Hi Dong, It looks like this vote passed. Can you close this thread and update the KIP table?
Thanks, Apurva On Tue, Jan 24, 2017 at 1:30 PM, Jun Rao <j...@confluent.io> wrote: > Hi, Dong, > > The changes sound good to me. Also, thanks for the explanation of returning > a future from purgeDataFrom(). We can keep it that way. > > Thanks, > > Jun > > On Mon, Jan 23, 2017 at 4:24 PM, Dong Lin <lindon...@gmail.com> wrote: > > > Hi all, > > > > When I am implementing the patch, I realized that the current usage of > > "low_watermark" is a bit confusing. So I made the following interface > > changes in the KIP: > > > > - The newly added checkpoint file will be named > log-begin-offset-checkpoint > > - Replace low_watermark with log_begin_offset in FetchRequestPartition > and > > FetchResponsePartitionHeader > > > > The problem with the previous naming conversion is that, low_watermark > > implies minimum log begin offset of all replicas (similar to high > > watermark) and we return this value in the PurgeResponse. In other words, > > low_watermark can not be incremented if a follower is not live. Therefore > > we can not use low_watermark in the checkpoint file or in the > FetchResponse > > from leader to followers if we want to persists the offset-to-purge > > received from user across broker rebounce. > > > > You can find the changes in KIP here > > <https://cwiki.apache.org/confluence/pages/diffpagesbyversion.action? > > pageId=67636826&selectedPageVersions=13&selectedPageVersions=14>. > > Please let me know if you have any concern with this change. > > > > Thanks, > > Dong > > > > On Mon, Jan 23, 2017 at 11:20 AM, Dong Lin <lindon...@gmail.com> wrote: > > > > > Thanks for the comment Jun. > > > > > > Yeah, I think there is use-case where this can be useful. Allowing for > > > asynchronous delete will be useful if an application doesn't need > strong > > > guarantee of purgeDataFrom(), e.g. if it is done to help reduce disk > > usage > > > of kafka. The application may want to purge data for every time it does > > > auto-commit without wait for future object to complete. On the other > > hand, > > > synchronous delete will be useful if an application wants to make sure > > that > > > the sensitive or bad data is definitely deleted. I think returning a > > future > > > makes both choice available to user and it doesn't complicate > > > implementation much. > > > > > > > > > On Mon, Jan 23, 2017 at 10:45 AM, Jun Rao <j...@confluent.io> wrote: > > > > > >> I feel that it's simpler to just keep the format of the checkpoint > file > > as > > >> it is and just add a separate checkpoint for low watermark. Low > > watermark > > >> and high watermark are maintained independently. So, not sure if there > > is > > >> significant benefit of storing them together. > > >> > > >> Looking at the KIP again. I actually have another question on the api. > > Is > > >> there any benefit of returning a Future in the purgeDataBefore() api? > > >> Since > > >> admin apis are used infrequently, it seems that it's simpler to just > > have > > >> a > > >> blocking api and returns Map<TopicPartition, PurgeDataResult>? > > >> > > >> Thanks, > > >> > > >> Jun > > >> > > >> On Sun, Jan 22, 2017 at 3:56 PM, Dong Lin <lindon...@gmail.com> > wrote: > > >> > > >> > Thanks for the comment Guozhang. Please don't worry about being > late. > > I > > >> > would like to update the KIP if there is clear benefit of the new > > >> approach. > > >> > I am wondering if there is any use-case or operation aspects that > > would > > >> > benefit from the new approach. > > >> > > > >> > I am not saying that these checkpoint files have the same priority. > I > > >> > mentioned other checkpoint files to suggest that it is OK to add one > > >> more > > >> > checkpoint file. To me three checkpoint files is not much different > > from > > >> > four checkpoint files. I am just inclined to not update the KIP if > the > > >> only > > >> > benefit is to avoid addition of a new checkpoint file. > > >> > > > >> > > > >> > > > >> > On Sun, Jan 22, 2017 at 3:48 PM, Guozhang Wang <wangg...