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From Romain Manni-Bucau <rmannibu...@gmail.com>
Subject Re: makes bundle concept usable?
Date Wed, 15 Nov 2017 09:58:04 GMT
Overall goal is to ensure each 100 elements max, a "backend" (as
datastore) flush/commit/push is done and is aligned with beam
checkpoints. You can see it as bringing the "general" commit-interval
notion to beam and kind of get rid of the bundle notion which is
almost impossible to use today.

Romain Manni-Bucau
@rmannibucau |  Blog | Old Blog | Github | LinkedIn


2017-11-15 10:27 GMT+01:00 Reuven Lax <relax@google.com.invalid>:
> It's in the dev list archives, not sure if there's a doc yet.
>
> I'm not quite sure I understand what you mean by a "flush" Can you describe
> the problem you're trying to solve?
>
> Reuven
>
> On Wed, Nov 15, 2017 at 5:25 PM, Romain Manni-Bucau <rmannibucau@gmail.com>
> wrote:
>
>> Hmm, I didn't find the doc - if you have the link not far it would be
>> appreciated - but "before" sounds not enough, it should be "after" in
>> case there was a "flush" no?
>>
>> Romain Manni-Bucau
>> @rmannibucau |  Blog | Old Blog | Github | LinkedIn
>>
>>
>> 2017-11-15 10:10 GMT+01:00 Reuven Lax <relax@google.com.invalid>:
>> > If you set @StableReplay before a ParDo, it forces a checkpoint before
>> that
>> > ParDo.
>> >
>> > On Wed, Nov 15, 2017 at 5:07 PM, Romain Manni-Bucau <
>> rmannibucau@gmail.com>
>> > wrote:
>> >
>> >> It sounds a good start. I'm not sure how a group by key (and not by
>> >> size) can help controlling the checkpointing interval. Wonder if we
>> >> shouldn't be able to have a CheckpointPolicy { boolean
>> >> shouldCheckpoint() } used in the processing event loop. Default could
>> >> be up to the runner but if set on the transform (or dofn) it would be
>> >> used to control when the checkpoint is done. Thinking out loud it
>> >> sounds close to jbatch checkpoint algorithm
>> >> (https://docs.oracle.com/javaee/7/api/javax/batch/api/
>> >> chunk/CheckpointAlgorithm.html)
>> >>
>> >> Romain Manni-Bucau
>> >> @rmannibucau |  Blog | Old Blog | Github | LinkedIn
>> >>
>> >>
>> >> 2017-11-15 9:55 GMT+01:00 Jean-Baptiste Onofré <jb@nanthrax.net>:
>> >> > Yes, @StableReplay, that's the annotation. Thanks.
>> >> >
>> >> >
>> >> > On 11/15/2017 09:52 AM, Reuven Lax wrote:
>> >> >>
>> >> >> Romain,
>> >> >>
>> >> >> I think the @StableReplay semantic that Kenn proposed a month or
so
>> ago
>> >> is
>> >> >> what is needed here.
>> >> >>
>> >> >> Essentially it will ensure that the GroupByKey iterable is stable
and
>> >> >> checkpointed. So on replay, the GroupByKey is guaranteed to receive
>> the
>> >> >> exact same iterable as it did before. The annotation can be put
on a
>> >> ParDo
>> >> >> as well, in which case it ensures stability (and checkpointing)
of
>> the
>> >> >> individual ParDo elements.
>> >> >>
>> >> >> Reuven
>> >> >>
>> >> >> On Wed, Nov 15, 2017 at 4:49 PM, Romain Manni-Bucau
>> >> >> <rmannibucau@gmail.com>
>> >> >> wrote:
>> >> >>
>> >> >>> 2017-11-15 9:46 GMT+01:00 Jean-Baptiste Onofré <jb@nanthrax.net>:
>> >> >>>>
>> >> >>>> Hi Romain,
>> >> >>>>
