Re: Is cleanup is required if cluster topology changes

[Jeff Jirsa]

You should 100% trigger cleanup each time or you’ll almost certainly resurrect data sooner or later If you’re using leveled compaction it’s especially cheap. Stcs and twcs are worse, but if you’re really scaling that often, I’d be considering lcs and running cleanup just before or just after each scaling  On May 4, 2023, at 9:25 PM, Jaydeep Chovatia <chovatia.jayd...@gmail.com> wrote:  Thanks, Jeff! But in our environment we replace nodes quite often for various optimization purposes, etc. say, almost 1 node per day (node addition followed by node decommission, which of course changes the topology), and we have a cluster of size 100 nodes with 300GB per node. If we have to run cleanup on 100 nodes after every replacement, then it could take forever.  What is the recommendation until we get this fixed in Cassandra itself as part of compaction (w/o externally triggering cleanup)? Jaydeep On Thu, May 4, 2023 at 8:14 PM Jeff Jirsa <jji...@gmail.com> wrote: Cleanup is fast and cheap and basically a no-op if you haven’t changed the ring  After cassandra has transactional cluster metadata to make ring changes strongly consistent, cassandra should do this in every compaction. But until then it’s left for operators to run when they’re sure the state of the ring is correct . On May 4, 2023, at 7:41 PM, Jaydeep Chovatia <chovatia.jayd...@gmail.com> wrote:  Isn't this considered a kind of bug in Cassandra because as we know cleanup is a lengthy and unreliable operation, so relying on the cleanup means higher chances of data resurrection? Do you think we should discard the unowned token-ranges as part of the regular compaction itself? What are the pitfalls of doing this as part of compaction itself? Jaydeep On Thu, May 4, 2023 at 7:25 PM guo Maxwell <cclive1...@gmail.com> wrote: compact ion will just merge duplicate data and remove delete data in this node .if you add or remove one node for the cluster, I think clean up is needed. if clean up failed, I think we should come to see the reason. Runtian Liu <curly...@gmail.com> 于2023年5月5日周五 06:37写道： Hi all, Is cleanup the sole method to remove data that does not belong to a specific node? In a cluster, where nodes are added or decommissioned from time to time, failure to run cleanup may lead to data resurrection issues, as deleted data may remain on the node that lost ownership of certain partitions. Or is it true that normal compactions can also handle data removal for nodes that no longer have ownership of certain data? Thanks, Runtian -- you are the apple of my eye !