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https://issues.apache.org/jira/browse/CASSANDRA-14570?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16546991#comment-16546991
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Joshua McKenzie commented on CASSANDRA-14570:
---------------------------------------------
A couple concerns:
# If your volume for CDC logs doesn't have available space left for
{code:java}
size + conf.commitlog_total_space_in_mb{code}
, assuming size 0 and cl size > free_space on volume, this patch will still set
that value to our cdc_total in mb which would be problematic. We should take
into consideration whether size + cl size is > the estimated value of the
volume and consider the best way to handle that error there (be it warn, fail
startup, respect CL failure policy, etc)
# This is now a misleading property name since cdc storage space will now be
"desired cdc 'buffer' plus cl size on disk". It would probably make sense (and
be more user friendly) to rename \{cdc_total_space_in_mb} to
\{cdc_extra_buffer_space} and comment that param to mention the relationship
between it and the CL space. Probably also want to keep respecting and using
the old property name for backwards compat. purposes.
That being said, great catch on those silly / nonsensical defaults, problem
w/CDC post hard-linking.
> Improper default value of cdc_total_space_in_mb
> -----------------------------------------------
>
> Key: CASSANDRA-14570
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14570
> Project: Cassandra
> Issue Type: Bug
> Components: Configuration
> Reporter: Shichao An
> Assignee: Shichao An
> Priority: Minor
> Labels: CDC
>
> The code for calculating cdc_total_space_in_mb in DatabaseDescriptor.java
> does not reflect the latest architecture introduced by CASSANDRA-12148.
> In short, cdc_total_space_in_mb should be equal or greater than
> commitlog_total_space_in_mb; otherwise, the writes will fail when on-disk
> commit logs size reaches the value of cdc_total_space_in_mb. For example, If
> cdc_total_space_in_mb is 4096 and commitlog_total_space_in_mb is 8192, when
> we enabled the cdc_enabled flag (even if we didn't enable cdc=true on any
> table), when total size of commit logs reaches 4096 MB, there is the same of
> amount of hard links in cdc_raw directory, that is, 4096 MB of cdc logs. Then
> the CommitLogSegmentManagerCDC will be unable to process new CL segments.
> (See CommitLogSegmentManagerCDC.processNewSegment method)
>
> I will attach patches later.
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