With this approach close(timeout > 0) will not actually close by the
elapsed timeout right? This semantics mismatch is a bit concerning to me..
Guozhang
On Fri, Mar 20, 2015 at 2:37 PM, Jun Rao <j...@confluent.io> wrote:
> Yes, that probably is simpler. Basically, close() and close(timeout) will
> always wait for the sender thread to complete. Close(0) will just initiate
> the shutdown of the sender thread, but not waiting for the thread to
> complete.
>
> Thanks,
>
> Jun
>
> On Fri, Mar 20, 2015 at 11:29 AM, Jiangjie Qin <j...@linkedin.com.invalid>
> wrote:
>
> > That’s a very good point.
> > Currently if timeout > 0, it will wait up to timeout for the sender
> thread
> > to complete. After that it will do a force close but not block.
> >
> > Maybe we should make it to be:
> > If timeout > 0, wait up to timeout for the sender thread to complete.
> > After that, make a force close but still try to join the sender thread.
> > If timeout = 0, it is non-blocking.
> >
> > Jiangjie (Becket) Qin
> >
> > On 3/20/15, 9:16 AM, "Jun Rao" <j...@confluent.io> wrote:
> >
> > >Got it. Just to clarify, does close(timeout) always wait for the sender
> > >thread to complete?
> > >
> > >Thanks,
> > >
> > >Jun
> > >
> > >On Fri, Mar 20, 2015 at 7:41 AM, Jiangjie Qin <j...@linkedin.com.invalid
> >
> > >wrote:
> > >
> > >> I think the we agreed that we are going to log an error and block. By
> > >> doing this we can make sure the error log to be checked by user in all
> > >> cases.
> > >> If we silently replace close() to close(0) in sender thread, in some
> > >>cases
> > >> such as send error during a normal close(), user might not notice
> > >> something went wrong.
> > >>
> > >> On 3/19/15, 10:34 PM, "Joel Koshy" <jjkosh...@gmail.com> wrote:
> > >>
> > >> >close can probably just getCurrentThread and check if ==
> senderThread.
> > >> >I'm actually not sure from this thread if there was clear agreement
> on
> > >> >whether it should change close(timeout)/close() to close(0) or if it
> > >> >should
> > >> >log an error and block up to the timeout.
> > >> >
> > >> >On Thursday, March 19, 2015, Jun Rao <j...@confluent.io> wrote:
> > >> >
> > >> >> So in (1), if a close() or close(timeout) is called from a
> callback,
> > >>we
> > >> >> will just turn that into a close(0)? Implementation wise, how do we
> > >>know
> > >> >> whether a close() call is made from the sender thread or not?
> > >> >>
> > >> >> Thanks,
> > >> >>
> > >> >> Jun
> > >> >>
> > >> >> On Wed, Mar 18, 2015 at 2:13 PM, Jiangjie Qin
> > >> >><j...@linkedin.com.invalid>
> > >> >> wrote:
> > >> >>
> > >> >> > It looks we have another option and are now deciding between the
> > >> >> following
> > >> >> > two interfaces:
> > >> >> >
> > >> >> > 1. Close() + close(timeout)
> > >> >> > - timeout could be either positive or zero.
> > >> >> > - only close(0) can be called from sender thread
> > >> >> >
> > >> >> > 2. Close() + abort() + close(timeout)
> > >> >> > - timeout can either be positive or zero
> > >> >> > - only abort() can be called from sender thread
> > >> >> >
> > >> >> > - abort() is equivalent to close(0) in 1) but does not join
> > >>sender
> > >> >> > thread and does not close metrics.
> > >> >> > - Another thread has to call close() or close(timeout) in order
> > >>to
> > >> >>make
> > >> >> > sure the resources in producer are gone.
> > >> >> >
> > >> >> > The tow approach provides the same function we need, the
> > >>difference is
> > >> >> > approach 2) follows convention of close() and abort(). On the
> other
> > >> >>hand,
> > >> >> > approach 1) saves one interface compared with approach 2) but
> does
> > >>not
> > >> >> > follow the convention.
> > >> >> >
> > >> >> > When the two approaches come to user code, it is probably
> something
> > >> >>like
> > >> >> > this:
> > >> >> >
> > >> >> > Try {
> > >> >> > While(!finished)
> > >> >> > Producer.send(record, callback)
> > >> >> > } catch (Exception e) {
> > >> >> > Producer.close(5)
> > >> >> > }
> > >> >> >
> > >> >> > Class CallbackImpl implements Callback {
> > >> >> > onCompletion(RecordMetadata metadata Exception e) {
> > >> >> > If (e != null)
> > >> >> > Abort() / close()
> > >> >> > }
> > >> >> > }
> > >> >> >
> > >> >> > Because the two approach leads to almost the same user code,
> > >>assuming
> > >> >> > users are always calling producer.close() as a clean up step,
> > >> >>personally
> > >> >> I
> > >> >> > prefer approach 2) as it follows convention.
> > >> >> >
> > >> >> > Any thoughts?
> > >> >> >
> > >> >> > Jiangjie (Becket) Qin
> > >> >> >
> > >> >> >
> > >> >> > On 3/17/15, 10:25 AM, "Jiangjie Qin" <j...@linkedin.com
> > >> >><javascript:;>>
> > >> >> wrote:
> > >> >> >
> > >> >> > >Hi Jun,
> > >> >> > >
> > >> >> > >Yes, as Guozhang said, the main reason we set a flag is because
> > >> >>close(0)
> > >> >> > >is expected to be called by sender thread itself.
> > >> >> > >If we want to maintain the semantic meaning of close(), one
> > >> >>alternative
> > >> >> is
> > >> >> > >to have an abort() method does the same thing as close(0) except
> > >> >> cleanup.
> > >> >> > >And in close(timeout), after timeout we call abort() and join
> the
> > >> >>sender
> > >> >> > >thread. This was one of the previous proposal. We merged abort
> to
> > >> >> close(0)
> > >> >> > >because they are almost doing the same thing. But from what you
> > >> >> mentioned,
> > >> >> > >it might make sense to have two separate methods.
> > >> >> > >
> > >> >> > >Thanks.
