to before some problem state existed. This happens more > >> > often > >> > > > than > >> > > > > > anyone would like. > >> > > > > > > >> > > > > > To handle this now we need to constantly export the broker's > >> offset > >> > > for > >> > > > > > every partition to a time-series database and then use > external > >> > > > processes > >> > > > > > to query this. I know we're not the only ones doing this. The > way > >> > the > >> > > > > > broker handles requests for offsets by timestamp is a little > >> obtuse > >> > > > > > (explain it to anyone without intimate knowledge of the > internal > >> > > > workings > >> > > > > > of the broker - every time I do I see this). In addition, as > >> Becket > >> > > > > pointed > >> > > > > > out, it causes problems specifically with retention of > messages > >> by > >> > > time > >> > > > > > when you move partitions around. > >> > > > > > > >> > > > > > I'm deliberately avoiding the discussion of what timestamp to > >> use. > >> > I > >> > > > can > >> > > > > > see the argument either way, though I tend to lean towards the > >> idea > >> > > > that > >> > > > > > the broker timestamp is the only viable source of truth in > this > >> > > > > situation. > >> > > > > > > >> > > > > > -Todd > >> > > > > > > >> > > > > > > >> > > > > > On Sun, Sep 6, 2015 at 7:08 PM, Ewen Cheslack-Postava < > >> > > > e...@confluent.io > >> > > > > > > >> > > > > > wrote: > >> > > > > > > >> > > > > > > On Sun, Sep 6, 2015 at 4:57 PM, Jay Kreps <j...@confluent.io > > > >> > > wrote: > >> > > > > > > > >> > > > > > > > > >> > > > > > > > 2. Nobody cares what time it is on the server. > >> > > > > > > > > >> > > > > > > > >> > > > > > > This is a good way of summarizing the issue I was trying to > get > >> > at, > >> > > > > from > >> > > > > > an > >> > > > > > > app's perspective. Of the 3 stated goals of the KIP, #2 (lot > >> > > > retention) > >> > > > > > is > >> > > > > > > reasonably handled by a server-side timestamp. I really just > >> care > >> > > > that > >> > > > > a > >> > > > > > > message is there long enough that I have a chance to process > >> it. > >> > #3 > >> > > > > > > (searching by timestamp) only seems useful if we can > guarantee > >> > the > >> > > > > > > server-side timestamp is close enough to the original > >> client-side > >> > > > > > > timestamp, and any mirror maker step seems to break that > (even > >> > > > ignoring > >> > > > > > any > >> > > > > > > issues with broker availability). > >> > > > > > > > >> > > > > > > I'm also wondering whether optimizing for > search-by-timestamp > >> on > >> > > the > >> > > > > > broker > >> > > > > > > is really something we want to do given that messages aren't > >> > really > >> > > > > > > guaranteed to be ordered by application-level timestamps on > the > >> > > > broker. > >> > > > > > Is > >> > > > > > > part of the need for this just due to the current consumer > APIs > >> > > being > >> > > > > > > difficult to work with? For example, could you implement > this > >> > > pretty > >> > > > > > easily > >> > > > > > > client side just the way you would broker-side? I'd imagine > a > >> > > couple > >> > > > of > >> > > > > > > random seeks + reads during very rare occasions (i.e. when > the > >> > app > >> > > > > starts > >> > > > > > > up) wouldn't be a problem performance-wise. Or is it also > that > >> > you > >> > > > need > >> > > > > > the > >> > > > > > > broker to enforce things like monotonically increasing > >> timestamps > >> > > > since > >> > > > > > you > >> > > > > > > can't do the query properly and efficiently without that > >> > guarantee, > >> > > > and > >> > > > > > > therefore what applications are actually looking for *is* > >> > > broker-side > >> > > > > > > timestamps? > >> > > > > > > > >> > > > > > > -Ewen > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > > Consider