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Posted to dev@kafka.apache.org by Bruno Cadonna <br...@confluent.io> on 2021/01/27 20:34:16 UTC
Re: [VOTE] KIP-663: API to Start and Shut Down Stream Threads and to
Request Closing of Kafka Streams Clients
Hi all,
During the implementation, we notices that method removeStreamThread()
may block indefinitely when the stream thread chosen for removal is
blocked and cannot be shut down. Thus, we will add an overload that
takes a timeout. The newly added method will throw a TimeoutException,
when the timeout is exceeded.
We updated the KIP accordingly.
KIP: https://cwiki.apache.org/confluence/x/FDd4CQ
Best,
Bruno
On 30.09.20 13:51, Bruno Cadonna wrote:
> Thank you all for voting!
>
> This KIP is accepted with 3 binding +1 (Guozhang, John, Matthias).
>
> Best,
> Bruno
>
> On 29.09.20 22:24, Matthias J. Sax wrote:
>> +1 (binding)
>>
>> I am not super happy with the impact on the client state. For example, I
>> don't understand why it's ok to scale out if we lose one thread out of
>> four, but why it's not ok to scale out if we lose one thread out of one
>> (for this case, we would enter ERROR state and cannot add new threads
>> afterwards).
>>
>> However, this might be an issue for a follow up KIP.
>>
>>
>> -Matthias
>>
>> On 9/29/20 7:20 AM, John Roesler wrote:
>>> Thanks, Bruno, this sounds good to me.
>>> -John
>>>
>>> On Tue, Sep 29, 2020, at 03:13, Bruno Cadonna wrote:
>>>> Hi all,
>>>>
>>>> I did two minor modifications to the KIP.
>>>>
>>>> - I removed the rather strict guarantee "Dead stream threads are
>>>> removed
>>>> from a Kafka Streams client at latest after the next call to
>>>> KafkaStreams#addStreamThread() or KafkaStreams#removeStreamThread()
>>>> following the transition to state DEAD."
>>>> Dead stream threads will be still removed, but the behavior will be
>>>> less
>>>> strict.
>>>>
>>>> - Added a sentence that states that the Kafka Streams client will
>>>> transit to ERROR if the last alive stream thread dies exceptionally.
>>>> This corresponds to the current behavior.
>>>>
>>>> I will not restart voting and keep the votes so far.
>>>>
>>>> Best,
>>>> Bruno
>>>>
>>>> On 22.09.20 01:19, John Roesler wrote:
>>>>> I’m +1 also. Thanks, Bruno!
>>>>> -John
>>>>>
>>>>> On Mon, Sep 21, 2020, at 17:08, Guozhang Wang wrote:
>>>>>> Thanks Bruno. I'm +1 on the KIP.
>>>>>>
>>>>>> On Mon, Sep 21, 2020 at 2:49 AM Bruno Cadonna <br...@confluent.io>
>>>>>> wrote:
>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> I would like to restart from zero the voting on KIP-663 that
>>>>>>> proposes to
>>>>>>> add methods to the Kafka Streams client to add and remove stream
>>>>>>> threads
>>>>>>> during execution.
>>>>>>>
>>>>>>>
>>>>>>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-663%3A+API+to+Start+and+Shut+Down+Stream+Threads
>>>>>>>
>>>>>>>
>>>>>>> Matthias, if you are still +1, please vote again.
>>>>>>>
>>>>>>> Best,
>>>>>>> Bruno
>>>>>>>
>>>>>>> On 04.09.20 23:12, John Roesler wrote:
>>>>>>>> Hi Sophie,
>>>>>>>>
>>>>>>>> Uh, oh, it's never a good sign when the discussion moves
>>>>>>>> into the vote thread :)
>>>>>>>>
>>>>>>>> I agree with you, it seems like a good touch for
>>>>>>>> removeStreamThread() to return the name of the thread that
>>>>>>>> got removed, rather than a boolean flag. Maybe the return
>>>>>>>> value would be `null` if there is no thread to remove.
>>>>>>>>
>>>>>>>> If we go that way, I'd suggest that addStreamThread() also
>>>>>>>> return the name of the newly created thread, or null if no
>>>>>>>> thread can be created right now.
>>>>>>>>
>>>>>>>> I'm not completely sure if I think that callers of this
>>>>>>>> method would know exactly how many threads there are. Sure,
>>>>>>>> if a human being is sitting there looking at the metrics or
>>>>>>>> logs and decides to call the method, it would work out, but
>>>>>>>> I'd expect this kind of method to find its way into
>>>>>>>> automated tooling that reacts to things like current system
>>>>>>>> load or resource saturation. Those kinds of toolchains often
>>>>>>>> are part of a distributed system, and it's probably not that
>>>>>>>> easy to guarantee that the thread count they observe is
>>>>>>>> fully consistent with the number of threads that are
>>>>>>>> actually running. Therefore, an in-situ `int
>>>>>>>> numStreamThreads()` method might not be a bad idea. Then
>>>>>>>> again, it seems sort of optional. A caller can catch an
>>>>>>>> exception or react to a `null` return value just the same
>>>>>>>> either way. Having both add/remove methods behave similarly
>>>>>>>> is probably more valuable.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> -John
>>>>>>>>
>>>>>>>>
>>>>>>>> On Thu, 2020-09-03 at 12:15 -0700, Sophie Blee-Goldman
>>>>>>>> wrote:
>>>>>>>>> Hey, sorry for the late reply, I just have one minor
>>>>>>>>> suggestion. Since
>>>>>>> we
>>>>>>>>> don't
>>>>>>>>> make any guarantees about which thread gets removed or allow
>>>>>>>>> the user to
>>>>>>>>> specify, I think we should return either the index or full name
>>>>>>>>> of the
>>>>>>>>> thread
>>>>>>>>> that does get removed by removeThread().
>>>>>>>>>
>>>>>>>>> I know you just updated the KIP to return true/false if there
>>>>>>> are/aren't any
>>>>>>>>> threads to be removed, but I think this would be more
>>>>>>>>> appropriate as an
>>>>>>>>> exception than as a return type. I think it's reasonable to expect
>>>>>>> users to
>>>>>>>>> have some sense to how many threads are remaining, and not try
>>>>>>>>> to remove
>>>>>>>>> a thread when there is none left. To me, that indicates
>>>>>>>>> something wrong
>>>>>>>>> with the user application code and should be treated as an
>>>>>>>>> exceptional
>>>>>>> case.
>>>>>>>>> I don't think the same code clarify argument applies here as to
>>>>>>>>> the
>>>>>>>>> addStreamThread() case, as there's no reason for an application
>>>>>>>>> to be
>>>>>>>>> looping and retrying removeStreamThread() since if that fails,
>>>>>>>>> it's
>>>>>>> because
>>>>>>>>> there are no threads left and thus it will continue to always
>>>>>>>>> fail. And
>>>>>>> if
>>>>>>>>> the
>>>>>>>>> user actually wants to shut down all threads, they should just
>>>>>>>>> close the
>>>>>>>>> whole application rather than call removeStreamThread() in a loop.