> > >> >> > >
> > >> >> > >Jiangjie (Becket) Qin
> > >> >> > >
> > >> >> > >On 3/16/15, 10:31 PM, "Guozhang Wang" <wangg...@gmail.com
> > >> >> <javascript:;>> wrote:
> > >> >> > >
> > >> >> > >>Yeah in this sense the sender thread will not exist immediately
> > >>in
> > >> >>the
> > >> >> > >>close(0) call, but will only terminate after the current
> response
> > >> >>batch
> > >> >> > >>has
> > >> >> > >>been processed, as will the producer instance itself.
> > >> >> > >>
> > >> >> > >>There is a reason for this though: for a clean shutdown the
> > >>caller
> > >> >> thread
> > >> >> > >>has to wait for the sender thread to join before closing the
> > >> >>producer
> > >> >> > >>instance, but this cannot be achieve if close(0) is called by
> the
> > >> >> sender
> > >> >> > >>thread itself (for example in KAFKA-1659, there is a proposal
> > >>from
> > >> >> Andrew
> > >> >> > >>Stein on using thread.interrupt and thread.stop, but if it is
> > >> >>called by
> > >> >> > >>the
> > >> >> > >>ioThread itself the stop call will fail). Hence we came up with
> > >>the
> > >> >> flag
> > >> >> > >>approach to let the sender thread to close as soon as it is at
> > >>the
> > >> >> > >>barrier
> > >> >> > >>of the run loop.
> > >> >> > >>
> > >> >> > >>Guozhang
> > >> >> > >>
> > >> >> > >>On Mon, Mar 16, 2015 at 9:41 PM, Jun Rao <j...@confluent.io
> > >> >> <javascript:;>> wrote:
> > >> >> > >>
> > >> >> > >>> Hmm, does that mean that after close(0), the sender thread is
> > >>not
> > >> >> > >>>necessary
> > >> >> > >>> gone? Normally, after closing an entity, we expect all
> internal
> > >> >> threads
> > >> >> > >>> associated with the entity are shut down completely.
> > >> >> > >>>
> > >> >> > >>> Thanks,
> > >> >> > >>>
> > >> >> > >>> Jun
> > >> >> > >>>
> > >> >> > >>> On Mon, Mar 16, 2015 at 3:18 PM, Jiangjie Qin
> > >> >> > >>><j...@linkedin.com.invalid>
> > >> >> > >>> wrote:
> > >> >> > >>>
> > >> >> > >>> > Hi Jun,
> > >> >> > >>> >
> > >> >> > >>> > Close(0) will set two flags in sender. Running=false and a
> > >>newly
> > >> >> > >>>added
> > >> >> > >>> > forceClose=true. It will also set accumulator.closed=true
> so
> > >>no
> > >> >> > >>>further
> > >> >> > >>> > producer.send() will succeed.
> > >> >> > >>> > The sender thread will finish executing all the callbacks
> in
> > >> >> current
> > >> >> > >>> batch
> > >> >> > >>> > of responses, then it will see the forceClose flag. It will
> > >>just
> > >> >> fail
> > >> >> > >>>all
> > >> >> > >>> > the incomplete batches in the producer and exit.
> > >> >> > >>> > So close(0) is a non-blocking call and sender thread will
> not
> > >> >>try
> > >> >> to
> > >> >> > >>>join
> > >> >> > >>> > itself in close(0).
> > >> >> > >>> >
> > >> >> > >>> > Thanks.
> > >> >> > >>> >
> > >> >> > >>> > Jiangjie (Becket) Qin
> > >> >> > >>> >
> > >> >> > >>> > On 3/16/15, 2:50 PM, "Jun Rao" <j...@confluent.io
> > >> <javascript:;>>
> > >> >> wrote:
> > >> >> > >>> >
> > >> >> > >>> > >How does close(0) work if it's called from the sender
> > >>thread?
> > >> >>If
> > >> >> > >>> close(0)
> > >> >> > >>> > >needs to wait for the sender thread to join, wouldn't this
> > >> >>cause a
> > >> >> > >>> > >deadlock?
> > >> >> > >>> > >
> > >> >> > >>> > >Thanks,
> > >> >> > >>> > >
> > >> >> > >>> > >Jun
> > >> >> > >>> > >
> > >> >> > >>> > >On Mon, Mar 16, 2015 at 2:26 PM, Jiangjie Qin
> > >> >> > >>><j...@linkedin.com.invalid
> > >> >> > >>> >
> > >> >> > >>> > >wrote:
> > >> >> > >>> > >
> > >> >> > >>> > >> Thanks Guozhang. It wouldn’t be as thoroughly considered
> > >> >>without
> > >> >> > >>> > >> discussing with you :)
> > >> >> > >>> > >>
> > >> >> > >>> > >> Jiangjie (Becket) Qin
> > >> >> > >>> > >>
> > >> >> > >>> > >> On 3/16/15, 1:07 PM, "Guozhang Wang" <
> wangg...@gmail.com
> > >> >> <javascript:;>> wrote:
> > >> >> > >>> > >>
> > >> >> > >>> > >> >Thanks Jiangjie,
> > >> >> > >>> > >> >
> > >> >> > >>> > >> >After talking to you offline on this, I have been
> > >>convinced
> > >> >>and
> > >> >> > >>> > >>changed my
> > >> >> > >>> > >> >preference to blocking. The immediate shutdown approach
> > >>does
> > >> >> have
> > >> >> > >>> some
> > >> >> > >>> > >> >unsafeness in some cases.
> > >> >> > >>> > >> >
> > >> >> > >>> > >> >Guozhang
> > >> >> > >>> > >> >
> > >> >> > >>> > >> >On Mon, Mar 16, 2015 at 11:50 AM, Jiangjie Qin
> > >> >> > >>> > >><j...@linkedin.com.invalid
> > >> >> > >>> > >> >
> > >> >> > >>> > >> >wrote:
> > >> >> > >>> > >> >
> > >> >> > >>> > >> >> It looks that the problem we want to solve and the
> > >> >>purpose we
> > >> >> > >>>want
> > >> >> > >>> to
> > >> >> > >>> > >> >> achieve is:
> > >> >> > >>> > >> >> If user uses close() in callback, we want to let user
> > >>be
> > >> >> aware
> > >> >> > >>>that
> > >> >> > >>> > >>they
> > >> >> > >>> > >> >> should use close(0) instead of close() in the
> callback.