cases where data is being copied from a database > or > >> > from > >> > > > log > >> > > > > > > > files. In steady-state the server time is very close to > the > >> > > client > >> > > > > time > >> > > > > > > if > >> > > > > > > > their clocks are sync'd (see 1) but there will be times of > >> > large > >> > > > > > > divergence > >> > > > > > > > when the copying process is stopped or falls behind. When > >> this > >> > > > occurs > >> > > > > > it > >> > > > > > > is > >> > > > > > > > clear that the time the data arrived on the server is > >> > irrelevant, > >> > > > it > >> > > > > is > >> > > > > > > the > >> > > > > > > > source timestamp that matters. This is the problem you are > >> > trying > >> > > > to > >> > > > > > fix > >> > > > > > > by > >> > > > > > > > retaining the mm timestamp but really the client should > >> always > >> > > set > >> > > > > the > >> > > > > > > time > >> > > > > > > > with the use of server-side time as a fallback. It would > be > >> > worth > >> > > > > > talking > >> > > > > > > > to the Samza folks and reading through this blog post ( > >> > > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > >> > > > >> > > >> > http://radar.oreilly.com/2015/08/the-world-beyond-batch-streaming-101.html > >> > > > > > > > ) > >> > > > > > > > on this subject since we went through similar learnings on > >> the > >> > > > stream > >> > > > > > > > processing side. > >> > > > > > > > > >> > > > > > > > I think the implication of these two is that we need a > >> proposal > >> > > > that > >> > > > > > > > handles potentially very out-of-order timestamps in some > kind > >> > of > >> > > > > sanish > >> > > > > > > way > >> > > > > > > > (buggy clients will set something totally wrong as the > time). > >> > > > > > > > > >> > > > > > > > -Jay > >> > > > > > > > > >> > > > > > > > On Sun, Sep 6, 2015 at 4:22 PM, Jay Kreps < > j...@confluent.io> > >> > > > wrote: > >> > > > > > > > > >> > > > > > > > > The magic byte is used to version message format so > we'll > >> > need > >> > > to > >> > > > > > make > >> > > > > > > > > sure that check is in place--I actually don't see it in > the > >> > > > current > >> > > > > > > > > consumer code which I think is a bug we should fix for > the > >> > next > >> > > > > > release > >> > > > > > > > > (filed KAFKA-2523). The purpose of that field is so > there > >> is > >> > a > >> > > > > clear > >> > > > > > > > check > >> > > > > > > > > on the format rather than the scrambled scenarios Becket > >> > > > describes. > >> > > > > > > > > > >> > > > > > > > > Also, Becket, I don't think just fixing the java client > is > >> > > > > sufficient > >> > > > > > > as > >> > > > > > > > > that would break other clients--i.e. if anyone writes a > v1 > >> > > > > messages, > >> > > > > > > even > >> > > > > > > > > by accident, any non-v1-capable consumer will break. I > >> think > >> > we > >> > > > > > > probably > >> > > > > > > > > need a way to have the server ensure a particular > message > >> > > format > >> > > > > > either > >> > > > > > > > at > >> > > > > > > > > read or write time. > >> > > > > > > > > > >> > > > > > > > > -Jay > >> > > > > > > > > > >> > > > > > > > > On Thu, Sep 3, 2015 at 3:47 PM, Jiangjie Qin > >> > > > > > <j...@linkedin.com.invalid > >> > > > > > > > > >> > > > > > > > > wrote: > >> > > > > > > > > > >> > > > > > > > >> Hi Guozhang, > >> > > > > > > > >> > >> > > > > > > > >> I checked the code again. Actually CRC check probably > >> won't > >> > > > fail. > >> > > > > > The > >> > > > > > > > >> newly > >> > > > > > > > >> added timestamp field might be treated as keyLength > >> instead, > >> > > so > >> > > > we > >> > > > > > are > >> > > > > > > > >> likely to receive an IllegalArgumentException when try > to > >> > read > >> > > > the > >> > > > > > > key. > >> > > > > > > > >> I'll update the KIP. > >> > > > > > > > >> > >> > > > > > > > >> Thanks, > >> > > > > > > > >> > >> > > > > > > > >> Jiangjie (Becket) Qin > >> > > > > > > > >> > >> > > > > > > > >> On Thu, Sep 3, 2015 at 12:48 PM, Jiangjie Qin < > >> > > > j...