>>>>>>>>>
>>>>>>>>> While I generally think it should be straightforward for users
>>>>>>>>> to track
>>>>>>> how
>>>>>>>>> many stream threads they have running, maybe it would be nice
>>>>>>>>> to add
>>>>>>>>> a small utility method that does this for them. Something like
>>>>>>>>>
>>>>>>>>> // Returns the number of currently alive threads
>>>>>>>>> boolean runningStreamThreads();
>>>>>>>>>
>>>>>>>>> On Thu, Sep 3, 2020 at 7:41 AM Matthias J. Sax <mj...@apache.org>
>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> +1 (binding)
>>>>>>>>>>
>>>>>>>>>> On 9/3/20 6:16 AM, Bruno Cadonna wrote:
>>>>>>>>>>> Hi,
>>>>>>>>>>>
>>>>>>>>>>> I would like to start the voting on KIP-663 that proposes to add
>>>>>>> methods
>>>>>>>>>>> to the Kafka Streams client to add and remove stream threads
>>>>>>>>>>> during
>>>>>>>>>>> execution.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-663%3A+API+to+Start+and+Shut+Down+Stream+Threads
>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> Best,
>>>>>>>>>>> Bruno
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> -- Guozhang
>>>>>>
>>>>
Re: [VOTE] KIP-663: API to Start and Shut Down Stream Threads and to
Request Closing of Kafka Streams Clients
Posted by "Matthias J. Sax" <mj...@apache.org>.
Yes. Sorry about this mistake.
On 6/16/21 2:29 PM, Israel Ekpo wrote:
> Thanks for clarifying that @Sophie it is in regards to KIP-633
>
> On Wed, Jun 16, 2021 at 4:00 PM Sophie Blee-Goldman
> <so...@confluent.io.invalid> wrote:
>
>> Matthias, I'm guessing you meant to send this to the KIP-633 list? This is
>> KIP-663
>>
>> On Wed, Jun 16, 2021 at 12:37 PM Matthias J. Sax <mj...@apache.org> wrote:
>>
>>> Quick follow up. I did a small update to the KIP with regard to
>>> https://issues.apache.org/jira/browse/KAFKA-12909
>>>
>>> Israel, Sophie, and Guozhang did agree to this change. I don't think we
>>> need to re-vote.
>>>
>>> Please let us know if there are any concerns.
>>>
>>>
>>> -Matthias
>>>
>>> On 1/27/21 12:48 PM, Sophie Blee-Goldman wrote:
>>>> Thanks Bruno, that sounds like a good addition. +1
>>>>
>>>> On Wed, Jan 27, 2021 at 12:34 PM Bruno Cadonna <br...@confluent.io>
>>> wrote:
>>>>
>>>>> Hi all,
>>>>>
>>>>> During the implementation, we notices that method removeStreamThread()
>>>>> may block indefinitely when the stream thread chosen for removal is
>>>>> blocked and cannot be shut down. Thus, we will add an overload that
>>>>> takes a timeout. The newly added method will throw a TimeoutException,
>>>>> when the timeout is exceeded.
>>>>>
>>>>> We updated the KIP accordingly.
>>>>>
>>>>> KIP: https://cwiki.apache.org/confluence/x/FDd4CQ
>>>>>
>>>>> Best,
>>>>> Bruno
>>>>>
>>>>> On 30.09.20 13:51, Bruno Cadonna wrote:
>>>>>> Thank you all for voting!
>>>>>>
>>>>>> This KIP is accepted with 3 binding +1 (Guozhang, John, Matthias).
>>>>>>
>>>>>> Best,
>>>>>> Bruno
>>>>>>
>>>>>> On 29.09.20 22:24, Matthias J. Sax wrote:
>>>>>>> +1 (binding)
>>>>>>>
>>>>>>> I am not super happy with the impact on the client state. For
>>> example, I
>>>>>>> don't understand why it's ok to scale out if we lose one thread out
>> of
>>>>>>> four, but why it's not ok to scale out if we lose one thread out of
>>> one
>>>>>>> (for this case, we would enter ERROR state and cannot add new
>> threads
>>>>>>> afterwards).
>>>>>>>
>>>>>>> However, this might be an issue for a follow up KIP.
>>>>>>>
>>>>>>>
>>>>>>> -Matthias
>>>>>>>
>>>>>>> On 9/29/20 7:20 AM, John Roesler wrote:
>>>>>>>> Thanks, Bruno, this sounds good to me.
>>>>>>>> -John
>>>>>>>>
>>>>>>>> On Tue, Sep 29, 2020, at 03:13, Bruno Cadonna wrote:
>>>>>>>>> Hi all,
>>>>>>>>>
>>>>>>>>> I did two minor modifications to the KIP.
>>>>>>>>>
>>>>>>>>> - I removed the rather strict guarantee "Dead stream threads are
>>>>>>>>> removed
>>>>>>>>> from a Kafka Streams client at latest after the next call to
>>>>>>>>> KafkaStreams#addStreamThread() or
>> KafkaStreams#removeStreamThread()
>>>>>>>>> following the transition to state DEAD."
>>>>>>>>> Dead stream threads will be still removed, but the behavior will
>> be
>>>>>>>>> less
>>>>>>>>> strict.
>>>>>>>>>
>>>>>>>>> - Added a sentence that states that the Kafka Streams client will
>>>>>>>>> transit to ERROR if the last alive stream thread dies
>> exceptionally.
>>>>>>>>> This corresponds to the current behavior.
>>>>>>>>>
>>>>>>>>> I will not restart voting and keep the votes so far.
>>>>>>>>>
>>>>>>>>> Best,
>>>>>>>>> Bruno
>>>>>>>>>
>>>>>>>>> On 22.09.20 01:19, John Roesler wrote:
>>>>>>>>>> I’m +1 also. Thanks, Bruno!
>>>>>>>>>> -John
>>>>>>>>>>
>>>>>>>>>> On Mon, Sep 21, 2020, at 17:08, Guozhang Wang wrote:
>>>>>>>>>>> Thanks Bruno. I'm +1 on the KIP.
>>>>>>>>>>>
>>>>>>>>>>> On Mon, Sep 21, 2020 at 2:49 AM Bruno Cadonna <
>> bruno@confluent.io
>>>>
>>>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Hi,
>>>>>>>>>>>>
>>>>>>>>>>>> I would like to restart from zero the voting on KIP-663 that
>>>>>>>>>>>> proposes to
>>>>>>>>>>>> add methods to the Kafka Streams client to add and remove
>> stream
>>>>>>>>>>>> threads
>>>>>>>>>>>> during execution.
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>
>>>
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-663%3A+API+to+Start+and+Shut+Down+Stream+Threads
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> Matthias, if you are still +1, please vote again.
>>>>>>>>>>>>
>>>>>>>>>>>> Best,
>>>>>>>>>>>> Bruno
>>>>>>>>>>>>
>>>>>>>>>>>> On 04.09.20 23:12, John Roesler wrote:
>>>>>>>>>>>>> Hi Sophie,
>>>>>>>>>>>>>
>>>>>>>>>>>>> Uh, oh, it's never a good sign when the discussion moves
>>>>>>>>>>>>> into the vote thread :)
>>>>>>>>>>>>>
>>>>>>>>>>>>> I agree with you, it seems like a good touch for
>>>>>>>>>>>>> removeStreamThread() to return the name of the thread that
>>>>>>>>>>>>> got removed, rather than a boolean flag. Maybe the return
>>>>>>>>>>>>> value would be `null` if there is no thread to remove.
>>>>>>>>>>>>>
>>>>>>>>>>>>> If we go that way, I'd suggest that addStreamThread() also
>>>>>>>>>>>>> return the name of the newly created thread, or null if no
>>>>>>>>>>>>> thread can be created right now.