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >> We have agreed that we will have an error log to
> inform
> > >> >>user
> > >> >> > >>>about
> > >> >> > >>> > >>this
> > >> >> > >>> > >> >> mis-usage. The options differ in the way how we can
> > >>force
> > >> >> user
> > >> >> > >>>to
> > >> >> > >>> > >>take a
> > >> >> > >>> > >> >> look at that error log.
> > >> >> > >>> > >> >> There are two scenarios:
> > >> >> > >>> > >> >> 1. User does not expect the program to exit.
> > >> >> > >>> > >> >> 2. User expect the program to exit.
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >> For scenario 1), blocking will probably delay the
> > >> >>discovery
> > >> >> of
> > >> >> > >>>the
> > >> >> > >>> > >> >> problem. Calling close(0) exposes the problem
> quicker.
> > >>In
> > >> >> this
> > >> >> > >>> > >>scenario
> > >> >> > >>> > >> >> producer just encounter a send failure when running
> > >> >>normally.
> > >> >> > >>> > >> >> For scenario 2), blocking will expose the problem
> > >>quick.
> > >> >> > >>>Calling
> > >> >> > >>> > >> >>close(-1)
> > >> >> > >>> > >> >> might hide the problem. This scenario might include:
> a)
> > >> >>Unit
> > >> >> > >>>test
> > >> >> > >>> > >>for a
> > >> >> > >>> > >> >> send failure. b) Message sending during a close()
> call
> > >> >>from a
> > >> >> > >>>user
> > >> >> > >>> > >> >>thread.
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >> So as a summary table:
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >> Scenario 1)
> > >> >> Scenario
> > >> >> > >>>2)
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >> Blocking Delay problem discovery
> > >>Guaranteed
> > >> >> > >>>problem
> > >> >> > >>> > >> >>discovery
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >> Close(-1) Immediate problem discovery Problem
> > >> >>might
> > >> >> be
> > >> >> > >>> hidden
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >> Personally I prefer blocking because it seems
> providing
> > >> >>more
> > >> >> > >>> > >>guarantees
> > >> >> > >>> > >> >> and safer.
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >> Thanks.
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >> Jiangjie (Becket) Qin
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >> On 3/16/15, 10:11 AM, "Guozhang Wang"
> > >><wangg...@gmail.com
> > >> >> <javascript:;>>
> > >> >> > >>>wrote:
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >> >HI Jiangjie,
> > >> >> > >>> > >> >> >
> > >> >> > >>> > >> >> >As far as I understand calling close() in the
> > >>ioThread is
> > >> >> not
> > >> >> > >>> > >>common,
> > >> >> > >>> > >> >>as
> > >> >> > >>> > >> >> >it
> > >> >> > >>> > >> >> >may only trigger when we saw some non-retriable
> error.
> > >> >>Hence
> > >> >> > >>>when
> > >> >> > >>> > >>user
> > >> >> > >>> > >> >>run
> > >> >> > >>> > >> >> >their program it is unlikely that close() will be
> > >> >>triggered
> > >> >> > >>>and
> > >> >> > >>> > >>problem
> > >> >> > >>> > >> >> >will be detected. So it seems to me that from the
> > >>error
> > >> >> > >>>detection
> > >> >> > >>> > >> >>aspect
> > >> >> > >>> > >> >> >these two options seems to be the same as people
> will
> > >> >> usually
> > >> >> > >>> > >>detect it
> > >> >> > >>> > >> >> >from the producer metrics all dropping to 0.
> > >> >> > >>> > >> >> >
> > >> >> > >>> > >> >> >Guozhang
> > >> >> > >>> > >> >> >
> > >> >> > >>> > >> >> >On Mon, Mar 16, 2015 at 9:52 AM, Jiangjie Qin
> > >> >> > >>> > >> >><j...@linkedin.com.invalid>
> > >> >> > >>> > >> >> >wrote:
> > >> >> > >>> > >> >> >
> > >> >> > >>> > >> >> >> It seems there are two options we can choose from
> > >>when
> > >> >> > >>>close()
> > >> >> > >>> is
> > >> >> > >>> > >> >>called
> > >> >> > >>> > >> >> >> from sender thread (callback):
> > >> >> > >>> > >> >> >> 1. Log an error and close the producer using
> > >>close(-1)
> > >> >> > >>> > >> >> >> 2. Log an error and block.
> > >> >> > >>> > >> >> >> (Throwing an exception will not work because we
> > >>catch
> > >> >>all
> > >> >> > >>>the
> > >> >> > >>> > >> >>exception
> > >> >> > >>> > >> >> >> thrown from user callback. It will just lead to an
> > >> >>error
> > >> >> > >>>log.)
> > >> >> > >>> > >> >> >>
> > >> >> > >>> > >> >> >> My concern for the first option is that the
> producer
> > >> >>will
> > >> >> be
> > >> >> > >>> > >>closed
> > >> >> > >>> > >> >>even
> > >> >> > >>> > >> >> >> if we logged and error. I am wondering if some
> user
> > >> >>would
> > >> >> > >>>not
> > >> >> > >>> even
> > >> >> > >>> > >> >>take
> > >> >> > >>> > >> >> >>a
> > >> >> > >>> > >> >> >> look at the log if producer is closed normally.
> > >>Because
> > >> >> from
> > >> >> > >>>the
> > >> >> > >>> > >> >> >>programs
> > >> >> > >>> > >> >> >> behavior, everything looks good. If that is the
> > >>case,
> > >> >>the
> > >> >> > >>>error
> > >> >> > >>> > >> >>message
> > >> >> > >>> > >> >> >>we
> > >> >> > >>> > >> >> >> logged probably will just be ignored until some
> day
> > >> >>when
> > >> >> > >>>people
> > >> >> > >>> > >>check
> > >> >> > >>> > >> >> >>the
> > >> >> > >>> > >> >> >> log and see it.