>> >> >>>> You are right: currently, the chunking is related to bundles.
>> Today,
>> >> the
>> >> >>>> bundle size is under the runner responsibility.
>> >> >>>>
>> >> >>>> I think it's fine because only the runner know an efficient
bundle
>> >> size.
>> >> >>>
>> >> >>> I'm
>> >> >>>>
>> >> >>>> afraid giving the "control" of the bundle size to the end
user (via
>> >> >>>> pipeline) can result to huge performances issue depending
of the
>> >> runner.
>> >> >>>>
>> >> >>>> It doesn't mean that we can't use an uber layer: it's what
we do in
>> >> >>>> ParDoWithBatch or DoFn in IO Sink where we have a batch
size.
>> >> >>>>
>> >> >>>> Anyway, the core problem is about the checkpoint: why a
checkpoint
>> is
>> >> >>>> not
>> >> >>>> "respected" by an IO or runner ?
>> >> >>>
>> >> >>>
>> >> >>>
>> >> >>> Take the example of a runner deciding the bundle size is 4
and the
>> IO
>> >> >>> deciding the commit-interval (batch semantic) is 2, what happens
if
>> >> >>> the 3rd record fails? You have pushed to the store 2 records
which
>> can
>> >> >>> be reprocessed by a restart of the bundle and you can get
>> duplicates.
>> >> >>>
>> >> >>> Rephrased: I think we need as a framework a batch/chunk solution
>> which
>> >> >>> is reliable. I understand bundles is mapped on the runner and
not
>> >> >>> really controlled but can we get something more reliable for
the
>> user?
>> >> >>> Maybe we need a @BeforeBatch or something like that.
>> >> >>>
>> >> >>>>
>> >> >>>> Regards
>> >> >>>> JB
>> >> >>>>
>> >> >>>>
>> >> >>>> On 11/15/2017 09:38 AM, Romain Manni-Bucau wrote:
>> >> >>>>>
>> >> >>>>>
>> >> >>>>> Hi guys,
>> >> >>>>>
>> >> >>>>> The subject is a bit provocative but the topic is real
and coming
>> >> >>>>> again and again with the beam usage: how a dofn can
handle some
>> >> >>>>> "chunking".
>> >> >>>>>
>> >> >>>>> The need is to be able to commit each N records but
with N not too
>> >> big.
>> >> >>>>>
>> >> >>>>> The natural API for that in beam is the bundle one
but bundles are
>> >> not
>> >> >>>>> reliable since they can be very small (flink) - we
can say it is
>> "ok"
>> >> >>>>> even if it has some perf impacts - or too big (spark
does full
>> size /
>> >> >>>>> #workers).
>> >> >>>>>
>> >> >>>>> The workaround is what we see in the ES I/O: a maxSize
which does
>> an
>> >> >>>>> eager flush. The issue is that then the checkpoint
is not
>> respected
>> >> >>>>> and you can process multiple times the same records.
>> >> >>>>>
>> >> >>>>> Any plan to make this API reliable and controllable
from a beam
>> point
>> >> >>>>> of view (at least in a max manner)?
>> >> >>>>>
>> >> >>>>> Thanks,
>> >> >>>>> Romain Manni-Bucau
>> >> >>>>> @rmannibucau |  Blog | Old Blog | Github | LinkedIn
>> >> >>>>>
>> >> >>>>
>> >> >>>> --
>> >> >>>> Jean-Baptiste Onofré
>> >> >>>> jbonofre@apache.org
>> >> >>>> http://blog.nanthrax.net
>> >> >>>> Talend - http://www.talend.com
>> >> >>>
>> >> >>>
>> >> >>
>> >> >
>> >> > --
>> >> > Jean-Baptiste Onofré
>> >> > jbonofre@apache.org
>> >> > http://blog.nanthrax.net
>> >> > Talend - http://www.talend.com
>> >>
>>

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