>>>>>>>>>>>>>
>>>>>>>>>>>>> I'm not completely sure if I think that callers of this
>>>>>>>>>>>>> method would know exactly how many threads there are. Sure,
>>>>>>>>>>>>> if a human being is sitting there looking at the metrics or
>>>>>>>>>>>>> logs and decides to call the method, it would work out, but
>>>>>>>>>>>>> I'd expect this kind of method to find its way into
>>>>>>>>>>>>> automated tooling that reacts to things like current system
>>>>>>>>>>>>> load or resource saturation. Those kinds of toolchains often
>>>>>>>>>>>>> are part of a distributed system, and it's probably not that
>>>>>>>>>>>>> easy to guarantee that the thread count they observe is
>>>>>>>>>>>>> fully consistent with the number of threads that are
>>>>>>>>>>>>> actually running. Therefore, an in-situ `int
>>>>>>>>>>>>> numStreamThreads()` method might not be a bad idea. Then
>>>>>>>>>>>>> again, it seems sort of optional. A caller can catch an
>>>>>>>>>>>>> exception or react to a `null` return value just the same
>>>>>>>>>>>>> either way. Having both add/remove methods behave similarly
>>>>>>>>>>>>> is probably more valuable.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>> -John
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Thu, 2020-09-03 at 12:15 -0700, Sophie Blee-Goldman
>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>> Hey, sorry for the late reply, I just have one minor
>>>>>>>>>>>>>> suggestion. Since
>>>>>>>>>>>> we
>>>>>>>>>>>>>> don't
>>>>>>>>>>>>>> make any guarantees about which thread gets removed or allow
>>>>>>>>>>>>>> the user to
>>>>>>>>>>>>>> specify, I think we should return either the index or full
>> name
>>>>>>>>>>>>>> of the
>>>>>>>>>>>>>> thread
>>>>>>>>>>>>>> that does get removed by removeThread().
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I know you just updated the KIP to return true/false if there
>>>>>>>>>>>> are/aren't any
>>>>>>>>>>>>>> threads to be removed, but I think this would be more
>>>>>>>>>>>>>> appropriate as an
>>>>>>>>>>>>>> exception than as a return type. I think it's reasonable to
>>>>> expect
>>>>>>>>>>>> users to
>>>>>>>>>>>>>> have some sense to how many threads are remaining, and not
>> try
>>>>>>>>>>>>>> to remove
>>>>>>>>>>>>>> a thread when there is none left. To me, that indicates
>>>>>>>>>>>>>> something wrong
>>>>>>>>>>>>>> with the user application code and should be treated as an
>>>>>>>>>>>>>> exceptional
>>>>>>>>>>>> case.
>>>>>>>>>>>>>> I don't think the same code clarify argument applies here as
>> to
>>>>>>>>>>>>>> the
>>>>>>>>>>>>>> addStreamThread() case, as there's no reason for an
>> application
>>>>>>>>>>>>>> to be
>>>>>>>>>>>>>> looping and retrying removeStreamThread() since if that
>> fails,
>>>>>>>>>>>>>> it's
>>>>>>>>>>>> because
>>>>>>>>>>>>>> there are no threads left and thus it will continue to always
>>>>>>>>>>>>>> fail. And
>>>>>>>>>>>> if
>>>>>>>>>>>>>> the
>>>>>>>>>>>>>> user actually wants to shut down all threads, they should
>> just
>>>>>>>>>>>>>> close the
>>>>>>>>>>>>>> whole application rather than call removeStreamThread() in a
>>>>> loop.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> While I generally think it should be straightforward for
>> users
>>>>>>>>>>>>>> to track
>>>>>>>>>>>> how
>>>>>>>>>>>>>> many stream threads they have running, maybe it would be nice
>>>>>>>>>>>>>> to add
>>>>>>>>>>>>>> a small utility method that does this for them. Something
>> like
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> // Returns the number of currently alive threads
>>>>>>>>>>>>>> boolean runningStreamThreads();
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On Thu, Sep 3, 2020 at 7:41 AM Matthias J. Sax <
>>> mjsax@apache.org
>>>>>>
>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> +1 (binding)
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On 9/3/20 6:16 AM, Bruno Cadonna wrote:
>>>>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> I would like to start the voting on KIP-663 that proposes
>> to
>>>>> add
>>>>>>>>>>>> methods
>>>>>>>>>>>>>>>> to the Kafka Streams client to add and remove stream
>> threads
>>>>>>>>>>>>>>>> during
>>>>>>>>>>>>>>>> execution.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>
>>>
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-663%3A+API+to+Start+and+Shut+Down+Stream+Threads
>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Best,
>>>>>>>>>>>>>>>> Bruno
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> --
>>>>>>>>>>> -- Guozhang
>>>>>>>>>>>
>>>>>>>>>
>>>>>
>>>>
>>>
>>
>
Re: [VOTE] KIP-663: API to Start and Shut Down Stream Threads and to
Request Closing of Kafka Streams Clients
Posted by Israel Ekpo <is...@gmail.com>.
Thanks for clarifying that @Sophie it is in regards to KIP-633
On Wed, Jun 16, 2021 at 4:00 PM Sophie Blee-Goldman
<so...@confluent.io.invalid> wrote:
> Matthias, I'm guessing you meant to send this to the KIP-633 list? This is
> KIP-663
>
> On Wed, Jun 16, 2021 at 12:37 PM Matthias J. Sax <mj...@apache.org> wrote:
>
> > Quick follow up. I did a small update to the KIP with regard to
> > https://issues.apache.org/jira/browse/KAFKA-12909
> >
> > Israel, Sophie, and Guozhang did agree to this change. I don't think we
> > need to re-vote.
> >
> > Please let us know if there are any concerns.
> >
> >
> > -Matthias
> >
> > On 1/27/21 12:48 PM, Sophie Blee-Goldman wrote:
> > > Thanks Bruno, that sounds like a good addition. +1
> > >
> > > On Wed, Jan 27, 2021 at 12:34 PM Bruno Cadonna <br...@confluent.io>
> > wrote:
> > >
> > >> Hi all,
> > >>
> > >> During the implementation, we notices that method removeStreamThread()
> > >> may block indefinitely when the stream thread chosen for removal is
> > >> blocked and cannot be shut down. Thus, we will add an overload that
> > >> takes a timeout. The newly added method will throw a TimeoutException,
> > >> when the timeout is exceeded.
> > >>
> > >> We updated the KIP accordingly.
> > >>
> > >> KIP: https://cwiki.apache.org/confluence/x/FDd4CQ
> > >>
> > >> Best,
> > >> Bruno
> > >>
> > >> On 30.09.20 13:51, Bruno Cadonna wrote:
> > >>> Thank you all for voting!
> > >>>
> > >>> This KIP is accepted with 3 binding +1 (Guozhang, John, Matthias).
> > >>>
> > >>> Best,
> > >>> Bruno
> > >>>
> > >>> On 29.09.20 22:24, Matthias J. Sax wrote:
> > >>>> +1 (binding)
> > >>>>
> > >>>> I am not super happy with the impact on the client state. For
> > example, I
> > >>>> don't understand why it's ok to scale out if we lose one thread out
> of
> > >>>> four, but why it's not ok to scale out if we lose one thread out of
> > one
> > >>>> (for this case, we would enter ERROR state and cannot add new
> threads
> > >>>> afterwards).
> > >>>>
> > >>>> However, this might be an issue for a follow up KIP.
> > >>>>
> > >>>>
> > >>>> -Matthias
> > >>>>
> > >>>> On 9/29/20 7:20 AM, John Roesler wrote:
> > >>>>> Thanks, Bruno, this sounds good to me.
> > >>>>> -John
> > >>>>>
> > >>>>> On Tue, Sep 29, 2020, at 03:13, Bruno Cadonna wrote:
> > >>>>>> Hi all,
> > >>>>>>
> > >>>>>> I did two minor modifications to the KIP.
