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https://issues.apache.org/jira/browse/CASSANDRA-15379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16971010#comment-16971010
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Joey Lynch commented on CASSANDRA-15379:
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[~djoshi] per your feedback in slack I've added the ability for the user to
control the flush via a yaml option while doing the right thing by default.
In order to implement the "don't compress during the flush" [option you
suggested|https://the-asf.slack.com/archives/CK23JSY2K/p1572905922120300?thread_ts=1572905763.117000&cid=CK23JSY2K]
I figured that the easiest was was to just implement the simple
[NoopCompressor|https://github.com/apache/cassandra/commit/9030d8abcf593c06e85f549947ad41621d4776d1]
everyone has been mentioning for years. I was having a hard time turning off
compression at the level of abstraction BigTableWriter operates at since it
doesn't control that e.g. the compression offset file get's written. This way
even if you select "none" your flush is still protected by block level
checksums. Separately it gives us a good path forward for mitigating
CASSANDRA-12682 and CASSANDRA-9264 if we want it to I think.
> 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
> Fix For: 4.0-alpha
>
>
> [~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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