Glad to see the KIP, Richard. This has been a really long pending issue. The original arguments from Jay for using config, such as max.block.ms, instead of using timeout parameters was that people will always hard code the timeout, and the hard coded timeout is rarely correct because it has to consider different scenarios. For example, users may receive timeout exception when the group coordinator moves. Having a configuration with some reasonable default value will make users' life easier.
That said, in practice, it seems more useful to have timeout parameters. We have seen some library, using the consumers internally, needs to provide an external flexible timeout interface. Also, user can easily hard code a value to get the same as a config based solution. The KIP looks good overall. A few comments: 1. There are a few other blocking methods that are not included, e.g. offsetsForTimes(), beginningOffsets(), endOffsets(). Is there any reason? 2. I am wondering can we take the KIP as a chance to clean up our timeout exception(s)? More specifically, instead of reusing TimeoutException, can we introduce a new ClientTimeoutException with different causes, e.g. UnknownTopicOrPartition, RequestTimeout, LeaderNotAvailable, etc. As of now, the TimeoutException is used in the following three cases: 1. TimeoutException is a subclass of ApiException which indicates the exception was returned by the broker. The TimeoutException was initially returned by the leaders when replication was not done within the specified timeout in the ProduceRequest. It has an error code of 7, which is returned by the broker. 2. When we migrate to Java clients, in Errors definition, we extended it to indicate request timeout, i.e. a request was sent but the response was not received before timeout. In this case, the clients did not have a return code from the broker. 3. Later at some point, we started to use the TimeoutException for clients method call timeout. It is neither related to any broker returned error code, nor to request timeout on the wire. Due to the various interpretations, users can easily be confused. As an example, when a timeout is thrown with "Failed to refresh metadata in X ms", it is hard to tell what exactly happened. Since we are changing the API here, it would be good to avoid introducing more ambiguity and see whether this can be improved. It would be at least one step forward to remove the usage of case 3. Thanks, Jiangjie (Becket) Qin On Mon, Mar 26, 2018 at 5:50 PM, Guozhang Wang <wangg...@gmail.com> wrote: > @Richard: TimeoutException inherits from RetriableException which inherits > from ApiException. So users should explicitly try to capture > RetriableException in their code and handle the exception. > > @Isamel, Ewen: I'm trying to push progress forward on this one, are we now > on the same page for using function parameters than configs? > > > Guozhang > > > On Fri, Mar 23, 2018 at 4:42 PM, Ismael Juma <ism...@juma.me.uk> wrote: > > > Hi Ewen, > > > > Yeah, I mentioned KAFKA-2391 where some of this was discussed. Jay was > > against having timeouts in the methods at the time. However, as Jason > said > > offline, we did end up with a timeout parameter in `poll`. > > > > Ismael > > > > On Fri, Mar 23, 2018 at 4:26 PM, Ewen Cheslack-Postava < > e...@confluent.io> > > wrote: > > > > > Regarding the flexibility question, has someone tried to dig up the > > > discussion of the new consumer APIs when they were being written? I > > vaguely > > > recall these exact questions about using APIs vs configs and > flexibility > > vs > > > bloating the API surface area having already been discussed. (Not that > we > > > shouldn't revisit, just that it might also be a faster way to get to a > > full > > > understanding of the options, concerns, and tradeoffs). > > > > > > -Ewen > > > > > > On Thu, Mar 22, 2018 at 7:19 AM, Richard Yu < > yohan.richard...