The comment is valid. It falls exactly into this topic, it has exactly
todo with this!
Even when we have a statefull operation last. We move it to the very
first processor (KtableSource)
and therefore cant present a proper RecordContext.
Regarding the other Jiras you are referring to. They harm the project
more than they do good!
There is no need for this kind of optimizer and meta representation and
what not. I hope they
never get implemented.
Best Jan
On 22.11.2017 14:44, Damian Guy wrote:
Jan, i think you comment with respect to filtering is valid, though not for
this KIP. We have separate JIRAs for topology optimization of which this
falls into.
Thanks,
Damian
On Wed, 22 Nov 2017 at 02:25 Guozhang Wang <wangg...@gmail.com> wrote:
Jan,
Not sure I understand your argument that "we still going to present
change.oldValue to the filter even though the record context() is for
change.newValue". Are you referring to `KTableFilter#process()`? If yes
could you point to me which LOC are you concerning about?
Guozhang
On Mon, Nov 20, 2017 at 9:29 PM, Jan Filipiak <jan.filip...@trivago.com>
wrote:
a remark of mine that got missed during migration:
There is this problem that even though we have source.table.filter.join
the state-fullness happens at the table step not a the join step. In a
filter
we still going to present change.oldValue to the filter even though the
record context() is for change.newValue. I would go as far as applying
the filter before the table processor. Not to just get KIP-159, but
because
I think its a side effect of a non ideal topology layout. If i can filter
99% of my
records. my state could be way smaller. Also widely escalates the context
of the KIP
I can only see upsides of executing the filter first.
Best Jan
On 20.11.2017 22:22, Matthias J. Sax wrote:
I am moving this back to the DISCUSS thread... Last 10 emails were sent
to VOTE thread.
Copying Guozhang's last summary below. Thanks for this summary. Very
comprehensive!
It seems, we all agree, that the current implementation of the context
at PAPI level is ok, but we should not leak it into DSL.
Thus, we can go with (2) or (3), were (3) is an extension to (2)
carrying the context to more operators than just sources. It also seems,
that we all agree, that many-to-one operations void the context.
I still think, that just going with plain (2) is too restrictive -- but
I am also fine if we don't go with the full proposal of (3).
Also note, that the two operators filter() and filterNot() don't modify
the record and thus for both, it would be absolutely valid to keep the
context.
I personally would keep the context for at least all one-to-one
operators. One-to-many is debatable and I am fine to not carry the
context further: at least the offset information is questionable for
this case -- note thought, that semantically, the timestamp is inherited
via one-to-many, and I also think this applies to "topic" and
"partition". Thus, I think it's still valuable information we can carry
downstreams.
-Matthias
Jan: which approach are you referring to as "the approach that is on the
table would be perfect"?
Note that in today's PAPI layer we are already effectively exposing the
record context which has the issues that we have been discussing right
now,
and its semantics is always referring to the "processing record" at
hand.
More specifically, we can think of processing a record a bit different:
1) the record traversed the topology from source to sink, it may be
transformed into new object or even generate multiple new objects
(think:
branch) along the traversal. And the record context is referring to
this
processing record. Here the "lifetime" of the record lasts for the
entire
topology traversal and any new records of this traversal is treated as
different transformed values of this record (this applies to join and
aggregations as well).
2) the record being processed is wiped out in the first operator after
the
source, and NEW records are forwarded to downstream operators. I.e.
each
record only lives between two adjacent operators, once it reached the
new
operator it's lifetime has ended and new records are generated.
I think in the past we have talked about Streams under both context,
and
we
do not have a clear agreement. I agree that 2) is logically more
understandable for users as it does not leak any internal
implementation
details (e.g. for stream-table joins, table record's traversal ends at
the
join operator as it is only be materialized, while stream record's
traversal goes through the join operator to further down until sinks).
However if we are going to interpret following 2) above then even for
non-stateful operators we would not inherit record context. What we're
discussing now, seems to infer a third semantics:
3) a record would traverse "through" one-to-one (non-stateful)
operators,
will "replicate" at one-to-many (non-stateful) operators (think:
"mapValues"
) and will "end" at many-to-one (stateful) operators where NEW
records
will be generated and forwarded to the downstream operators.
Just wanted to lay the ground for discussions so we are all on the same
page before chatting more.
Guozhang
On 11/6/17 1:41 PM, Jeyhun Karimov wrote:
Hi Matthias,
Thanks a lot for correcting. It is a leftover from the past designs
when
punctuate() was not deprecated.