> > >> >> > >>> > >> >> >>
> > >> >> > >>> > >> >> >> As for the second option, because producer does
> not
> > >> >>close
> > >> >> > >>>but
> > >> >> > >>> > >>blocks.
> > >> >> > >>> > >> >> >>User
> > >> >> > >>> > >> >> >> will notice this the first time they run the
> > >>program.
> > >> >>They
> > >> >> > >>> > >>probably
> > >> >> > >>> > >> >>will
> > >> >> > >>> > >> >> >> look at the log to see why producer could not be
> > >>closed
> > >> >> and
> > >> >> > >>>they
> > >> >> > >>> > >>will
> > >> >> > >>> > >> >> >>see
> > >> >> > >>> > >> >> >> the error log we put there. So they will get
> > >>informed
> > >> >> about
> > >> >> > >>>this
> > >> >> > >>> > >> >> >>mis-usage
> > >> >> > >>> > >> >> >> of close() in sender thread the first time they
> run
> > >>the
> > >> >> code
> > >> >> > >>> > >>instead
> > >> >> > >>> > >> >>of
> > >> >> > >>> > >> >> >> some time later.
> > >> >> > >>> > >> >> >>
> > >> >> > >>> > >> >> >> Personally I prefer the second one because it is
> > >>more
> > >> >> > >>>obvious
> > >> >> > >>> that
> > >> >> > >>> > >> >> >> something was wrong.
> > >> >> > >>> > >> >> >>
> > >> >> > >>> > >> >> >> Jiangjie (Becket) Qin
> > >> >> > >>> > >> >> >>
> > >> >> > >>> > >> >> >> On 3/15/15, 4:27 PM, "Guozhang Wang"
> > >> >><wangg...@gmail.com
> > >> >> <javascript:;>>
> > >> >> > >>> wrote:
> > >> >> > >>> > >> >> >>
> > >> >> > >>> > >> >> >> >Yeah I agree we should not silently change the
> > >> >>behavior
> > >> >> of
> > >> >> > >>>the
> > >> >> > >>> > >> >>function
> > >> >> > >>> > >> >> >> >with the given parameters; and I would prefer
> > >> >> > >>> > >> >> >>error-logging-and-shutdown
> > >> >> > >>> > >> >> >> >over blocking when close(>0) is used, since as
> Neha
> > >> >> > >>>suggested
> > >> >> > >>> > >> >>blocking
> > >> >> > >>> > >> >> >> >would also not proceed with sending any data, bu
> > >>will
> > >> >> just
> > >> >> > >>>let
> > >> >> > >>> > >> >>users to
> > >> >> > >>> > >> >> >> >realize the issue later than sooner.
> > >> >> > >>> > >> >> >> >
> > >> >> > >>> > >> >> >> >On Sun, Mar 15, 2015 at 3:25 PM, Neha Narkhede
> > >> >> > >>> > >><n...@confluent.io <javascript:;>>
> > >> >> > >>> > >> >> >>wrote:
> > >> >> > >>> > >> >> >> >
> > >> >> > >>> > >> >> >> >> >
> > >> >> > >>> > >> >> >> >> > And I also agree it is better if we can make
> > >> >>producer
> > >> >> > >>>block
> > >> >> > >>> > >>when
> > >> >> > >>> > >> >> >> >> > close() is called from sender thread so user
> > >>will
> > >> >> > >>>notice
> > >> >> > >>> > >> >>something
> > >> >> > >>> > >> >> >> >>went
> > >> >> > >>> > >> >> >> >> > wrong.
> > >> >> > >>> > >> >> >> >>
> > >> >> > >>> > >> >> >> >>
> > >> >> > >>> > >> >> >> >> This isn't a great experience either. Why can't
> > >>we
> > >> >>just
> > >> >> > >>>throw
> > >> >> > >>> > >>an
> > >> >> > >>> > >> >> >> >>exception
> > >> >> > >>> > >> >> >> >> for a behavior we know is incorrect and we'd
> like
> > >> >>the
> > >> >> > >>>user to
> > >> >> > >>> > >> >>know.
> > >> >> > >>> > >> >> >> >> Blocking as a means of doing that seems wrong
> and
> > >> >> > >>>annoying.
> > >> >> > >>> > >> >> >> >>
> > >> >> > >>> > >> >> >> >> On Sun, Mar 15, 2015 at 11:56 AM, Jay Kreps
> > >> >> > >>> > >><jay.kr...@gmail.com <javascript:;>>
> > >> >> > >>> > >> >> >> wrote:
> > >> >> > >>> > >> >> >> >>
> > >> >> > >>> > >> >> >> >> > Cool.
> > >> >> > >>> > >> >> >> >> >
> > >> >> > >>> > >> >> >> >> > I think blocking is good or alternately
> > >>throwing
> > >> >>an
> > >> >> > >>> exception
> > >> >> > >>> > >> >> >>directly
> > >> >> > >>> > >> >> >> >> from
> > >> >> > >>> > >> >> >> >> > close(). Basically I would just worry about
> > >>subtly
> > >> >> > >>>doing
> > >> >> > >>> > >> >>something
> > >> >> > >>> > >> >> >> >> slightly
> > >> >> > >>> > >> >> >> >> > different from what the user asked for as it
> > >>will
> > >> >>be
> > >> >> > >>>hard
> > >> >> > >>> to
> > >> >> > >>> > >> >>notice
> > >> >> > >>> > >> >> >> >>that
> > >> >> > >>> > >> >> >> >> > behavior difference.
