My understanding from the proposal is that Sidecar would be able to migrate from a Cassandra instance that is already dead and cannot recover. This is a scenario that is possible where Sidecar should still be able to migrate to a new instance.
Alternatively, Cassandra itself could have some flag to start up with limited subsystems enabled to allow live migration. In any case, we'll need to weigh in the pros and cons of each alternative and decide if the live migration process can be handled within the C* process itself or if we allow this functionality to be handled by Sidecar. I am looking forward to this feature though, as it will be of great value for many users across the ecosystem. On 2024/04/18 22:25:23 Jon Haddad wrote: > Hmm... I guess if you're using encryption you can't use ZCS so there's that. > > It probably makes sense to implement kernel TLS: > https://www.kernel.org/doc/html/v5.7/networking/tls.html > > Then we can get ZCS all the time, for bootstrap & replacements. > > Jon > > > On Thu, Apr 18, 2024 at 12:50 PM Jon Haddad <j...@jonhaddad.com> wrote: > > > Ariel, having it in C* process makes sense to me. > > > > Please correct me if I'm wrong here, but shouldn't using ZCS to transfer > > have no distinguishable difference in overhead from doing it using the > > sidecar? Since the underlying call is sendfile, never hitting userspace, I > > can't see why we'd opt for the transfer in sidecar. What's the > > advantage of duplicating the work that's already been done? > > > > I can see using the sidecar for coordination to start and stop instances > > or do things that require something out of process. > > > > Jon > > > > > > On Thu, Apr 18, 2024 at 12:44 PM Ariel Weisberg <ar...@weisberg.ws> wrote: > > > >> Hi, > >> > >> If there is a faster/better way to replace a node why not have Cassandra > >> support that natively without the sidecar so people who aren’t running the > >> sidecar can benefit? > >> > >> Copying files over a network shouldn’t be slow in C* and it would also > >> already have all the connectivity issues solved. > >> > >> Regards, > >> Ariel > >> > >> On Fri, Apr 5, 2024, at 6:46 AM, Venkata Hari Krishna Nukala wrote: > >> > >> Hi all, > >> > >> I have filed CEP-40 [1] for live migrating Cassandra instances using the > >> Cassandra Sidecar. > >> > >> When someone needs to move all or a portion of the Cassandra nodes > >> belonging to a cluster to different hosts, the traditional approach of > >> Cassandra node replacement can be time-consuming due to repairs and the > >> bootstrapping of new nodes. Depending on the volume of the storage service > >> load, replacements (repair + bootstrap) may take anywhere from a few hours > >> to days. > >> > >> Proposing a Sidecar based solution to address these challenges. This > >> solution proposes transferring data from the old host (source) to the new > >> host (destination) and then bringing up the Cassandra process at the > >> destination, to enable fast instance migration. This approach would help to > >> minimise node downtime, as it is based on a Sidecar solution for data > >> transfer and avoids repairs and bootstrap. > >> > >> Looking forward to the discussions. > >> > >> [1] > >> https://cwiki.apache.org/confluence/display/CASSANDRA/CEP-40%3A+Data+Transfer+Using+Cassandra+Sidecar+for+Live+Migrating+Instances > >> > >> Thanks! > >> Hari > >> > >> > >> >