I corrected.
Cheers,
Jeyhun
On Mon, Nov 6, 2017 at 5:30 PM Matthias J. Sax <matth...@confluent.io>
wrote:
I just re-read the KIP.
One minor comment: we don't need to introduce any deprecated methods.
Thus, RichValueTransformer#punctuate can be removed completely instead
of introducing it as deprecated.
Otherwise looks good to me.
Thanks for being so patient!
-Matthias
On 11/1/17 9:16 PM, Guozhang Wang wrote:
Jeyhun,
I think I'm convinced to not do KAFKA-3907 in this KIP. We should
think
carefully if we should add this functionality to the DSL layer moving
forward since from what we discovered working on it the conclusion is
that
it would require revamping the public APIs quite a lot, and it's not
clear
if it is a good trade-off than asking users to call process()
instead.
Guozhang
On Wed, Nov 1, 2017 at 4:50 AM, Damian Guy <damian....@gmail.com>
wrote:
Hi Jeyhun, thanks, looks good.
Do we need to remove the line that says:
- on-demand commit() feature
Cheers,
Damian
On Tue, 31 Oct 2017 at 23:07 Jeyhun Karimov <je.kari...@gmail.com>
wrote:
Hi,
I removed the 'commit()' feature, as we discussed. It simplified
the
overall design of KIP a lot.
If it is ok, I would like to start a VOTE thread.
Cheers,
Jeyhun
On Fri, Oct 27, 2017 at 5:28 PM Matthias J. Sax <
matth...@confluent.io
wrote:
Thanks. I understand what you are saying, but I don't agree that
but also we need a commit() method
I would just not provide `commit()` at DSL level and close the
corresponding Jira as "not a problem" or similar.
-Matthias
On 10/27/17 3:42 PM, Jeyhun Karimov wrote:
Hi Matthias,
Thanks for your comments. I agree that this is not the best way
to
do.
A
bit of history behind this design.
Prior doing this, I tried to provide ProcessorContext itself as
an
argument
in Rich interfaces. However, we dont want to give users that
flexibility
and “power”. Moreover, ProcessorContext contains processor level
information and not Record level info. The only thing we need ij
ProcessorContext is commit() method.
So, as far as I understood, we need recor context (offset,
timestamp
and
etc) but also we need a commit() method ( we dont want to provide
ProcessorContext as a parameter so users can use
ProcessorContext.commit()
).
As a result, I thought to “propagate” commit() call from
RecordContext
to
ProcessorContext() .
If there is a misunderstanding in motvation/discussion of
KIP/included
jiras please let me know.
Cheers,
Jeyhun
On Fri 27. Oct 2017 at 12:39, Matthias J. Sax <
matth...@confluent.io
wrote:
I am personally still not convinced, that we should add
`commit()`
at
all.
@Guozhang: you created the original Jira. Can you elaborate a
little
bit? Isn't requesting commits a low level API that should not be
exposed
in the DSL? Just want to understand the motivation better. Why
would
anybody that uses the DSL ever want to request a commit? To me,
requesting commits is useful if you manipulated state
explicitly,
ie,
via Processor API.
Also, for the solution: it seem rather unnatural to me, that we
add
`commit()` to `RecordContext` -- from my understanding,
`RecordContext`
is an helper object that provide access to record meta data.
Requesting
a commit is something quite different. Additionally, a commit does
not
commit a specific record but a `RecrodContext` is for a specific
record.
To me, this does not seem to be a sound API design if we follow
this
path.
-Matthias
On 10/26/17 10:41 PM, Jeyhun Karimov wrote:
Hi,
Thanks for your suggestions.
I have some comments, to make sure that there is no
misunderstanding.
1. Maybe we can deprecate the `commit()` in ProcessorContext,
to
enforce
user to consolidate this call as
"processorContext.recordContext().commit()". And internal
implementation
of
`ProcessorContext.commit()` in `ProcessorContextImpl` is also
changed
to
this call.
- I think we should not deprecate `ProcessorContext.commit()`.
The
main
intuition that we introduce `commit()` in `RecordContext` is that,
`RecordContext` is the one which is provided in Rich
interfaces.