> > >> >> > >>> > >> >> >> >> >
> > >> >> > >>> > >> >> >> >> > -Jay
> > >> >> > >>> > >> >> >> >> >
> > >> >> > >>> > >> >> >> >> > On Sat, Mar 14, 2015 at 5:48 PM, Jiangjie Qin
> > >> >> > >>> > >> >> >> >><j...@linkedin.com.invalid
> > >> >> > >>> > >> >> >> >> >
> > >> >> > >>> > >> >> >> >> > wrote:
> > >> >> > >>> > >> >> >> >> >
> > >> >> > >>> > >> >> >> >> > > Hi Jay,
> > >> >> > >>> > >> >> >> >> > >
> > >> >> > >>> > >> >> >> >> > > I have modified the KIP as you suggested. I
> > >> >>thinks
> > >> >> as
> > >> >> > >>> long
> > >> >> > >>> > >>as
> > >> >> > >>> > >> >>we
> > >> >> > >>> > >> >> >> >>have
> > >> >> > >>> > >> >> >> >> > > consistent define for timeout across Kafka
> > >> >> interface,
> > >> >> > >>> there
> > >> >> > >>> > >> >>would
> > >> >> > >>> > >> >> >> >>be no
> > >> >> > >>> > >> >> >> >> > > problem. And I also agree it is better if
> we
> > >>can
> > >> >> make
> > >> >> > >>> > >>producer
> > >> >> > >>> > >> >> >>block
> > >> >> > >>> > >> >> >> >> when
> > >> >> > >>> > >> >> >> >> > > close() is called from sender thread so
> user
> > >> >>will
> > >> >> > >>>notice
> > >> >> > >>> > >> >> >>something
> > >> >> > >>> > >> >> >> >>went
> > >> >> > >>> > >> >> >> >> > > wrong.
> > >> >> > >>> > >> >> >> >> > >
> > >> >> > >>> > >> >> >> >> > > Thanks.
> > >> >> > >>> > >> >> >> >> > >
> > >> >> > >>> > >> >> >> >> > > Jiangjie (Becket) Qin
> > >> >> > >>> > >> >> >> >> > >
> > >> >> > >>> > >> >> >> >> > > On 3/14/15, 11:37 AM, "Jay Kreps"
> > >> >> > >>><jay.kr...@gmail.com <javascript:;>>
> > >> >> > >>> > >> wrote:
> > >> >> > >>> > >> >> >> >> > >
> > >> >> > >>> > >> >> >> >> > > >Hey Jiangjie,
> > >> >> > >>> > >> >> >> >> > > >
> > >> >> > >>> > >> >> >> >> > > >I think this is going to be very confusing
> > >>that
> > >> >> > >>> > >> >> >> >> > > > close(0) waits indefinitely and
> > >> >> > >>> > >> >> >> >> > > > close(-1) waits for 0.
> > >> >> > >>> > >> >> >> >> > > >I understand this appears in other apis,
> > >>but it
> > >> >> is a
> > >> >> > >>> > >>constant
> > >> >> > >>> > >> >> >> >>cause of
> > >> >> > >>> > >> >> >> >> > > >bugs. Let's not repeat that mistake.
> > >> >> > >>> > >> >> >> >> > > >
> > >> >> > >>> > >> >> >> >> > > >Let's make close(0) wait for 0. We don't
> > >>need a
> > >> >> way
> > >> >> > >>>to
> > >> >> > >>> > >>wait
> > >> >> > >>> > >> >> >> >> indefinitely
> > >> >> > >>> > >> >> >> >> > > >as
> > >> >> > >>> > >> >> >> >> > > >we already have close() so having a
> magical
> > >> >> constant
> > >> >> > >>>for
> > >> >> > >>> > >> >>that is
> > >> >> > >>> > >> >> >> >> > > >redundant.
> > >> >> > >>> > >> >> >> >> > > >
> > >> >> > >>> > >> >> >> >> > > >Calling close() from the I/O thread was
> > >>already
> > >> >> > >>>possible
> > >> >> > >>> > >>and
> > >> >> > >>> > >> >> >>would
> > >> >> > >>> > >> >> >> >> block
> > >> >> > >>> > >> >> >> >> > > >indefinitely. I think trying to silently
> > >>change
> > >> >> the
> > >> >> > >>> > >>behavior
> > >> >> > >>> > >> >>is
> > >> >> > >>> > >> >> >> >> probably
> > >> >> > >>> > >> >> >> >> > > >not right. I.e. if the user calls close()
> in
> > >> >>the
> > >> >> > >>> callback
> > >> >> > >>> > >> >>there
> > >> >> > >>> > >> >> >>is
> > >> >> > >>> > >> >> >> >> > > >actually
> > >> >> > >>> > >> >> >> >> > > >some misunderstanding and they need to
> think
> > >> >>more,
> > >> >> > >>> > >>silently
> > >> >> > >>> > >> >> >>making
> > >> >> > >>> > >> >> >> >> this
> > >> >> > >>> > >> >> >> >> > > >not
> > >> >> > >>> > >> >> >> >> > > >block will hide the problem from them
> which
> > >>is
> > >> >>the
> > >> >> > >>> > >>opposite
> > >> >> > >>> > >> >>of
> > >> >> > >>> > >> >> >> >>what we
> > >> >> > >>> > >> >> >> >> > > >want.
> > >> >> > >>> > >> >> >> >> > > >
> > >> >> > >>> > >> >> >> >> > > >-Jay
> > >> >> > >>> > >> >> >> >> > > >
> > >> >> > >>> > >> >> >> >> > > >On Thu, Mar 12, 2015 at 1:49 AM, Jiangjie
> > >>Qin
> > >> >> > >>> > >> >> >> >> <j...@linkedin.com.invalid
> > >> >> > >>> > >> >> >> >> > >
> > >> >> > >>> > >> >> >> >> > > >wrote:
> > >> >> > >>> > >> >> >> >> > > >
> > >> >> > >>> > >> >> >> >> > > >> Hey Joe & Jay,
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > > >> Thanks for the comments on the voting
> > >>thread.
> > >> >> > >>>Since it
> > >> >> > >>> > >> >>seems
> > >> >> > >>> > >> >> >>we
> > >> >> > >>> > >> >> >> >> > probably
> > >> >> > >>> > >> >> >> >> > > >> will have more discussion on this, I am
> > >>just
> > >> >> > >>>replying
> > >> >> > >>> > >>from
> > >> >> > >>> > >> >>the
> > >> >> > >>> > >> >> >> >> > > >>discussion
> > >> >> > >>> > >> >> >> >> > > >> thread here.