> > >>>>>>
> > >>>>>> - I removed the rather strict guarantee "Dead stream threads are
> > >>>>>> removed
> > >>>>>> from a Kafka Streams client at latest after the next call to
> > >>>>>> KafkaStreams#addStreamThread() or
> KafkaStreams#removeStreamThread()
> > >>>>>> following the transition to state DEAD."
> > >>>>>> Dead stream threads will be still removed, but the behavior will
> be
> > >>>>>> less
> > >>>>>> strict.
> > >>>>>>
> > >>>>>> - Added a sentence that states that the Kafka Streams client will
> > >>>>>> transit to ERROR if the last alive stream thread dies
> exceptionally.
> > >>>>>> This corresponds to the current behavior.
> > >>>>>>
> > >>>>>> I will not restart voting and keep the votes so far.
> > >>>>>>
> > >>>>>> Best,
> > >>>>>> Bruno
> > >>>>>>
> > >>>>>> On 22.09.20 01:19, John Roesler wrote:
> > >>>>>>> I’m +1 also. Thanks, Bruno!
> > >>>>>>> -John
> > >>>>>>>
> > >>>>>>> On Mon, Sep 21, 2020, at 17:08, Guozhang Wang wrote:
> > >>>>>>>> Thanks Bruno. I'm +1 on the KIP.
> > >>>>>>>>
> > >>>>>>>> On Mon, Sep 21, 2020 at 2:49 AM Bruno Cadonna <
> bruno@confluent.io
> > >
> > >>>>>>>> wrote:
> > >>>>>>>>
> > >>>>>>>>> Hi,
> > >>>>>>>>>
> > >>>>>>>>> I would like to restart from zero the voting on KIP-663 that
> > >>>>>>>>> proposes to
> > >>>>>>>>> add methods to the Kafka Streams client to add and remove
> stream
> > >>>>>>>>> threads
> > >>>>>>>>> during execution.
> > >>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>>>
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-663%3A+API+to+Start+and+Shut+Down+Stream+Threads
> > >>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>>> Matthias, if you are still +1, please vote again.
> > >>>>>>>>>
> > >>>>>>>>> Best,
> > >>>>>>>>> Bruno
> > >>>>>>>>>
> > >>>>>>>>> On 04.09.20 23:12, John Roesler wrote:
> > >>>>>>>>>> Hi Sophie,
> > >>>>>>>>>>
> > >>>>>>>>>> Uh, oh, it's never a good sign when the discussion moves
> > >>>>>>>>>> into the vote thread :)
> > >>>>>>>>>>
> > >>>>>>>>>> I agree with you, it seems like a good touch for
> > >>>>>>>>>> removeStreamThread() to return the name of the thread that
> > >>>>>>>>>> got removed, rather than a boolean flag. Maybe the return
> > >>>>>>>>>> value would be `null` if there is no thread to remove.
> > >>>>>>>>>>
> > >>>>>>>>>> If we go that way, I'd suggest that addStreamThread() also
> > >>>>>>>>>> return the name of the newly created thread, or null if no
> > >>>>>>>>>> thread can be created right now.
> > >>>>>>>>>>
> > >>>>>>>>>> I'm not completely sure if I think that callers of this
> > >>>>>>>>>> method would know exactly how many threads there are. Sure,
> > >>>>>>>>>> if a human being is sitting there looking at the metrics or
> > >>>>>>>>>> logs and decides to call the method, it would work out, but
> > >>>>>>>>>> I'd expect this kind of method to find its way into
> > >>>>>>>>>> automated tooling that reacts to things like current system
> > >>>>>>>>>> load or resource saturation. Those kinds of toolchains often
> > >>>>>>>>>> are part of a distributed system, and it's probably not that
> > >>>>>>>>>> easy to guarantee that the thread count they observe is
> > >>>>>>>>>> fully consistent with the number of threads that are
> > >>>>>>>>>> actually running. Therefore, an in-situ `int
> > >>>>>>>>>> numStreamThreads()` method might not be a bad idea. Then
> > >>>>>>>>>> again, it seems sort of optional. A caller can catch an
> > >>>>>>>>>> exception or react to a `null` return value just the same
> > >>>>>>>>>> either way. Having both add/remove methods behave similarly
> > >>>>>>>>>> is probably more valuable.
> > >>>>>>>>>>
> > >>>>>>>>>> Thanks,
> > >>>>>>>>>> -John
> > >>>>>>>>>>
> > >>>>>>>>>>
> > >>>>>>>>>> On Thu, 2020-09-03 at 12:15 -0700, Sophie Blee-Goldman
> > >>>>>>>>>> wrote:
> > >>>>>>>>>>> Hey, sorry for the late reply, I just have one minor
> > >>>>>>>>>>> suggestion. Since
> > >>>>>>>>> we
> > >>>>>>>>>>> don't
> > >>>>>>>>>>> make any guarantees about which thread gets removed or allow
> > >>>>>>>>>>> the user to
> > >>>>>>>>>>> specify, I think we should return either the index or full
> name
> > >>>>>>>>>>> of the
> > >>>>>>>>>>> thread
> > >>>>>>>>>>> that does get removed by removeThread().
> > >>>>>>>>>>>
> > >>>>>>>>>>> I know you just updated the KIP to return true/false if there
> > >>>>>>>>> are/aren't any
> > >>>>>>>>>>> threads to be removed, but I think this would be more
> > >>>>>>>>>>> appropriate as an
> > >>>>>>>>>>> exception than as a return type. I think it's reasonable to
> > >> expect
> > >>>>>>>>> users to
> > >>>>>>>>>>> have some sense to how many threads are remaining, and not
> try
> > >>>>>>>>>>> to remove
> > >>>>>>>>>>> a thread when there is none left. To me, that indicates
> > >>>>>>>>>>> something wrong
> > >>>>>>>>>>> with the user application code and should be treated as an
> > >>>>>>>>>>> exceptional
> > >>>>>>>>> case.
> > >>>>>>>>>>> I don't think the same code clarify argument applies here as
> to
> > >>>>>>>>>>> the
> > >>>>>>>>>>> addStreamThread() case, as there's no reason for an
> application
> > >>>>>>>>>>> to be
> > >>>>>>>>>>> looping and retrying removeStreamThread() since if that
> fails,
> > >>>>>>>>>>> it's
> > >>>>>>>>> because
> > >>>>>>>>>>> there are no threads left and thus it will continue to always
> > >>>>>>>>>>> fail. And
> > >>>>>>>>> if
> > >>>>>>>>>>> the
> > >>>>>>>>>>> user actually wants to shut down all threads, they should
> just
> > >>>>>>>>>>> close the
> > >>>>>>>>>>> whole application rather than call removeStreamThread() in a
> > >> loop.
> > >>>>>>>>>>>
> > >>>>>>>>>>> While I generally think it should be straightforward for
> users
> > >>>>>>>>>>> to track
> > >>>>>>>>> how
> > >>>>>>>>>>> many stream threads they have running, maybe it would be nice
> > >>>>>>>>>>> to add
> > >>>>>>>>>>> a small utility method that does this for them. Something
> like
> > >>>>>>>>>>>
> > >>>>>>>>>>> // Returns the number of currently alive threads
> > >>>>>>>>>>> boolean runningStreamThreads();
> > >>>>>>>>>>>
> > >>>>>>>>>>> On Thu, Sep 3, 2020 at 7:41 AM Matthias J. Sax <
> > mjsax@apache.org
> > >>>
> > >>>>>>>>> wrote:
> > >>>>>>>>>>>
> > >>>>>>>>>>>> +1 (binding)
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> On 9/3/20 6:16 AM, Bruno Cadonna wrote:
> > >>>>>>>>>>>>> Hi,
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> I would like to start the voting on KIP-663 that proposes
> to
> > >> add
> > >>>>>>>>> methods
> > >>>>>>>>>>>>> to the Kafka Streams client to add and remove stream
> threads
> > >>>>>>>>>>>>> during
> > >>>>>>>>>>>>> execution.