@linkedin.com> > >> > > > > > > > wrote: > >> > > > > > > > >> > >> > > > > > > > >> > Hi, Guozhang, > >> > > > > > > > >> > > >> > > > > > > > >> > Thanks for reading the KIP. By "old consumer", I > meant > >> the > >> > > > > > > > >> > ZookeeperConsumerConnector in trunk now, i.e. without > >> this > >> > > bug > >> > > > > > > fixed. > >> > > > > > > > >> If we > >> > > > > > > > >> > fix the ZookeeperConsumerConnector then it will throw > >> > > > exception > >> > > > > > > > >> complaining > >> > > > > > > > >> > about the unsupported version when it sees message > >> format > >> > > V1. > >> > > > > > What I > >> > > > > > > > was > >> > > > > > > > >> > trying to say is that if we have some > >> > > > ZookeeperConsumerConnector > >> > > > > > > > running > >> > > > > > > > >> > without the fix, the consumer will complain about CRC > >> > > mismatch > >> > > > > > > instead > >> > > > > > > > >> of > >> > > > > > > > >> > unsupported version. > >> > > > > > > > >> > > >> > > > > > > > >> > Thanks, > >> > > > > > > > >> > > >> > > > > > > > >> > Jiangjie (Becket) Qin > >> > > > > > > > >> > > >> > > > > > > > >> > On Thu, Sep 3, 2015 at 12:15 PM, Guozhang Wang < > >> > > > > > wangg...@gmail.com> > >> > > > > > > > >> wrote: > >> > > > > > > > >> > > >> > > > > > > > >> >> Thanks for the write-up Jiangjie. > >> > > > > > > > >> >> > >> > > > > > > > >> >> One comment about migration plan: "For old > consumers, > >> if > >> > > they > >> > > > > see > >> > > > > > > the > >> > > > > > > > >> new > >> > > > > > > > >> >> protocol the CRC check will fail".. > >> > > > > > > > >> >> > >> > > > > > > > >> >> Do you mean this bug in the old consumer cannot be > >> fixed > >> > > in a > >> > > > > > > > >> >> backward-compatible way? > >> > > > > > > > >> >> > >> > > > > > > > >> >> Guozhang > >> > > > > > > > >> >> > >> > > > > > > > >> >> > >> > > > > > > > >> >> On Thu, Sep 3, 2015 at 8:35 AM, Jiangjie Qin > >> > > > > > > > <j...@linkedin.com.invalid > >> > > > > > > > >> > > >> > > > > > > > >> >> wrote: > >> > > > > > > > >> >> > >> > > > > > > > >> >> > Hi, > >> > > > > > > > >> >> > > >> > > > > > > > >> >> > We just created KIP-31 to propose a message format > >> > change > >> > > > in > >> > > > > > > Kafka. > >> > > > > > > > >> >> > > >> > > > > > > > >> >> > > >> > > > > > > > >> >> > > >> > > > > > > > >> >> > >> > > > > > > > >> > >> > > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > >> > > > >> > > >> > https://cwiki.apache.org/confluence/display/KAFKA/KIP-31+-+Message+format+change+proposal > >> > > > > > > > >> >> > > >> > > > > > > > >> >> > As a summary, the motivations are: > >> > > > > > > > >> >> > 1. Avoid server side message re-compression > >> > > > > > > > >> >> > 2. Honor time-based log roll and retention > >> > > > > > > > >> >> > 3. Enable offset search by timestamp at a finer > >> > > > granularity. > >> > > > > > > > >> >> > > >> > > > > > > > >> >> > Feedback and comments are welcome! > >> > > > > > > > >> >> > > >> > > > > > > > >> >> > Thanks, > >> > > > > > > > >> >> > > >> > > > > > > > >> >> > Jiangjie (Becket) Qin > >> > > > > > > > >> >> > > >> > > > > > > > >> >> > >> > > > > > > > >> >> > >> > > > > > > > >> >> > >> > > > > > > > >> >> -- > >> > > > > > > > >> >> -- Guozhang > >> > > > > > > > >> >> > >> > > > > > > > >> > > >> > > > > > > > >> > > >> > > > > > > > >> > >> > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > -- > >> > > > > > > Thanks, > >> > > > > > > Ewen > >> > > > > > > > >> > > > > > > >> > > > > > >> > > > > >> > > > >> > > > >> > > > >> > > -- > >> > > Thanks, > >> > > Neha > >> > > > >> > > >> >
