Thank you Sylvain and Benedict for the patch and thank you to everybody
that took the time to contribute to this discussion :-)
On Fri, Nov 27, 2020 at 5:15 PM Sylvain Lebresne wrote:
> I hope I haven't misread this, but it appears we've reached a kind of
> consensus for committing the fix,
I hope I haven't misread this, but it appears we've reached a kind of
consensus for committing the fix, so I went ahead and did it.
I added a NEWS entry that I hope is clear (and points to the flag that
disables the fix if someone wants to go that route), but any committers can
feel free to
I am +1 on Benjamin’s proposal
and less interruptions during upgrades. For more visibility maybe we can
also write a short article about the options and the tradeoffs, further to
NEWS.txt (that’s not something to decide now, of course :-) )
On Tue, 24 Nov 2020 at 9:13, Benjamin Lerer
wrote:
>
> Benedict suggested that Sylvain and I made the choice. Sylvain did not want
> to make the final call.
> I chose correctness. If it is a problem and people prefer to vote. It is
> perfectly fine for me too :-)
+1
Appreciate it having been raised for exposure and discussion Benjamin, and
Fair points. I retract the yaml suggestion and +1 to go with the
correctness route.
Em ter., 24 de nov. de 2020 às 11:13, Benjamin Lerer <
benjamin.le...@datastax.com> escreveu:
> Paulo, what you propose with the yaml seems different from default to
> *correctness*. It means to me that we are
Paulo, what you propose with the yaml seems different from default to
*correctness*. It means to me that we are forcing the user to choose
between *correctness *and *performance*. Most of us have a good
understanding of the problem and it is a hard choice for us. I imagine that
most of the users
> I think the keyword there is "normally" - if we can't say _certainly_,
> then this is probably an unsafe change to make.
>
> I can imagine any number of hacky upgrade processes that would be
> dangerous with this change.
>
I agree. We just don't know what users are doing, this is risky.
IMO
I think the keyword there is "normally" - if we can't say _certainly_, then
this is probably an unsafe change to make.
I can imagine any number of hacky upgrade processes that would be dangerous
with this change.
But, happy to defer to the consensus of others.
On 24/11/2020, 11:04, "Paulo
In this case the breaking change is a feature, not a bug. The exact
intention of this is to require manual intervention to raise awareness
about the potential performance degradation. This sounds reasonable, once
we already broke the contract of not introducing performance regressions in
a minor.
In my parlance the config property would be a breaking change, whereas the LWT
behaviour would be a performance regression. This latter might cause partial
outages or service degradation, but refusing to start a prod cluster without
manual intervention is potentially a much worse situation,
Isn't the plan to change LWT implementation (and performance expectation)
in a patch version? This is a breaking change by itself, I'm just proposing
to make the trade-off choice explicit in the yaml to prevent unexpected
performance degradation during upgrade (for users who are not aware of the
What do you mean by minor upgrade? We can't break patch upgrades for any of
3.x, as this could also cause surprise outages.
On 23/11/2020, 23:51, "Paulo Motta" wrote:
I was thinking about the YAML requirement during the 3.X minor upgrade to
make the decision explicit (need to update
I was thinking about the YAML requirement during the 3.X minor upgrade to
make the decision explicit (need to update yaml) rather than implicit (by
upgrading you agree with the change), since the latter can go unnoticed by
those who don't pay attention to NEWS.txt
Em seg., 23 de nov. de 2020 às
What's the value of the yaml? The user is likely to have upgraded to latest 3.x
as part of the upgrade process to 4.0, so they'll already have had a decision
made for them. If correctness didn't break anything, there doesn't any longer
seem much point in offering a choice?
On 23/11/2020,
+1 to both as well.
On Mon, Nov 23, 2020, 4:42 PM Blake Eggleston
wrote:
> +1 to correctness, and I like the yaml idea
>
> > On Nov 23, 2020, at 4:20 AM, Paulo Motta
> wrote:
> >
> > +1 to defaulting for correctness.
> >
> > In addition to that, how about making it a mandatory cassandra.yaml
+1 to correctness, and I like the yaml idea
> On Nov 23, 2020, at 4:20 AM, Paulo Motta wrote:
>
> +1 to defaulting for correctness.
>
> In addition to that, how about making it a mandatory cassandra.yaml
> property defaulting to correctness? This would make upgrades with an old
>
+1 to defaulting for correctness.
In addition to that, how about making it a mandatory cassandra.yaml
property defaulting to correctness? This would make upgrades with an old
cassandra.yaml fail unless an option is explicitly specified, making
operators aware of the issue and forcing them to make
Thank you very much to everybody that provided feedback. It helped a lot to
limit our options.
Unfortunately, it seems that some poor soul (me, really!!!) will have to
make the final call between #3 and #4.
If I reformulate the question to: Do we default to *correctness *or to
*performance*?