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>
> > >>>>>>>>>
> > >>
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-663%3A+API+to+Start+and+Shut+Down+Stream+Threads
> > >>>>>>>>>
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> Best,
> > >>>>>>>>>>>>> Bruno
> > >>>>>>>>>>
> > >>>>>>>>>
> > >>>>>>>>
> > >>>>>>>>
> > >>>>>>>> --
> > >>>>>>>> -- Guozhang
> > >>>>>>>>
> > >>>>>>
> > >>
> > >
> >
>
Re: [VOTE] KIP-663: API to Start and Shut Down Stream Threads and to
Request Closing of Kafka Streams Clients
Posted by Sophie Blee-Goldman <so...@confluent.io.INVALID>.
Matthias, I'm guessing you meant to send this to the KIP-633 list? This is
KIP-663
On Wed, Jun 16, 2021 at 12:37 PM Matthias J. Sax <mj...@apache.org> wrote:
> Quick follow up. I did a small update to the KIP with regard to
> https://issues.apache.org/jira/browse/KAFKA-12909
>
> Israel, Sophie, and Guozhang did agree to this change. I don't think we
> need to re-vote.
>
> Please let us know if there are any concerns.
>
>
> -Matthias
>
> On 1/27/21 12:48 PM, Sophie Blee-Goldman wrote:
> > Thanks Bruno, that sounds like a good addition. +1
> >
> > On Wed, Jan 27, 2021 at 12:34 PM Bruno Cadonna <br...@confluent.io>
> wrote:
> >
> >> Hi all,
> >>
> >> During the implementation, we notices that method removeStreamThread()
> >> may block indefinitely when the stream thread chosen for removal is
> >> blocked and cannot be shut down. Thus, we will add an overload that
> >> takes a timeout. The newly added method will throw a TimeoutException,
> >> when the timeout is exceeded.
> >>
> >> We updated the KIP accordingly.
> >>
> >> KIP: https://cwiki.apache.org/confluence/x/FDd4CQ
> >>
> >> Best,
> >> Bruno
> >>
> >> On 30.09.20 13:51, Bruno Cadonna wrote:
> >>> Thank you all for voting!
> >>>
> >>> This KIP is accepted with 3 binding +1 (Guozhang, John, Matthias).
> >>>
> >>> Best,
> >>> Bruno
> >>>
> >>> On 29.09.20 22:24, Matthias J. Sax wrote:
> >>>> +1 (binding)
> >>>>
> >>>> I am not super happy with the impact on the client state. For
> example, I
> >>>> don't understand why it's ok to scale out if we lose one thread out of
> >>>> four, but why it's not ok to scale out if we lose one thread out of
> one
> >>>> (for this case, we would enter ERROR state and cannot add new threads
> >>>> afterwards).
> >>>>
> >>>> However, this might be an issue for a follow up KIP.
> >>>>
> >>>>
> >>>> -Matthias
> >>>>
> >>>> On 9/29/20 7:20 AM, John Roesler wrote:
> >>>>> Thanks, Bruno, this sounds good to me.
> >>>>> -John
> >>>>>
> >>>>> On Tue, Sep 29, 2020, at 03:13, Bruno Cadonna wrote:
> >>>>>> Hi all,
> >>>>>>
> >>>>>> I did two minor modifications to the KIP.
> >>>>>>
> >>>>>> - I removed the rather strict guarantee "Dead stream threads are
> >>>>>> removed
> >>>>>> from a Kafka Streams client at latest after the next call to
> >>>>>> KafkaStreams#addStreamThread() or KafkaStreams#removeStreamThread()
> >>>>>> following the transition to state DEAD."
> >>>>>> Dead stream threads will be still removed, but the behavior will be
> >>>>>> less
> >>>>>> strict.
> >>>>>>
> >>>>>> - Added a sentence that states that the Kafka Streams client will
> >>>>>> transit to ERROR if the last alive stream thread dies exceptionally.
> >>>>>> This corresponds to the current behavior.
> >>>>>>
> >>>>>> I will not restart voting and keep the votes so far.
> >>>>>>
> >>>>>> Best,
> >>>>>> Bruno
> >>>>>>
> >>>>>> On 22.09.20 01:19, John Roesler wrote:
> >>>>>>> I’m +1 also. Thanks, Bruno!
> >>>>>>> -John
> >>>>>>>
> >>>>>>> On Mon, Sep 21, 2020, at 17:08, Guozhang Wang wrote:
> >>>>>>>> Thanks Bruno. I'm +1 on the KIP.
> >>>>>>>>
> >>>>>>>> On Mon, Sep 21, 2020 at 2:49 AM Bruno Cadonna <bruno@confluent.io
> >
> >>>>>>>> wrote:
> >>>>>>>>
> >>>>>>>>> Hi,
> >>>>>>>>>
> >>>>>>>>> I would like to restart from zero the voting on KIP-663 that
> >>>>>>>>> proposes to
> >>>>>>>>> add methods to the Kafka Streams client to add and remove stream
> >>>>>>>>> threads
> >>>>>>>>> during execution.
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-663%3A+API+to+Start+and+Shut+Down+Stream+Threads
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> Matthias, if you are still +1, please vote again.
> >>>>>>>>>
> >>>>>>>>> Best,
> >>>>>>>>> Bruno
> >>>>>>>>>
> >>>>>>>>> On 04.09.20 23:12, John Roesler wrote:
> >>>>>>>>>> Hi Sophie,
> >>>>>>>>>>
> >>>>>>>>>> Uh, oh, it's never a good sign when the discussion moves
> >>>>>>>>>> into the vote thread :)
> >>>>>>>>>>
> >>>>>>>>>> I agree with you, it seems like a good touch for
> >>>>>>>>>> removeStreamThread() to return the name of the thread that
> >>>>>>>>>> got removed, rather than a boolean flag. Maybe the return
> >>>>>>>>>> value would be `null` if there is no thread to remove.
> >>>>>>>>>>
> >>>>>>>>>> If we go that way, I'd suggest that addStreamThread() also
> >>>>>>>>>> return the name of the newly created thread, or null if no
> >>>>>>>>>> thread can be created right now.
> >>>>>>>>>>
> >>>>>>>>>> I'm not completely sure if I think that callers of this
> >>>>>>>>>> method would know exactly how many threads there are. Sure,
> >>>>>>>>>> if a human being is sitting there looking at the metrics or
> >>>>>>>>>> logs and decides to call the method, it would work out, but
> >>>>>>>>>> I'd expect this kind of method to find its way into
> >>>>>>>>>> automated tooling that reacts to things like current system
> >>>>>>>>>> load or resource saturation. Those kinds of toolchains often
> >>>>>>>>>> are part of a distributed system, and it's probably not that
> >>>>>>>>>> easy to guarantee that the thread count they observe is
> >>>>>>>>>> fully consistent with the number of threads that are
> >>>>>>>>>> actually running. Therefore, an in-situ `int
> >>>>>>>>>> numStreamThreads()` method might not be a bad idea. Then
> >>>>>>>>>> again, it seems sort of optional. A caller can catch an
> >>>>>>>>>> exception or react to a `null` return value just the same
> >>>>>>>>>> either way. Having both add/remove methods behave similarly
> >>>>>>>>>> is probably more valuable.
