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https://issues.apache.org/jira/browse/CASSANDRA-14515?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16509876#comment-16509876
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Aleksey Yeschenko commented on CASSANDRA-14515:
-----------------------------------------------
It came up during CASSANDRA-14330 investigation/resolution that a read response
doesn't necessarily close its outstanding RT. This happens because we stop
constructing the response as soon as we've counted sufficient rows to satisfy
the requested limit from a node. The fix was incomplete, however, and rather
than fixing the assertion we should instead fix the underlying issue, and put
an artificial lid on any read response. Otherwise the following sequence of
events is possible:
1. The coordinator is sending one of requests to node {{A}}, with limit of {{n}}
2. Node {{A}} replies with a sequence: {{rt-[}}, {{row-0}}, {{row-1}},
{{row-2}}, ..., {{row-n}}
3. {{rt}} is past gc grace, and gets compacted away
4. Some of the rows from {{A}} end up shadowed by deletions from other
replicas, and SRP triggers a follow-up read request
5. Node {{A}} replies with a sequence that doesn't contain {{rt-]}}, because
it's been compacted away
As a result we have an open-ended RT that can propagate over RR and erase rows
it was never intended to erase.
> Short read protection in presence of almost-purgeable range tombstones may
> cause permanent data loss
> ----------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-14515
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14515
> Project: Cassandra
> Issue Type: Bug
> Reporter: Aleksey Yeschenko
> Assignee: Aleksey Yeschenko
> Priority: Major
> Fix For: 3.0.x, 3.11.x, 4.0.x
>
>
> Because read responses don't necessarily close their open RT bounds, it's
> possible to lose data during short read protection, if a closing bound is
> compacted away between two adjacent reads from a node.
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