Rei Odaira created CASSANDRA-14062:
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Summary: Pluggable CommitLog
Key: CASSANDRA-14062
URL: https://issues.apache.org/jira/browse/CASSANDRA-14062
Project: Cassandra
Issue Type: Improvement
Components: Core
Reporter: Rei Odaira
Fix For: 4.x
Attachments: pluggable-commitlog-src.patch,
pluggable-commitlog-test.patch
This proposal is to make CommitLog pluggable, as discussed in [the Cassandra
dev mailing
list|https://lists.apache.org/thread.html/1936194d86f5954fa099ced9a0733458eb3249bff3fae3e03e2d1bd8@%3Cdev.cassandra.apache.org%3E].
We are developing a Cassandra plugin to store CommitLog on our low-latency
Flash device (CAPI-Flash). To do that, the original CommitLog interface must be
changed to allow plugins. Synching to CommitLog is one of the performance
bottlenecks in Cassandra especially with batch commit. I think the pluggable
CommitLog will allow other interesting alternatives, such as one using SPDK.
Our high-level design is similar to the CacheProvider framework
in org.apache.cassandra.cache:
* Introduce a new interface, ICommitLog, with methods like
getCurrentPosition(), add(), shutdownBlocking(), etc.
* CommitLog implements ICommitLog.
* Introduce a new interface, CommitLogProvider, with a create() method,
returning ICommitLog.
* Introduce a new class FileCommitLogProvider implementing CommitLogProvider,
to return a singleton instance of CommitLog.
* Introduce a new property in cassandra.yaml, commitlog_class_name, which
specifies what CommitLogProvider to use. The default is FileCommitLogProvider.
* Introduce a new class, CommitLogHelper, that loads the class specified by the
commitlog_class_name property, creates an instance, and stores it to
CommitLogHelper.instance.
* Replace all of the references to CommitLog.instance with
CommitLogHelper.instance.
Attached are two patches. "pluggable-commitlog-src.patch" is for changes in the
src directory, and "pluggable-commitlog-test.patch" is for the test directory.
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