@gmail.com> > > >> wrote: > > >> > > > >> > > To me the distinction between recovery-checkpoint and > > >> > > replication-checkpoint are different from the distinction between > > >> these > > >> > two > > >> > > hw checkpoint values: when broker starts up and act as the leader > > for > > >> a > > >> > > partition, it can live without seeing the recovery checkpoint, but > > >> just > > >> > > cannot rely on the existing last log segment and need to fetch > from > > >> other > > >> > > replicas; but if the replication-checkpoint file is missing, it > is a > > >> > > correctness issue, as it does not know from where to truncate its > > >> data, > > >> > and > > >> > > also how to respond to a fetch request. That is why I think we can > > >> > separate > > >> > > these two types of files, since the latter one is more important > > than > > >> the > > >> > > previous one. > > >> > > > > >> > > That being said, I do not want to recall another vote on this > since > > >> it is > > >> > > my bad not responding before the vote is called. Just wanted to > > point > > >> out > > >> > > for the record that this approach may have some operational > > scenarios > > >> > where > > >> > > one of the replication files is missing and we need to treat them > > >> > > specifically. > > >> > > > > >> > > > > >> > > Guozhang > > >> > > > > >> > > > > >> > > On Sun, Jan 22, 2017 at 1:56 PM, Dong Lin <lindon...@gmail.com> > > >> wrote: > > >> > > > > >> > > > Yeah, your solution of adding new APIs certainly works and I > don't > > >> > think > > >> > > > that is an issue. On the other hand I don't think it is an issue > > to > > >> > add a > > >> > > > new checkpoint file as well since we already have multiple > > >> checkpoint > > >> > > > files. The benefit of the new approach you mentioned is probably > > >> not an > > >> > > > issue in the current approach since high watermark and low > > watermark > > >> > > works > > >> > > > completely independently. Since there is no strong reason to > > choose > > >> > > either > > >> > > > of them, I am inclined to choose the one that makes less format > > >> change > > >> > > and > > >> > > > simpler in the Java API. The current approach seems better w.r.t > > >> this > > >> > > minor > > >> > > > reason. > > >> > > > > > >> > > > If you are strong that we should use the new approach, I can do > > >> that as > > >> > > > well. Please let me know if you think so, and I will need to ask > > >> > > > Jun/Joel/Becket to vote on this again since this changes the > > >> interface > > >> > of > > >> > > > the KIP. > > >> > > > > > >> > > > On Sun, Jan 22, 2017 at 9:35 AM, Guozhang Wang < > > wangg...@gmail.com> > > >> > > wrote: > > >> > > > > > >> > > > > I think this is less of an issue: we can use the same patterns > > as > > >> in > > >> > > the > > >> > > > > request protocol, i.e.: > > >> > > > > > > >> > > > > write(Map[TP, Long]) // write the checkout point in v0 format > > >> > > > > write(Map[TP, Pair[Long, Long]]) // write the checkout point > in > > v1 > > >> > > format > > >> > > > > > > >> > > > > CheckpointedOffsets read() // read the file relying on its > > >> version id > > >> > > > > > > >> > > > > class CheckpointedOffsets { > > >> > > > > > > >> > > > > Integer getVersion(); > > >> > > > > Long getFirstOffset(); > > >> > > > > Long getSecondOffset(); // would return NO_AVAILABLE > with > > v0 > > >> > > format > > >> > > > > } > > >> > > > > > > >> > > > > > > >> > > > > As I think of it, another benefit is that we wont have a > > partition > > >> > that > > >> > > > > only have one of the watermarks in case of a failure in > between > > >> > writing > > >> > > > two > > >> > > > > files. > > >> > > > > > > >> > > > > Guozhang > > >> > > > > > > >> > > > > On Sun, Jan 22, 2017 at 12:03 AM, Dong Lin < > lindon...