[jira] [Commented] (CASSANDRA-15379) Make it possible to flush with a different compression strategy than we compact with

["Benedict Elliott Smith (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-15379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16964742#comment-16964742 ] 

Benedict Elliott Smith commented on CASSANDRA-15379:
----------------------------------------------------

In principle this seems reasonable to me, though since this is a temporary measure, and anyway because {{String}} are a bad way to communicate intent (particularly with a specific concept like "unsuitability"), perhaps just something like:

{code}
default boolean useOnMemtableFlush() { return true; }
{code}

Or alternatively
{code}
default ICompressor useOnMemtableFlush() { return this; }
{code}

> Make it possible to flush with a different compression strategy than we compact with
> ------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-15379
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-15379
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Local/Compaction, Local/Config, Local/Memtable
>            Reporter: Joey Lynch
>            Assignee: Joey Lynch
>            Priority: Normal
>
> [~josnyder] and I have been testing out CASSANDRA-14482 (Zstd compression) on some of our most dense clusters and have been observing close to 50% reduction in footprint with Zstd on some of our workloads! Unfortunately though we have been running into an issue where the flush might take so long (Zstd is slower to compress than LZ4) that we can actually block the next flush and cause instability.
> Internally we are working around this with a very simple patch which flushes SSTables as the default compression strategy (LZ4) regardless of the table params. This is a simple solution but I think the ideal solution though might be for the flush compression strategy to be configurable separately from the table compression strategy (while defaulting to the same thing). Instead of adding yet another compression option to the yaml (like hints and commitlog) I was thinking of just adding it to the table parameters and then adding a {{default_table_parameters}} yaml option like:
> {noformat}
> # Default table properties to apply on freshly created tables. The currently supported defaults are:
> # * compression       : How are SSTables compressed in general (flush, compaction, etc ...)
> # * flush_compression : How are SSTables compressed as they flush
> # supported
> default_table_parameters:
>   compression:
>     class_name: 'LZ4Compressor'
>     parameters:
>       chunk_length_in_kb: 16
>   flush_compression:
>     class_name: 'LZ4Compressor'
>     parameters:
>       chunk_length_in_kb: 4
> {noformat}
> This would have the nice effect as well of giving our configuration a path forward to providing user specified defaults for table creation (so e.g. if a particular user wanted to use a different default chunk_length_in_kb they can do that).
> So the proposed (~mandatory) scope is:
> * Flush with a faster compression strategy
> I'd like to implement the following at the same time:
> * Per table flush compression configuration
> * Ability to default the table flush and compaction compression in the yaml.



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