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From radai <radai.rosenbl...@gmail.com>
Subject Re: [DISCUSS] KIP-81: Max in-flight fetches
Date Mon, 14 Nov 2016 18:25:17 GMT
+1 - there's is a need for an effective way to control kafka memory
consumption - both on the broker and on clients.
i think we could even reuse the exact same param name - *queued.max.bytes *-
as it would serve the exact same purpose.

also (and again its the same across the broker and clients) this bound
should also cover decompression, at some point.
the problem with that is that to the best of my knowledge the current wire
protocol does not declare the final, uncompressed size of anything up front
- all we know is the size of the compressed buffer. this may require a
format change in the future to properly support?

On Mon, Nov 14, 2016 at 10:03 AM, Mickael Maison <mickael.maison@gmail.com>
wrote:

> Thanks for all the replies.
>
> I've updated the KIP:
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-
> 81%3A+Bound+Fetch+memory+usage+in+the+consumer
> The main point is to selectively read from sockets instead of
> throttling FetchRequests sends. I also mentioned it will be reusing
> the MemoryPool implementation created in KIP-72 instead of adding
> another memory tracking method.
>
> Please have another look. As always, comments are welcome !
>
> On Thu, Nov 10, 2016 at 2:47 AM, radai <radai.rosenblatt@gmail.com> wrote:
> > selectively reading from sockets achieves memory control (up to and not
> > including talk of (de)compression)
> >
> > this is exactly what i (also, even mostly) did for kip-72 - which i hope
> in
> > itself should be a reason to think about both KIPs at the same time
> because
> > the changes will be similar (at least in intent) and might result in
> > duplicated effort.
> >
> > a pool API is a way to "scale" all the way from just maintaining a
> variable
> > holding amount of available memory (which is what my current kip-72 code
> > does and what this kip proposes IIUC) all the way up to actually re-using
> > buffers without any changes to the code using the pool - just drop in a
> > different pool impl.
> >
> > for "edge nodes" (producer/consumer) the performance gain in actually
> > pooling large buffers may be arguable, but i suspect for brokers
> regularly
> > operating on 1MB-sized requests (which is the norm at linkedin) the
> > resulting memory fragmentation is an actual bottleneck (i have initial
> > micro-benchmark results to back this up but have not had the time to do a
> > full profiling run).
> >
> > so basically I'm saying we may be doing (very) similar things in mostly
> the
> > same areas of code.
> >
> > On Wed, Nov 2, 2016 at 11:35 AM, Mickael Maison <
> mickael.maison@gmail.com>
> > wrote:
> >
> >> electively reading from the socket should enable to
> >> control the memory usage without impacting performance. I've had look
> >> at that today and I can see how that would work.
> >> I'll update the KIP accordingly tomorrow.
> >>
>

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