On 1/31/20 9:58 AM, Dimitar Dimitrov wrote:
one corollary of the way the algorithm works (or more
precisely might not work) with multiple seeds or simultaneous
multi-node bootstraps or decommissions, is that a lot of dtests
start failing due to deterministic token conflicts. I wasn't
able to fix that by changing solely ccm and the dtests
I appreciate all the detailed discussion. For a little historic context,
since I brought up this topic in the contributors zoom meeting, unstable
dtests was precisely the reason we moved the dtest configurations to
'num_tokens: 32'. That value has been used in CI dtest since something
like 2014, when we found that this helped stabilize a large segment of
flaky dtest failures. No real science there, other than "this hurts less."
I have no real opinion on the suggestions of using 4 or 16, other than I
believe most "default config using" new users are starting with smaller
numbers of nodes. The small-but-growing users and veteran large cluster
admins should be gaining more operational knowledge and be able to
adjust their own config choices according to their needs (and good
comment suggestions in the yaml). Whatever default config value is
chosen for num_tokens, I think it should suit the new users with smaller
clusters. The suggestion Mick makes that 16 makes a better choice for
small numbers of nodes, well, that would seem to be the better choice
for those users we are trying to help the most with the default.
I fully agree that science, maths, and support/ops experience should
guide the choice, but I don't believe that large/giant clusters and
admins are the target audience for the value we select.
--
Kind regards,
Michael
---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org
For additional commands, e-mail: dev-h...@cassandra.apache.org