> > >> >> > >>> > >> >> >> >> > > >> I’ve updated the KIP page to make it
> less
> > >> >>like
> > >> >> > >>> > >>half-baked,
> > >> >> > >>> > >> >> >> >>apologize
> > >> >> > >>> > >> >> >> >> > for
> > >> >> > >>> > >> >> >> >> > > >> the rush...
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > > >> The contract in current KIP is:
> > >> >> > >>> > >> >> >> >> > > >> 1. close() - wait until all requests
> > >>either
> > >> >> are
> > >> >> > >>>sent
> > >> >> > >>> > >>or
> > >> >> > >>> > >> >> >>reach
> > >> >> > >>> > >> >> >> >> > request
> > >> >> > >>> > >> >> >> >> > > >> timeout.
> > >> >> > >>> > >> >> >> >> > > >> 2. close(-1, TimeUnit.MILLISECONDS) -
> > >>close
> > >> >> > >>> > >>immediately
> > >> >> > >>> > >> >> >> >> > > >> 3. close(0, TimeUnit.MILLISECONDS) -
> > >> >> equivalent
> > >> >> > >>>to
> > >> >> > >>> > >> >>close(),
> > >> >> > >>> > >> >> >> >>i.e.
> > >> >> > >>> > >> >> >> >> > Wait
> > >> >> > >>> > >> >> >> >> > > >> until all requests are sent or reach
> > >>request
> > >> >> > >>>timeout
> > >> >> > >>> > >> >> >> >> > > >> 4. close(5, TimeUnit.MILLISECONDS) -
> try
> > >> >>the
> > >> >> > >>>best to
> > >> >> > >>> > >> >>finish
> > >> >> > >>> > >> >> >> >> sending
> > >> >> > >>> > >> >> >> >> > > >>in 5
> > >> >> > >>> > >> >> >> >> > > >> milliseconds, if something went wrong,
> > >>just
> > >> >> > >>>shutdown
> > >> >> > >>> the
> > >> >> > >>> > >> >> >>producer
> > >> >> > >>> > >> >> >> >> > > >>anyway,
> > >> >> > >>> > >> >> >> >> > > >> my callback will handle the failures.
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > > >> About how we define what timeout value
> > >>stands
> > >> >> for,
> > >> >> > >>>I
> > >> >> > >>> > >> >>actually
> > >> >> > >>> > >> >> >> >> > struggled
> > >> >> > >>> > >> >> >> >> > > >>a
> > >> >> > >>> > >> >> >> >> > > >> little bit when wrote the patch.
> > >>Intuitively,
> > >> >> > >>>close(0)
> > >> >> > >>> > >> >>should
> > >> >> > >>> > >> >> >> >>mean
> > >> >> > >>> > >> >> >> >> > > >> immediately, however it seems that all
> the
> > >> >> > >>>existing
> > >> >> > >>> java
> > >> >> > >>> > >> >>class
> > >> >> > >>> > >> >> >> >>have
> > >> >> > >>> > >> >> >> >> > this
> > >> >> > >>> > >> >> >> >> > > >> convention of timeout=0 means no timeout
> > >>or
> > >> >> never
> > >> >> > >>> > >>timeout
> > >> >> > >>> > >> >> >> >> > > >>(Thread.join(0),
> > >> >> > >>> > >> >> >> >> > > >> Object.wait(0), etc.) So here the
> dilemma
> > >>is
> > >> >> > >>>either we
> > >> >> > >>> > >> >>follow
> > >> >> > >>> > >> >> >>the
> > >> >> > >>> > >> >> >> >> > > >> intuition or we follow the convention.
> > >>What I
> > >> >> > >>>chose is
> > >> >> > >>> > >>to
> > >> >> > >>> > >> >> >>follow
> > >> >> > >>> > >> >> >> >>the
> > >> >> > >>> > >> >> >> >> > > >> convention but document the interface to
> > >>let
> > >> >> user
> > >> >> > >>>be
> > >> >> > >>> > >>aware
> > >> >> > >>> > >> >>of
> > >> >> > >>> > >> >> >>the
> > >> >> > >>> > >> >> >> >> > usage.
> > >> >> > >>> > >> >> >> >> > > >> The reason is that I think
> > >>producer.close()
> > >> >>is a
> > >> >> > >>> public
> > >> >> > >>> > >> >> >> >>interface so
> > >> >> > >>> > >> >> >> >> > it
> > >> >> > >>> > >> >> >> >> > > >> might be better to follow java
> convention.
> > >> >> Whereas
> > >> >> > >>> > >> >>selector is
> > >> >> > >>> > >> >> >> >>not a
> > >> >> > >>> > >> >> >> >> > > >> public interface that used by user, so
> as
> > >> >>long
> > >> >> as
> > >> >> > >>>it
> > >> >> > >>> > >>makes
> > >> >> > >>> > >> >> >>sense
> > >> >> > >>> > >> >> >> >>to
> > >> >> > >>> > >> >> >> >> > us,
> > >> >> > >>> > >> >> >> >> > > >>it
> > >> >> > >>> > >> >> >> >> > > >> is less a problem to be different from
> > >>java
> > >> >> > >>> convention.
> > >> >> > >>> > >> >>That
> > >> >> > >>> > >> >> >>said
> > >> >> > >>> > >> >> >> >> > since
> > >> >> > >>> > >> >> >> >> > > >> consumer.poll(timeout) is also a public
> > >> >> interface,
> > >> >> > >>>I
> > >> >> > >>> > >>think
> > >> >> > >>> > >> >>it
> > >> >> > >>> > >> >> >> >>also
> > >> >> > >>> > >> >> >> >> > makes
> > >> >> > >>> > >> >> >> >> > > >> sense to make producer.close() to have
> the
> > >> >>same
> > >> >> > >>> > >>definition
> > >> >> > >>> > >> >>of
> > >> >> > >>> > >> >> >> >> > > >> consumer.poll(timeout).
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > > >> The main argument for keeping a timeout
> in
> > >> >>close
> > >> >> > >>>would
> > >> >> > >>> > >>be
> > >> >> > >>> > >> >> >> >>separating
> > >> >> > >>> > >> >> >> >> > the
> > >> >> > >>> > >> >> >> >> > > >> close timeout from request timeout,
> which
> > >> >> probably
> > >> >> > >>> makes
> > >> >> > >>> > >> >> >>sense. I
> > >> >> > >>> > >> >> >> >> > would
> > >> >> > >>> > >> >> >> >> > > >> guess typically the request timeout
> would
> > >>be
> > >> >> long
> > >> >> > >>> (e.g.
