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https://issues.apache.org/jira/browse/CASSANDRA-20514?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17940929#comment-17940929
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Michael Semb Wever edited comment on CASSANDRA-20514 at 4/4/25 10:10 AM:
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this broke CI (`ant check` fails).
https://ci-cassandra.apache.org/job/Cassandra-5.0/430/cloudbees-pipeline-explorer/?filter=1154
was (Author: michaelsembwever):
this broke CI (`ant lint` fails).
https://ci-cassandra.apache.org/job/Cassandra-5.0/430/cloudbees-pipeline-explorer/?filter=1154
> Paxos mixed mode infinite loop with ttl'd state
> -----------------------------------------------
>
> Key: CASSANDRA-20514
> URL: https://issues.apache.org/jira/browse/CASSANDRA-20514
> Project: Apache Cassandra
> Issue Type: Bug
> Components: Feature/Lightweight Transactions
> Reporter: Blake Eggleston
> Assignee: Blake Eggleston
> Priority: Normal
> Fix For: 4.1.x, 5.0.x, 5.x
>
>
> This is similar to the bug fixed in CASSANDRA-20493.
> CEP-14 changed the ttl behavior of legacy paxos state to expire based off the
> ballot time of the operation being persisted, not the time a commit is
> persisted. This eliminated the race addressed by CASSANDRA-12043, and so the
> check it added to the most recent commit prepare logic was removed.
> When operating in mixed mode though, this race can still be a problem. If a
> 4.1 or higher node is coordinating a paxos operation with 2 or more replicas
> on 4.0 or lower, this race becomes a problem again. You need 3 things to make
> this an infinite loop
> 1. a 4.1 node coordinating a paxos operation with 2x 4.0 replicas
> 2. replica A) a 4.0 node returns a most recent commit for a ballot that's
> could have been ttld
> 3. replica B) a 4.0 node has ttl'd that mrc AND converted the ttld cells into
> tombstones
> The 4.1 coordinator receives the mrc from replica A, but since it no longer
> disregards missing most recent commits past the ttl window, it sends the
> "missing" commit to replica B. Since replica B now has a tombstone for that
> mrc, and tombstones win when reconciled with live cells, even ones with ttls,
> the commit is a noop and it continues to report nothing for its mrc value
> when the coordinator restarts the prepare phase. This loops until the query
> times out
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