@gmail.com> > > > wrote: > > > > > > > I do have one question though: in the current KIP, throwing > > > > TimeoutException to mark > > > > that time limit is exceeded is applied to all new methods introduced > in > > > > this proposal. > > > > However, how would users respond when a TimeoutException (since it is > > > > considered > > > > a RuntimeException)? > > > > > > > > Thanks, > > > > Richard > > > > > > > > > > > > > > > > On Mon, Mar 19, 2018 at 6:10 PM, Richard Yu < > > yohan.richard...@gmail.com> > > > > wrote: > > > > > > > > > Hi Ismael, > > > > > > > > > > You have a great point. Since most of the methods in this KIP have > > > > similar > > > > > callbacks (position() and committed() both use > > fetchCommittedOffsets(), > > > > > and > > > > > commitSync() is similar to position(), except just updating > offsets), > > > the > > > > > amount of time > > > > > they block should be also about equal. > > > > > > > > > > However, I think that we need to take into account a couple of > > things. > > > > For > > > > > starters, > > > > > if the new methods were all reliant on one config, there is > > likelihood > > > > > that the > > > > > shortcomings for this approach would be similar to what we faced if > > we > > > > let > > > > > request.timeout.ms control all method timeouts. In comparison, > > adding > > > > > overloads > > > > > does not have this problem. > > > > > > > > > > If you have further thoughts, please let me know. > > > > > > > > > > Richard > > > > > > > > > > > > > > > On Mon, Mar 19, 2018 at 5:12 PM, Ismael Juma <ism...@juma.me.uk> > > > wrote: > > > > > > > > > >> Hi, > > > > >> > > > > >> An option that is not currently covered in the KIP is to have a > > > separate > > > > >> config max.block.ms, which is similar to the producer config with > > the > > > > >> same > > > > >> name. This came up during the KAFKA-2391 discussion. I think it's > > > clear > > > > >> that we can't rely on request.timeout.ms, so the decision is > > between > > > > >> adding > > > > >> overloads or adding a new config. People seemed to be leaning > > towards > > > > the > > > > >> latter in KAFKA-2391, but Jason makes a good point that the > > overloads > > > > are > > > > >> more flexible. A couple of questions from me: > > > > >> > > > > >> 1. Do we need the additional flexibility? > > > > >> 2. If we do, do we need it for every blocking method? > > > > >> > > > > >> Ismael > > > > >> > > > > >> On Mon, Mar 19, 2018 at 5:03 PM, Richard Yu < > > > yohan.richard...@gmail.com > > > > > > > > > >> wrote: > > > > >> > > > > >> > Hi Guozhang, > > > > >> > > > > > >> > I made some clarifications to KIP-266, namely: > > > > >> > 1. Stated more specifically that commitSync will accept user > > input. > > > > >> > 2. fetchCommittedOffsets(): Made its role in blocking more clear > > to > > > > the > > > > >> > reader. > > > > >> > 3. Sketched what would happen when time limit is exceeded. > > > > >> > > > > > >> > These changes should make the KIP easier to understand. > > > > >> > > > > > >> > Cheers, > > > > >> > Richard > > > > >> > > > > > >> > On Mon, Mar 19, 2018 at 9:33 AM, Guozhang Wang < > > wangg...@gmail.com> > > > > >> wrote: > > > > >> > > > > > >> > > Hi Richard, > > > > >> > > > > > > >> > > I made a pass over the KIP again, some more clarifications / > > > > comments: > > > > >> > > > > > > >> > > 1. seek() call itself is not blocking, only the following > poll() > > > > call > > > > >> may > > > > >> > > be blocking as the actually metadata rq will happen. > > > > >> > > > > > > >> > > 2. I saw you did not include Consumer.partitionFor(), > > > > >> > > Consumer.OffsetAndTimestamp() and Consumer.listTopics() in > your > > > KIP. > > > > >> > After > > > > >> > > a second thought, I think this may be a better idea to not > > tackle > > > > >> them in > > > > >> > > the same KIP, and probably we should consider whether we would > > > > change > > > > >> the > > > > >> > > behavior or not in another discussion. So I agree to not > include > > > > them. > > > > >> > > > > > > >> > > 3. In your wiki you mentioned "Another change shall be made to > > > > >> > > KafkaConsumer#poll(), due to its call to > updateFetchPositions() > > > > which > > > > >> > > blocks indefinitely." This part may a bit obscure to most > > readers > > > > >> who's > > > > >> > not > > > > >> > > familiar with the KafkaConsumer internals, could you please > add > > > more > > > > >> > > elaborations. More specifically, I think the root causes of > the > > > > public > > > > >> > APIs > > > > >> > > mentioned are a bit different while the KIP's explanation > sounds > > > > like > > > > >> > they > > > > >> > > are due to the same reason: > > > > >> > > > > > > >> > > 3.1 fetchCommittedOffsets(): this internal call will block > > forever > > > > if > > > > >> the > > > > >> > > committed offsets cannot be fetched successfully and affect > > > > position() > > > > >> > and > > > > >> > > committed(). We need to break out of its internal while loop. > > > > >> > > 3.2 position() itself will while loop when offsets cannot be > > > > >> retrieved in > > > > >> > > the underlying async call. We need to break out this while > loop. > > > > >> > > 3.3 commitSync() passed Long.MAX_VALUE as the timeout value, > we > > > > should > > > > >> > take > > > > >> > > the user specified timeouts when applicable. > > > > >> > > > > > > >> > > > > > > >> > > > > > > >> > > Guozhang > > > > >> > > > > > > >> > > On Sat, Mar 17, 2018 at 4:44 PM, Richard Yu < > > > > >> yohan.richard...@gmail.com> > > > > >> > > wrote: > > > > >> > > > > > > >> > > > Actually, what I said above is inaccurate. In > > > > >> > > > testSeekAndCommitWithBrokerFailures, > TestUtils.waitUntilTrue > > > > >> blocks, > > > > >> > not > > > > >> > > > seek. > > > > >> > > > My assumption is that seek did not update correctly. I will > be > > > > >> digging > > > > >> > > > further into this. > > > > >> > > > > > > > >> > > > > > > > >> > > > > > > > >> > > > On Sat, Mar 17, 2018 at 4:16 PM, Richard Yu < > > > > >> > yohan.richard...@gmail.com> > > > > >> > > > wrote: > > > > >> > > > > > > > >> > > > > One more thing: when looking through tests, I have > realized > > > that > > > > >> > seek() > > > > >> > > > > methods can potentially block indefinitely. As you well > > know, > > > > >> seek() > > > > >> > is > > > > >> > > > > called when pollOnce() or position() is active. Thus, if > > > > >> position() > > > > >> > > > blocks > > > > >> > > > > indefinitely, then so would seek(). Should bounding seek() > > > also > > > > be > > > > >> > > > included > > > > >> > > > > in this KIP? > > > > >> > > > > > > > > >> > > > > Thanks, Richard > > > > >> > > > > > > > > >> > > > > On Sat, Mar 17, 2018 at 1:16 PM, Richard Yu < > > > > >> > > yohan.richard...@gmail.com> > > > > >> > > > > wrote: > > > > >> > > > > > > > > >> > > > >> Thanks for the advice, Jason > > > > >> > > > >> > > > > >> > > > >> I have modified KIP-266 to include the java doc for > > > committed() > > > > >> and > > > > >> > > > other > > > > >> > > > >> blocking methods, and I also > > > > >> > > > >> mentioned poll() which will also be bounded. Let me know > if > > > > >> there is > > > > >> > > > >> anything else. :) > > > > >> > > > >> > > > > >> > > > >> Sincerely, Richard > > > > >> > > > >> > > > > >> > > > >> > > > > >> > > > >> > > > > >> > > > >> > > > > >> > > > >> > > > > >> > > > >> On Sat, Mar 17, 2018 at 12:00 PM, Jason Gustafson < > > > > >> > ja...