So
if
user
wants to commit, then there should be some method inside
`RecordContext`
to
do so. Internally, `RecordContext.commit()` calls
`ProcessorContext.commit()` (see the last code snippet in
KIP-159):
@Override
public void process(final K1 key, final V1 value) {
recordContext = new RecordContext() { //
recordContext initialization is added in this KIP
@Override
public void commit() {
context().commit();
}
@Override
public long offset() {
return context().recordContext().offset();
}
@Override
public long timestamp() {
return context().recordContext().timestamp();
}
@Override
public String topic() {
return context().recordContext().topic();
}
@Override
public int partition() {
return context().recordContext().partition();
}
};
So, we cannot deprecate `ProcessorContext.commit()` in this
case
IMO.
2. Add the `task` reference to the impl class,
`ProcessorRecordContext`,
so
that it can implement the commit call itself.
- Actually, I don't think that we need `commit()` in
`ProcessorRecordContext`. The main intuition is to "transfer"
`ProcessorContext.commit()` call to Rich interfaces, to support
user-specific committing.
To do so, we introduce `commit()` method in `RecordContext()`
just
only
to
call ProcessorContext.commit() inside. (see the above code
snippet)
So, in Rich interfaces, we are not dealing with
`ProcessorRecordContext`
at all, and we leave all its methods as it is.
In this KIP, we made `RecordContext` to be the parent class of
`ProcessorRecordContext`, just because of they share quite
amount
of
methods and it is logical to enable inheritance between those two.
3. In the wiki page, the statement that "However, call to a
commit()
method,
is valid only within RecordContext interface (at least for
now),
we
throw
an exception in ProcessorRecordContext.commit()." and the code
snippet
below would need to be updated as well.
- I think above explanation covers this as well.
I want to gain some speed to this KIP, as it has gone though
many
changes
based on user/developer needs, both in
documentation-/implementation-wise.
Cheers,
Jeyhun
On Tue, Oct 24, 2017 at 1:41 AM Guozhang Wang <
wangg...@gmail.com>
wrote:
Thanks for the information Jeyhun. I had also forgot about
KAFKA-3907
with
this KIP..
Thinking a bit more, I'm now inclined to go with what we
agreed
before,
to
add the commit() call to `RecordContext`. A few minor tweaks on
its
implementation:
1. Maybe we can deprecate the `commit()` in ProcessorContext,
to
enforce
user to consolidate this call as
"processorContext.recordContext().commit()". And internal
implementation
of
`ProcessorContext.commit()` in `ProcessorContextImpl` is also
changed
to
this call.
2. Add the `task` reference to the impl class,
`ProcessorRecordContext`, so
that it can implement the commit call itself.
3. In the wiki page, the statement that "However, call to a
commit()
method,
is valid only within RecordContext interface (at least for
now),
we
throw
an exception in ProcessorRecordContext.commit()." and the code
snippet
below would need to be updated as well.
Guozhang
On Mon, Oct 23, 2017 at 1:40 PM, Matthias J. Sax <
matth...@confluent.io
wrote:
Fair point. This is a long discussion and I totally forgot
that
we
discussed this.
Seems I changed my opinion about including KAFKA-3907...
Happy to hear what others think.
-Matthias
On 10/23/17 1:20 PM, Jeyhun Karimov wrote:
Hi Matthias,
It is probably my bad, the discussion was a bit long in this
thread. I
proposed the related issue in the related KIP discuss thread [1]
and
got
an
approval [2,3].
Maybe I misunderstood.
[1]
http://search-hadoop.com/m/Kafka/uyzND19Asmg1GKKXT1?subj=
Re+DISCUSS+KIP+159+Introducing+Rich+functions+to+Streams
[2]
http://search-hadoop.com/m/Kafka/uyzND1kpct22GKKXT1?subj=
Re+DISCUSS+KIP+159+Introducing+Rich+functions+to+Streams
[3]
http://search-hadoop.com/m/Kafka/uyzND1G6TGIGKKXT1?subj=
Re+DISCUSS+KIP+159+Introducing+Rich+functions+to+Streams
On Mon, Oct 23, 2017 at 8:44 PM Matthias J. Sax <
matth...@confluent.io
wrote:
Interesting.
I thought that https://issues.apache.org/
jira/browse/KAFKA-4125
is
the
main motivation for this KIP :)
I also think, that we should not expose the full
ProcessorContext
at
DSL
level.
Thus, overall I am not even sure if we should fix
KAFKA-3907
at
all.
Manual commits are something DSL users should not worry about
--
and
if
one really needs this, an advanced user can still insert a
dummy
`transform` to request a commit from there.
-Matthias
On 10/18/17 5:39 AM, Jeyhun Karimov wrote:
Hi,
The main intuition is to solve [1], which is part of this
KIP.
