Hi,
Regarding this subject I wrote a blog article that gives details about
the watermark architecture proposal that was discussed in the design doc
and in the PR:
https://echauchot.blogspot.com/2020/11/watermark-architecture-proposal-for.html
Best
Etienne
On 29/09/2020 03:24, Yuanjian Li wrote:
Thanks for the great discussion!
Also interested in this feature and did some investigation before. As
Arun mentioned, similar to the "update" mode, the "complete" mode also
needs more design. We might need an operation level output mode for
the complete mode support. That is to say, if we use "complete" mode
for every aggregation operators, the wrong result will return.
SPARK-26655 would be a good start, which only considers about "append"
mode. Maybe we need more discussion on the watermark interface. I will
take a close look at the doc and PR. Hope we will have the first
version with limitations and fix/remove them gradually.
Best,
Yuanjian
Jungtaek Lim <kabhwan.opensou...@gmail.com
<mailto:kabhwan.opensou...@gmail.com>> 于2020年9月26日周六 上午10:31写道：
Thanks Etienne! Yeah I forgot to say nice talking with you again.
And sorry I forgot to send the reply (was in draft).
Regarding investment in SS, well, unfortunately I don't know - I'm
just an individual. There might be various reasons to do so, most
probably "priority" among the stuff. There's not much I could change.
I agree the workaround is sub-optimal, but unless I see sufficient
support in the community I probably couldn't make it go forward.
I'll just say there's an elephant in the room - as the project
goes forward for more than 10 years, backward compatibility is a
top priority concern in the project, even across the major
versions along the features/APIs. It is great for end users to
migrate the version easily, but also blocks devs to fix the bad
design once it ships. I'm the one complaining about these issues
in the dev list, and I don't see willingness to correct them.
On Fri, Sep 4, 2020 at 5:55 PM Etienne Chauchot
<echauc...@apache.org <mailto:echauc...@apache.org>> wrote:
Hi Jungtaek Lim,
Nice to hear from you again since last time we talked :) and
congrats on becoming a Spark committer in the meantime ! (if
I'm not mistaking you were not at the time)
I totally agree with what you're saying on merging structural
parts of Spark without having a broader consensus. What I
don't understand is why there is not more investment in SS.
Especially because in another thread the community is
discussing about deprecating the regular DStream streaming
framework.
Is the orientation of Spark now mostly batch ?
PS: yeah I saw your update on the doc when I took a look at
3.0 preview 2 searching for this particular feature. And
regarding the workaround, I'm not sure it meets my needs as it
will add delays and also may mess up with watermarks.
Best
Etienne Chauchot
On 04/09/2020 08:06, Jungtaek Lim wrote:
Unfortunately I don't see enough active committers working on
Structured Streaming; I don't expect major
features/improvements can be brought in this situation.
Technically I can review and merge the PR on major
improvements in SS, but that depends on how huge the proposal
is changing. If the proposal brings conceptual change, being
reviewed by a committer wouldn't still be enough.
So that's not due to the fact we think it's worthless. (That
might be only me though.) I'd understand as there's not much
investment on SS. There's also a known workaround for
multiple aggregations (I've documented in the SS guide doc,
in "Limitation of global watermark" section), though I
totally agree the workaround is bad.
On Tue, Sep 1, 2020 at 12:28 AM Etienne Chauchot
<echauc...@apache.org <mailto:echauc...@apache.org>> wrote:
Hi all,
I'm also very interested in this feature but the PR is
open since January 2019 and was not updated. It raised a
design discussion around watermarks and a design doc was
written
(https://docs.google.com/document/d/1IAH9UQJPUiUCLd7H6dazRK2k1szDX38SnM6GVNZYvUo/edit#heading=h.npkueh4bbkz1).
We also commented this design but no matter what it seems
that the subject is still stale.
Is there any interest in the community in delivering this
feature or is it considered worthless ? If the latter,
can you explain why ?
Best
Etienne
On 22/05/2019 03:38, 张万新 wrote:
Thanks, I'll check it out.
Arun Mahadevan <ar...@apache.org
<mailto:ar...@apache.org>> 于 2019年5月21日周二 01:31写道：
Heres the proposal for supporting it in "append"
mode - https://github.com/apache/spark/pull/23576.
You could see if it addresses your requirement and
post your feedback in the PR.
For "update" mode its going to be much harder to
support this without first adding support for
"retractions", otherwise we would end up with wrong
results.
- Arun
On Mon, 20 May 2019 at 01:34, Gabor Somogyi
<gabor.g.somo...@gmail.com
<mailto:gabor.g.somo...@gmail.com>> wrote:
There is PR for this but not yet merged.
On Mon, May 20, 2019 at 10:13 AM 张万新
<kevinzwx1...@gmail.com
<mailto:kevinzwx1...@gmail.com>> wrote:
Hi there,
I'd like to know what's the root reason why
multiple aggregations on streaming dataframe
is not allowed since it's a very useful
feature, and flink has supported it for a
long time.
Thanks.