@confluent.io > > > > >> > > > > > > > >> > > > >> wrote: > > > > >> > > > >> > > > > >> > > > >>> Hi Richard, > > > > >> > > > >>> > > > > >> > > > >>> Thanks for the updates. I'm really glad you picked this > > up. > > > A > > > > >> > couple > > > > >> > > > >>> minor > > > > >> > > > >>> comments: > > > > >> > > > >>> > > > > >> > > > >>> 1. Can you list the full set of new APIs explicitly in > the > > > > KIP? > > > > >> > > > >>> Currently I > > > > >> > > > >>> only see the javadoc for `position()`. > > > > >> > > > >>> > > > > >> > > > >>> 2. We should consider adding `TimeUnit` to the new > methods > > > to > > > > >> avoid > > > > >> > > > unit > > > > >> > > > >>> confusion. I know it's inconsistent with the poll() API, > > > but I > > > > >> > think > > > > >> > > it > > > > >> > > > >>> was > > > > >> > > > >>> probably a mistake not to include it there, so better > not > > to > > > > >> double > > > > >> > > > down > > > > >> > > > >>> on > > > > >> > > > >>> that mistake. And note that we do already have > > `close(long, > > > > >> > > TimeUnit)`. > > > > >> > > > >>> > > > > >> > > > >>> Other than that, I think the current KIP seems > reasonable. > > > > >> > > > >>> > > > > >> > > > >>> Thanks, > > > > >> > > > >>> Jason > > > > >> > > > >>> > > > > >> > > > >>> On Wed, Mar 14, 2018 at 5:00 PM, Richard Yu < > > > > >> > > > yohan.richard...@gmail.com> > > > > >> > > > >>> wrote: > > > > >> > > > >>> > > > > >> > > > >>> > Note to all: I have included bounding commitSync() and > > > > >> > committed() > > > > >> > > in > > > > >> > > > >>> this > > > > >> > > > >>> > KIP. > > > > >> > > > >>> > > > > > >> > > > >>> > On Sun, Mar 11, 2018 at 5:05 PM, Richard Yu < > > > > >> > > > >>> yohan.richard...@gmail.com> > > > > >> > > > >>> > wrote: > > > > >> > > > >>> > > > > > >> > > > >>> > > Hi all, > > > > >> > > > >>> > > > > > > >> > > > >>> > > I updated the KIP where overloading position() is > now > > > the > > > > >> > favored > > > > >> > > > >>> > approach. > > > > >> > > > >>> > > Bounding position() using requestTimeoutMs has been > > > listed > > > > >> as > > > > >> > > > >>> rejected. > > > > >> > > > >>> > > > > > > >> > > > >>> > > Any thoughts? > > > > >> > > > >>> > > > > > > >> > > > >>> > > On Tue, Mar 6, 2018 at 6:00 PM, Guozhang Wang < > > > > >> > > wangg...@gmail.com> > > > > >> > > > >>> > wrote: > > > > >> > > > >>> > > > > > > >> > > > >>> > >> I agree that adding the overloads is most flexible. > > But > > > > >> going > > > > >> > > for > > > > >> > > > >>> that > > > > >> > > > >>> > >> direction we'd do that for all the blocking call > that > > > > I've > > > > >> > > listed > > > > >> > > > >>> above, > > > > >> > > > >>> > >> with this timeout value covering the end-to-end > > waiting > > > > >> time. > > > > >> > > > >>> > >> > > > > >> > > > >>> > >> > > > > >> > > > >>> > >> Guozhang > > > > >> > > > >>> > >> > > > > >> > > > >>> > >> On Tue, Mar 6, 2018 at 10:02 AM, Ted Yu < > > > > >> yuzhih...@gmail.com> > > > > >> > > > >>> wrote: > > > > >> > > > >>> > >> > > > > >> > > > >>> > >> > bq. The most flexible option is to add overloads > to > > > the > > > > >> > > consumer > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > This option is flexible. > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > Looking at the tail of SPARK-18057, Spark dev > > voiced > > > > the > > > > >> > same > > > > >> > > > >>> choice. > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > +1 for adding overload with timeout parameter. > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > Cheers > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > On Mon, Mar 5, 2018 at 2:42 PM, Jason Gustafson < > > > > >> > > > >>> ja...