> > >> >> > >>> > >>60
> > >> >> > >>> > >> >> >> >>seconds)
> > >> >> > >>> > >> >> >> >> > > >> because we might want to consider
> retries
> > >> >>with
> > >> >> > >>>back
> > >> >> > >>> off
> > >> >> > >>> > >> >>time.
> > >> >> > >>> > >> >> >>If
> > >> >> > >>> > >> >> >> >>we
> > >> >> > >>> > >> >> >> >> > have
> > >> >> > >>> > >> >> >> >> > > >> multiple batches in accumulator, in
> worst
> > >> >>case
> > >> >> > >>>that
> > >> >> > >>> > >>could
> > >> >> > >>> > >> >>take
> > >> >> > >>> > >> >> >> >>up to
> > >> >> > >>> > >> >> >> >> > > >> several minutes to complete all the
> > >>requests.
> > >> >> But
> > >> >> > >>>when
> > >> >> > >>> > >>we
> > >> >> > >>> > >> >> >>close a
> > >> >> > >>> > >> >> >> >> > > >> producer, we might not want to wait for
> > >>that
> > >> >> long
> > >> >> > >>>as
> > >> >> > >>> it
> > >> >> > >>> > >> >>might
> > >> >> > >>> > >> >> >> >>cause
> > >> >> > >>> > >> >> >> >> > some
> > >> >> > >>> > >> >> >> >> > > >> other problem like deployment tool
> > >>timeout.
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > > >> There is also a subtle difference
> between
> > >> >> > >>> close(timeout)
> > >> >> > >>> > >> >>and
> > >> >> > >>> > >> >> >> >> > > >> flush(timeout). The only purpose for
> > >>flush()
> > >> >>is
> > >> >> to
> > >> >> > >>> write
> > >> >> > >>> > >> >>data
> > >> >> > >>> > >> >> >>to
> > >> >> > >>> > >> >> >> >>the
> > >> >> > >>> > >> >> >> >> > > >> broker, so it makes perfect sense to
> wait
> > >> >>until
> > >> >> > >>> request
> > >> >> > >>> > >> >> >>timeout.
> > >> >> > >>> > >> >> >> >>I
> > >> >> > >>> > >> >> >> >> > think
> > >> >> > >>> > >> >> >> >> > > >> that is why flush(timeout) looks
> strange.
> > >>On
> > >> >>the
> > >> >> > >>>other
> > >> >> > >>> > >> >>hand,
> > >> >> > >>> > >> >> >>the
> > >> >> > >>> > >> >> >> >>top
> > >> >> > >>> > >> >> >> >> > > >> priority for close() is to close the
> > >>producer
> > >> >> > >>>rather
> > >> >> > >>> > >>than
> > >> >> > >>> > >> >> >>flush()
> > >> >> > >>> > >> >> >> >> > data,
> > >> >> > >>> > >> >> >> >> > > >>so
> > >> >> > >>> > >> >> >> >> > > >> close(timeout) gives guarantee on
> bounded
> > >> >> waiting
> > >> >> > >>>for
> > >> >> > >>> > >>its
> > >> >> > >>> > >> >>main
> > >> >> > >>> > >> >> >> >>job.
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > > >> Sorry for the confusion about forceClose
> > >> >>flag.
> > >> >> It
> > >> >> > >>>is
> > >> >> > >>> > >>not a
> > >> >> > >>> > >> >> >>public
> > >> >> > >>> > >> >> >> >> > > >> interface. I mentioned it in Proposed
> > >>Changes
> > >> >> > >>>section
> > >> >> > >>> > >> >>which I
> > >> >> > >>> > >> >> >> >> thought
> > >> >> > >>> > >> >> >> >> > > >>was
> > >> >> > >>> > >> >> >> >> > > >> supposed to provide implementation
> > >>details.
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > > >> Thanks again for all the comments and
> > >> >> suggestions!
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > > >> Jiangjie (Becket) Qin
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > > >> On 3/10/15, 8:57 PM, "Jiangjie Qin" <
> > >> >> > >>> j...@linkedin.com <javascript:;>>
> > >> >> > >>> > >> >> wrote:
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > > >> >The KIP page has been updated per Jay¹s
> > >> >> comments.
> > >> >> > >>> > >> >> >> >> > > >> >I¹d like to initiate the voting process
> > >>if
> > >> >>no
> > >> >> > >>>further
> > >> >> > >>> > >> >> >>comments
> > >> >> > >>> > >> >> >> >>are
> > >> >> > >>> > >> >> >> >> > > >> >received by tomorrow.
> > >> >> > >>> > >> >> >> >> > > >> >
> > >> >> > >>> > >> >> >> >> > > >> >Jiangjie (Becket) Qin
> > >> >> > >>> > >> >> >> >> > > >> >
> > >> >> > >>> > >> >> >> >> > > >> >On 3/8/15, 9:45 AM, "Jay Kreps"
> > >> >> > >>><jay.kr...@gmail.com <javascript:;>
> > >> >> > >>> >
> > >> >> > >>> > >> >>wrote:
> > >> >> > >>> > >> >> >> >> > > >> >
> > >> >> > >>> > >> >> >> >> > > >> >>Hey Jiangjie,
> > >> >> > >>> > >> >> >> >> > > >> >>
> > >> >> > >>> > >> >> >> >> > > >> >>Can you capture the full motivation
> and
> > >>use
> > >> >> > >>>cases
> > >> >> > >>> for
> > >> >> > >>> > >>the
> > >> >> > >>> > >> >> >> >>feature?