I
I think I meant #4 __♂️
On 20/11/2020, 21:11, "Blake Eggleston" wrote:
I’d also prefer #3 over #4
> On Nov 20, 2020, at 10:03 AM, Benedict Elliott Smith
wrote:
>
> Well, I expressed a preference for #3 over #4, particularly for the 3.x
series. However at this point, I
I’d also prefer #3 over #4
> On Nov 20, 2020, at 10:03 AM, Benedict Elliott Smith
> wrote:
>
> Well, I expressed a preference for #3 over #4, particularly for the 3.x
> series. However at this point, I think the lack of a clear project decision
> means we can punt it back to you and
Well, I expressed a preference for #3 over #4, particularly for the 3.x series.
However at this point, I think the lack of a clear project decision means we
can punt it back to you and Sylvain to make the final call.
On 20/11/2020, 16:23, "Benjamin Lerer" wrote:
I will try to summarize
I will try to summarize the discussion to clarify the outcome.
Mick is in favor of #4
Summanth is in favor of #4
Sylvain answer was not clear for me. I understood it like I prefer #3 to #4
and I am also fine with #1
Jeff is in favor of #3 and will understand #4
David is in favor #3 (fix bug and
I feel that #4 (fix bug and add flag to roll back to old behavior) is best.
About the alternative implementation, I am fine adding it to 3.x and 4.0,
but should treat it as a different path disabled by default that you can
opt-into, with a plan to opt-in by default "eventually".
On Wed, Nov 18,
Perhaps there might be broader appetite to weigh in on which major releases we
might target for work that fixes the correctness bug without serious
performance regression?
i.e., if we were to fix the correctness bug now, introducing a serious
performance regression (either opt-in or opt-out),
This is complicated and relatively few people on earth understand it, so
having little feedback is mostly expected, unfortunately.
My normal emotional response is "correctness is required, opt-in to
performance improvements that sacrifice strict correctness", but I'm also
sure this is going to
It doesn't seem like there's much enthusiasm for any of the options available
here...
On 12/11/2020, 14:37, "Benedict Elliott Smith" wrote:
> Is the new implementation a separate, distinctly modularized new body of
work
It’s primarily a distinct, modularised and new body of work,
> Is the new implementation a separate, distinctly modularized new body of work
It’s primarily a distinct, modularised and new body of work, however there is
some shared code that has been modified - namely PaxosState, in which legacy
code is maintained but modified for compatibility, and the
Is the new implementation a separate, distinctly modularized new body of
work or does it make substantial changes to existing implementation and
subsume it?
On Thu, Nov 12, 2020 at 3:56 AM Sylvain Lebresne wrote:
> Regarding option #4, I'll remark that experience tends to suggest users
> don't
Regarding option #4, I'll remark that experience tends to suggest users
don't consistently read the `NEWS.txt` file on upgrade, so option #4 will
likely essentially mean "LWT has a correctness issue, but once it broke
your data enough that you'll notice, you'll be able to dig the proper flag
to
Knowing there is a correctness issue in LWT, and given users use LWT
primarily for correctness, my opinion is we should commit the correctness
patch (makes it one of #1, #3 or #4)
I agree we should not cause further delay to 4.0 release (making it one of
#3 or #4).
Con for #3 would be,
In my opinion, a similar calculus should be applied to 3.0 and 3.11. This is
a(n arguably quite serious) bug, so whatever is not overly onerous to backport
should be considered while they are supported. The work under discussion has
two components: a replacement to the core consensus
> Regarding CASSANDRA-12126 and 4.0 we are facing several options and
> Benedict, Sylvain and I wanted to get the community feedback on them.
>
> We can:
>
>1. Try to use Benedict proposal for 4.0 if the community has the
>appetite for it. The main issue there is some potential extra
Got it.
Thanks for the extra context.
No real opinion here. :)
On Wed, Nov 11, 2020 at 11:29 AM Benedict Elliott Smith
wrote:
> It's been there since the beginning.
>
> If we were to consider the alternative proposal for 4.0, it would not have
> to be blocking for release. I had planned to
It's been there since the beginning.
If we were to consider the alternative proposal for 4.0, it would not have to
be blocking for release. I had planned to come forward after 4.0, primarily
because I did not want to create further political complexities for the project
at this time, but also
How old is the C-12126 surfaced defect? i.e. is this a thing we've had
since initial introduction of paxos or is it a regression we introduced
somewhere along the way?
On Wed, Nov 11, 2020 at 11:03 AM Benjamin Lerer
wrote:
> CASSANDRA-12126 addresses one correctness issue of Light Weight
>
CASSANDRA-12126 addresses one correctness issue of Light Weight
Transactions. Unfortunately, the current patch developed by Sylvain and
Benedict requires an extra round trip between the coordinator and the
replicas for SERIAL and LOCAL_SERIAL reads.
After some experimentations, Benedict discovered
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