It's a bit unfortunate that NTS does not maintain the ability to lose a
rack without loss of quorum for RF > #racks > 2, since this can be easily
achieved by evenly placing replicas across all racks.
Since RackAwareTopologyStrategy is a superset of NetworkTopologyStrategy,
can't we just use the
A huge number of people use this legal and unsafe combination - like anyone
running RF=3 in AWS us-west-1 (or any other region with only 2 accessible
AZs), and no patch is going to suddenly make that safe, and banning it
hurts users a lot.
If we're really going to ship a less-bad version of this,
1) It does seem a like a big footgun. I think it violates the principle of
least surprise if someone has configured NTS thinking that they are
improving availability
2) I don't know that we want to ban it outright, since maybe there's a case
for someone to be using a different CL that would be OK
Modifying NTS in place would not be possible if it changes rack placement in a
way that breaks existing clusters on upgrade. A strategy introducing a change
to placement like this would need a new name. A new strategy would be fine in
trunk.
Logging a warning seems appropriate if RF > rack
On Sun, Mar 5, 2023 at 11:00 PM Paulo Motta wrote:
> I found this a bit surprising, since I would expect a snapshot with the same
> name on different tables to represent the same logical snapshot taken at the
> same point-in-time.
I would expect this too, 100%.
> This affects the design of
Hi all,
some time ago we identified an issue with NetworkTopologyStrategy. The problem
is that when RF > number of racks, it may happen that NTS places replicas in
such a way that when whole rack is lost, we lose QUORUM and data are not
available anymore if QUORUM CL is used.
To illustrate
Sorry, I realized that when I started the discussion I probably did not
frame it enough as I see that it is now going into different directions.
The concerns I am seeing are:
1) A too small amount of time between releases is inefficient from a
development perspective and from a user perspective.
A bit of organization - I've created
https://issues.apache.org/jira/browse/CASSANDRA-18300 epic to track tickets
related to the downgradability. Please add the tickets you are aware of.
thanks
- - -- --- - -
Jacek Lewandowski
czw., 23 lut 2023 o 17:47 Benedict