I agree with you that this might not seem semantically
correct
as
we
are
not committing record state.
Alternatively, we can remove commit() from RecordContext
and
add
ProcessorContext (which has commit() method) as an extra
argument
to
Rich
methods:
instead of
public interface RichValueMapper<V, VR, K> {
VR apply(final V value,
final K key,
final RecordContext recordContext);
}
we can adopt
public interface RichValueMapper<V, VR, K> {
VR apply(final V value,
final K key,
final RecordContext recordContext,
final ProcessorContext processorContext);
}
However, in this case, a user can get confused as
ProcessorContext
and
RecordContext share some methods with the same name.
Cheers,
Jeyhun
[1] https://issues.apache.org/jira/browse/KAFKA-3907
On Tue, Oct 17, 2017 at 3:19 AM Guozhang Wang <
wangg...@gmail.com
wrote:
Regarding #6 above, I'm still not clear why we would need
`commit()`
in
both ProcessorContext and RecordContext, could you elaborate
a
bit
more?
To me `commit()` is really a processor context not a record
context
logically: when you call that function, it means we would
commit
the
state
of the whole task up to this processed record, not only
that
single
record
itself.
Guozhang
On Mon, Oct 16, 2017 at 9:19 AM, Jeyhun Karimov <
je.kari...@gmail.com
wrote:
Hi,
Thanks for the feedback.
0. RichInitializer definition seems missing.
- Fixed.
I'd suggest moving the key parameter in the
RichValueXX
and
RichReducer
after the value parameters, as well as in the templates;
e.g.
public interface RichValueJoiner<V1, V2, VR, K> {
VR apply(final V1 value1, final V2 value2, final K
key,
final
RecordContext
recordContext);
}
- Fixed.
2. Some of the listed functions are not necessary since
their
pairing
APIs
are being deprecated in 1.0 already:
<KR> KGroupedStream<KR, V> groupBy(final
RichKeyValueMapper<?
super
K,
?
super V, KR> selector,
final Serde<KR>
keySerde,
final Serde<V>
valSerde);
<VT, VR> KStream<K, VR> leftJoin(final KTable<K, VT> table,
final
RichValueJoiner<?
super
K,
?
super
V,
? super VT, ? extends VR> joiner,
final Serde<K>
keySerde,
final Serde<V>
valSerde);
-Fixed
3. For a few functions where we are adding three APIs
for
a
combo
of
both
mapper / joiner, or both initializer / aggregator, or
adder /
subtractor,
I'm wondering if we can just keep one that use "rich"
functions
for
both;
so that we can have less overloads and let users who
only
want
to
access
one of them to just use dummy parameter declarations.
For
example:
<GK, GV, RV> KStream<K, RV> join(final GlobalKTable<GK, GV>
globalKTable,
final
RichKeyValueMapper<?
super
K, ?
super
V, ? extends GK> keyValueMapper,
final
RichValueJoiner<?
super
K,
?
super
V,
? super GV, ? extends RV> joiner);
-Agreed. Fixed.
4. For TimeWindowedKStream, I'm wondering why we do not
make
its
Initializer also "rich" functions? I.e.
- It was a typo. Fixed.
5. We need to move "RecordContext" from
o.a.k.processor.internals
to
o.a.k.processor.
6. I'm not clear why we want to move `commit()` from
ProcessorContext
to
RecordContext?
-
Because it makes sense logically and to reduce code
maintenance
(both
interfaces have offset() timestamp() topic() partition()
methods), I
inherit ProcessorContext from RecordContext.
Since we need commit() method both in ProcessorContext
and
in
RecordContext
I move commit() method to parent class (RecordContext).
Cheers,
Jeyhun
On Wed, Oct 11, 2017 at 12:59 AM, Guozhang Wang <
wangg...@gmail.com>
wrote:
Jeyhun,
Thanks for the updated KIP, here are my comments.
0. RichInitializer definition seems missing.
1. I'd suggest moving the key parameter in the
RichValueXX
and
RichReducer
after the value parameters, as well as in the
templates;
e.g.
public interface RichValueJoiner<V1, V2, VR, K> {
VR apply(final V1 value1, final V2 value2, final K
key,
final
RecordContext
recordContext);
}
My motivation is that for lambda expression in J8,
users
that
would
not
care about the key but only the context, or vice versa, is
likely
to
write
it as (value1, value2, dummy, context) -> ... than
putting
the
dummy
at
the
beginning of the parameter list. Generally speaking
we'd
like
to
make
all
--
-- Guozhang