@gmail.com > > > > > >> > > wrote: > > >> > > > > > > >> > > > > > Hey Guozhang, > > >> > > > > > > > >> > > > > > Thanks for the review:) Yes it is possible to combine them. > > Both > > >> > > > solution > > >> > > > > > will have the same performance. But I think the current > > solution > > >> > will > > >> > > > > give > > >> > > > > > us simpler Java class design. Note that we will have to > change > > >> Java > > >> > > API > > >> > > > > > (e.g. read() and write()) of OffsetCheckpoint class in order > > to > > >> > > > provide a > > >> > > > > > map from TopicPartition to a pair of integers when we write > to > > >> > > > checkpoint > > >> > > > > > file. This makes this class less generic since this API is > not > > >> used > > >> > > by > > >> > > > > log > > >> > > > > > recovery checkpoint and log cleaner checkpoint which are > also > > >> using > > >> > > > > > OffsetCheckpoint class. > > >> > > > > > > > >> > > > > > Dong > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > > > On Sat, Jan 21, 2017 at 12:28 PM, Guozhang Wang < > > >> > wangg...@gmail.com> > > >> > > > > > wrote: > > >> > > > > > > > >> > > > > > > Hi Dong, > > >> > > > > > > > > >> > > > > > > Sorry for being late on reviewing this KIP. It LGTM > overall, > > >> but > > >> > > I'm > > >> > > > > > > wondering if we can save adding the > > >> "replication-low-watermark- > > >> > > > > > checkpoint" > > >> > > > > > > file by just bumping up the version number of > > >> > "replication-offset- > > >> > > > > > > checkpoint" > > >> > > > > > > to let it have two values for each partition, i.e.: > > >> > > > > > > > > >> > > > > > > 1 // version number > > >> > > > > > > [number of partitions] > > >> > > > > > > [topic name] [partition id] [lwm] [hwm] > > >> > > > > > > > > >> > > > > > > > > >> > > > > > > This will affects the upgrade path a bit, but I think not > by > > >> > large, > > >> > > > and > > >> > > > > > all > > >> > > > > > > other logic will not be affected. > > >> > > > > > > > > >> > > > > > > > > >> > > > > > > Guozhang > > >> > > > > > > > > >> > > > > > > > > >> > > > > > > > > >> > > > > > > On Wed, Jan 18, 2017 at 6:12 PM, Dong Lin < > > >> lindon...@gmail.com> > > >> > > > wrote: > > >> > > > > > > > > >> > > > > > > > Thanks to everyone who voted and provided feedback! > > >> > > > > > > > > > >> > > > > > > > This KIP is now adopted with 3 binding +1s (Jun, Joel, > > >> Becket) > > >> > > and > > >> > > > 2 > > >> > > > > > > > non-binding +1s (Radai, Mayuresh). > > >> > > > > > > > > > >> > > > > > > > Thanks, > > >> > > > > > > > Dong > > >> > > > > > > > > > >> > > > > > > > On Wed, Jan 18, 2017 at 6:05 PM, Jun Rao < > > j...@confluent.io> > > >> > > wrote: > > >> > > > > > > > > > >> > > > > > > > > Hi, Dong, > > >> > > > > > > > > > > >> > > > > > > > > Thanks for the update. +1 > > >> > > > > > > > > > > >> > > > > > > > > Jun > > >> > > > > > > > > > > >> > > > > > > > > On Wed, Jan 18, 2017 at 1:44 PM, Dong Lin < > > >> > lindon...@gmail.com > > >> > > > > > >> > > > > > wrote: > > >> > > > > > > > > > > >> > > > > > > > > > Hi Jun, > > >> > > > > > > > > > > > >> > > > > > > > > > After some more thinking, I agree with you that it > is > > >> > better > > >> > > to > > >> > > > > > > simply > > >> > > > > > > > > > throw OffsetOutOfRangeException and not update > > >> > low_watermark > > >> > > if > > >> > > > > > > > > > offsetToPurge is larger than high_watermark. > > >> > > > > > > > > > > > >> > > > > > > > > > My use-case of allowing low_watermark > > high_watermark > > >> in > > >> > > 2(b) > > >> > > > is > > >> > > > > > to > > >> > > > > > > > > allow > > >> > > > > > > > > > user to purge all the data in the log even if that > > data > > >> is > > >> > > not > > >> > > > > > fully > > >> > > > > > > > > > replicated to followers. An offset higher than > > >> > high_watermark > > >> > > > may > > >> > > > > > be > > >> > > > > > > > > > returned to user either through producer's > > >> RecordMetadata, > > >> > or > > >> > > > > > through > > >> > > > > > > > > > ListOffsetResponse if from_consumer option is false. > > >> > However, > > >> > > > > this > > >> > > > > > > may > > >> > > > > > > > > > cause problem in case of unclean leader election or > > when > > >> > > > consumer > > >> > > > > > > seeks > > >> > > > > > > > > to > > >> > > > > > > > > > the largest offset of the partition. It will > > complicate > > >> > this > > >> > > > KIP > > >> > > > > if > > >> > > > > > > we > > >> > > > > > > > > were > > >> > > > > > > > > > to address these two problems. > > >> > > > > > > > > > > > >> > > > > > > > > > At this moment I prefer to keep this KIP simple by > > >> > requiring > > >> > > > > > > > > low_watermark > > >> > > > > > > > > > <= high_watermark. The caveat is that if user does > > want > > >> to > > >> > > > purge > > >> > > > > > > *all* > > >> > > > > > > > > the > > >> > > > > > > > > > data that is already produced, then he needs to stop > > all > > >> > > > > producers > > >> > > > > > > that > > >> > > > > > > > > are > > >> > > > > > > > > > producing into this topic, wait long enough for all > > >> > followers > > >> > > > to > > >> > > > > > > catch > > >> > > > > > > > > up, > > >> > > > > > > > > > and then purge data using the latest offset of this > > >> > > partition, > > >> > > > > i.e. > > >> > > > > > > > > > high_watermark. We can revisit this if some strong > > >> use-case > > >> > > > comes > > >> > > > > > up > > >> > > > > > > in > > >> > > > > > > > > the > > >> > > > > > > > > > future. > > >> > > > > > > > > > > > >> > > > > > > > > > I also updated the KIP to allow user to use offset > -1L > > >> to > > >> > > > > indicate > > >> > > > > > > > > > high_watermark in the PurgeRequest. In the future we > > can > > >> > > allow > > >> > > > > > users > > >> > > > > > > to > > >> > > > > > > > > use > > >> > > > > > > > > > offset -2L to indicate that they want to purge all > > data > > >> up > > >> > to > > >> > > > > > > > > logEndOffset. > > >> > > > > > > > > > > > >> > > > > > > > > > Thanks! > > >> > > > > > > > > > Dong > > >> > > > > > > > > > > > >> > > > > > > > > > > > >> > > > > > > > > > On Wed, Jan 18, 2017 at 10:37 AM, Jun Rao < > > >> > j...@confluent.io> > > >> > > > > > wrote: > > >> > > > > > > > > > > > >> > > > > > > > > > > Hi, Dong, > > >> > > > > > > > > > > > > >> > > > > > > > > > > For 2(b), it seems a bit weird to allow > > highWatermark > > >> to > > >> > be > > >> > > > > > smaller > > >> > > > > > > > > than > > >> > > > > > > > > > > lowWatermark. Also, from the consumer's > perspective, > > >> > > messages > > >> > > > > are > > >> > > > > > > > > > available > > >> > > > > > > > > > > only up to highWatermark. What if we simply throw > > >> > > > > > > > > > OffsetOutOfRangeException > > >> > > > > > > > > > > if offsetToPurge is larger than highWatermark? > > >> > > > > > > > > > > > > >> > > > > > > > > > > Thanks, > > >> > > > > > > > > > > > > >> > > > > > > > > > > Jun > > >> > > > > > > > > > > > > >> > > > > > > > > > > On Tue, Jan 17, 2017 at 9:54 PM, Dong Lin < > > >> > > > lindon...@gmail.com > > >> > > > > > > > >> > > > > > > > wrote: > > >> > > > > > > > > > > > > >> > > > > > > > > > > > Hi Jun, > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > Thank you. Please see my answers below. The KIP > is > > >> > > updated > > >> > > > to > > >> > > > > > > > answer > > >> > > > > > > > > > > these > > >> > > > > > > > > > > > questions (see here > > >> > > > > > > > > > > > <https://cwiki.apache.org/confluence/pages/ > > >> > > > > > > > diffpagesbyversion.action > > >> > > > > > > > > ? > > >> > > > > > > > > > > > pageId=67636826&selectedPageVersions=5& > > >> > > > > selectedPageVersions=6> > > >> > > > > > > > > > > > ). > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > 1. Yes, in this KIP we wait for all replicas. > This > > >> is > > >> > the > > >> > > > > same > > >> > > > > > as > > >> > > > > > > > if > > >> > > > > > > > > > > > producer sends a messge with ack=all and > > >> > > isr=all_replicas. > > >> > > > So > > >> > > > > > it > > >> > > > > > > > > seems > > >> > > > > > > > > > > that > > >> > > > > > > > > > > > the comparison is OK? > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > 2. Good point! I haven't thought about the case > > >> where > > >> > the > > >> > > > > > > > > > user-specified > > >> > > > > > > > > > > > offset > logEndOffset. Please see answers below. > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > a) If offsetToPurge < lowWatermark, the first > > >> condition > > >> > > > > > > > > > > > of DelayedOperationPurgatory will be satisfied > > >> > > immediately > > >> > > > > when > > >> > > > > > > > > broker > > >> > > > > > > > > > > > receives PurgeRequest. Broker will send > > >> PurgeResponse > > >> > to > > >> > > > > admin > > >> > > > > > > > client > > >> > > > > > > > > > > > immediately. The response maps this partition to > > the > > >> > > > > > > lowWatermark. > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > This case is covered as the first condition of > > >> > > > > > > > > > DelayedOperationPurgatory > > >> > > > > > > > > > > in > > >> > > > > > > > > > > > the current KIP. > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > b) If highWatermark < offsetToPurge < > > logEndOffset, > > >> > > leader > > >> > > > > will > > >> > > > > > > > send > > >> > > > > > > > > > > > FetchResponse with low_watermark=offsetToPurge. > > >> > Follower > > >> > > > > > records > > >> > > > > > > > the > > >> > > > > > > > > > > > offsetToPurge as low_watermark and sends > > >> FetchRequest > > >> > to > > >> > > > the > > >> > > > > > > leader > > >> > > > > > > > > > with > > >> > > > > > > > > > > > the new low_watermark. Leader will then send > > >> > > PurgeResponse > > >> > > > to > > >> > > > > > > admin > > >> > > > > > > > > > > client > > >> > > > > > > > > > > > which maps this partition to the new > > low_watermark. > > >> The > > >> > > > data > > >> > > > > in > > >> > > > > > > the > > >> > > > > > > > > > range > > >> > > > > > > > > > > > [highWatermark, offsetToPurge] will still be > > >> appended > > >> > > from > > >> > > > > > leader > > >> > > > > > > > to > > >> > > > > > > > > > > > followers but will not be exposed to consumers. > > And > > >> in > > >> > a > > >> > > > > short > > >> > > > > > > > period > > >> > > > > > > > > > of > > >> > > > > > > > > > > > time low_watermark on the follower will be > higher > > >> than > > >> > > > their > > >> > > > > > > > > > > highWatermark. > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > This case is also covered in the current KIP so > no > > >> > change > > >> > > > is > > >> > > > > > > > > required. > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > c) If logEndOffset < offsetToPurge, leader will > > send > > >> > > > > > > PurgeResponse > > >> > > > > > > > to > > >> > > > > > > > > > > admin > > >> > > > > > > > > > > > client immediately. The response maps this > > >> partition to > > >> > > > > > > > > > > > OffsetOutOfRangeException. > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > This case is not covered by the current KIP. I > > just > > >> > added > > >> > > > > this > > >> > > > > > as > > >> > > > > > > > the > > >> > > > > > > > > > > > second condition for the PurgeRequest to be > > removed > > >> > from > > >> > > > > > > > > > > > DelayedOperationPurgatory (in the Proposed > Change > > >> > > section). > > >> > > > > > Since > > >> > > > > > > > the > > >> > > > > > > > > > > > PurgeRequest is satisfied immediately when the > > >> leader > > >> > > > > receives > > >> > > > > > > it, > > >> > > > > > > > it > > >> > > > > > > > > > > > actually won't be put into the > > >> > DelayedOperationPurgatory. > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > 3. Yes, lowWatermark will be used when > > >> smallest_offset > > >> > is > > >> > > > > used > > >> > > > > > in > > >> > > > > > > > the > > >> > > > > > > > > > > > ListOffsetRequest. I just updated Proposed > Change > > >> > section > > >> > > > to > > >> > > > > > > > specify > > >> > > > > > > > > > > this. > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > Thanks, > > >> > > > > > > > > > > > Dong > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > On Tue, Jan 17, 2017 at 6:53 PM, Jun Rao < > > >> > > j...@confluent.io > > >> > > > > > > >> > > > > > > wrote: > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > > Hi, Dong, > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > Thanks for the KIP. Looks good overall. Just a > > few > > >> > more > > >> > > > > > > comments. > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > 1."Note that the way broker handles > PurgeRequest > > >> is > > >> > > > similar > > >> > > > > > to > > >> > > > > > > > how > > >> > > > > > > > > it > > >> > > > > > > > > > > > > handles ProduceRequest with ack = -1 and > > >> > > > isr=all_replicas". > > >> > > > > > It > > >> > > > > > > > > seems > > >> > > > > > > > > > > that > > >> > > > > > > > > > > > > the implementation is a bit different. In this > > >> KIP, > > >> > we > > >> > > > wait > > >> > > > > > for > > >> > > > > > > > all > > >> > > > > > > > > > > > > replicas. But in producer, acks=all means > > waiting > > >> for > > >> > > all > > >> > > > > > > in-sync > > >> > > > > > > > > > > > replicas. > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > 2. Could you describe the behavior when the > > >> specified > > >> > > > > > > > offsetToPurge > > >> > > > > > > > > > is > > >> > > > > > > > > > > > (a) > > >> > > > > > > > > > > > > smaller than lowWatermark, (b) larger than > > >> > > highWatermark, > > >> > > > > but > > >> > > > > > > > > smaller > > >> > > > > > > > > > > > than > > >> > > > > > > > > > > > > log end offset, (c) larger than log end > offset? > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > 3. In the ListOffsetRequest, will lowWatermark > > be > > >> > > > returned > > >> > > > > > when > > >> > > > > > > > the > > >> > > > > > > > > > > > > smallest_offset option is used? > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > Thanks, > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > Jun > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > On Wed, Jan 11, 2017 at 1:01 PM, Dong Lin < > > >> > > > > > lindon...@gmail.com > > >> > > > > > > > > > >> > > > > > > > > > wrote: > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > Hi all, > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > It seems that there is no further concern > with > > >> the > > >> > > > > KIP-107. > > >> > > > > > > At > > >> > > > > > > > > this > > >> > > > > > > > > > > > point > > >> > > > > > > > > > > > > > we would like to start the voting process. > The > > >> KIP > > >> > > can > > >> > > > be > > >> > > > > > > found > > >> > > > > > > > > at > > >> > > > > > > > > > > > > > https://cwiki.apache.org/confl > > >> > > uence/display/KAFKA/KIP- > > >> > > > > 107 > > >> > > > > > > > > > > > > > %3A+Add+purgeDataBefore%28%29+ > > >> API+in+AdminClient. > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > Thanks, > > >> > > > > > > > > > > > > > Dong > > >> > > > > > > > > > > > > > > > >> > > > > > > > > > > > > > > >> > > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > >> > > > > > > > > >> > > > > > > > > >> > > > > > > > > >> > > > > > > -- > > >> > > > > > > -- Guozhang > > >> > > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > > >> > > > > > > >> > > > > -- > > >> > > > > -- Guozhang > > >> > > > > > > >> > > > > > >> > > > > >> > > > > >> > > > > >> > > -- > > >> > > -- Guozhang > > >> > > > > >> > > > >> > > > > > > > > >
