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https://issues.apache.org/jira/browse/CASSANDRA-10421?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14952746#comment-14952746
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Benedict commented on CASSANDRA-10421:
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FTR, IMO (as I expressed on IRC), I think it is both safer and easier to
implement duplication to all disks. Since this data is low traffic it also
shouldn't be a major issue that we do this:
Implementation-wise, the changes can be extremely minimal to the existing
logic: on read, we read all files simultaneously, line-by-line, corroborating
they are the same (we can even have a special reader that wraps all files, so
that the current logic is completely unchanged). If at any point they differ,
we confirm there is no proceeding line (if there is we leave everything as is,
as it is corruption, much like we normally would), and otherwise we confirm
that every file's last line is a prefix-match of every other. On write we can
do similar, ensuring we write to all of them in sequence, treating it as a
single action from the POV of the existing logic. This means the only
modifications are at the very outermost parts of the logic, so we don't have to
revisit the safety of the basic functionality.
This also leaves us with much less complexity reasoning about the safety under
different scenarios wrt disk corruption, failure, accidental user-error, etc.
So, it seems like a win-win AFAICT. The only downside is that users modifying
these files would need to modify them all, but this is not overly onerous.
> Potential issue with LogTransaction as it only checks in a single directory
> for files
> -------------------------------------------------------------------------------------
>
> Key: CASSANDRA-10421
> URL: https://issues.apache.org/jira/browse/CASSANDRA-10421
> Project: Cassandra
> Issue Type: Bug
> Reporter: Marcus Eriksson
> Assignee: Stefania
> Priority: Blocker
> Fix For: 3.0.0 rc2
>
>
> When creating a new LogTransaction we try to create the new logfile in the
> same directory as the one we are writing to, but as we use
> {{[directories.getDirectoryForNewSSTables()|https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/db/lifecycle/LogTransaction.java#L125]}}
> this might end up in "any" of the configured data directories. If it does,
> we will not be able to clean up leftovers as we check for files in the same
> directory as the logfile was created:
> https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/db/lifecycle/LogRecord.java#L163
> cc [~Stefania]
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