[jira] [Comment Edited] (CASSANDRA-16071) max_compaction_flush_memory_in_mb is interpreted as bytes

["Michael Semb Wever (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-16071?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17183111#comment-17183111 ] 

Michael Semb Wever edited comment on CASSANDRA-16071 at 8/24/20, 9:47 AM:
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Patches
 - [3.11|https://github.com/apache/cassandra/compare/trunk...thelastpickle:mck/cassandra-3.11_max_compaction_flush_memory_in_mb_fix] 
 - [trunk|https://github.com/apache/cassandra/compare/trunk...thelastpickle:mck/trunk_max_compaction_flush_memory_in_mb_fix] 

(will update with tests and CI run later today…)


was (Author: michaelsembwever):
Patches
 - [3.11|https://github.com/apache/cassandra/compare/trunk...thelastpickle:mck/cassandra-3.11_max_compaction_flush_memory_in_mb_fix] 
 - [trunk|https://github.com/apache/cassandra/compare/trunk...thelastpickle:mck/trunk_max_compaction_flush_memory_in_mb_fix] 

(will update with CI later today…)

> max_compaction_flush_memory_in_mb is interpreted as bytes
> ---------------------------------------------------------
>
>                 Key: CASSANDRA-16071
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-16071
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Feature/SASI
>            Reporter: Michael Semb Wever
>            Assignee: Michael Semb Wever
>            Priority: Normal
>             Fix For: 3.11.x, 4.0-beta
>
>
> In CASSANDRA-12662, [~scottcarey] [reported|https://issues.apache.org/jira/browse/CASSANDRA-12662?focusedCommentId=17070055&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-17070055] that the {{max_compaction_flush_memory_in_mb}} setting gets incorrectly interpreted in bytes rather than megabytes as its name implies.
> {quote}
> 1.  the setting 'max_compaction_flush_memory_in_mb' is a misnomer, it is actually memory in BYTES.  If you take it at face value, and set it to say, '512' thinking that means 512MB,  you will produce a million temp files rather quickly in a large compaction, which will exhaust even large values of max_map_count rapidly, and get the OOM: Map Error issue above and possibly have a very difficult situation to get a cluster back into a place where nodes aren't crashing while initilaizing or soon after.  This issue is minor if you know about it in advance and set the value IN BYTES.
> {quote}



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