[jira] [Assigned] (CASSANDRA-21443) CEP-45: Lost witness marker race

["Blake Eggleston (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-21443?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Blake Eggleston reassigned CASSANDRA-21443:
-------------------------------------------

    Assignee: Blake Eggleston

> CEP-45: Lost witness marker race
> --------------------------------
>
>                 Key: CASSANDRA-21443
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-21443
>             Project: Apache Cassandra
>          Issue Type: Bug
>            Reporter: Blake Eggleston
>            Assignee: Blake Eggleston
>            Priority: Normal
>
> We periodically persist offsets we’ve witnessed to a system table (currently every 1s, with a todo to increase to period to 60s)
> On startup, we load these offsets from disk, and then play back the mutation journal for mutations that weren’t flushed to sstables, and record those mutations as witnessed in memory. However, if a memtable containing mutations not yet durably recorded as witnessed is flushed to an sstable and then the node is shutdown before recording them, they won’t be replayed on startup and the node will forget that it has seen them, and not include them in mutation summaries (but still returning data for them in reads). This will cause non-monotonic read results and will break the journal sync barrier guarantees.
> We should include some additional metadata with the persisted witness data indicating the most recent full journal segment it has seen, and then read anything afterwards when replaying the journal, skipping the write path for anything already flushed to an sstable.



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