Joshua McKenzie created CASSANDRA-15196:
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Summary: Refactor inheritance around CommitLogSegment management
and allocation
Key: CASSANDRA-15196
URL: https://issues.apache.org/jira/browse/CASSANDRA-15196
Project: Cassandra
Issue Type: Improvement
Components: Local/Commit Log
Reporter: Joshua McKenzie
Assignee: Joshua McKenzie
Back when I wrote CASSANDRA-8844 and CASSANDRA-12148, a few things about the
CommitLog stood out to me that I wasn't in love with. At the time I was much
more of the mind of "When in Rome..." regarding some of our structures, our
naming, and specifically regarding our penchant for inheritance vs.
composition. Turns out I have an itch here I need to scratch.
This patch refactors the CommitLog in a few key ways:
* Removes inheritence for CommitLogSegmentManagerX, instead has a single
CommitLogSegmentManager and a CommitLogSegmentAllocator interface
** This interface is implemented by CommitLogSegmentAllocatorStandard and
CommitLogSegmentAllocatorCDC
* Renames a few variables and methods within the segment manager to make their
purpose and role more clear from names alone (hopefully):
** allocatingFrom --> activeSegment
** allocatingFrom() --> getActiveSegment()
** advanceAllocatingFrom() – switchToNewSegment()
** activeSegments --> unflushedSegments
** getActiveSegments --> getUnflushedSegments()
** awaitAvailableSegment(...) --> awaitSegmentAllocation(...)
** isStillAllocating() --> hasRoom()
* Reorders some of the "allocation-and-compare-in-while-loop-decl) to more
idiomatic style
* Adds some comments to various under-documented methods, mostly related to
CDC and timing
As far as we are in the 4.0 testing, I don't expect this to hit pre 4.0. Given
it's a relatively minor refactor in well-tested code, doesn't change
functionality, and doesn't impact any of the publicly exposed APIs in the
CommitLog ecosystem, I'd be comfortable with it going in a minor release after
4.0 is out. But I'm open to alternative viewpoints.
Have run unit tests locally w/out issue on both regular and cdc-targets; need
to get CI against the branch internally for full dtest run and I'll post when
it's done. Just wanted to get visibility to this out there in case anyone was
curious or thinking of working on the same thing.
[ Link to branch on
github|https://github.com/apache/cassandra/compare/trunk...josh-mckenzie:clean_cl_comp]
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