> > >> >> > >>> > >> >> >> >> > > >>This
> > >> >> > >>> > >> >> >> >> > > >> >>mentions your interest in having a way
> > >>of
> > >> >> > >>>aborting
> > >> >> > >>> > >>from
> > >> >> > >>> > >> >> >>inside
> > >> >> > >>> > >> >> >> >>the
> > >> >> > >>> > >> >> >> >> > > >> >>Callback. But it doesn't really
> explain
> > >> >>that
> > >> >> > >>>usage
> > >> >> > >>> or
> > >> >> > >>> > >>why
> > >> >> > >>> > >> >> >>other
> > >> >> > >>> > >> >> >> >> > people
> > >> >> > >>> > >> >> >> >> > > >> >>would want to do that. It also doesn't
> > >>list
> > >> >> the
> > >> >> > >>> > >>primary
> > >> >> > >>> > >> >>use
> > >> >> > >>> > >> >> >> >>case
> > >> >> > >>> > >> >> >> >> for
> > >> >> > >>> > >> >> >> >> > > >> >>having
> > >> >> > >>> > >> >> >> >> > > >> >>close with a bounded timeout which was
> > >>to
> > >> >> avoid
> > >> >> > >>> > >>blocking
> > >> >> > >>> > >> >>too
> > >> >> > >>> > >> >> >> >>long
> > >> >> > >>> > >> >> >> >> on
> > >> >> > >>> > >> >> >> >> > > >> >>shutdown.
> > >> >> > >>> > >> >> >> >> > > >> >>
> > >> >> > >>> > >> >> >> >> > > >> >>-Jay
> > >> >> > >>> > >> >> >> >> > > >> >>
> > >> >> > >>> > >> >> >> >> > > >> >>
> > >> >> > >>> > >> >> >> >> > > >> >>
> > >> >> > >>> > >> >> >> >> > > >> >>On Sat, Mar 7, 2015 at 12:25 PM,
> > >>Jiangjie
> > >> >>Qin
> > >> >> > >>> > >> >> >> >> > > >><j...@linkedin.com.invalid
> > >> >> > >>> > >> >> >> >> > > >> >
> > >> >> > >>> > >> >> >> >> > > >> >>wrote:
> > >> >> > >>> > >> >> >> >> > > >> >>
> > >> >> > >>> > >> >> >> >> > > >> >>> Hi,
> > >> >> > >>> > >> >> >> >> > > >> >>>
> > >> >> > >>> > >> >> >> >> > > >> >>> I just created a KIP for adding a
> > >> >> > >>>close(timeout)
> > >> >> > >>> to
> > >> >> > >>> > >>new
> > >> >> > >>> > >> >> >> >> producer.
> > >> >> > >>> > >> >> >> >> > > >>Most
> > >> >> > >>> > >> >> >> >> > > >> >>>of
> > >> >> > >>> > >> >> >> >> > > >> >>> the previous discussions are in
> > >> >>KAFKA-1660
> > >> >> > >>>where
> > >> >> > >>> > >>Parth
> > >> >> > >>> > >> >> >> >> Brahmbhatt
> > >> >> > >>> > >> >> >> >> > > >>has
> > >> >> > >>> > >> >> >> >> > > >> >>> already done a lot of work.
> > >> >> > >>> > >> >> >> >> > > >> >>> Since this is an interface change so
> > >>we
> > >> >>are
> > >> >> > >>>going
> > >> >> > >>> > >> >>through
> > >> >> > >>> > >> >> >>the
> > >> >> > >>> > >> >> >> >> KIP
> > >> >> > >>> > >> >> >> >> > > >> >>>process.
> > >> >> > >>> > >> >> >> >> > > >> >>> Here is the KIP link:
> > >> >> > >>> > >> >> >> >> > > >> >>>
> > >> >> > >>> > >> >> >> >> > > >> >>>
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > >
> > >> >> > >>> > >> >> >> >>
> > >> >> > >>> > >> >> >>
> > >> >> > >>> > >> >>
> > >> >> > >>> > >>
> > >> >> > >>> >
> > >> >> > >>>
> > >> >> >
> > >>
> > >>>>
> > https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=537397
> > >>>>8
> > >> >> > >>> > >> >> >> >> > > >> >>>2
> > >> >> > >>> > >> >> >> >> > > >> >>>
> > >> >> > >>> > >> >> >> >> > > >> >>> Thanks.
> > >> >> > >>> > >> >> >> >> > > >> >>>
> > >> >> > >>> > >> >> >> >> > > >> >>> Jiangjie (Becket) Qin
> > >> >> > >>> > >> >> >> >> > > >> >>>
> > >> >> > >>> > >> >> >> >> > > >> >
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > > >>
> > >> >> > >>> > >> >> >> >> > >
> > >> >> > >>> > >> >> >> >> > >
> > >> >> > >>> > >> >> >> >> >
> > >> >> > >>> > >> >> >> >>
> > >> >> > >>> > >> >> >> >>
> > >> >> > >>> > >> >> >> >>
> > >> >> > >>> > >> >> >> >> --
> > >> >> > >>> > >> >> >> >> Thanks,
> > >> >> > >>> > >> >> >> >> Neha
> > >> >> > >>> > >> >> >> >>
> > >> >> > >>> > >> >> >> >
> > >> >> > >>> > >> >> >> >
> > >> >> > >>> > >> >> >> >
> > >> >> > >>> > >> >> >> >--
> > >> >> > >>> > >> >> >> >-- Guozhang
> > >> >> > >>> > >> >> >>
> > >> >> > >>> > >> >> >>
> > >> >> > >>> > >> >> >
> > >> >> > >>> > >> >> >
> > >> >> > >>> > >> >> >--
> > >> >> > >>> > >> >> >-- Guozhang
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >>
> > >> >> > >>> > >> >
> > >> >> > >>> > >> >
> > >> >> > >>> > >> >--
> > >> >> > >>> > >> >-- Guozhang
> > >> >> > >>> > >>
> > >> >> > >>> > >>
> > >> >> > >>> >
> > >> >> > >>> >
> > >> >> > >>>
> > >> >> > >>
> > >> >> > >>
> > >> >> > >>
> > >> >> > >>--
> > >> >> > >>-- Guozhang
> > >> >> > >
> > >> >> >
> > >> >> >
> > >> >>
> > >> >
> > >> >
> > >> >--
> > >> >Sent from Gmail Mobile
> > >>
> > >>
> >
> >
>
--
-- Guozhang