@confluent.io> > > > > >> > > > >>> > >> > wrote: > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > @Guozhang I probably have suggested all options > > at > > > > some > > > > >> > > point > > > > >> > > > or > > > > >> > > > >>> > >> another, > > > > >> > > > >>> > >> > > including most recently, the current KIP! I was > > > > >> thinking > > > > >> > > that > > > > >> > > > >>> > >> practically > > > > >> > > > >>> > >> > > speaking, the request timeout defines how long > > the > > > > >> user is > > > > >> > > > >>> willing > > > > >> > > > >>> > to > > > > >> > > > >>> > >> > wait > > > > >> > > > >>> > >> > > for a response. The consumer doesn't really > have > > a > > > > >> complex > > > > >> > > > send > > > > >> > > > >>> > >> process > > > > >> > > > >>> > >> > > like the producer for any of these APIs, so I > > > wasn't > > > > >> sure > > > > >> > > how > > > > >> > > > >>> much > > > > >> > > > >>> > >> > benefit > > > > >> > > > >>> > >> > > there would be from having more granular > control > > > over > > > > >> > > timeouts > > > > >> > > > >>> (in > > > > >> > > > >>> > the > > > > >> > > > >>> > >> > end, > > > > >> > > > >>> > >> > > KIP-91 just adds a single timeout to control > the > > > > whole > > > > >> > > send). > > > > >> > > > >>> That > > > > >> > > > >>> > >> said, > > > > >> > > > >>> > >> > it > > > > >> > > > >>> > >> > > might indeed be better to avoid overloading the > > > > config > > > > >> as > > > > >> > > you > > > > >> > > > >>> > suggest > > > > >> > > > >>> > >> > since > > > > >> > > > >>> > >> > > at least it avoids inconsistency with the > > > producer's > > > > >> > usage. > > > > >> > > > >>> > >> > > > > > > >> > > > >>> > >> > > The most flexible option is to add overloads to > > the > > > > >> > consumer > > > > >> > > > so > > > > >> > > > >>> that > > > > >> > > > >>> > >> > users > > > > >> > > > >>> > >> > > can pass the timeout directly. I'm not sure if > > that > > > > is > > > > >> > more > > > > >> > > or > > > > >> > > > >>> less > > > > >> > > > >>> > >> > > annoying than a new config, but I've found > config > > > > >> > timeouts a > > > > >> > > > >>> little > > > > >> > > > >>> > >> > > constraining in practice. For example, I could > > > > imagine > > > > >> > users > > > > >> > > > >>> wanting > > > > >> > > > >>> > >> to > > > > >> > > > >>> > >> > > wait longer for an offset commit operation > than a > > > > >> position > > > > >> > > > >>> lookup; > > > > >> > > > >>> > if > > > > >> > > > >>> > >> the > > > > >> > > > >>> > >> > > latter isn't timely, users can just pause the > > > > partition > > > > >> > and > > > > >> > > > >>> continue > > > > >> > > > >>> > >> > > fetching on others. If you cannot commit > offsets, > > > > >> however, > > > > >> > > it > > > > >> > > > >>> might > > > > >> > > > >>> > be > > > > >> > > > >>> > >> > > safer for an application to wait availability > of > > > the > > > > >> > > > coordinator > > > > >> > > > >>> > than > > > > >> > > > >>> > >> > > continuing. > > > > >> > > > >>> > >> > > > > > > >> > > > >>> > >> > > -Jason > > > > >> > > > >>> > >> > > > > > > >> > > > >>> > >> > > On Sun, Mar 4, 2018 at 10:14 PM, Guozhang Wang > < > > > > >> > > > >>> wangg...@gmail.com> > > > > >> > > > >>> > >> > wrote: > > > > >> > > > >>> > >> > > > > > > >> > > > >>> > >> > > > Hello Richard, > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > Thanks for the proposed KIP. I have a couple > of > > > > >> general > > > > >> > > > >>> comments: > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > 1. I'm not sure if piggy-backing the timeout > > > > >> exception > > > > >> > on > > > > >> > > > the > > > > >> > > > >>> > >> > > > existing requestTimeoutMs configured in " > > > > >> > > request.timeout.ms > > > > >> > > > " > > > > >> > > > >>> is a > > > > >> > > > >>> > >> good > > > > >> > > > >>> > >> > > > idea > > > > >> > > > >>> > >> > > > since a) it is a general config that applies > > for > > > > all > > > > >> > types > > > > >> > > > of > > > > >> > > > >>> > >> requests, > > > > >> > > > >>> > >> > > and > > > > >> > > > >>> > >> > > > 2) using it to cover all the phases of an API > > > call, > > > > >> > > > including > > > > >> > > > >>> > >> network > > > > >> > > > >>> > >> > > round > > > > >> > > > >>> > >> > > > trip and potential metadata refresh is shown > to > > > not > > > > >> be a > > > > >> > > > good > > > > >> > > > >>> > idea, > > > > >> > > > >>> > >> as > > > > >> > > > >>> > >> > > > illustrated