[
https://issues.apache.org/jira/browse/KAFKA-20716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18090165#comment-18090165
]
Federico Valeri commented on KAFKA-20716:
-----------------------------------------
Basically there is a divergence between the Txn Coordinator state
(__transaction_state) and data partitions' state (the ones involved in the txn).
> LSO stuck after unclean leader election
> ---------------------------------------
>
> Key: KAFKA-20716
> URL: https://issues.apache.org/jira/browse/KAFKA-20716
> Project: Kafka
> Issue Type: Bug
> Reporter: Luke Chen
> Priority: Major
>
> When a topic has an unclean leader election, the new leader might contain txn
> data without COMMIT/ABORT markers. However, the data in __transaction_state
> shows the transaction is committed/aborted, so the transaction timeout will
> not expire here. This causes the LSO stuck and READ_COMMITTED will never
> proceed.
>
> reproduce steps:
> 1. Create a cluster with 2 brokers
> 2. Create a topic with unclean leader election enabled
> {code:java}
> bin/kafka-topics.sh --create --topic t1 --bootstrap-server localhost:9091
> --replication-factor 2 --config unclean.leader.election.enable=true {code}
> 3. write a txn record to the topic t1, but don't commit it, yet.
> 4. Before the record committed in step (3), shutdown the follower broker
> (suppose it's broker 2)
> 5. commit the step (3) record.
> 6. Now, the the topic t1-0 in broker 1 contains [offset 0 (data) and offset 1
> (commit)], but broker 2 only contains [offset 0 (data)]
> 7. shutdown broker 1, so both broker 1 and 2 are down, but broker 2 is not
> the last leader or ELR
> 8. start up broker 2, unclean leader election triggered
> 9. start up broker 1, log truncation on t1-0, so the log becomes [offset 0
> (data)]
> 10. appending more non-txn data to t1-0
> 11. consume with READ_COMMITTED, it'll return nothing.
>
> We never document anywhere about unclean leader election unsupported in
> transaction feature, I think this should be supported and we have to find out
> a solution for it.
>
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