> >>>>>>>>>>
> >>>>>>>>>> Thanks,
> >>>>>>>>>> -John
> >>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>> On Thu, 2020-09-03 at 12:15 -0700, Sophie Blee-Goldman
> >>>>>>>>>> wrote:
> >>>>>>>>>>> Hey, sorry for the late reply, I just have one minor
> >>>>>>>>>>> suggestion. Since
> >>>>>>>>> we
> >>>>>>>>>>> don't
> >>>>>>>>>>> make any guarantees about which thread gets removed or allow
> >>>>>>>>>>> the user to
> >>>>>>>>>>> specify, I think we should return either the index or full name
> >>>>>>>>>>> of the
> >>>>>>>>>>> thread
> >>>>>>>>>>> that does get removed by removeThread().
> >>>>>>>>>>>
> >>>>>>>>>>> I know you just updated the KIP to return true/false if there
> >>>>>>>>> are/aren't any
> >>>>>>>>>>> threads to be removed, but I think this would be more
> >>>>>>>>>>> appropriate as an
> >>>>>>>>>>> exception than as a return type. I think it's reasonable to
> >> expect
> >>>>>>>>> users to
> >>>>>>>>>>> have some sense to how many threads are remaining, and not try
> >>>>>>>>>>> to remove
> >>>>>>>>>>> a thread when there is none left. To me, that indicates
> >>>>>>>>>>> something wrong
> >>>>>>>>>>> with the user application code and should be treated as an
> >>>>>>>>>>> exceptional
> >>>>>>>>> case.
> >>>>>>>>>>> I don't think the same code clarify argument applies here as to
> >>>>>>>>>>> the
> >>>>>>>>>>> addStreamThread() case, as there's no reason for an application
> >>>>>>>>>>> to be
> >>>>>>>>>>> looping and retrying removeStreamThread() since if that fails,
> >>>>>>>>>>> it's
> >>>>>>>>> because
> >>>>>>>>>>> there are no threads left and thus it will continue to always
> >>>>>>>>>>> fail. And
> >>>>>>>>> if
> >>>>>>>>>>> the
> >>>>>>>>>>> user actually wants to shut down all threads, they should just
> >>>>>>>>>>> close the
> >>>>>>>>>>> whole application rather than call removeStreamThread() in a
> >> loop.
> >>>>>>>>>>>
> >>>>>>>>>>> While I generally think it should be straightforward for users
> >>>>>>>>>>> to track
> >>>>>>>>> how
> >>>>>>>>>>> many stream threads they have running, maybe it would be nice
> >>>>>>>>>>> to add
> >>>>>>>>>>> a small utility method that does this for them. Something like
> >>>>>>>>>>>
> >>>>>>>>>>> // Returns the number of currently alive threads
> >>>>>>>>>>> boolean runningStreamThreads();
> >>>>>>>>>>>
> >>>>>>>>>>> On Thu, Sep 3, 2020 at 7:41 AM Matthias J. Sax <
> mjsax@apache.org
> >>>
> >>>>>>>>> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>>> +1 (binding)
> >>>>>>>>>>>>
> >>>>>>>>>>>> On 9/3/20 6:16 AM, Bruno Cadonna wrote:
> >>>>>>>>>>>>> Hi,
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> I would like to start the voting on KIP-663 that proposes to
> >> add
> >>>>>>>>> methods
> >>>>>>>>>>>>> to the Kafka Streams client to add and remove stream threads
> >>>>>>>>>>>>> during
> >>>>>>>>>>>>> execution.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>>
> >>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-663%3A+API+to+Start+and+Shut+Down+Stream+Threads
> >>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> Best,
> >>>>>>>>>>>>> Bruno
> >>>>>>>>>>
> >>>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> --
> >>>>>>>> -- Guozhang
> >>>>>>>>
> >>>>>>
> >>
> >
>
Re: [VOTE] KIP-663: API to Start and Shut Down Stream Threads and to
Request Closing of Kafka Streams Clients
Posted by "Matthias J. Sax" <mj...@apache.org>.
Quick follow up. I did a small update to the KIP with regard to
https://issues.apache.org/jira/browse/KAFKA-12909
Israel, Sophie, and Guozhang did agree to this change. I don't think we
need to re-vote.
Please let us know if there are any concerns.
-Matthias
On 1/27/21 12:48 PM, Sophie Blee-Goldman wrote:
> Thanks Bruno, that sounds like a good addition. +1
>
> On Wed, Jan 27, 2021 at 12:34 PM Bruno Cadonna <br...@confluent.io> wrote:
>
>> Hi all,
>>
>> During the implementation, we notices that method removeStreamThread()
>> may block indefinitely when the stream thread chosen for removal is
>> blocked and cannot be shut down. Thus, we will add an overload that
>> takes a timeout. The newly added method will throw a TimeoutException,
>> when the timeout is exceeded.
>>
>> We updated the KIP accordingly.
>>
>> KIP: https://cwiki.apache.org/confluence/x/FDd4CQ
>>
>> Best,
>> Bruno
>>
>> On 30.09.20 13:51, Bruno Cadonna wrote:
>>> Thank you all for voting!
>>>
>>> This KIP is accepted with 3 binding +1 (Guozhang, John, Matthias).
>>>
>>> Best,
>>> Bruno
>>>
>>> On 29.09.20 22:24, Matthias J. Sax wrote:
>>>> +1 (binding)
>>>>
>>>> I am not super happy with the impact on the client state. For example, I
>>>> don't understand why it's ok to scale out if we lose one thread out of
>>>> four, but why it's not ok to scale out if we lose one thread out of one
>>>> (for this case, we would enter ERROR state and cannot add new threads
>>>> afterwards).
>>>>
>>>> However, this might be an issue for a follow up KIP.
>>>>
>>>>
>>>> -Matthias
>>>>
>>>> On 9/29/20 7:20 AM, John Roesler wrote:
>>>>> Thanks, Bruno, this sounds good to me.
>>>>> -John
>>>>>
>>>>> On Tue, Sep 29, 2020, at 03:13, Bruno Cadonna wrote:
>>>>>> Hi all,
>>>>>>
>>>>>> I did two minor modifications to the KIP.
>>>>>>
>>>>>> - I removed the rather strict guarantee "Dead stream threads are
>>>>>> removed
>>>>>> from a Kafka Streams client at latest after the next call to
>>>>>> KafkaStreams#addStreamThread() or KafkaStreams#removeStreamThread()
>>>>>> following the transition to state DEAD."
>>>>>> Dead stream threads will be still removed, but the behavior will be
>>>>>> less
>>>>>> strict.
>>>>>>
>>>>>> - Added a sentence that states that the Kafka Streams client will
>>>>>> transit to ERROR if the last alive stream thread dies exceptionally.
>>>>>> This corresponds to the current behavior.
>>>>>>
>>>>>> I will not restart voting and keep the votes so far.
>>>>>>
>>>>>> Best,
>>>>>> Bruno
>>>>>>
>>>>>> On 22.09.20 01:19, John Roesler wrote:
>>>>>>> I’m +1 also. Thanks, Bruno!
>>>>>>> -John
>>>>>>>
>>>>>>> On Mon, Sep 21, 2020, at 17:08, Guozhang Wang wrote:
>>>>>>>> Thanks Bruno. I'm +1 on the KIP.
