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From John Roesler <j...@confluent.io>
Subject Re: [DISCUSS] KIP-471: Expose RocksDB Metrics in Kafka Streams
Date Mon, 20 May 2019 17:48:13 GMT
Hi Bruno,

Looks really good overall. This is going to be an awesome addition.

My only thought was that we have "bytes-flushed-(rate|total) and
flush-time-(avg|min|max)" metrics, and the description states that
these are specifically for Memtable flush operations. What do you
think about calling it "memtable-bytes-flushed... (etc)"? On one hand,
I could see this being redundant, since that's the only thing that
gets "flushed" inside of Rocks. But on the other, we have an
independent "flush" operation in streams, which might be confusing.
Plus, it might help people who are looking at the full "menu" of
hundreds of metrics. They can't read and remember every description
while trying to understand the full list of metrics, so going for
maximum self-documentation in the name seems nice.

But that's a minor thought. Modulo the others' comments, this looks good to me.

Thanks,
-John

On Mon, May 20, 2019 at 11:07 AM Bill Bejeck <bbejeck@gmail.com> wrote:
>
> Hi Bruno,
>
> Thanks for the KIP, this will be a useful addition.
>
> Overall the KIP looks good to me, and I have two minor comments.
>
> 1. For the tags should, I'm wondering if rocksdb-state-id should be
> rocksdb-store-id
> instead?
>
> 2. With the compaction metrics, would it be possible to add total
> compactions and an average number of compactions?  I've taken a look at the
> available RocksDB metrics, and I'm not sure.  But users can control how
> many L0 files it takes to trigger compaction so if it is possible; it may
> be useful.
>
> Thanks,
> Bill
>
>
> On Mon, May 20, 2019 at 9:15 AM Bruno Cadonna <bruno@confluent.io> wrote:
>
> > Hi Sophie,
> >
> > Thank you for your comments.
> >
> > It's a good idea to supplement the metrics with configuration option
> > to change the metrics. I also had some thoughts about it. However, I
> > think I need some experimentation to get this right.
> >
> > I added the block cache hit rates for index and filter blocks to the
> > KIP. As far as I understood, they should stay at zero, if users do not
> > configure RocksDB to include index and filter blocks into the block
> > cache. Did you also understand this similarly? I guess also in this
> > case some experimentation would be good to be sure.
> >
> > Best,
> > Bruno
> >
> >
> > On Sat, May 18, 2019 at 2:29 AM Sophie Blee-Goldman <sophie@confluent.io>
> > wrote:
> > >
> > > Actually I wonder if it might be useful to users to be able to break up
> > the
> > > cache hit stats by type? Some people may choose to store index and filter
> > > blocks alongside data blocks, and it would probably be very helpful for
> > > them to know who is making more effective use of the cache in order to
> > tune
> > > how much of it is allocated to each. I'm not sure how common this really
> > is
> > > but I think it would be invaluable to those who do. RocksDB performance
> > can
> > > be quite opaque..
> > >
> > > Cheers,
> > > Sophie
> > >
> > > On Fri, May 17, 2019 at 5:01 PM Sophie Blee-Goldman <sophie@confluent.io
> > >
> > > wrote:
> > >
> > > > Hey Bruno!
> > > >
> > > > This all looks pretty good to me, but one suggestion I have is to
> > > > supplement each of the metrics with some info on how the user can
> > control
> > > > them. In other words, which options could/should they set in
> > > > RocksDBConfigSetter should they discover a particular bottleneck?
> > > >
> > > > I don't think this necessarily needs to go into the KIP, but I do
> > think it
> > > > should be included in the docs somewhere (happy to help build up the
> > list
> > > > of associated options when the time comes)
> > > >
> > > > Thanks!
> > > > Sophie
> > > >
> > > > On Fri, May 17, 2019 at 2:54 PM Bruno Cadonna <bruno@confluent.io>
> > wrote:
> > > >
> > > >> Hi all,
> > > >>
> > > >> this KIP describes the extension of the Kafka Streams' metrics to
> > include
> > > >> RocksDB's internal statistics.
> > > >>
> > > >> Please have a look at it and let me know what you think. Since I am
> > not a
> > > >> RocksDB expert, I am thankful for any additional pair of eyes that
> > > >> evaluates this KIP.
> > > >>
> > > >>
> > > >>
> > https://cwiki.apache.org/confluence/display/KAFKA/KIP-471:+Expose+RocksDB+Metrics+in+Kafka+Streams
> > > >>
> > > >> Best regards,
> > > >> Bruno
> > > >>
> > > >
> >

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