in KIP-91: > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > https://cwiki.apache.org/confl > > > > >> uence/display/KAFKA/KIP- > > > > >> > > > >>> > >> > > > 91+Provide+Intuitive+User+ > > > Timeouts+in+The+Producer > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > In fact, I think in KAFKA-4879 which is aimed > > for > > > > the > > > > >> > same > > > > >> > > > >>> issue > > > > >> > > > >>> > as > > > > >> > > > >>> > >> > > > KAFKA-6608, > > > > >> > > > >>> > >> > > > Jason has suggested we use a new config for > the > > > > API. > > > > >> > Maybe > > > > >> > > > >>> this > > > > >> > > > >>> > >> would > > > > >> > > > >>> > >> > be > > > > >> > > > >>> > >> > > a > > > > >> > > > >>> > >> > > > more intuitive manner than reusing the > > > > >> > request.timeout.ms > > > > >> > > > >>> config. > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > 2. Besides the Consumer.position() call, > there > > > are > > > > a > > > > >> > > couple > > > > >> > > > of > > > > >> > > > >>> > more > > > > >> > > > >>> > >> > > > blocking calls today that could result in > > > infinite > > > > >> > > blocking: > > > > >> > > > >>> > >> > > > Consumer.commitSync() and > Consumer.committed(), > > > > >> should > > > > >> > > they > > > > >> > > > be > > > > >> > > > >>> > >> > considered > > > > >> > > > >>> > >> > > > in this KIP as well? > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > 3. There are a few other APIs that are today > > > > relying > > > > >> on > > > > >> > > > >>> > >> > > request.timeout.ms > > > > >> > > > >>> > >> > > > already for breaking the infinite blocking, > > > namely > > > > >> > > > >>> > >> > > Consumer.partitionFor(), > > > > >> > > > >>> > >> > > > Consumer.OffsetAndTimestamp() and > > > > >> Consumer.listTopics(), > > > > >> > > if > > > > >> > > > >>> we are > > > > >> > > > >>> > >> > making > > > > >> > > > >>> > >> > > > the other blocking calls to be relying a new > > > config > > > > >> as > > > > >> > > > >>> suggested > > > > >> > > > >>> > in > > > > >> > > > >>> > >> 1) > > > > >> > > > >>> > >> > > > above, should we also change the semantics of > > > these > > > > >> API > > > > >> > > > >>> functions > > > > >> > > > >>> > >> for > > > > >> > > > >>> > >> > > > consistency? > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > Guozhang > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > On Sun, Mar 4, 2018 at 11:13 AM, Richard Yu < > > > > >> > > > >>> > >> > yohan.richard...@gmail.com> > > > > >> > > > >>> > >> > > > wrote: > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > > Hi all, > > > > >> > > > >>> > >> > > > > > > > > >> > > > >>> > >> > > > > I would like to discuss a potential change > > > which > > > > >> would > > > > >> > > be > > > > >> > > > >>> made > > > > >> > > > >>> > to > > > > >> > > > >>> > >> > > > > KafkaConsumer: > > > > >> > > > >>> > >> > > > > https://cwiki.apache.org/ > > > > confluence/pages/viewpage > > > > >> . > > > > >> > > > >>> > >> > > > action?pageId=75974886 > > > > >> > > > >>> > >> > > > > > > > > >> > > > >>> > >> > > > > Thanks, > > > > >> > > > >>> > >> > > > > Richard Yu > > > > >> > > > >>> > >> > > > > > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > -- > > > > >> > > > >>> > >> > > > -- Guozhang > > > > >> > > > >>> > >> > > > > > > > >> > > > >>> > >> > > > > > > >> > > > >>> > >> > > > > > >> > > > >>> > >> > > > > >> > > > >>> > >> > > > > >> > > > >>> > >> > > > > >> > > > >>> > >> -- > > > > >> > > > >>> > >> -- Guozhang > > > > >> > > > >>> > >> > > > > >> > > > >>> > > > > > > >> > > > >>> > > > > > > >> > > > >>> > > > > > >> > > > >>> > > > > >> > > > >> > > > > >> > > > >> > > > > >> > > > > > > > > >> > > > > > > > >> > > > > > > >> > > > > > > >> > > > > > > >> > > -- > > > > >> > > -- Guozhang > > > > >> > > > > > > >> > > > > > >> > > > > > > > > > > > > > > > > > > > > > > > -- > -- Guozhang >