>>>>>>>>
>>>>>>>> On Mon, Sep 21, 2020 at 2:49 AM Bruno Cadonna <br...@confluent.io>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Hi,
>>>>>>>>>
>>>>>>>>> I would like to restart from zero the voting on KIP-663 that
>>>>>>>>> proposes to
>>>>>>>>> add methods to the Kafka Streams client to add and remove stream
>>>>>>>>> threads
>>>>>>>>> during execution.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-663%3A+API+to+Start+and+Shut+Down+Stream+Threads
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Matthias, if you are still +1, please vote again.
>>>>>>>>>
>>>>>>>>> Best,
>>>>>>>>> Bruno
>>>>>>>>>
>>>>>>>>> On 04.09.20 23:12, John Roesler wrote:
>>>>>>>>>> Hi Sophie,
>>>>>>>>>>
>>>>>>>>>> Uh, oh, it's never a good sign when the discussion moves
>>>>>>>>>> into the vote thread :)
>>>>>>>>>>
>>>>>>>>>> I agree with you, it seems like a good touch for
>>>>>>>>>> removeStreamThread() to return the name of the thread that
>>>>>>>>>> got removed, rather than a boolean flag. Maybe the return
>>>>>>>>>> value would be `null` if there is no thread to remove.
>>>>>>>>>>
>>>>>>>>>> If we go that way, I'd suggest that addStreamThread() also
>>>>>>>>>> return the name of the newly created thread, or null if no
>>>>>>>>>> thread can be created right now.
>>>>>>>>>>
>>>>>>>>>> I'm not completely sure if I think that callers of this
>>>>>>>>>> method would know exactly how many threads there are. Sure,
>>>>>>>>>> if a human being is sitting there looking at the metrics or
>>>>>>>>>> logs and decides to call the method, it would work out, but
>>>>>>>>>> I'd expect this kind of method to find its way into
>>>>>>>>>> automated tooling that reacts to things like current system
>>>>>>>>>> load or resource saturation. Those kinds of toolchains often
>>>>>>>>>> are part of a distributed system, and it's probably not that
>>>>>>>>>> easy to guarantee that the thread count they observe is
>>>>>>>>>> fully consistent with the number of threads that are
>>>>>>>>>> actually running. Therefore, an in-situ `int
>>>>>>>>>> numStreamThreads()` method might not be a bad idea. Then
>>>>>>>>>> again, it seems sort of optional. A caller can catch an
>>>>>>>>>> exception or react to a `null` return value just the same
>>>>>>>>>> either way. Having both add/remove methods behave similarly
>>>>>>>>>> is probably more valuable.
>>>>>>>>>>
>>>>>>>>>> Thanks,
>>>>>>>>>> -John
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Thu, 2020-09-03 at 12:15 -0700, Sophie Blee-Goldman
>>>>>>>>>> wrote:
>>>>>>>>>>> Hey, sorry for the late reply, I just have one minor
>>>>>>>>>>> suggestion. Since
>>>>>>>>> we
>>>>>>>>>>> don't
>>>>>>>>>>> make any guarantees about which thread gets removed or allow
>>>>>>>>>>> the user to
>>>>>>>>>>> specify, I think we should return either the index or full name
>>>>>>>>>>> of the
>>>>>>>>>>> thread
>>>>>>>>>>> that does get removed by removeThread().
>>>>>>>>>>>
>>>>>>>>>>> I know you just updated the KIP to return true/false if there
>>>>>>>>> are/aren't any
>>>>>>>>>>> threads to be removed, but I think this would be more
>>>>>>>>>>> appropriate as an
>>>>>>>>>>> exception than as a return type. I think it's reasonable to
>> expect
>>>>>>>>> users to
>>>>>>>>>>> have some sense to how many threads are remaining, and not try
>>>>>>>>>>> to remove
>>>>>>>>>>> a thread when there is none left. To me, that indicates
>>>>>>>>>>> something wrong
>>>>>>>>>>> with the user application code and should be treated as an
>>>>>>>>>>> exceptional
>>>>>>>>> case.
>>>>>>>>>>> I don't think the same code clarify argument applies here as to
>>>>>>>>>>> the
>>>>>>>>>>> addStreamThread() case, as there's no reason for an application
>>>>>>>>>>> to be
>>>>>>>>>>> looping and retrying removeStreamThread() since if that fails,
>>>>>>>>>>> it's
>>>>>>>>> because
>>>>>>>>>>> there are no threads left and thus it will continue to always
>>>>>>>>>>> fail. And
>>>>>>>>> if
>>>>>>>>>>> the
>>>>>>>>>>> user actually wants to shut down all threads, they should just
>>>>>>>>>>> close the
>>>>>>>>>>> whole application rather than call removeStreamThread() in a
>> loop.
>>>>>>>>>>>
>>>>>>>>>>> While I generally think it should be straightforward for users
>>>>>>>>>>> to track
>>>>>>>>> how
>>>>>>>>>>> many stream threads they have running, maybe it would be nice
>>>>>>>>>>> to add
>>>>>>>>>>> a small utility method that does this for them. Something like
>>>>>>>>>>>
>>>>>>>>>>> // Returns the number of currently alive threads
>>>>>>>>>>> boolean runningStreamThreads();
>>>>>>>>>>>
>>>>>>>>>>> On Thu, Sep 3, 2020 at 7:41 AM Matthias J. Sax <mjsax@apache.org
>>>
>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> +1 (binding)
>>>>>>>>>>>>
>>>>>>>>>>>> On 9/3/20 6:16 AM, Bruno Cadonna wrote:
>>>>>>>>>>>>> Hi,
>>>>>>>>>>>>>
>>>>>>>>>>>>> I would like to start the voting on KIP-663 that proposes to
>> add
>>>>>>>>> methods
>>>>>>>>>>>>> to the Kafka Streams client to add and remove stream threads
>>>>>>>>>>>>> during
>>>>>>>>>>>>> execution.
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-663%3A+API+to+Start+and+Shut+Down+Stream+Threads
>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> Best,
>>>>>>>>>>>>> Bruno
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>> -- Guozhang
>>>>>>>>
>>>>>>
>>
>
Re: [VOTE] KIP-663: API to Start and Shut Down Stream Threads and to
Request Closing of Kafka Streams Clients
Posted by Sophie Blee-Goldman <so...@confluent.io>.
Thanks Bruno, that sounds like a good addition. +1
On Wed, Jan 27, 2021 at 12:34 PM Bruno Cadonna <br...@confluent.io> wrote:
> Hi all,
>
> During the implementation, we notices that method removeStreamThread()
> may block indefinitely when the stream thread chosen for removal is
> blocked and cannot be shut down. Thus, we will add an overload that
> takes a timeout. The newly added method will throw a TimeoutException,
> when the timeout is exceeded.
>
> We updated the KIP accordingly.
>
> KIP: https://cwiki.apache.org/confluence/x/FDd4CQ
>
> Best,
> Bruno
>
> On 30.09.20 13:51, Bruno Cadonna wrote:
> > Thank you all for voting!
> >
> > This KIP is accepted with 3 binding +1 (Guozhang, John, Matthias).
> >
> > Best,
> > Bruno
> >
> > On 29.09.20 22:24, Matthias J. Sax wrote:
> >> +1 (binding)
> >>
> >> I am not super happy with the impact on the client state. For example, I
> >> don't understand why it's ok to scale out if we lose one thread out of
> >> four, but why it's not ok to scale out if we lose one thread out of one
> >> (for this case, we would enter ERROR state and cannot add new threads
> >> afterwards).
> >>
> >> However, this might be an issue for a follow up KIP.
