Re: Coordinator Write Metrics per CF

[Sumanth Pasupuleti <sp...@netflix.com.INVALID>]

I have submitted a patch for
https://issues.apache.org/jira/browse/CASSANDRA-14232. Looking for
reviewers/feedback.

Thanks,
Sumanth

On Tue, Feb 13, 2018 at 2:06 PM, Benedict Elliott Smith <benedict@apache.org
> wrote:

> Sorry, I guess I'm tired.  I thought this was discussing local write
> latency.
>
> I'm surprised we have that and not coordinator write latency.
>
> Please do ignore me, I'm not sure why I got involved!
>
> On 13 February 2018 at 21:48, Benedict Elliott Smith <be...@apache.org>
> wrote:
>
> > For the record, I'm not certain there *is* a great deal of value in this.
> >
> > The read latency metrics are expected to vary a great deal, since the
> > entire IO subsystem is involved.
> >
> > Writes, however, go straight to a memtable.  They only block on IO if we
> > exceed our commit log flush bandwidth for an extended period of time.  We
> > already have a metric for tracking this: CommitLog.WaitingOnCommit.
> >
> > I'm not saying there won't be any latency distribution, but it is
> unlikely
> > to be terribly interesting in very many situations.  I can't off the top
> of
> > my head think of a good reason to consult this metric, that couldn't
> better
> > be answered elsewhere.
> >
> >
> >
> > On 13 February 2018 at 19:18, Sumanth Pasupuleti <
> spasupuleti@netflix.com.
> > invalid> wrote:
> >
> >> Thanks Kurt and Chris for your valuable inputs. Created
> >> https://issues.apache.org/jira/browse/CASSANDRA-14232; I shall start
> >> working on this.
> >>
> >> Thanks,
> >> Sumanth
> >>
> >> On Mon, Feb 12, 2018 at 7:43 AM, Chris Lohfink <cl...@apple.com>
> >> wrote:
> >>
> >> > It would be good to have it. Its not that its not there because its
> >> > difficult or anything. I think its more that the read latency metric
> was
> >> > needed for speculative retry so it was added but the write side wasn't
> >> > needed for that feature so wasn't added at same time. It would be very
> >> > useful in determining the table that the coordinator writes are slow
> to.
> >> >
> >> > Chris
> >> >
> >> > > On Feb 11, 2018, at 10:33 PM, kurt greaves <ku...@instaclustr.com>
> >> wrote:
> >> > >
> >> > > I've tried to search around for a reason for this in the past and
> >> haven't
> >> > > found one. I don't think it's a bad idea. Would be a helpful metric
> to
> >> > > diagnose internode networking issues - although I'll note that the
> >> read
> >> > > metric will also achieve this assuming you have enough reads to get
> >> some
> >> > > useful information out of it.
> >> > >
> >> > > On 9 February 2018 at 17:43, Sumanth Pasupuleti <
> >> > > sumanth.pasupuleti.is@gmail.com> wrote:
> >> > >
> >> > >> There is an existing CoordinatorReadLatency table metric. I am
> >> looking
> >> > to
> >> > >> add CoordinatorWriteLatency table metric - however, before I
> attempt
> >> a
> >> > shot
> >> > >> at it, would like to know if anyone has context around why we
> >> currently
> >> > do
> >> > >> not have such metric (while we have the read metric) - if someone
> has
> >> > >> already attempted and realized its a bad idea for some reason.
> >> > >>
> >> > >> Thanks,
> >> > >> Sumanth
> >> > >>
> >> >
> >> >
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> >> >
> >> >
> >>
> >
> >
>