> >>
> >>
> >> -Matthias
> >>
> >> On 9/29/20 7:20 AM, John Roesler wrote:
> >>> Thanks, Bruno, this sounds good to me.
> >>> -John
> >>>
> >>> On Tue, Sep 29, 2020, at 03:13, Bruno Cadonna wrote:
> >>>> Hi all,
> >>>>
> >>>> I did two minor modifications to the KIP.
> >>>>
> >>>> - I removed the rather strict guarantee "Dead stream threads are
> >>>> removed
> >>>> from a Kafka Streams client at latest after the next call to
> >>>> KafkaStreams#addStreamThread() or KafkaStreams#removeStreamThread()
> >>>> following the transition to state DEAD."
> >>>> Dead stream threads will be still removed, but the behavior will be
> >>>> less
> >>>> strict.
> >>>>
> >>>> - Added a sentence that states that the Kafka Streams client will
> >>>> transit to ERROR if the last alive stream thread dies exceptionally.
> >>>> This corresponds to the current behavior.
> >>>>
> >>>> I will not restart voting and keep the votes so far.
> >>>>
> >>>> Best,
> >>>> Bruno
> >>>>
> >>>> On 22.09.20 01:19, John Roesler wrote:
> >>>>> I’m +1 also. Thanks, Bruno!
> >>>>> -John
> >>>>>
> >>>>> On Mon, Sep 21, 2020, at 17:08, Guozhang Wang wrote:
> >>>>>> Thanks Bruno. I'm +1 on the KIP.
> >>>>>>
> >>>>>> On Mon, Sep 21, 2020 at 2:49 AM Bruno Cadonna <br...@confluent.io>
> >>>>>> wrote:
> >>>>>>
> >>>>>>> Hi,
> >>>>>>>
> >>>>>>> I would like to restart from zero the voting on KIP-663 that
> >>>>>>> proposes to
> >>>>>>> add methods to the Kafka Streams client to add and remove stream
> >>>>>>> threads
> >>>>>>> during execution.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-663%3A+API+to+Start+and+Shut+Down+Stream+Threads
> >>>>>>>
> >>>>>>>
> >>>>>>> Matthias, if you are still +1, please vote again.
> >>>>>>>
> >>>>>>> Best,
> >>>>>>> Bruno
> >>>>>>>
> >>>>>>> On 04.09.20 23:12, John Roesler wrote:
> >>>>>>>> Hi Sophie,
> >>>>>>>>
> >>>>>>>> Uh, oh, it's never a good sign when the discussion moves
> >>>>>>>> into the vote thread :)
> >>>>>>>>
> >>>>>>>> I agree with you, it seems like a good touch for
> >>>>>>>> removeStreamThread() to return the name of the thread that
> >>>>>>>> got removed, rather than a boolean flag. Maybe the return
> >>>>>>>> value would be `null` if there is no thread to remove.
> >>>>>>>>
> >>>>>>>> If we go that way, I'd suggest that addStreamThread() also
> >>>>>>>> return the name of the newly created thread, or null if no
> >>>>>>>> thread can be created right now.
> >>>>>>>>
> >>>>>>>> I'm not completely sure if I think that callers of this
> >>>>>>>> method would know exactly how many threads there are. Sure,
> >>>>>>>> if a human being is sitting there looking at the metrics or
> >>>>>>>> logs and decides to call the method, it would work out, but
> >>>>>>>> I'd expect this kind of method to find its way into
> >>>>>>>> automated tooling that reacts to things like current system
> >>>>>>>> load or resource saturation. Those kinds of toolchains often
> >>>>>>>> are part of a distributed system, and it's probably not that
> >>>>>>>> easy to guarantee that the thread count they observe is
> >>>>>>>> fully consistent with the number of threads that are
> >>>>>>>> actually running. Therefore, an in-situ `int
> >>>>>>>> numStreamThreads()` method might not be a bad idea. Then
> >>>>>>>> again, it seems sort of optional. A caller can catch an
> >>>>>>>> exception or react to a `null` return value just the same
> >>>>>>>> either way. Having both add/remove methods behave similarly
> >>>>>>>> is probably more valuable.
> >>>>>>>>
> >>>>>>>> Thanks,
> >>>>>>>> -John
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> On Thu, 2020-09-03 at 12:15 -0700, Sophie Blee-Goldman
> >>>>>>>> wrote:
> >>>>>>>>> Hey, sorry for the late reply, I just have one minor
> >>>>>>>>> suggestion. Since
> >>>>>>> we
> >>>>>>>>> don't
> >>>>>>>>> make any guarantees about which thread gets removed or allow
> >>>>>>>>> the user to
> >>>>>>>>> specify, I think we should return either the index or full name
> >>>>>>>>> of the
> >>>>>>>>> thread
> >>>>>>>>> that does get removed by removeThread().
> >>>>>>>>>
> >>>>>>>>> I know you just updated the KIP to return true/false if there
> >>>>>>> are/aren't any
> >>>>>>>>> threads to be removed, but I think this would be more
> >>>>>>>>> appropriate as an
> >>>>>>>>> exception than as a return type. I think it's reasonable to
> expect
> >>>>>>> users to
> >>>>>>>>> have some sense to how many threads are remaining, and not try
> >>>>>>>>> to remove
> >>>>>>>>> a thread when there is none left. To me, that indicates
> >>>>>>>>> something wrong
> >>>>>>>>> with the user application code and should be treated as an
> >>>>>>>>> exceptional
> >>>>>>> case.
> >>>>>>>>> I don't think the same code clarify argument applies here as to
> >>>>>>>>> the
> >>>>>>>>> addStreamThread() case, as there's no reason for an application
> >>>>>>>>> to be
> >>>>>>>>> looping and retrying removeStreamThread() since if that fails,
> >>>>>>>>> it's
> >>>>>>> because
> >>>>>>>>> there are no threads left and thus it will continue to always
> >>>>>>>>> fail. And
> >>>>>>> if
> >>>>>>>>> the
> >>>>>>>>> user actually wants to shut down all threads, they should just
> >>>>>>>>> close the
> >>>>>>>>> whole application rather than call removeStreamThread() in a
> loop.
> >>>>>>>>>
> >>>>>>>>> While I generally think it should be straightforward for users
> >>>>>>>>> to track
> >>>>>>> how
> >>>>>>>>> many stream threads they have running, maybe it would be nice
> >>>>>>>>> to add
> >>>>>>>>> a small utility method that does this for them. Something like
> >>>>>>>>>
> >>>>>>>>> // Returns the number of currently alive threads
> >>>>>>>>> boolean runningStreamThreads();
> >>>>>>>>>
> >>>>>>>>> On Thu, Sep 3, 2020 at 7:41 AM Matthias J. Sax <mjsax@apache.org
> >
> >>>>>>> wrote:
> >>>>>>>>>
> >>>>>>>>>> +1 (binding)
> >>>>>>>>>>
> >>>>>>>>>> On 9/3/20 6:16 AM, Bruno Cadonna wrote:
> >>>>>>>>>>> Hi,
> >>>>>>>>>>>
> >>>>>>>>>>> I would like to start the voting on KIP-663 that proposes to
> add
> >>>>>>> methods
> >>>>>>>>>>> to the Kafka Streams client to add and remove stream threads
> >>>>>>>>>>> during
> >>>>>>>>>>> execution.
> >>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-663%3A+API+to+Start+and+Shut+Down+Stream+Threads
> >>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>> Best,
> >>>>>>>>>>> Bruno
> >>>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>>
> >>>>>> --
> >>>>>> -- Guozhang
> >>>>>>
> >>>>
>